Activity update: volcanoes and earthquakes Thrusday night 2/2/2012

New Activity/Unrest:

CLEVELAND Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m

AVO reported that on 31 January the Volcano Alert Level for Cleveland was raised to Watch and the Aviation Color Code was raised to Orange due to the formation of a new 40-m-wide lava dome in the summit crater that was observed in satellite imagery on 30 January. The lava dome that formed during the past fall and winter was removed by explosive activity on 25 and 29 December 2011. No current seismic information was available because Cleveland does not have a real-time seismic network.

Geologic Summary. Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

GAMALAMA Halmahera 0.80°N, 127.33°E; summit elev. 1715 m

CVGHM lowered the Alert Level for Gamalama from 3 to 2 (on a scale of 1-4) on 24 January based on visual observations of white plumes rising as high as 100 m above the crater and a decrease in seismicity since the last eruption on 23 December 2011.

Geologic Summary. Gamalama (Peak of Ternate) is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera and is one of Indonesia’s most active volcanoes. The island of Ternate was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama’s historical activity. Three cones, progressively younger to the N, form the summit of Gamalama, which reaches 1,715 m. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)

Gamalama Information from the Global Volcanism Program

KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m

CVGHM lowered the Alert Level for Anak Krakatau from 3 to 2 (on a scale of 1-4) on 26 January. No details or reasons for the change were given in the report.

Geologic Summary. Renowned Krakatau volcano lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan, has been the site of frequent eruptions since 1927.

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)

Krakatau Information from the Global Volcanism Program

LEWOTOLO Lomblen Island (Indonesia) 8.272°S, 123.505°E; summit elev. 1423 m

On 25 January CVGHM lowered the Alert Level for Lewotolo from 3 to 2 (on a scale of 1-4) based on decreased seismicity and visual observations during 5-15 January. During 5-15 January fumarolic plumes rose 200-500 m above the summit and incandescence was observed.

Geologic Summary. Anchoring the eastern end of an elongated peninsula that is connected to Lomblen Island by a narrow isthmus and extends northward into the Flores Sea, Lewotolo rises to 1,423 m. Lewotolo is a symmetrical stratovolcano as viewed from the N and E. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano’s high point. Many lava flows have reached the coastline. Historical eruptions, recorded since 1660, have consisted of explosive activity from the summit crater.

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)

Lewotolo Information from the Global Volcanism Program

NYAMURAGIRA Democratic Republic of Congo 1.408°S, 29.20°E; summit elev. 3058 m

The VolcanoDiscovery Team observed the fissure eruption at Nyamuragira that began on 6 November 2011 during 22-25 January 2012 from the newly formed cinder cones located about 10 km E of the summit crater. They reported three coalescent cones with the largest cone containing a small lava lake. The lake ejected spatter every few seconds as high as 200 m above the summit; individual bombs reached the base of the cone. Lava flows from the vent extended several kilometers N. Numerous small breakouts formed secondary flows, and a large breakout about 2 km N of the cone fed a large lava flow about 20 m wide. Burning forests were reported to the NNE.

Geologic Summary. Africa’s most active volcano, Nyamuragira (Also spelled Nyamulagira) is a massive basaltic shield volcano N of Lake Kivu and NW of Nyiragongo volcano. Lava flows from Nyamuragira cover 1,500 sq km of the East African Rift. The 3058-m-high summit is truncated by a small 2 x 2.3 km summit caldera that has walls up to about 100 m high. About 40 historical eruptions have occurred since the mid-19th century within the summit caldera and from numerous fissures and cinder cones on the volcano’s flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938. Twentieth-century flank lava flows extend more than 30 km from the summit, reaching as far as Lake Kivu.

Source: VolcanoDiscovery

Nyamuragira Information from the Global Volcanism Program

PALUWEH Lesser Sunda Islands (Indonesia) 8.32°S, 121.708°E; summit elev. 875 m

Seismic activity from Paluweh (also known as Rokatenda) increased during 12-18 January, prompting CVGHM to raise the Alert Level from 1 to 2 (on a scale of 1-4) on 19 January. Fog prevented visual observations of the volcano.

Geologic Summary. Paluweh volcano, also known as Rokatenda, forms the 8-km-wide island of Paluweh N of the volcanic arc that cuts across Flores Island. Although the volcano rises about 3,000 m above the sea floor, its summit reaches only 875 m above sea level. The broad irregular summit region contains overlapping craters up to 900 m wide and several lava domes. Several flank vents occur along a NW-trending fissure. The largest historical eruption of Paluweh occurred in 1928, when a strong explosive eruption was accompanied by landslide-induced tsunamis and lava-dome emplacement.