Sumatra, Indonesia volcano erupts after 400 years

[AlaskaDenise]

Volcano erupts on Indonesia's Sumatra after 400 years

A volcano erupted on the Indonesia island of Sumatra on Sunday for the first time in four centuries, sending smoke 1,500 meters (about 5,000 feet) into the air and prompting the evacuation of thousands of residents, officials said.

There were no reports of casualties so far and aviation in the area was unaffected.

Mount Sinabung in the north of Sumatra began erupting around midnight after rumbling for several days and lava was overflowing its crater, Surono, head of Indonesia's vulcanology center, told Reuters. The volcano had been placed on red level, the highest alert.

"Despite decreasing activities since the eruption, we haven't downgraded the status level," said Surono, who goes by one name, like many Indonesians.

"This is the first time since 1600 that Sinabung erupted and we have little knowledge in terms on its eruptive patterns and general forms."

Authorities evacuated at least 12,000 people from high risk areas on the slopes of the 2,460-meter volcano to temporary shelters. The area around the volcano is largely agricultural.

The Health Ministry put health posts on standby and distributed face masks, though there were no reports of casualties, according to Mudjiarto, head of the health ministry's crisis center.

The nearest big city to the volcano is Medan and there were no disruptions to flights.

Indonesia is located on the so-called Pacific Rim of Fire, an arc of volcanoes and geological fault lines surrounding the Pacific Basin.

http://www.reuters.com/article/idUSTRE67S06O20100829

 

[AlaskaDenise]

Re: Sumatra, Indonesia volcano erupts after 400 years

The volcano is uncomfortably close to lake Toba - site of the largest supervolcanic eruption 69K-77K years ago. The Toba eruptions is said to be responsible for a population bottleneck that impacted people around the globe.

See: http://www.answers.com/topic/toba

.

 

[Ronan Kelly]

Re: Sumatra, Indonesia volcano erupts after 400 years

Extract from: Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans
Stanley H. Ambrose
Journal of Human Evolution (1998) 34, 623?651
Article No. hu980219


Volcanic winter. Was a cataclysmic geological event responsible for the bottleneck? Rampino & Self (1992, 1993; Rampino et al., 1988) have proposed that the supereruption of Mt Toba, located in northwest Sumatra, caused a volcanic winter lasting several years. The Toba eruption is dated to 273,500&2000 bp by K/Ar (Chesner et al., 1991) and in ice cores it is dated to 71 ka (Zeilinski et al., 1996a, 1996b). Toba was an order of magnitude larger than any other known Quaternary explosive volcanic eruption (Dawson, 1992; Rose & Chesner, 1990; Huff et al., 1992) and is widely considered to have had a significant impact on Quaternary climate, possibly contributing to the rapid onset and extreme cold of stage 4 (Rampino & Self, 1992, 1993).

Toba?s volcanic ash can be traced west across the Indian Ocean and northwest across India (Rose & Chesner, 1990). In some Indian Ocean cores the ash is over 12 cm thick (Dawson, 1992). It is a widespread terrestrial marker bed in India, where it occurs as primary and reworked airfall ash, in beds that are commonly one to three, and occasionally up to six meters thick
(Acharyya & Basu, 1993).

The dense rock equivalent (DRE) volume of a volcanic ash layer is a standard measure of the magnitude of an explosive eruption. The largest known eruption of the last 454 million years is represented by the Ordovician Millbrig Beds in eastern North America, which correlate with the Big Bentonite of northwestern Europe (Huff et al., 1992). The Millbrig/Big Bentonite DRE is 1140 km3 of solid rock (Huff et al., 1992). Tambora F5, the largest known historic eruption, displaced 20 km3 and Mt St Helens produced 0?2 km3 of volcanic ash (Huff et al., 1992). Toba had a DRE of about 800 km3 (Rose & Chesner, 1990). It was thus 40 times larger than the largest eruption of the last two centuries and apparently the second largest known explosive eruption in Phanerozoic history.

The high-resolution record of climate and explosive volcanism in Greenland ice cores clarifies the chronostratigraphic position of the Toba super-eruption, its relationship to the onset of the last ice age and to dramatic climatic deterioration at 71 ka (Zielinski et al., 1996a, 1996b; Dansgaard et al., 1993). Oxygen isotope ratios, calcium and sulfur concentrations and electrical conductivity of ice show Toba erupted about 71 ka, between the interstadials (warm periods) of Dansgaard-Oschlger (D-O) events 19 and 20 (Zeilinski et al. 1996b). The eruption is marked by a 6-year period during which the largest amount of volcanic sulfur of the last 110 ka was deposited in the ice core, and marks the termination of the interstadial of D-O event 20. This dramatic volcanic event is followed by 1000 years of the absolutely
lowest ice core oxygen isotope ratios of the last glacial period. In other words, for 1000 years immediately following the Toba eruption, the earth witnessed temperatures relentlessly colder than during the Last Glacial Maximum at 18?21 ka. The first 200 years of this stadial event are marked by
increased calcium deposition, indicating high atmospheric dust concentrations, probably from aeolian erosion due to reduced vegetation cover and sediments exposed by a drop in sea level.

full paper at; http://ice2.uab.cat/argo/Argo_actualitzacio/argo_butlleti/ccee/geologia/arxius/1Ambrose 1998.pdf

 

[tetano]

Re: Sumatra, Indonesia volcano erupts after 400 years

KABANJAHE, Indonesia (AFP) ? An Indonesian volcano that returned to life after four centuries of inactivity threw an ash cloud thousands of metres into the air Tuesday in its most most violent eruption yet.

Witnesses said lava, rock, ash and gas shot into the sky from the crater of 2,460-metre (8,000 feet) Mount Sinabung in northern Sumatra shortly after midnight.

The eruption lasted five minutes and was felt about eight kilometres (five miles) away.

"Its latest eruption was double the previous outburst and we recorded a tower of ash reaching 5,000 metres," government volcanologist Agus Budianto told AFP.

More than 20,000 people have fled their homes since the volcano first erupted late August and remain in emergency shelters.

Indonesian President Susilo Bambang Yudhoyono visited the area on Monday and asked displaced people to be patient.

"Sinabung is very active with a series of eruptions. For your safety please stay in the shelter for the time being.... I hope it will not last very long," he said.

With each new eruption, concern grows for those villagers who have stayed on the mountain to guard their homes or tend to their crops.

Anto Sembiring, 37, said his family had gone to a shelter but he had stayed to take care of their house, which is inside a six-kilometre exclusion zone around the mountain.

"I'm worried about my future. The volcano seems unwilling to stay calm," he told AFP.

"My children haven't gone to school for almost two weeks and they have to stay in the crowded shelter in unhealthy conditions."

Volcanologists said Sinabung's long dormant period had made it highly unpredictable.

The sprawling Indonesian archipelago has 69 active volcanoes with histories of eruptions and straddles major seismic fault-lines in a region known as the "Pacific Ring of Fire".

Four people disappeared last month after the 1,784-metre Mount Karangetang erupted on the island of Siau, North Sulawesi province.

Volcanoes have killed scores of thousands of Indonesians over the past 200 years, including more than 70,000 in the 1815 eruption of Mount Tomboro on the island of Sumbawa.

Mount Sinabung is near Lake Toba, a 100-kilometre long volcanic crater that some archaeologists believe was the site of an eruption that almost wiped out the human race when it erupted 69,000-77,000 years ago.

http://news.yahoo.com/s/afp/20100907/wl_asia_afp/indonesiavolcano