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Posts tagged Caldera

Emission of Steam or Sulphurous Gas from Ambrym Island, Vanuatu

16.2S 168.1E

December 23rd, 2012 Category: Volcanoes

Vanuatu – December 11th, 2012

Ambrym Island is a volcanic island in the archipelago of Vanuatu (formerly known as the New Hebrides).  Located near the center of the long Vanuatuan archipelago (here, the second large island from the bottom in the row of islands lined up parallel to the right edge), Ambryn is roughly triangular in shape, about 50 km (31 mi) wide.

The island is well known for its highly active volcanic activity. Here, although it is mostly covered by clouds, a plume of steam or sulfurous gas can be seen blowing northward from it. Such plumes are frequently emitted by Ambrym’s active lava lakes within its caldera.

City of Asella on Ethiopia’s High Central Plateau – March 14th, 2010

7.9N 39.1E

March 14th, 2010 Category: Image of the day, Mountains

Ethiopia - February 19th, 2010

Ethiopia - February 19th, 2010

This orthorectified image shows the mountainous terrain near the city of Asella, in central Ethiopia. It can be identified here as a bright white area in the upper left quadrant, west of a structure that appears to be a volcanic caldera. Located in the Arsi Zone of the Oromia Region about 175 kilometers south of Addis Ababa, the city has an elevation of 2430 meters.

Ethiopia’s high central plateau varies from 1,290 to 3,000 m (4,232 to 9,843 ft) above sea level, with the highest mountain reaching 4,533 m (14,872 ft). Elevation is generally highest just before the point of descent to the Great Rift Valley, which splits the plateau diagonally.

Cabeço Gordo Caldera on Faial Island, in the Azores

38.5N 28.6W

March 5th, 2010 Category: Volcanoes

Azores Islands - February 19th, 2010

Azores Islands - February 19th, 2010

Faial Island is a Portuguese island of the Central Group (Grupo Central) of the Azores (Açores). The nearest island is Pico Island to the east (visible upon opening the full version of this orthorectified image).

Along with other islands in the Azores archipelago, Faial is of volcanic origin and is close to the tectonic divide between the European and American Plates. Indeed, the island can be considered (from a geophysical perspective) the westernmost point of Europe (the two islands west of Faial, Flores and Corvo, are already on the American plate).

It is an irregular pentagonal-shaped island that occupies an area of approximately 173 km² along a leaky transform fault from the mid-Atlantic Ridge to Hirondella fault. This is the same fault that bisects the remainder of the Central Group islands along a west-northwest to east-southeast orientation.

It is an island composed of a central stratovolcano crater, with relatively geological relief showing little signs of major erosion. The highest point occurs along the southern rim, at the peak of Cabeço Gordo (1,043 m above sea level). The caldera is almost circular, 2000 m perimeter, with a 400 m depth below the summit of Cabeço Gordo (almost 570 m above sea level).

Volcanoes on Coastal Plain of El Salvador – November 26th, 2009

13.4N 88.1W

November 26th, 2009 Category: Image of the day, Volcanoes

El Salvador - November 14th, 2009

El Salvador - November 14th, 2009

Many volcanic peaks dot the landscape of central-eastern El Salvador, to the east of the Lempa River and north of Jiquilisco Bay, in this orthorectified image. To the east of these clusters of volcanoes is San Miguel, the fourth most populous city in El Salvador.

San Miguel is also the name of the stratovolcano located about 15km southwest of the city. The volcano, also known as Chaparrastique, is one of the most active volcanoes in the country.

North of the San Miguel volcano is Chinameca (also known as El Pacayal), a stratovolcano that rises over the town of Chinameca. The volcano is topped by a 2 km wide caldera known as Laguna Seca del Pacayal. A satellite cone on the west side, Cerro el Limbo, rises higher than the caldera rim. Fumaroles can be found on the north side, and it has been the site of a geothermal exploration program.

Continuing westward, the large stratovolcano Usulután can be identified as the peak on the coastal plain closest to the bay. The volcano is topped by a 1.3 km wide summit crater which is breached to the east.

West of Usulután is the Taburete stratovolcano. It is topped by a well-preserved, 150-300 m (500–1000 ft) deep summit crater, with the true summit on the south side of the crater rim.

Overlapping Krasheninnikov Stratovolcanoes, Russia

54.5N 160.2E

November 11th, 2009 Category: Volcanoes

Kamchatka Peninsula, Russia - October 7th, 2009

Kamchatka Peninsula, Russia - October 7th, 2009

The Krasheninnikov Volcano (above, center) is actually two stratovolcanoes that overlap inside a large caldera located in the eastern part of Kamchatka Peninsula, Russia.

The northern cone resembles a Russian doll: it is crowned with a caldera, the caldera encloses a small stratovolcano, and the crater of this volcano hosts a small lava cone.

Multiple adventive vents are located on the flanks of the volcano and outside the caldera. The latter are aligned along the fissure zones parallel to the general strike of the Eastern volcanic belt.

Landslide and rockfall deposits derived from the volcano slopes overlap some lava flows. No historical eruptions of Krasheninnikov volcano are known, but it has been termed active based on fresh morphology and weak fumarolic activity.

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