Weekly Volcanic Activity and Significant EQ report!

Significant Earthquakes (from the list of USGS significant earthquakes, full list can be found here):

April 7, 2011
Magnitude 7.1 NEAR THE EAST COAST OF HONSHU, JAPAN

Magnitude 6.5 VERACRUZ, MEXICO

April 3, 2011
Magnitude 6.7 SOUTH OF JAVA, INDONESIA

The following is a list of activity for the last week, only the details of the new activity have been posted here, please see the actual weekly update page for the Smithsonian for all the info and links!

Smithsonian Weekly Volcanic Activity Update

30 March-5 April 2011

New Activity/Unrest

KARANGETANG [API SIAU] Siau I 2.78°N, 125.40°E; summit elev. 1784 m

CVGHM reported that during 30-31 March incandescence emanated from Karangetang’s main crater as well as bluish and white gas plumes. Lava flows originating from the main crater traveled 2 km down the flanks. Incandescent avalanches from the main crater and from the lava-flow fronts traveled up to 1.8 km down the flanks. On 31 March a thunderous sound was accompanied by a gray plume that rose 200 m above the crater. The Alert Level remained at 3 (on a scale of 1-4).

Geologic Summary. Karangetang (also known as Api Siau) lies at the northern end of the island of Siau, N of Sulawesi, and contains five summit craters strung along a N-S line. One of Indonesia’s most active volcanoes, Karangetang has had more than 40 recorded eruptions since 1675. Twentieth-century eruptions have included frequent explosions, sometimes accompanied by pyroclastic flows and lahars.

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

Karangetang [Api Siau] Information from the Global Volcanism Program

KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m

HVO reported that the lava lake in the deep pit within Kilauea’s Halema’uma’u crater was mostly crusted over during 30 March-5 April. Incandescence was observed through the web camera on 30 March, and lava was visible at times during 31 March and 3-4 April. A gas plume from the vent deposited very small amounts of ash nearby, derived from rockfalls and occasional spatter from the lake. At Pu’u ‘O’o crater, the lava lake was fed from a few sources in the center or W portions of the lake. The deepest part of the crater was episodically filled and drained. During 4-5 April the central lava sources produced two or three small lava flows and infrequent spatter.

Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world’s most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 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.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

Kilauea Information from the Global Volcanism Program

RUAPEHU North Island (New Zealand) 39.28°S, 175.57°E; summit elev. 2797 m

On 5 April, GeoNet reported that the temperature of Ruapehu’s summit Crater Lake had been high for a sustained period and was currently between 38 and 39 degrees Celsius. The highest temperature since unrest began in October 2010 was 41 degrees Celsius, measured on 1 March. The report also noted that during the previous few weeks there was an increase in carbon dioxide gas emissions, increased seismicity, and changes in Crater Lake water chemistry. The unrest prompted GeoNet to raise the Aviation Colour Code although the Volcanic Alert Level remained at 1 (some signs of volcano unrest).

Geologic Summary. Ruapehu, one of New Zealand’s most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes. The 110 cu km volcanic massif is elongated in a NNE-SSW direction and is surrounded by another 100 cu km ring plain of volcaniclastic debris. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flanks have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to river valleys below the volcano.

Source: New Zealand GeoNet Project

Ruapehu Information from the Global Volcanism Program

Sally Kuhn Sennert – Weekly Report Editor
URL: http://www.volcano.si.edu/reports/usgs/