ExploreVolcanoesNow™

Gaua, Vanuatu

ExploreNow Editor — Wed, 22 Feb 2012 23:21:29 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2010
Summit Elevation:    797 m    2,615 feet
Latitude:    14.27°S    14°16’0″S
Longitude:    167.50°E    167°30’0″E

The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank of Mount Garat in 1962 ended a long period of dormancy.

Around the volcano

Gaua is a large shield volcano with gentle outer slopes, a large caldera lake (Lake Letas), and summit cinder cone (Mt Garet). The caldera is 8 x 6 km in diameter. Lake Letas occupies half the caldera with an area of 19.7 sq km. It is about 100 m deep and flat bottomed. There is warm, sulphur stained water near Mt Garet cone. Gaua Island lies just north of the Santa Maria Fracture Zone, which runs perpendicular to the north New Hebrides Trench.

Originally posted 2010-08-20 04:59:37.

Nyiragongo, Congo

ExploreNow Editor — Wed, 22 Feb 2012 10:53:12 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2010 (continuing)
Summit Elevation:    3470 m    11,384 feet
Latitude:    1.52°S    1°31’0″S
Longitude:    29.25°E    29°15’0″E

One of Africa’s most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, 3470-m-high Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks of the volcano, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Nyiragongo eruption

Nyiragongo volcano is one of the most active volcanoes in Africa. It is noted for long active lava lakes which appear in the summit crater. Nyiragongo is one of eight volcanoes in the Virunga Mountains. The volcano is located near the town of Goma in the eastern Democratic Republic of Congo.

Nyiragongo eruption

The summit of the volcano contains a 1 km wide caldera. The summit is 2000 m above the level of Lake Kivu. Two other peaks in the complex are Baruta (3100 m) and Shaheru (2800 m). From 1928 to 1977 there was a long active lava lake in the summit crater. In 1982 there was a lava pond which rapidly cooled. The fissure eruption at the volcano in 1977 was related to regional tectonic activity. A major eruption began at Nyiragongo Volcano on Thursday 17th January 2002 with lava flows reaching the city of Goma. The 2002 eruption of Nyiragongo displaced 500,000 people.

Stratovolcano

Nyiragongo from a distance (decadevolcano.net)

Nyiragongo Volcano (Ingrid Christof)

Cone of the flanks of Mount Nyiragongo (Nick Hobgood)

The inner pit with the new lava lake formed after the 2002 lateral eruption (Marc Caillet)

Lava lake in the crater of Mount Nyiragongo

A view of Nyiragongo's lava lake

View of the lava lake at night (decadevolcano.net)

A closer view of the Nyiragongo lava lake (weblo.com)

Originally posted 2010-08-29 04:44:04.

Wudalianchi Volcanic Field, China

ExploreNow Editor — Tue, 21 Feb 2012 22:44:17 +0000

Nangelaquishan cinder cone of the Wudalianchi volcanic field

Volcano Type: Volcanic field
Volcano Status: Historical
Last Known Eruption: 1776
Summit Elevation: 597 m 1,959 feet
Latitude: 48.72°N * 48°43’0″N
Longitude: 126.12°E 126°7’0″E

The Wudalianchi volcanic field, named for a string of five scenic lava-dammed lakes, consists of 14 cinder cones capping a 500 sq km shield-like lava plateau in NE China. The volcanic field, whose name means “Five Connected Pools” was formed during five eruptive cycles from the early Pleistocene to historical time. Its ancient name was “Nine Hills,” which after the historical eruptions now number 14 hills. The cinder cones were erupted through basement sedimentary and granitic rocks and show a preferred alignment along three chains at the intersection of NE- and NW-trending lineaments. In addition to the historical cinder cones of Laoheishan and Huoshaoshan, Xilongmenshan and Donglongmenshan are Holocene in age. The freshly preserved cones of Laoheishan and Huoshaoshan were formed during eruptions in 1720-21. Fissures at the base of the two new cinder cones fed glassy pahoehoe and aa lava flows that covered 65 sq km and formed the five lakes of Wudalianchi at their eastern and northern margins. Renewed eruptions took place in 1776.

The Pleistocene Nangelaquishan cinder cone, capped by a 500-m-wide flat-bottomed crater, is one of 14 cones forming the Wudalianchi volcanic field in Manchuria, NE China. The cinder cones, four of which are Holocene in age, show a preferred alignment along three parallel NE-SW trends. The Wudalianchi volcanic field was named for five scenic lakes dammed by lava flows during a 1719-21 eruption, which formed two new cinder cones and produced a 65 sq km lava field.

Wudalianchi Cones

Wudalianchi Map

Originally posted 2010-07-06 17:19:59.

Mount Adagdak, Alaska, USA

Volcano Explorer — Tue, 21 Feb 2012 10:22:03 +0000

Adagdak Volcano by unknown

Volcano Type:      Stratovolcano
Volcano Status:    Pleistocene-Hot Springs
Last Known Eruption:     Pleistocene
Summit Elevation:     610 m    2,001 feet
Latitude:     51.988°N    51°59’16″N
Longitude:     176.592°W   176°35’30″W

Mount Adagdak is a Pleistocene age stratovolcano on the northernmost extremity of Adak Island in the Aleutian Islands, Alaska. Located about 1,180 miles (1,900 km) from Anchorage, the mountain is located about 1.4 kilometres (0.9 mi) south of Cape Adagdak, for which it was named in 1948 by the United States Geological Survey.

Mount Adagdak

John Hunter of Quicklaunch has twice proposed the use of Mount Adagdak’s western slope as the emplacement site for a light gas gun to launch small payloads into orbit for use at ISS.

Mount Adagdak by paul roberts

adagdak by travis s

Originally posted 2011-06-08 19:06:23.

Mount Manengouba, Cameroon

ExploreNow Editor — Mon, 20 Feb 2012 22:13:48 +0000

Volcano Type: Stratovolcano
Volcano Status: Holocene
Last Known Eruption: Unknown
Summit Elevation: 2411 m 7,910 feet
Latitude: 5.03°N 5°2’0″N
Longitude: 9.83°E 9°50’0″E

The well-preserved Manengouba stratovolcano rises to 2411 m across the Tombel Graben from Mount Cameroon and has two concentric summit calderas, Elengoum and Eboga. The older 6-km-wide Elengoum caldera is poorly defined and probably formed between about 800,000 and 600,000 years ago. Large lava flows traveled down the NE flanks from a breach on the eastern caldera rim. The younger 3-km-wide Eboga caldera is thought to have formed about 250,000 years ago. Younger volcanism of unknown age has constructed a SW-NE line of crater lakes and cinder cones across the caldera floor of the dominantly basaltic-to-trachytic volcano.

Panoramic view of Mount Manengouba (Markus Betz)

Mount Manengouba (Markus Betz)

Originally posted 2010-10-21 04:52:09.

San Cristóbal, Nicaragua

ExploreNow Editor — Mon, 20 Feb 2012 10:07:04 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2009
Summit Elevation:    1745 m    5,725 feet
Latitude:    12.702°N    12°42’6″N
Longitude:    87.004°W    87°0’13″W

The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua’s highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km to the west of San Cristóbal; it and the eroded Moyotepe volcano, 4 km to the NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the San Cristóbal complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Ash column produced by San Cristóbal

San Cristobal is a stratovolcano located in Nicaragua and is a basaltic cone with a flattened top. This cone is built of alternating layers of lava and tephra. The volcano would never have grown as large as it is without these lava layers to support the slopes and keep the tephra from eroding. It is the youngest volcano in the San Cristobal complex, which consists of five volcanoes. It is also the most active of the five. It has erupted eight times, the latest being in 1977. The communities of El Viejo and Chinandega are located near San Cristobal, but are only threatened by ashfall.

Steaming San Cristóbal

Lava from San Cristobal is aa. It is uniformly basaltic with many phenocrysts. These lavas are also very rich in vesicles. Lava flows from San Cristobal are usually between 10 and 13 km in length. A single vent leads to each flow. Several small cinder cones have also formed at these vents at the base of the volcano. San Cristobal spent almost three centuries in a dormant state between 1685 and 1971. In 1971, San Cristobal had 3 craters. These began to sink with renewed activity and had gone down almost 90 meters after eruptions in late 1976.

San Cristóbal from a distance (John Coletti)

Volcano San Cristobal in Nicaragua (Ryan Ballantyne)

Steaming crater of San Cristóbal

Road to San Cristóbal Volcano

San Cristóbal Volcano

Steaming crater of San Cristóbal

Originally posted 2010-08-26 04:52:30.

Bárdarbunga, Iceland

ExploreNow Editor — Sun, 19 Feb 2012 21:50:49 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    1910
Summit Elevation:    2009 m    6,591 feet
Latitude:    64.63°N    64°38’0″N
Longitude:    17.53°W    17°32’0″W

The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

Bárdarbunga, a large central volcano, had its last major eruption in 1477 when it produced a large ash and pumice fall-out deposit. It also produced the largest known lava flow during the past 10,000 years on earth (more than 21 cubic kilometers of volume).

The volcano is hidden beneath the northwestern part of the Vatnajökull glacier, and contains a 700-m-deep caldera that is hidden beneath ice and has extensive flank fissures, from where eruptions have taken place: the Veidivötn fissure extends for over 100 km to the SW, almost reaching Torfajökull volcano, while the Trollagigar fissure extends 50 km to the NE touching Askja volcano. A major risk from Bárdarbunga are jökulhlaups (glacier-outburst floods), that can be hazardous for areas in all directions around Bárdarbunga.

Originally posted 2010-08-24 04:15:13.

Fuerteventura, Canary Islands

ExploreNow Editor — Sun, 19 Feb 2012 09:27:41 +0000

Volcano Type:     Fissure vents
Volcano Status:   Holocene
Last Known Eruption:    Unknown
Summit Elevation:    529 m    1,736 feet
Latitude:    28.358°N    28°21’30″N
Longitude:    14.02°W    14°1’0″W

Pleistocene and Holocene cinder cones and lava flows cover large portions of elongated Fuerteventura Island at the SE end of the Canary Islands. The youngest lavas are found at the northern and central portions of the arid, sparsely vegetated island. Malpais de la Arena, the Northern Malpais, and the Lobos Island areas at the northern tip of Fuerteventura are the sites of broad fields of youthful cinder cones and lava flows. The Malpais Chico, Malpais Grande, and Malpais de Jacomar areas on the south-central part of the island represent smaller zones of youthful volcanism, as do the volcanoes of Pajara, which were constructed on the older plutonic massif west of the axis of the island. No historical eruptions have occurred on Fuerteventura.

Fuerteventura Island

Along the shores

Fuerteventura is the oldest and largest island in the Canary archipelago, 100 km off the coast of Western Saraha. The island consists of two structural elements; Basal Complex and the Subaerial Volcanic Series.

Fuerteventura

The Basal Complex is a thick Late Cretaceous sedimentary sequence overlain by submarine volcanics. The sequence is intruded by dike swarms generated mainly during the stage of submarine growth of the island. The Basal Complex is exposed in the western part of the island. On the Subaerial Volcanic Series, the earliest and most important of the subaerial volcanic series is the Old Basalts Series. Three major volcanoes have formed during this series – Central, Northern and Southern.

Aerial View of the volcano's crater

Fuerteventura (Jesus de Blas)

Fuerteventura

Fuerteventura (Ken Scott)

Fuerteventura (Matthieu Milliot)

Fuerteventura

Originally posted 2010-09-06 12:34:42.

Popocatépetl, México

ExploreNow Editor — Sat, 18 Feb 2012 21:19:15 +0000

Volcano Type:     Stratovolcanoes
Volcano Status:   Historical
Last Known Eruption:    2010 (continuing)
Summit Elevation:    5426 m    17,802 feet
Latitude:    19.023°N    19°1’24″N
Longitude:    98.622°W    98°37’20″W

Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America’s 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas south of the volcano. The modern volcano was constructed to the south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 AD, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.

Volcán Popocatépetl Eruption

Popocatepetl is a large, partly glacier-covered, composite andesitic volcano. It is located 60 km southeast of Mexico City on the volcanic front of the central Mexican magmatic arc. Popocatépetl is the third highest active volcano in the Northern Hemisphere. The volcano presents a great hazard to Mexico City and to other nearby cities and towns from a possible major volcanic eruption.

Sunset in Popocatépetl (Diana Aguirre)

Volcán Popocatépetl

Popocatépetl at sunset (Gloria Zelaya)

Popocatépetl Eruption (Edgar Xolot)

Originally posted 2010-08-07 04:35:32.

Domuyo, Argentina

ExploreNow Editor — Sat, 18 Feb 2012 09:07:32 +0000

Volcano Type: Stratovolcano
Volcano Status: Holocene
Last Known Eruption: Unknown
Summit Elevation: 4709 m 15,449 feet
Latitude: 36.58°S 36°35’0″S
Longitude: 70.42°W 70°25’0″W

Volcán Domuyo is a 4709-m-high Argentinian stratovolcano of late-Pleistocene or possibly Holocene age. At least 14 dacitic lava domes and other eruptive centers were constructed within a broad 15-km-wide caldera, and at least another 5 lie outside the caldera. The largest of the latter is Volcán Chanque-Mallín on the ESE flank. It is truncated by a 4-km-wide caldera and contains a resurgent dome.

Originally posted 2010-11-08 04:45:51.

Ardoukôba, Djibouti, Africa

ExploreNow Editor — Fri, 17 Feb 2012 20:57:17 +0000

Volcano Type:     Fissure vents
Volcano Status:   Historical
Last Known Eruption:    1978
Summit Elevation:    298 m    978 feet
Latitude:    11.58°N *    11°35’0″N
Longitude:    42.47°E    42°28’0″E

The Ardoukôba (Asal) Rift in Djibouti, trending NW from the Red Sea, contains a broad area of youthful fissure vents between Lake Asal and the Ghoubbat al Kharab gulf. The rift is subaerially exposed over a 12 km distance between these two bodies of water and contains numerous basaltic cinder and spatter cones. The silicic centers of Eger Alayta and Asa Aleyta, on the north and south sides of the rift, are remnants of a Pleistocene silicic center that has been disrupted and spread apart by the rift. Magma-water interaction has produced tuff cones, some of which form islands or are breached by the sea. The most recent lava flows are younger than lake sediments deposited 5300 years ago. These lavas were thought to have been erupted during the past 3000 years (Delibrias et al., 1975). The Ardoukôba fissure erupted in 1978, producing a small cinder cone and lava flows that covered part of the rift floor near the Red Sea.

Ardoukoba Volcano is located on the coast 100 km from Djibouti city. Ardoukoba Volcano erupted in 1978 for one week after an earthquake created a 1.8 m fissure. This was the first eruption of Ardoukoba Volcano in 3000 years. Two lava flows were erupted, 1 km to the SE, and 0.5 km to the NW. Ash emissions reached 300 m altitude, and a crater 30 wide and 100 m high was formed. The Ardoukoba rift is 17 km wide and 800 m deep. The most recent flows are concentrated within the Inner Floor. Exposed rocks of the Ardoukoba Rift trend from basalts to ferrobasalts (~15% total Fe), with andesine basalts the most abundant group recognized. The maximum thickness of recent flows in the Ardoukoba rift is 10 m, which gives a minimum eruption rate of 3000 cubic m/km/year over a 3000 year period. The Inner Floor is the area of thinnest and weakest lithosphere. In the Ardoukoba Rift it is the site of active extension with fissures and faulting.

Originally posted 2010-08-25 03:51:19.

Kueishantao, Taiwan

ExploreNow Editor — Fri, 17 Feb 2012 08:38:33 +0000

Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1785 ± 10 years
Summit Elevation: 401 m    1,316 feet
Latitude: 24.85°N   24°51’0″N
Longitude: 121.92°E   121°55’0″E

Kueishantao Island, whose summit is 401 m above sea level, is the southernmost of five small volcanic islands off the NE coast of Taiwan. Kueishantao, also known as Guieshan Island, consists of andesitic lava flows and volcaniclastic material. Kueishantao is the southwesternmost volcano along the axis of the Okinawa Trough back-arc basin that extends to the NE from Taiwan to Unzen volcano in Kyushu.

The SW tip of the Okinawa Trough extends past Kueishantao onto the Ilao Plain on the island of Taiwan. The island is known as “Turtle Mountain Island” due to its profile as seen from some points on the coast of Taiwan. Historical accounts during the time of King Qianlong of the Qing Dynasty (1775-1795 AD) noted the Guieshan mountain split open with a blood-red lava flow. Kueishantao displays vigorous active submarine fumaroles and solfataras that discolor seawater over wide areas.

Originally posted 2010-10-08 06:18:06.

Mallahle, Ethiopia

ExploreNow Editor — Thu, 16 Feb 2012 20:18:20 +0000

Volcano Type: Stratovolcano
Volcano Status: Holocene
Last Known Eruption: Unknown
Summit Elevation: 1875 m 6,152 feet
Latitude: 13.27°N 13°16’0″N
Longitude: 41.65°E 41°39’0″E

Mallahle volcano is located in northern Ethiopia near the border with Eritrea. Mallahle is the central of three NE-SW-trending stratovolcanoes in the Danakil horst SW of Dubbi volcano, and lies SSW of Nabro volcano. These two volcanoes, along with Bara Ale and Sork’Ale, form the Bidu volcanic complex. The complex Mallahle stratovolcano is truncated by a steep-walled 6-km-wide caldera. Mallahle is formed of rhyolitic lava flows and pyroclastics. Basaltic lava flows blanket the slopes of the volcano. Recent obsidian flows are found on the NW flank of Mallahle and older obsidian flows were erupted on the northern caldera floor. Flank spatter and scoria cones are most numerous on the western side of the volcano. Extensive ignimbrite deposits associated with the collapse of Mallahle and Nabro volcanoes blanket the countryside.

Originally posted 2010-10-22 04:10:38.

Meidob Volcanic Field, Sudan

ExploreNow Editor — Thu, 16 Feb 2012 07:48:01 +0000

Volcano Type: Scoria cones
Volcano Status: Holocene
Last Known Eruption: 2950 BC ± 500 years
Summit Elevation: 2000? m 6,562 feet
Latitude: 15.32°N * 15°19’0″N
Longitude: 26.47°E 26°28’0″E

The alkaline Meidob volcanic field in western Sudan, at the NE end of the Dafur volcanic province, covers an area of 5000 sq km with nearly 700 Pliocene-to-Holocene vents. The volcanic field was constructed over an uplifted Precambrian igneous and metamorphic basement and is elongated in an E-W direction. Basaltic scoria cones and associated lava flows dominate, but trachytic-phonolitic lava domes, tuff rings, and maars are among the youngest volcanic products. Basaltic scoria cones are scattered throughout the field; their lavas have produced a broad lava plateau. The central part of the field consists of younger phonolitic lava flows, trachytic pumice-fall deposits, ignimbrites, and maars.

The volcano contains 316 scoria cones, lava flows, lava domes, tuff rings, and maars. Meidob volcanic field contains 700 eruptive vents. The total volume of erupted material at the volcano is 1400 cubic km, which forms a 400-m-thick plateau.

The Meidob Hills are divided into an elevated central area, topped by phonolitic mesa flows up to 2000 m above sea level, and a low elevation outer area (1000-1500 m) formed mostly from basaltic lava flows and scoria cones.

Scoria cones
Many cones at Meidob Volcano follow an east-west alignment. The average height of the cones above the surrounding plateau is 80 m (range: 20-300 m), and the basal diameter ranges from 500-1500 m. The internal, well-stratified structure of some
scoria cones has been exposed by later phreatomagmatic activity or erosion.

Mesa flow units
Forty mesa flows have been identified from aerial photographs. They are mostly located in the central volcanic field. The mesa flow units have a circular to slightly oval shape, and are about 200 m in height above the surrounding area (range: 40-420 m) with diameters from 300-4000 m. All have steep slopes, and bases which are mostly covered with talus.

Malha Crater
Malha Crater is the best known feature of Meidob volcano. The crater is situated at 220 km NNE of El Fasher, at an altitude of 905 m above sea level. It is a maar 150 m deep and 1050 m wide. The crater rim is between 105 and 130 m above the lake, is nearly circular in outline. The alkaline lake water has a pH of 9.5 to 10.3.

Eruption 5000 years ago
An eruption 5000 years ago produced a tuff ring and a lava flow.

Originally posted 2010-10-28 04:22:56.

Hekla, Iceland

ExploreNow Editor — Wed, 15 Feb 2012 19:32:27 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2000
Summit Elevation:    1491 m    4,892 feet
Latitude:    63.98°N    63°59’0″N
Longitude:    19.70°W    19°42’0″W

One of Iceland’s most prominent and active volcanoes, Hekla lies near the southern end of the eastern rift zone. Hekla occupies a rift-transform junction, and has produced basaltic andesites, in contrast to the tholeiitic basalts typical of Icelandic rift zone volcanoes. Vatnafjöll, a 40-km-long, 9-km-wide group of basaltic fissures and crater rows immediately SE of Hekla forms a part of the Hekla-Vatnafjöll volcanic system. A 5.5-km-long fissure, Heklugjá, cuts across the 1491-m-high Hekla volcano and is often active along its full length during major eruptions. Repeated eruptions along this rift, which is oblique to most rifting structures in the eastern volcanic zone, are responsible for Hekla’s elongated ENE-WSW profile. Frequent large silicic explosive eruptions during historical time have deposited tephra throughout Iceland, providing valuable time markers used to date eruptions from other Icelandic volcanoes. Hekla tephras are generally rich in fluorine and are consequently very hazardous to grazing animals. Extensive lava flows from Hekla’s historical eruptions, which date back to 1104 AD, cover much of the volcano’s flanks.

Hekla Volcano is located in southern Iceland 110 km east of Reykjavik, and 55 km from the coast. Hekla is the most active volcano in Iceland, and one of the world’s best known volcanoes. The structure of Hekla is considered intermediate between crater row of Laki-type, and stratovolcano of the Vesuvius-type. It is built on a 5 km long fissure. Repose periods at the volcano have lasted from 10 to 102 years.

The magma reservoir feeding Hekla is located at a depth of 5-9 km. During non-eruptive periods the volcano is virtually aseismic. Eruption-related seismicity starts only 30-80 minutes before its onset. Hundreds of small volcano-tectonic earthquakes (magnitude < 3), related to the intrusion of magma, occur during the first hours, when the eruption is violent and explosive. Since 1970, Hekla volcano has erupted about every 10 years. The initial phase of each Hekla eruption is always highly explosive. The duration and magnitude of the explosive phase is directly correlated with the length of the preceding repose period.

Originally posted 2010-08-21 05:00:52.

Agua, Guatemala

ExploreNow Editor — Wed, 15 Feb 2012 07:24:31 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Holocene
Last Known Eruption:    Unknown
Summit Elevation:    3760 m    12,336 feet
Latitude:    14.465°N    14°27’53″N
Longitude:    90.743°W    90°44’35″W

The symmetrical, forested Volcán de Agua stratovolcano forms an impressive backdrop to the historic former capital city of Antigua Guatemala, opposite the twin volcanoes of Fuego and Acatenango. The 3760-m-high basaltic-andesite to andesite Agua volcano has an isolated position that makes it a prominent landmark from all directions. A small, 280-m-wide circular crater is breached on the NNE side. Six small pit craters are located on the NW flank, and two small cones lie on the south flank. Agua’s symmetrical profile implies a relatively young age, although currently no dated Holocene tephra deposits are known. Agua has had no historical eruptions, but its name (the water volcano) originates from a devastating mudflow on September 11, 1541. The mudflow destroyed the first Guatemalan capital city established by the Spanish Conquistadors, which is now known as Ciudad Vieja. The catastrophe prompted the establishment of a new capital city at nearby Antigua.

Agua is a symmetrical volcano located in southern Guatemala. The volcano contains six small pit craters on the NW flank. The summit contains a circular, 250 m diameter crater, which is breached towards the NNE. The crater walls are vegetated. No historical eruptions have occurred at the volcano.

Agua Volcano is an inactive volcano that rises to an elevation of 3760 m. It’s located a few minutes away from La Antigua Guatemala, which makes it a characteristic landmark visible from any part of the city. Its shape is that of a symmetrical cone covered with vegetation. It’s name derives from a mudflow that destroyed the first Guatemala capital in 1541, when one side of the crater collapsed releasing the water inside it. As a result of this disaster, most of the city’s buildings where demolished. After the catastrophe, the capital was moved to the current La Antigua Guatemala.

Originally posted 2010-08-25 03:50:43.

Oku Volcanic Field, Cameroon

ExploreNow Editor — Tue, 14 Feb 2012 19:00:01 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Holocene?
Last Known Eruption:    Unknown
Summit Elevation:    3011 m    9,878 feet
Latitude:    6.25°N *    6°15’0″N
Longitude:    10.50°E    10°30’0″E

Numerous maars and basaltic cinder cones lie on or near the deeply dissected rhyolitic and trachytic Mount Oku massif along the Cameroon volcanic line. The Mount Oku stratovolcano is cut by a large caldera. The Oku volcanic field is noted for two crater lakes, Lake Nyos to the north and Lake Monoun to the south, that recently produced catastrophic carbon-dioxide gas release events. The August 15, 1984, gas release at Lake Monoun was attributed to overturn of stratified lake water, triggered by an earthquake and landslide. The Lake Nyos event on August 21, 1986, caused at least 1700 fatalities. The emission of around 1 cu km of magmatic carbon dioxide has been attributed either to overturn of stratified lake waters as a result of a non-volcanic process, or to phreatic explosions or injection of hot gas into the lake.

Oku Lake

Oku Volcanic field is located in NW Cameroon. The region is part of the Cameroon line of volcanoes which runs from Annobon Island in the Atlantic Ocean to Oku in NW Cameroon. North of Oku the line splits north to the Biu Plateau in Nigeria, and eastwards to Ngaoundere plateau in eastern Cameroon. Lake Nyos is a deep maar lake of explosive origin in NW Cameroon. The lake has an area of 1.49 sq km, 208 m deep, and a water volume of 132 million cubic m. The lake was formed by phreatomagmatic eruption several hundred years ago.

Lake Oku

Road to Oku

Ascending Mt. Oku

Looking down from Mt. Oku

Looking down on Lake Oku from Mt. Oku

Lake Oku

The side view of Lake Oku

Lake Oku (Mukong Aloysius)

Metchum Falls

Originally posted 2010-09-09 12:09:41.

Mt. Matutum, Philippines

ExploreNow Editor — Tue, 14 Feb 2012 06:44:11 +0000

Mt. Matutum

Volcano Type: Stratovolcano
Volcano Status: Radiocarbon
Last Known Eruption: 1290 ± 40 years
Summit Elevation: 2286 m    7,500 feet
Latitude: 6.37°N   6°22’0″N
Longitude: 125.07°E   125°4’0″E

The symmetrical Matutum stratovolcano rises to 2286 m in southern Mindanao, NW of Sarangani Bay. The summit of the andesitic-to-dacitic volcano is truncated by a well-preserved 320-m-wide crater that is breached by three gorges and has a 120-m-deep, densely forested floor. Widespread silicic pyroclastic-flow deposits surround the volcano, which overlooks the major city of General Santos. The youngest pyroclastic deposits were dated at about 2000 yrs BP. A report stated that Matutum volcano was “smoking” on March 7, 1911 (Neumann van Padang, 1953). The Akmoan and Lianan thermal areas are located on the WSW flank of the volcano.

Mt. Matutum

Matutum is a stratovolcano that rises 2,286 meters with a base diameter of 25 km. It has 2 hot springs, called Akjmoan and Linan, 5.7 km west-southwest of the volcano. Adjacent volcanic edifices are Landayao, Tampad, and Albulhek, which are all west of the volcano, and Magolo to the north. There is a well-preserved 320 metre wide crater at the volcano’s summit.

Mt. Matutum (Omar Gallinero)

View of Mt. Matutum at sundown (Mark Pedregosa)

Mt. Matutum bathed in golden light (Allan Barredo)

Originally posted 2010-07-26 04:08:59.

Mt. Binubulauan, Philippines

ExploreNow Editor — Mon, 13 Feb 2012 18:28:15 +0000

Volcano Type: Stratovolcano
Volcano Status: Holocene
Last Known Eruption: 1986
Summit Elevation: 2,329 m   7,641 feet
Latitude: 17°18′40″N    17.310982°N
Longitude: 121°06′13″E    121.103668°E

Binubulauan, is a remote stratovolcano, part of the volcanic Cordillera Central mountain range.

Groundwork in 2007 and 2008 as part of a comprehensive systematic survey, shows volcanic related activity to the NW, W, SW, S, SE, E, around Binubulauan, with the peak of Binubulauan in the centre of the half-ring of activity.

Bu-ot Fumarole field general

A little-known cluster of volcanoes in the Cordillera Central of northern Luzon is known as Ambalatungan by Alvir (1956) and the Philippine Commission of Volcanology (1981) and as Mount Binuluan by Wolfe (1982, pers. comm.). The dacitic Ambalatungan Group was described as consisting of three volcanoes constructed along a roughly E-W line. Ambalatungan volcano proper contains a steep-walled crater with hot springs and vigorous sulfur-encrusted fumarolic vents that produce loud noises. Bumabag volcano, 3 km east of Ambalatungan, has two craters that also show strong fumarolic activity. Podakan volcano, 1 km SE of Bumabag, also has a large steam vent. A possible steam eruption was reported from 2329-m-high Mount Binuluan (whose relationship to the previously mentioned volcanoes is unclear) in 1952, during which a sulfur-rich debris flow killed a dozen people.

Bum-bag Fumarole Field #1

Originally posted 2010-08-13 03:55:18.

Ijen, Indonesia

ExploreNow Editor — Mon, 13 Feb 2012 06:15:59 +0000

Volcano Type:     Stratovolcanoes
Volcano Status:    Historical
Last Known Eruption:     1999
Summit Elevation:     2799 m     9,183 feet
Latitude:     8.058°S     8°3’30″S
Longitude:     114.242°E     114°14’30″E

Ijen Crater

Kawah Ijen volcano is one of several volcanoes located in the 15km diameter Ijen Caldera in E Java, Indonesia. The caldera rim is still visible in places, but has been partially buried by Kawah Ijen, 2800m high Gunung Merapi (not to be confused with Merapi volcano near Yogyakarta), Gunung Rante and Gunung Pendil volcanoes. The caldera is today largely filled with coffee plantations. Kawah Ijen harbours a large warm acidic crater lake and an active sulphur mine. Due to its easy accessibility, turqoise lake and unique sulphur mining operation, the crater is regularly visited by tourists. The last recorded magmatic eruption of Kawah Ijen was in 1817. The eruption displaced the crater lake and resulted in inundation of several villages along the drainage route. Phreatic eruptions have been reported in 1796, 1917, 1936, 1950, 1952, 1993, 1994, 1999, 2000 (also minor ash emission), 2001, 2002 (with minor ash emission). The increasing frequency may reflect better reporting since the explosions are usually confined to the lake and cause little or no damage.

Volcano Type:     Stratovolcanoes
Volcano Status:   Historical
Last Known Eruption:    1999
Summit Elevation:    2799 m    9,183 feet
Latitude:    8.058°S    8°3’30″S
Longitude:    114.242°E    114°14’30″E

Kawah Ijen is the world’s largest acidic volcanic lake. It is located in east Java, Indonesia. The Ijen volcanic complex consists of several stratovolcanoes and cinder cones and a 20 km wide caldera. Ijen caldera is the largest in Java. The size of the crater is about 960 m x 600 m. The primary dangers at Ijen are pyroclastic flows, lahars, and lava flows. The Ijen volcano complex at the eastern end of Java consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera.

Ijen Crater

The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi stratovolcano, which forms the 2799 m high point of the Ijen complex. Immediately west of Gunung Merapi is the renowned historically active Kawah Ijen volcano, which contains a nearly 1-km-wide, turquoise-colored, acid crater lake. Picturesque Kawah Ijen is the world’s largest highly acidic lake and is the site of a labor-intensive sulfur mining operation in which sulfur-laden baskets are hand-carried from the crater floor. Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of post-caldera cones forms an E-W-trending zone across the southern side of the caldera. Coffee plantations cover much of the Ijen caldera floor, and tourists are drawn to its waterfalls, hot springs, and dramatic volcanic scenery. Kawah Ijen volcano is one of several volcanoes located in the 15km diameter Ijen Caldera in E Java, Indonesia. The caldera rim is still visible in places, but has been partially buried by Kawah Ijen, 2800m high Gunung Merapi (not to be confused with Merapi volcano near Yogyakarta), Gunung Rante and Gunung Pendil volcanoes.

Ijen Rim (Maciej Dakowicz)

The caldera is today largely filled with coffee plantations. Kawah Ijen harbours a large warm acidic crater lake and an active sulphur mine. Due to its easy accessibility, turqoise lake and unique sulphur mining operation, the crater is regularly visited by tourists. The last recorded magmatic eruption of Kawah Ijen was in 1817. The eruption displaced the crater lake and resulted in inundation of several villages along the drainage route. Phreatic eruptions have been reported in 1796, 1917, 1936, 1950, 1952, 1993, 1994, 1999, 2000 (also minor ash emission), 2001, 2002 (with minor ash emission). The increasing frequency may reflect better reporting since the explosions are usually confined to the lake and cause little or no damage.

Ijen Crater Steaming (Rick Wezenaar)

Originally posted 2010-08-19 03:53:30.

Kilauea, Hawaii

ExploreNow Editor — Sun, 12 Feb 2012 17:39:49 +0000

Volcano Type:     Shield volcano
Volcano Status:   Historical
Last Known Eruption:    2010 (continuing)
Summit Elevation:    1222 m    4,009 feet
Latitude:    19.421°N    19°25’16″N
Longitude:    155.287°W    155°17’12″W

Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii’s most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano’s surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.

Lava flow

Kīlauea is the youngest and southeastern most volcano on the Big Island of Hawai`i. Topographically Kīlauea appears as only a bulge on the southeastern flank of Mauna Loa, and so for many years Kīlauea was thought to be a mere satellite of its giant neighbor, not a separate volcano. However, research over the past few decades shows clearly that Kīlauea has its own magma-plumbing system, extending to the surface from more than 60 km deep in the earth.

Kilauea lava flow

Kīlauea is the home of Pele, the Hawaiian volcano goddess. Hawaiian chants and oral traditions tell in veiled form of many eruptions fomented by an angry Pele before the first European, the missionary Rev. William Ellis, saw the summit in 1823. The caldera was the site of nearly continuous activity during the 19th century and the early part of this century. Since 1952 there have been 34 eruptions, and since January 1983 eruptive activity has been continuous along the east rift zone. All told, Kīlauea ranks among the world’s most active volcanoes and may even top the list.

Originally posted 2010-08-19 04:23:25.

Ol Doinyo Lengai, Tanzania

ExploreNow Editor — Sun, 12 Feb 2012 05:14:04 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2010 (continuing)
Summit Elevation:    2962 m    9,718 feet
Latitude:    2.764°S    2°45’49″S
Longitude:    35.914°E    35°54’51″E

The symmetrical Ol Doinyo Lengai stratovolcano is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent volcano, known to the Maasai as “The Mountain of God,” rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage of the volcano ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra eruptions and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Ol Doinyo Lengai volcano (known by Maasai as the mountain of god) has an impressive cone shape and rises above the plain from Lake Natron. The cone is composed of ash and reaches a maximum slope of 42 deg. Ol Doinyo Lengai Volcano has the lowest temperature lava of any volcano on earth. It erupts at less than 600 deg C. Most eruptions at the volcano are small. Larger than normal eruptions occurred in 1917 when vegetation was destroyed on the volcano and ashfall caused destruction of grazing land and death of herds of maasai cattle. An eruption in 1940-41 lasted for six months and ash fell 100 km from the volcano.

Originally posted 2010-08-20 05:00:23.

Tenorio Volcano, Costa Rica

ExploreNow Editor — Sat, 11 Feb 2012 17:02:31 +0000

Volcano Type: Stratovolcanoes
Volcano Status: Holocene
Last Known Eruption: Unknown
Summit Elevation: 1916 m 6,286 feet
Latitude: 10.673°N 10°40’22″N
Longitude: 85.015°W 85°0’54″W

The 225 sq km dominantly andesitic Tenorio volcanic massif anchors the SE end of the Guanacaste Range and consists of a cluster of densely forested NNW-SSE-trending volcanic cones. Overlapping lava flows from the principal peak, Tenorio, blanket the NW-to-SW flanks and descend the NE flank. The NW-most of three craters of the central cone is sparsely vegetated and appears to be the most recently active. Volcán Montezuma to the north has twin craters, the northern of which fed a lava flow to the NE. Additional pyroclastic cones are found to the NE and SW of the central complex, and the Bijagua lava domes were constructed on the northern flank. A major debris avalanche covered about 100 sq km below the southern flank of the volcano. A legend exists of an eruption in 1816, but the volcano was densely forested at the time of an 1864 visit by Seebach and is not considered to have erupted in historical time. Fumarolic activity is present on the NE flank.

: Tenorio Volcano

The densely forested Tenorio volcanic complex forms a group of volcanic cones at the SE end of the Guanacaste Range. Only the NW crater of the central cone is sparsely vegetated. The age of the most recent eruption of the Tenorio group is not known. A legend exists of an eruption in 1816, but the volcano was densely forested at the time of an 1864 visit by Seebach and is not considered to have erupted in historical time. Fumarolic activity is present on the NE flank.

Tenorio Volcano

Tenorio Volcano (Ronald Zúñiga)

View of Tenorio Volcano from the east side (Daniel Jimenez)

Originally posted 2010-07-06 16:41:32.

Tengger Caldera, Java, Indonesia

ExploreNow Editor — Sat, 11 Feb 2012 04:32:20 +0000

Volcano Type:     Stratovolcanoes
Volcano Status:   Historical
Last Known Eruption:    2004
Summit Elevation:    2329 m    7,641 feet
Latitude:    7.942°S    7°56’30″S
Longitude:    112.95°E    112°57’0″E

Mt Bromo is a scenic tourist destination in East Java. The volcano is noted for its spectacular sunrises, and majestic views across to Semeru volcano to the south. Bromo is the only active crater in the Tengger caldera which contains seven eruptive centres. In 1838 the crater was filled with a lake.

Mt. Bromo

The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive Tengger volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the Tengger calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java’s most active and most frequently visited volcanoes.

Tengger Caldera

Mount Bromo (2392m) is a small pyroclastic cone which rises 133m above the surrounding floor of the massive (9x10km) Tengger Caldera. This caldera, also referred to as the sand-sea caldera due to its flat sandy floor, is the result of the collapse of the top half of a probably nearly 4500m high pre-caldera stratovolcano over 250000 years ago. Bromo has been frequently active since historical records began in 1804, with a total of over 50 eruptions being recorded up to the present date. Due to its location on the base of a steep-walled caldera, it generally only poses a local threat due to the impact of ballistics from explosive eruptions. These may occur with little warning. Such an eruption occurred on 08.06.2004 and accounted for 2 fatalities in the vicinity of the crater due to the impact of ballistics.

Originally posted 2010-08-09 20:21:05.

Rabaul, Papua New Guinea

ExploreNow Editor — Fri, 10 Feb 2012 16:17:27 +0000

Volcano Type:     Pyroclastic shield
Volcano Status:   Historical
Last Known Eruption:    2010 (continuing)
Summit Elevation:    688 m    2,257 feetl
Latitude:    4.271°S    4°16’15″S
Longitude:    152.203°E    152°12’10″E

The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island’s largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims of Rabaul. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Rabaul eruption

Rabaul is one of the most active volcanoes in Papua New Guinea, and one of its most dangerous. It is located on the north eastern end of New Britain Island, and is the eastern most volcano in the Bismarck arc. The caldera has an elliptical form (14 x 9 km) and is surrounded by a steep volcanic ridge several hundred meters high.

Rabaul eruption

Rabaul has had major eruptions 3500 and 1400 years ago. An eruption of Rabaul in 1994 destroyed Rabaul city, the largest town on New Britain Island. Eruptions severly affected Matupit Island in 2008-09, forcing most of the population to relocate to safer areas. Eruptive vents in Rabaul Caldera include; Turanguna, Tavurvur, Rabalanakia, Sulphur Creek, Kombiu (mother), and Beehives.

Tavurvur is a sub-vent of the Rabaul caldera (Rita Willaert)

Volcanic dust creating distinctive orange glow for sunset at Rabaul (Michael Thirnbeck)

Rabaul volcano (Michael Thirnbeck)

Active volcano on the eastern rim of Rabaul Caldera (Richard Arculus)

Dusty Rabaul (Michael Thirnbeck)

Rabaul volcano (Michael Thirnbeck)

Originally posted 2010-08-31 04:58:45.

Fort Portal, Uganda

ExploreNow Editor — Fri, 10 Feb 2012 04:04:48 +0000

Volcano Type: Tuff cones
Volcano Status: Radiocarbon
Last Known Eruption: 2120 BC ± 100 years
Summit Elevation: 1615 m 5,298 feet
Latitude: 0.70°N * 0°42’0″N
Longitude: 30.25°E 30°15’0″E

The carbonatite lavas and tuffs of the Fort Portal volcanic field in Uganda, NE of Mount Ruwenzori between Lake Albert and Lake Edward, consists of a group of tuff cones and maars covering an area of about 145 sq km. About 50 volcanic vents, some of which now contain crater lakes, were erupted through basement rocks of Precambrian gneiss in an WSW-ENE-trending area north of the town of Fort Portal.

Crater Lake Kyaninga (Mark Stewart)

Several additional vents are located in the Kasekere area to the NE. Radiocarbon dates of about 4700 to 4000 years ago were obtained from ash deposits from the Fort Portal volcanic field. Holmes noted that Kasensankaranga Crater in the Fort Portal area means “spewer of roasted material,” implying an historical age.

Fort Portal Volcano contains about 50 vents, and has erupted in three stages.

1) Two NE–SW lines of carbonatite tuff cones were erupted in the first stage.
2) A blanket of tuffs formed the major deposit, defining the Fort Portal field.
3) The final phase involved eruption of lava flows at the SW end of the main line of tuff cones.

Fort Portal (Aaron McFarlane)

Iron Age hill fort

Fort Portal views

Crater lake, Fort Portal (Ruth Hartnup)

Originally posted 2010-10-25 11:33:43.

Long Valley Caldera, California, USA

ExploreNow Editor — Thu, 09 Feb 2012 15:59:43 +0000

Volcano Type:     Caldera
Volcano Status:   Pleistocene-Fumarolic
Last Known Eruption:    Pleistocene
Summit Elevation:    3390 m    11,122 feet
Latitude:    37.70°N    37°42’0″N
Longitude:    118.87°W    118°52’0″W

Long Valley caldera, located at the boundary between the Sierra Nevada and the Basin and Range Province, is one of the largest Quaternary rhyolitic volcanic centers in North America. The caldera is elliptical in shape and 10 by 20 miles (15 by 30 km) in size. The elevation of the floor of the caldera is 6,500 feet (2,000 m) in the east and 8,500 feet (2600 m) in the west. The elevation of the walls of the caldera reach elevations of 9,800-11,500 feet (3000-3500 m) except in the east where the wall rises only 500 feet (150 m) to an elevation of 7,550 feet (2,300 m).

Long Valley (Obsidian Flow)

The large 17 x 32 km Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption about 760,000 years ago. Resurgent doming in the central part of the caldera occurred shortly afterwards, followed by rhyolitic eruptions from the caldera moat and the eruption of rhyodacite from outer ring fracture vents, ending about 50,000 years ago. During early resurgent doming the caldera was filled with a large lake that left strandlines on the caldera walls and the resurgent dome island; the lake eventually drained through the Owens River Gorge. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. The late-Pleistocene to Holocene Inyo Craters cut the NW topographic rim of the caldera, and along with Mammoth Mountain on the SW topographic rim, are west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system.

Upwelling in Hot Creek

Little Hot Creek

Originally posted 2010-08-16 08:24:40.

Tokachi, Hokkaido, Japan

ExploreNow Editor — Thu, 09 Feb 2012 03:42:39 +0000

Volcano Type:     Stratovolcanoes
Volcano Status:   Historical
Last Known Eruption:    2004
Summit Elevation:    2077 m    6,814 feet
Latitude:    43.416°N    43°24’56″N
Longitude:    142.690°E    142°41’25″E

Tokachi Volcano is located in central Hokkaido, Japan. Farmland near Tokachi is a popular places for viewing lavender fields. A debris avalanche and mudflow occurred during an eruption in 1926. Large eruptions occurred at the volcano in 1926 and 1962.

Steaming Crater

Tokachi volcano consists of a group of dominantly andesitic stratovolcanoes and lava domes arranged on a NE-SW line above a plateau of welded Pleistocene tuffs in central Hokkaido. Numerous explosion craters and cinder cones are located on the upper flanks of the small stratovolcanoes, with the youngest Holocene centers located at the NW end of the chain. Frequent historical eruptions, consisting mostly of mild-to-moderate phreatic explosions, have been recorded since the mid-19th century. Two larger eruptions occurred in 1926 and 1962. Partial cone collapse of the western flank of Tokachi-dake during the 1926 eruption produced a disastrous debris avalanche and mudflow.

Tokachi Volcano

Tokachi is made of overlapping stratovolcanoes. Several vents have produced 17 historic eruptions. The eruptions cluster into five periods: 1857, 1887 and 1889, 1925-1931, 1952 to 1962, and 1985 and 1989. Most of the eruptions were phreatic, small to moderate in size (VEI=1-2), and about half were explosive. There eruptions generated pyroclastic flows. Only the 1670 eruption produced lava flows. Eruptions in 1926 and 1962 caused damage and fatalities. Hot mudflows during the 1926 eruption mixed with snow and moved down Hurano valley. The mudflows covered 20 km in 26 minutes, destroying 5,080 homes and killing at least 146 people. Falling blocks killed five people in 1962. Fumaroles continue to release steam at Tokachi.

Tokachi Volcano

Steep volcanic sand slope (Dale Robinson)

Originally posted 2010-08-20 05:00:06.

Sarychev, Russia

ExploreNow Editor — Wed, 08 Feb 2012 15:27:12 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2009
Summit Elevation:    1496 m    4,908 feet
Latitude:    48.092°N    48°5’30″N
Longitude:    153.20°E    153°12’0″E

Sarychev Peak is located on Matua Island in central Kurile Islands. The volcano is 6 km in diameter and forms the north-western part of Matua Island. A summit crater has a width of 250 m and a depth of 250 m. Sarychev Peak is one of the most active volcanoes in the Kurile Islands, with eruptions reported since the 1700′s.

Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5 km wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows descend all sides of Sarychev Peak and often form capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760′s and include both quiet lava effusion and violent explosions. One of the largest historical eruptions of Sarychev Peak in 1946 produced pyroclastic flows that reached the sea.

The largest historical eruption of Sarychev Peak began on June, 11, 2009 and produced ash plumes rising to up to 14 kms and pyroclastic flows that reached the sea. The ash plumes drifting westwards at altitudes typical for commercial airplanes forced many flights with routes accross the northern Pacific to be cancelled or diverted.

Originally posted 2010-08-23 04:16:31.

Llullaillaco, Chile

ExploreNow Editor — Wed, 08 Feb 2012 02:59:09 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    1877
Summit Elevation:    6739 m    22,109 feet
Latitude:    24.72°S    24°43’0″S
Longitude:    68.53°W    68°32’0″W

The world’s highest historically active volcano, 6739-m-high Llullaillaco, sits astride the Chile-Argentina border. The summit is formed by a smaller well-preserved cone that was constructed on an older Pleistocene edifice. A major debris-avalanche deposit produced by collapse of the older volcano about 150,000 years ago extends eastward into Argentina and diverges around the north and south sides of the older Cerro Rosado stratovolcano 17 km east of Llullaillaco. Construction of several lava domes and flows was associated with growth of the modern cone. The two most prominent flows contain distinct flow levees and ridges and extend down the northern and southern flanks. These two extremely youthful-looking dacitic flows were initially considered to be of Holocene age, but more recent Ar/Ar dating indicates that they are of late Pleistocene age (Richards and Villeneuve, 2001). Two explosive eruptions and another that may have included lava effusion were reported from Llullaillaco in the 19th century.

Peak of Llullaillaco

Llullaillaco is the sixth highest mountain in South America. It is the high peak in a large area of high volcanic land rising in the widest stretch of the Altacama desert. Its aridity and remoteness make it a difficult mountain to approach, but the ascent of its gently sloping cone is otherwise straightforward. A winter ascent is recommended because snow may be the only source of water.

Llullaillaco Volcano

Like many of the mountains in the area, its summit holds the ruins of several Incan shelters. Llullaillaco is also a well-known archaeological site; the mummified remains of three Inca children, ritually sacrificed 500 years ago, were discovered on the summit in 1999.

La Doncella

Originally posted 2010-08-19 04:18:59.

Tungurahua, Ecuador

ExploreNow Editor — Tue, 07 Feb 2012 14:34:52 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2010
Summit Elevation:    5023 m    16,479 feet
Latitude:    1.467°S    1°28’1″S
Longitude:    78.442°W    78°26’30″W

Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador’s most active volcanoes. Three major volcanic edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano’s base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Tungurahua is a steep-sided stratovolcano with an almost perfect cone reaching 5016 m in the Eastern Cordillera of the Andes. Its geographical location is 1.467°S and 78.442°W, 15 km east of Ambato, Ecuador’s fourth largest city and capital of the province of the same name as the volcano. The steep flanks of the volcano are used for agriculture and many small villages and a larger town, called Baños cradle the mountain on the northern and western side, which were affected in various degrees by lahar and ashes in the last few years.

The process of the volcanic activity of Tungurahua is quite different to that of Pichincha. The volcano emits continuously ashes, smoke and lava (Strombolian activity). Magma rises up the chimney and reaches the opening of the volcano. The danger of a big eruption lies in the blockage of the exit vent by big boulders and other materials. If it cannot exit freely anymore, there is a chance that more and more pressure accumulates under the blockage and finally leads to a huge explosion with potential structural collapse. Should that happen and the peak should break away, then a huge catastrophe is at hand as Baños and the other surrounding villages will be completely destroyed and some 20000 people are in danger of losing their lives.

Originally posted 2010-08-22 05:16:08.

Crater Lake, Oregon, USA

ExploreNow Editor — Tue, 07 Feb 2012 02:16:54 +0000

Volcano Type:     Caldera
Volcano Status:   Radiocarbon
Last Known Eruption:    2850 BC (?)
Summit Elevation:    2487 m    8,159 feet
Latitude:    42.93°N    42°56’0″N
Longitude:    122.12°W    122°7’0″W

The spectacular 8 x 10 km Crater Lake caldera in the southern Cascades of Oregon formed about 6850 years ago as a result of the collapse of a complex of overlapping shield and stratovolcanoes known as Mount Mazama. The cone-building stage, during which at least five andesitic and dacitic shields and stratovolcanoes were constructed, took place between about 420 and 40 thousand years ago (ka).

Sunrise at the Crater Lake

Crater Lake was formed around 4680 BC when the volcanic Mount Mazama blew its top in spectacular fashion. The eruption, estimated to have been 42 times more powerful than Mt. St. Helens’ 1980 blast, reduced Mazama’s approximate 11,000 foot height by around half a mile. The mountain peak feel into the volcano’s partially emptied neck and magma chamber, and Crater Lake was formed in the new crater.

Snow around the Crater Lake

Crater Lake has long been revered as sacred by the Klamath tribe of Native Americans, whose myths embody the catastrophic event they witnessed thousands of years ago. The central legend tells of two Chiefs, Llao of the Underworld and Skell of the World Above, pitted in a battle which ended in the destruction of Llao’s home, Mt. Mazama.

Crater Lake

A series of rhyodacitic lava domes and flows and associated pyroclastic rocks were erupted between about 30 ka and the climactic eruption. The explosive eruptions triggering collapse of the 8-10 km wide caldera about 7500 years ago were among Earth’s largest known Holocene eruptions, distributing tephra as far away as Canada and producing pyroclastic flows that traveled 40 km from the volcano. A 5-km-wide ring fracture zone is thought to mark the original collapse diameter. The deep blue waters of North America’s second deepest lake, at 600 m, fill the caldera to within 150-600 m of its rim. Post-caldera eruptions within a few hundred years of caldera formation constructed a series of small lava domes on the caldera floor, including the partially subaerial Wizard Island cinder cone, and the completely submerged Merriam Cone. The latest eruptions produced a small rhyodacitic lava dome beneath the lake surface east of Wizard Island about 4200 years ago.

Originally posted 2010-08-17 05:24:55.

Mahawu, Indonesia

ExploreNow Editor — Mon, 06 Feb 2012 14:01:17 +0000

Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1977
Summit Elevation: 1324 m    4,344 feet
Latitude: 1.358°N   1°21’30″N
Longitude: 124.858°E    124°51’30″E

The elongated Mahawu volcano immediately east of Lokon-Empung volcano is the northernmost of a series of young volcanoes along a SSW-NNE line near the margin of the Quaternary Tondano caldera. Mahawu is capped by a 180-m-wide, 140-m-deep crater that sometimes contains a small crater lake, and has two pyroclastic cones on its northern flank.

Mahawu Crater

Less active than its neighbor, Lokon-Empung, Mahawu’s historical activity has been restricted to occasional small explosive eruptions recorded since 1789. In 1994 fumaroles, mudpots, and small geysers were observed along the shores of a greenish-colored crater lake.

Volcano Mahawu

Mahawu Mountain (Jérôme Micheletta)

Mahawu Trail

The crater of Mount Mahawu is 140 m deep

Mount Mahawu

Volcano Mahawu

The crater of the Mahawu volcano

The view towards the Lokon volcano from Mahawu

Crater of the Volcano (Romeo Voyages)

Originally posted 2010-10-13 03:56:30.

Lascar, Chile

ExploreNow Editor — Mon, 06 Feb 2012 01:36:32 +0000

Volcano Type:     Stratovolcanoes
Volcano Status:   Historical
Last Known Eruption:    2007
Summit Elevation:    5592 m    18,346 feet
Latitude:    23.37°S    23°22’0″S
Longitude:    67.73°W    67°44’0″W

Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km to the east, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption of Lascar took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded from Láscar in historical time since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away from the volcano. The largest historical eruption of Láscar took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Steaming volcano

Lascar Volcano is located in northern Chile. It is currently the most active volcano of the Central Volcanic Zone of the Andes. Lascar has two cones – the Western Extinct Cone and the Eastern or Active Cone. Major pyroclastic eruptions the the past have failed to produce a caldera. Volcán Aguas Calientes is an older higher stratovolcano located 5 km east of Láscar.

Eruption of the Lascar Volcano in 1993

A large eruption of Lascar volcano occurred in 1993 when pyroclastic flows reached 8.5km from the summit. Lascar is a popular target for mountaineers, due to its relatively low altitude is a good mountain to get acclimatized for higher tour. Under good weather conditions, warm clothes and trekking boot are enough, but after a snowfall or in the winter season, (June – August) you may need special gear for the summit area. The massif is composed of two strato-volcanoes whose center are 1.6km apart. Each crater measures approximatey 900m in diameter and 300m deep. At present day, Lascar is the only volcano in the region to be erupting Lava. Background activity varies from steam emissions to fumarolic emissions, but occasional minor vulcanian eruptions occur and slugs of ash and vapour are emitted.

Lascar Lava Flow

360° view at the crater's edge (Alexandre Buisse)

2006 eruption of Lascar Volcano

The Lascar volcano, seen from the Chaxas lagoon (Gerard Prins)

Lascar Volcano

View from Lascar (Wim Malfait)

Sunrise over the Lascar volcano (Gerard Prins)

Lascar Volcano (Jorge Jara Campos)

Lascar Volcano (Arianna Rosso)

Eruption of Lascar Volcano (Rodrigo Vega)

Lava Rocks

Originally posted 2010-08-22 04:42:07.

Aoga-shima, Izu Islands, Japan

ExploreNow Editor — Sun, 05 Feb 2012 13:22:14 +0000

Volcano Type:      Stratovolcano
Volcano Status:    Historical
Last Known Eruption:     1785
Summit Elevation:     423 m     1,388 feet
Latitude:     32.454°N     32°27’15″N
Longitude:     139.762°E     139°45’44″E

The small 2.5 x 3.5 km dominantly basaltic island of Aoga-shima is surrounded by steep cliffs and contains a small 1.7 x 1.5-km-wide caldera. Two pyroclastic cones were formed inside the caldera during the volcano’s latest eruption from 1780 to 1785. Growth of Aoga-shima volcano began with construction of the Kurosaki stratovolcano in the NW part of the island, after which the main stratovolcano began growing in the SE part of the island. Both summit and flank vents produced pyroclastic surges and lava flows. Late in the construction of the main cone a 1-1.5 km crater was formed on the SE flank. About 3000 years ago pyroclastic surges swept over the entire island. During about the next 600 years, lava flows and scoria deposits filled the SE crater, which also collapsed repeatedly. The current Ikenosawa crater was considered by Takada et al. (1992) to have formed by ring collapse at the time of a debris avalanche, after which the volcano was quiescent until the eruptions of historical time.

Aoga-shima Top Caldera View

Situated on the same latitude of Miyazaki in Kyushu, Aogashima is a subtropic paradise with a mild, humid climate under the influence of the Kuroshio warm current, and home for many different wild birds. The last known volcanic eruption of Aogashima in the late 18th century killed many villagers and forced the entire population to evacuate from the island. It took them almost fifty years to return to the island.

Aoga-shima Aerial View

Port of Aogashima Island, Izu Islands, Japan

Aoga-shima Photo by Richard Fiske (Smithsonian Institution)

Location of Aoga-shima volcano in the Island

Originally posted 2010-08-16 08:26:19.

Maipo, Argentina

Volcano Explorer — Sun, 05 Feb 2012 01:04:31 +0000

Maipo

Volcano Type: Caldera
Volcano Status: Stratovolcano
Last Known Eruption: 1908
Summit Elevation: 5264 m 17,270 feet
Latitude: 34.161°S 34°9’38″S
Longitude: 69.833°W 69°49’58″W

Maipo is a stratovolcano in the Andes, lying on the border between Argentina and Chile. It is located 90 km (55 miles) south of Tupungato and about 100 km (60 miles) southeast of Santiago.

Maipo retains a symmetrical, conical volcanic shape, unlike many of the other nearby peaks, making it the best known peak in the region, though it is not the highest. (Nearby Castillo is 5,485 m high.) Maipo is also almost the southernmost 5,000 metre peak in the Andes. (That honor goes to Sosneado, about 50 km to the south).

Maipo 2

Maipo is located within the Diamante Caldera, a feature of about 15 km by 20 km size that is about one-half million years old. It rises about 1,900 m (6,230 ft) above the floor of the caldera. Immediately to the east of the peak, on the eastern side of the caldera floor, is Laguna del Diamante, a picturesque lake that formed when lava flows blocked drainage channels from the caldera in 1826. The Diamante Caldera erupted 450 cubic kilometers (108 cu mi) of tephra, 450 ka.

The region’s climate is transitional between the drier Mediterranean climate of the peaks to the north and the cold, moist climate of Chilean Patagonia. Hence, while less glaciated than Patagonia, it has more permanent snow (on the wet, Chilean side) than peaks of similar elevation to the north.

maipo 3

Originally posted 2011-04-16 23:31:12.

Miravalles Volcano, Costa Rica

ExploreNow Editor — Sat, 04 Feb 2012 12:55:52 +0000

Volcano Type: Stratovolcano
Volcano Status: Historical
Last Known Eruption: 1946
Summit Elevation: 2028 m 6,653 feet
Latitude: 10.748°N 10°44’54″N
Longitude: 85.153°W 85°9’10″W

Miravalles is a 2028-m-high andesitic stratovolcano that is one of five post-caldera cones along a NE-trending line within the broad 15 x 20 km Guayabo (Miravalles) caldera. The caldera was formed during several major explosive eruptions that produced voluminous dacitic-rhyolitic pyroclastic flows between about 1.5 and 0.6 million years ago. Growth of post-caldera volcanoes in the eastern part of the caldera that overtopped much of the eastern and southern caldera rims was interrupted by edifice collapse that produced a major debris avalanche to the SW. Morphologically youthful lava flows cover the western and SW flanks of the post-caldera Miravalles complex, which rises above the town of Guayabo on the flat western caldera floor. The only reported historical eruptive activity was a small steam explosion on the SW flank in 1946. High heat flow remains, and Miravalles is the site of the largest developed geothermal field in Costa Rica.

Miravalles Volcano

Miravalles (2,208 meters) is an andesitic stratovolcano that is one of five post-caldera cones along a northeast-trending line within the Pleistocene, 15 x 20 kilometer Miravalles caldera. Morphologically youthful lava flows cover the western and SW flanks of the volcano. The only reported historical eruptive activity was a small steam explosion in 1946, although high heat flow remains and a geothermal field is located within the caldera.

Miravalles is situated along the volcanic front of Central America, just southeast of a postulated boundary between eastern Nicaragua and Costa Rican segments of the Cocos-Caribbean subduction zone (Stoiber and Carr, 1973).

Miravalles Volcano

Miravalles Caldera formed approximately 500,000 +/- 150,000 years ago (Tournon, 1984), after eruption of voluminous silicic ash flows. An andesitic stratovolcano of the same name grew within the caldera (Healy, 1969). At least five cones are recognizable in the summit area, distributed along a northeast-trending line (probable fault). The modern intracaldera cone may be the second of two; a previous postcaldera cone was destroyed (R. Fournier, oral commun., 1987). Melson and others (1986) note a preliminary age of 8,000 (?) years B.P. for a major plinian eruption from Miravalles, and an age of 7,000 (?) years B.P. for a large debris avalanche from Miravalles. A geothermal field is situated between the caldera scarp and Miravalles stratovolcano.

Miravalles Volcano

No significant eruption has occurred at Miravalles in historical time. However, on 14 September 1946, a small steam eruption occurred high on the south flank of the volcano, near the summit crater. Weak earthquakes were felt at the time. An explosion crater 20 meters in diameter formed, and steam, mud, and ash were thrown 100 meters high (Hantke, 1951, citing a letter from Sigismund von Preussen of the town of La Barranca). The hydrothermal field is a hot-water-dominated system, with a vapor-dominated cap (few tens of meters thick) in some parts of the geothermal field. Changes in the vapor-dominated cap can give rise to surface hydrologic changes and small blowouts. Fumarolic activity has reportedly decreased in recent years (as of late 1987) (R. Fournier, oral commun., 1987).

Miravalles Volcano

Originally posted 2010-07-06 10:53:25.

Jan Mayen, Norway

ExploreNow Editor — Sat, 04 Feb 2012 00:26:49 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    1985
Summit Elevation:    2277 m    7,470 feet
Latitude:    71.08°N    71°5’0″N
Longitude:    8.17°W    8°10’0″W

Remote Jan Mayen Island, located in the Norwegian Sea along the Mid-Atlantic Ridge about 650 km NE of Iceland, consists of two volcanic complexes separated by a narrow isthmus. The large Beerenberg basaltic stratovolcano (Nord-Jan) forms the NE end of the 40-km-long island, which is ringed by high cliffs. Beerenberg is a large 2277-m-high glacier-covered stratovolcano with a 1-km-wide summit crater and numerous cinder cones that were erupted along flank fissures. It is composed primarily of basaltic lava flows with minor amounts of tephra. Historical eruptions at Beerenberg date back to the 18th century. The Sor-Jan group of pyroclastic cones and lava domes occupies the SW tip of Jan Mayen. The Holocene Sor-Jan cinder cones, tephra rings, and trachytic lava domes were erupted from short fissures with a NE-SW trend.

Beerenberg Volcano

Beerenberg Volcano on Jan Mayen is the most northern (sub-aerial) active volcano in the world. Jan Mayen island is 40 km long and has high cliffs. Beerenberg is the highest mountain in the Artic Circle. The northern half of the island is dominated by Mt. Beerenberg. The volcano has an eruption frequency of 150 ± 75 years. A major eruption occurred on Jan Mayen in 1970 accompanied by strong earthquakes.

Beerenberg Volcano

Jan Mayen is located close to the intersection of the southern end of Mohns ridge and the central part of Jan Mayen fracture zone. Jan Mayen is the northernmost volcanic island on the mid- Atlantic ridge and the northernmost sub-aerial active volcano in the world. Nord Jan, the northern half of the 380 sq km island, is dominated by the large shield volcano, Beerenberg, which is about 25 km in diameter at sea level and is capped by a nearly symmetrical summit lava cone reaching an elevation of 2277 m above sea level.

Originally posted 2010-08-09 20:21:37.

Merapi, Java, Indonesia

ExploreNow Editor — Fri, 03 Feb 2012 12:01:35 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2007
Summit Elevation:    2968 m    9,737 feet
Latitude:    7.542°S    7°32’30″S
Longitude:    110.442°E    110°26’30″E

Merapi volcano is one of the world’s most active and dangerous volcanoes. It contains an active lava dome which regularly produces pyroclastic flows. Eruptions occur at intervals of 1-5 years and are of low gas pressure. Since magma is poor in gas, eruptions are usually less than VEI 3 in size.

Mount Merapi eruption

Merapi, one of Indonesia’s most active volcanoes, lies in one of the world’s most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. Merapi is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi volcano beginning during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the volcano’s western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory.

Mount Merapi eruption

Most eruptions of Merapi involve a collapse of the lava dome creating pyroclastic flows which travel 6 to 7 km from the summit. Some awan panas have traveled as far as 13 km from the summit, such as the deposit generated during the 1969 eruption. Velocity of pyroclastic flows can reach up to 110 km/hour. A slow up flow of andesitic magma leads to an extrusion of viscous magma, which accumulate and construct a dome in the crater.

Mount Merapi eruption

Merapi is one of the most active volcanoes in Indonesia and has produced more pyroclastic flows than any other volcano in the world. It has been active for 10,000 years.

Originally posted 2010-08-18 04:35:17.

Acatenango, Guatemala

ExploreNow Editor — Thu, 02 Feb 2012 23:38:57 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    1972
Summit Elevation:    3976 m    13,044 feet
Latitude:    14.501°N    14°30’2″N
Longitude:    90.876°W    90°52’33″W

Acatenango, along with its twin volcano to the south, Volcán Fuego, overlooks the historic former capital city of Antigua, Guatemala. Acatenango, which has two principal summits, was constructed during three eruptive periods post-dating the roughly 85,000-year-old Los Chocoyos tephra from Atitlán caldera. An ancestral Acatenango volcano collapsed to the south sometime prior to 43,000 years ago, forming La Democracia debris-avalanche deposit, which covers a wide area of the Pacific coastal plain. Construction of Yepocapa, the northern summit of Acatenango, was completed about 20,000 years ago, after which growth of the southern and highest cone, Pico Central (also known as Pico Mayor), began. The first well-documented eruptions of Acatenango took place from 1924 to 1927, although earlier historical eruptions may have occurred. Francisco Vasquez, writing in 1690, noted that in 1661 a volcano that lay aside of Fuego “opened a smoking mouth and still gives off smoke from another three, but without noise.”

A very imposing and voluminous cone, made up by the main cone, at 3976 meters above sea level, and a secondary cone, Yepocapa, at 3808 meters. It is a very hard climb, and the whole top part of the volcano is covered in fine sand, due to the eruptions of its twin volcano, Fuego. The view from the summit is breathtaking. Birdseye view of the Pacific Ocean, and the Guatemalan volcanic chain, including the volcanoes of Santa Maria, Toliman, Atitlan, San Pedro, Santo Tomas, Zunil, Tajumulco, Tacana, Agua, Fuego and Pacaya. Ascent takes aprox six hours. Beautiful camping spot about halfway up, called “El Conejo.”

Originally posted 2010-08-25 03:50:44.

Kilimanjaro, Tanzania

ExploreNow Editor — Thu, 02 Feb 2012 11:30:29 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Holocene
Last Known Eruption:    Unknown
Summit Elevation:    5895 m    19,340 feet
Latitude:    3.07°S    3°4’0″S
Longitude:    37.35°E    37°21’0″E

Massive Kilimanjaro, Africa’s highest mountain, consists of three large stratovolcanoes constructed along a NW-SE trend. The ice-capped, 5895-m-high summit towers 5200 m above the surrounding plains. Activity at the older cone of Shira that forms the broad WNW shoulder of Kilimanjaro began during the Pliocene, and the extensively dissected Mawenzi forms a prominent, sharp-topped peak of Pleistocene age on the upper ESE flank dominated by a densely packed radial dike swarm. More than 250 satellitic cones occupy a rift zone to the NW and SE of Kibo, the central stratovolcano. A 2.4 x 3.6 km caldera gives the summit of Kibo an elongated, broad profile. Most of Kilimanjaro was constructed during the Pleistocene, but a group of youthful-looking nested summit craters are of apparent Holocene age, and fumarolic activity continues.

Kilimanjaro

The mountain contains three volcanic cones – Kibo, Mawensi, and Shira. It is located on the eastern side of the African Rift Valley. Magma is located 400 m below the summit crater. The Ash Pit lies in the north-westerly part of Kibo, and is of recent origin. It is circular with sharp, well-preserved edges and steep walls. The pit diameter is about 400 m and 150 m deep. It is almost ringed round by a circular and higher bank 150 m away, which in its turn is completely ringed by yet another bank, considerably higher.

Kibo Summit of Kilimanjaro

Mount Kilimanjaro seen from the air

Kilimanjaro

Kilimanjaro (Angela M. Lobefaro)

Location of Kilimanjaro in Tanzania

Originally posted 2010-08-08 04:35:57.

Tarso Voon, Chad

ExploreNow Editor — Wed, 01 Feb 2012 23:17:42 +0000

Volcano Type: Stratovolcano
Volcano Status: Fumarolic
Last Known Eruption: Unknown
Summit Elevation: 3100 m 10,170 feet
Latitude: 20.92°N 20°55’0″N
Longitude: 17.28°E 17°17’0″E

Tarso Voon is a stratovolcano located in Chad. The broad summit of Tarso Voon volcano, located in the west-central part of the Tibesti Range, is truncated by a shallow 14 x 18 km wide caldera. Ignimbrite deposits surround the caldera to distances of 15-35 km. Tarso Voon was constructed over a basement of Precambrian schists. Youthful-looking Quaternary basaltic lava flows have been erupted from vents near the caldera rim over a 180 degree area extending counterclockwise from the NE and from Ehi Mousgau, a 3100-m-high stratovolcano located to the NW. The Soborom solfatara field, the largest in the Tibesti Range, is located in an area of volcano-tectonic uplift 5 km west of the caldera rim. Its fumaroles, active mud pots, and boiling waters are visited by Tibesti peoples for medicinal uses.

Satellite view of Tarso Voon

Chadian soldier at Tarso Voom (Carles Campsolinas Dresaire)

Originally posted 2010-10-21 04:52:14.

Akutan, Aleutian Islands, USA

ExploreNow Editor — Wed, 01 Feb 2012 11:08:49 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    1992
Summit Elevation:    1303 m    4,275 feet
Latitude:    54.134°N    54°8’4″N
Longitude:    165.986°W    165°59’10″W

One of the most active volcanoes of the Aleutian arc, Akutan contains 2-km-wide caldera with an active intracaldera cone. An older, largely buried caldera was formed during the late Pleistocene or early Holocene. Two volcanic centers are located on the NW flank. Lava Peak is of Pleistocene age, and a cinder cone lower on the flank produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. The 60-365 m deep younger caldera was formed during a major explosive eruption about 1600 years ago and contains at least three lakes. The currently active large cinder cone in the NE part of the caldera has been the source of frequent explosive eruptions with occasional lava effusion that blankets the caldera floor. A lava flow in 1978 traveled through a narrow breach in the north caldera rim almost to the coast. Fumaroles occur at the base of the caldera cinder cone, and hot springs are located NE of the caldera at the head of Hot Springs Bay valley and along the shores of Hot Springs Bay.

Akutan Volcano

Akutan Volcano is a stratovolcano on Akutan Island in the east-central Aleutian Islands of southwestern Alaska. The volcano is located about 1238 kilometres southwest of Anchorage, and about 56 kilometres east of Dutch Harbor/Unalaska. The summit contains a 2 km diameter caldera with a small lake. Coastal erosion has exposed numerous lava tubes which have formed spectacular bridges and caves. Akutan is one of the most volcanically active islands in the eastern Aleutian arc. Akutan Island is located at the transition between continental and oceanic crust.

Akutan Volcano

Eruptions at Akutan volcano are typically moderately explosive, short-duration, and Strombolian, lasting for a few weeks. Hazards at the volcano include ash clouds, ashfall, volcanic bombs, pyroclastic flows, lahars, lava flows, and debris avalanches.

Originally posted 2010-08-21 05:01:24.

Mehetia Volcano, Society Islands

ExploreNow Editor — Tue, 31 Jan 2012 22:44:09 +0000

Volcano Type: Stratovolcano
Volcano Status: Anthropology
Last Known Eruption: Unknown
Summit Elevation: 435 m 1,427 feet
Latitude: 17.87°S 17°52’0″S
Longitude: 148.07°W 148°4’0″W

The 1.5-km-wide, steep-sided island of Mehetia, the youngest and SE-most of the Society Islands, lacks a well-developed fringing coral reef. The 435-m-high island (known as Meetia or Meketia in the Tahitian and Tuamotuan languages, respectively) is the summit of a large volcano that rises 4000 m from the sea floor. An older edifice is formed of a lava flow sequence overlain by hydromagmatic deposits and strombolian ejecta. A well-preserved Holocene crater, 150 m wide and 80 m deep, is located NW of the summit and has been the source of the youngest lava flows on the island (Binard et al., 1993). Polynesian legends mention “large fires,” and the lack of vegetation on some lava flows suggests that the latest activity occurred within the last 2000 years (Talandier and Custer, 1976). Other recent activity at Tehetia originated from a submarine crater at 2500-2700 m depth on the SE flank.

: Mehetia Island and Volcano

The 1.5-km-wide, steep-sided island of Mehetia, seen here from the south, is the youngest and SE-most of the Society Islands. The 435-m-high island is the summit of a large volcano that rises 4000 m from the sea floor. Wave erosion has truncated lava flows of an older edifice, leaving steep cliffs that overlie coral reefs seen at the peninsula in the left foreground. The summit of the island is formed by a younger edifice that may have been the source of apparent eruptive events mentioned in Polynesian legends.

Originally posted 2010-07-06 16:51:58.

West Eifel Volcanic Field, Germany

ExploreNow Editor — Tue, 31 Jan 2012 10:08:42 +0000

Volcano Type: Maars
Volcano Status: Radiocarbon
Last Known Eruption: 8300 BC ± 300 years
Summit Elevation: 600 m   1,968 feet
Latitude: 50.17°N *   50°10’0″N
Longitude: 6.85°E   6°51’0″E

The West Eifel volcanic field in the Rhineland district of western Germany SW of the city of Bonn is a dominantly Pleistocene group of 240 scoria cones, maars, and small stratovolcanoes covering an area of about 600 sq km. The West Eifel volcanic field lies about 40 km SW of the smaller, but better known East Eifel volcanic field.

Individual vents, most of which cover a broad NW-SE-trending area extending about 50 km from the towns of Ormont on the NW to Bad Bertrich on the SE, were erupted above a mantle plume through Devonian sedimentary and metamorphic rocks. Scoria cones, about half of which have produced lava flows, form two-thirds of the volcanic centers, and about 30% are maars or tuff rings, many of which are occupied by lakes. About 230 eruptions have occurred during the past 730,000 years. The latest eruptions formed the Ulmener, Pulvermaar, and Strohn maars around the end of the Pleistocene and the beginning of the Holocene.

Originally posted 2010-10-18 04:00:33.

Manzaz Volcanic Field, Algeria

ExploreNow Editor — Mon, 30 Jan 2012 21:46:45 +0000

Volcano Type: Scoria cones
Volcano Status: Holocene
Last Known Eruption: Unknown
Summit Elevation: 1672 m 5,485 feet
Latitude: 23.92°N * 23°55’0″N
Longitude: 5.83°E 5°50’0″E

The Manzaz volcanic field, north of the Atakor volcanic field in the Hoggar (Ahaggar) volcanic district of Algeria, consists of a large number of scoria cones and associated lava flows. The volcanic field covers an area of 1500 sq km, overlying Precambrian metamorphic and plutonic rocks of the Tuareg shield. Many cones are breached, and the dominantly basaltic and basanitic volcanic products are rich in peridotite and pyroxenite xenoliths and megacrysts. The youngest volcanoes rest on Neolithic terraces and are of Holocene age.

Originally posted 2010-11-10 04:25:45.

Mount Adams, Washington, USA

Volcano Explorer — Mon, 30 Jan 2012 09:36:17 +0000

Mount Adams

Volcano Type:      Stratovolcano
Volcano Status:    Tephrochronology
Last Known Eruption:     About 550 BC ± 1000 years
Summit Elevation:     12,281 ft    (3,743 m)
Latitude:     46°12′8.68″N
Longitude:    121°29′27.22″W

Mount Adams is a potentially active stratovolcano in the Cascade Range and the second-highest mountain in the U.S. state of Washington. Adams is a member of the Cascade Volcanic Arc, and is one of the arc’s largest volcanoes, located in a remote wilderness approximately 31 miles (50 km) east of Mount St. Helens. The Mount Adams Wilderness comprises the upper and western part of the volcano’s cone. The eastern side of the mountain is part of the Yakama Nation.

: Mount Adams

Adams’ asymmetrical and broad body rises 1.5 miles (2.4 km) above the Cascade crest. Its nearly flat summit was formed as a result of cone-building eruptions from separated vents. Air travelers flying the busy routes above the area sometimes confuse Mount Adams with nearby Mount Rainier, which has a similar flat-topped shape.

Mount Adams

The Pacific Crest Trail traverses the western flank of the mountain. Although Adams has not erupted in over 1,400 years, it is not considered extinct.

Mount Adams

Originally posted 2011-05-09 00:55:12.

Sabancaya, Peru

ExploreNow Editor — Sun, 29 Jan 2012 21:27:00 +0000

Volcano Type: Stratovolcanoes
Volcano Status: Historical
Last Known Eruption: 2003
Summit Elevation: 5967 m 19,577 feet
Latitude: 15.78°S 15°47’0″S
Longitude: 71.85°W 71°51’0″W

Sabancaya, located on the saddle between 6288-m-high Ampato and 6025-m-high Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three volcanoes, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age.

Aerial view of Sabancaya Volcano

Both Nevado Ampato and Nevado Sabancaya are only slightly affected by glacial erosion and consist of a series of lava domes aligned along a NW-SW trend. The name of 5967-m-high Sabancaya (meaning “tongue of fire” in the Quechua Indian language) first appeared in records in 1595 AD, suggesting activity prior to that date.

Sabancaya Volcano eruption

Holocene activity has consisted of plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions of Sabancaya date back to 1750.

The volcano is covered with several glaciers, and several short lava flows extend radially around the summit crater.

Sabancaya Volcano crater

2003 Eruptions
On 31st July 2003 ashfall was noted at the volcano which covered the summit, and extended to the volcano’s base on the NE side.

2000 Eruptions
Small ash eruptions occurred in April and May 2000.

1998 Eruptions
Ash eruptions occurred at Sabancaya Volcano in August and September.

1990-95 Eruptions

Sabancaya Volcano eruption

Eruptions began on 29th May 1990. By 5th June 1990, eruptions became continuous, with ash emissions to 6 km altitude. On 8th June 1990 there violent explosions every 5-10 minutes.

Sabancaya Volcano eruption

Ash fell 20 km from the crater. In 1991 there was strong vulcanian eruptions and a mudflow which killed 20 people. On 19th February 1992, increased activity caused the evacuation of several towns in a 14 km radius of the volcano. Eruptions ended in May 1995.

1988 Eruptions
Between the 22-25 June 1988 voluminous steam pulses were emitted every few minutes.

1986 Eruptions
In December 1986 Sabancaya volcano showed strong fumarolic activity and glowing tephra ejections were visible at night. These were the first recorded eruption at the volcano in 200 years.

NASA's view of Sabancaya

Eruption of Sabancaya Volcano

Ash column of Sabancaya as seen from Colla Valley

View over Sabancaya volcano from Corporaque

Originally posted 2010-11-01 03:57:02.

Anatahan, Mariana Islands,

ExploreNow Editor — Sun, 29 Jan 2012 09:16:29 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2008
Summit Elevation:    790 m    2,592 feet
Latitude:    16.35°N    16°21’0″N
Longitude:    145.67°E    145°40’0″E

The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of a large stratovolcano with a 2.3 x 5 km, E-W-trending compound summit caldera. The larger western portion of the caldera is 2.3 x 3 km wide, and its western rim forms the island’s 790-m high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern portion of the caldera contained a steep-walled inner crater whose floor prior to the 2003 eruption was only 68 m above sea level. A submarine volcano, named NE Anatahan, rises to within 460 m of the sea surface on the NE flank of the volcano, and numerous other submarine vents are found on the NE-to-SE flanks. Sparseness of vegetation on the most recent lava flows on Anatahan had indicated that they were of Holocene age, but the first historical eruption of Anatahan did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera.

Anatahan Island is situated about 120 km north of Saipan – the capital of the Commonwealth of the Northern Mariana Islands. It lies at the southern end of the 1500-km-long Izu-Bonin- Mariana arc. The island of Anatahan is only 1% of the volume of the entire volcano, which is 3700 m high from submarine base to summit, and an average diameter of 35 km. The highest point on the island is immediately west of the caldera. Anatahan Island measures 9 km (east–west) by 3.7 km (north–south). The summit of the island contains an elongate caldera, 5 km by 2 km. The caldera is approximately 10 sq km in size and occupies about a third of the island’s area. The east crater is located in the eastern part of the caldera. It is a a pit crater 1.4 km by 1.2 km in diameter, and 200 m deep.

Originally posted 2010-08-25 03:51:02.

Heard Island, Australia

ExploreNow Editor — Sat, 28 Jan 2012 21:00:14 +0000

Volcano Type:     Stratovolcano
Volcano Status:   Historical
Last Known Eruption:    2008
Summit Elevation:    2745 m    9,006 feet
Latitude:    53.106°S    53°6’20″S
Longitude:    73.513°E    73°30’45″E

Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon volcano lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben volcano because of its extensive ice cover. The historically active Mawson Peak forms the island’s 2745-m high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported in historical time at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Heard Island

Heard Island is located 4000 kilometres southwest of Western Australia and contains one of Australia’s two currently active volcanoes. Volcanic activity has been reported at the island since the 1980′s. Heard Island covers an area of 368 sq km. Mawson Peak at 2745 m is the highest mountain on Australian territory, outside Australian Antarctic Territory.

Aerial view of Heard Island

Heard Island is located in the `Furious Fifties’ , where strong winds blow mainly from the west. A mean sea-level wind speed of 26 km/h and a maximum gust of 209 km/h were recorded between December 1947 and March 1955, when an Australian base was maintained at Atlas Cove on the western side of Big Ben. Heard Island sits on the submarine Kerguelen Plateau, which rises 3700 m above the sea floor, and deflects Antarctic circumpolar bottom water northward past Kerguelen Islands. The McDonald Island group lies 43.5 km west of Heard Island, and consists of McDonald Island (area 1 sq km), and the much smaller Flat Island and Meyer Rock.

Originally posted 2010-08-30 04:42:00.