An exciting few days for New Zealand geologists. Over 48 hours, two volcanoes in New Zealand have had minor eruptions. Early on Sunday morning (04.55 NZST on 5 August), White Island had a small explosive eruption. The eruption was captured on one of the webcams located in the crater area. White Island is New Zealand’s most active volcano, having been in frequent eruption between 1976 and 2000, though recently quiet.
Video of eruption:
The volcanic alert level was raised to 2 and aviation colour code to orange.
Less than 48 hours later, Tongariro had a phreatic eruption at 23.50 on 6 August, its first eruption in 115 years. The eruption lasted a couple of minutes and light ashfall was deposited to the north east of the volcano, closing roads and cancelling domestic flights. This followed an increase in seismic activity over the previous 3 weeks.
- NASA Earth Observatory image showing eruption plume of Tongariro, Aug.7, 2012
The volcanic alert level was raised to 2 and aviation colour code to red, although the latter was reduced to orange after 12 hours as activity seems to have subsided. Here’s a link to the hazard map of Tongariro.
- Locations of active volcanoes in New Zealand. USGS graphic.
Eruption info from GNS Science, New Zealand and NASA EOS.
Today’s featured volcano is the largest and one of the most active in Java, Indonesia. It has been active for the past few months, spewing out pyroclastic flows and building a small dome. Though it is popular with trekking groups, Semeru has a history of explosive activity and has caused the deaths of hikers and scientists alike.
(Also Mahameru – “Great Mountain”)
Semeru Volcano in Java, Indonesia. Photo by Tom Casadevall 1985, USGS.
Semeru Volcano in Indonesia. Photo by Jan-Pieter Nap 2004.
Semeru at a Glance:
||Stratovolcano (both ash and lava eruptions)
||3676 m (12,060 feet)
|Last Known Eruption:
||2012 (in eruption since 1967)
Most Recent Activity: CVGHM reported that during 1-29 February multiple pyroclastic flows from Semeru traveled up to 2,500 m into rivers on the S flank.. During 1 February-30 April dense gray-to-white plumes rose 100-500 m above Jongring Seloko crater and drifted W and N. Incandescence was visible up to 50 m above the crater during 1 February-31 March. Seismicity decreased from March to April. Observations indicated that the lava dome grew in April. On 2 May CVGHM lowered the Alert Level to 2 (on a scale of 1-4) and reminded the public not to approach the crater within a 4-km radius.
More photos of Semeru
Historic destructive activity:
1981 A heavy rain following years of pyroclastic flows and other ash-depositing eruptions resulted in a mudflow (lahar) which swept down a valley and killed over 250 people in villages downstream.
1946, 1909, 1895, 1884 Other eruptions which resulted in lahars, damage and fatalities.
Geologic History: Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Semeru has been in almost continuous eruption since 1967. Eruptions are typically vulcanian; mudflows are the greatest hazard.
Info from CVGHM and the Smithsonian Global Volcanism Network.
Here’s a neat little eruption: satellite imagery has revealed a newly-formed island in the Red Sea in the northern part of the Zabair Group of islands off the coast of Yemen. Ash-bearing steam and gas plumes were tracked from the growing cone, which now seems to have quieted down. This activity is occuring along the Red Sea rift, where the African and Arabian plates are splitting apart.
NASA satellite image of new island in Red Sea