February 27, 2006

Buried Indonesian Village Studied for Volcanic Clues

By Richard C. Lewis

SOUTH KINGSTOWN, Rhode Island (Reuters) - Scientists are unearthing an Indonesian village buried nearly two centuries ago by the largest volcanic eruption in recorded history to learn how fast volcanic eruptions can turn deadly.

Two years ago, a team of scientists from the University of Rhode Island, the University of North Carolina and the Indonesian Directorate of Volcanology began digging up the village of Tambora, which was buried by a volcanic eruption in 1815.

The excavation shows how Tambora's 10,000 residents were killed in moments by an avalanche of hot volcanic ash, rock and volcanic gas known as a pyroclastic flow, scientists said on Monday.

The village was buried in 10 feet of volcanic debris.

The eruption was the largest in recorded history, said Haraldur Sigurdsson, a University of Rhode Island professor who has studied Tambora since 1986. In all, 117,000 people were killed.

"Events of this type will occur in the future, and we should be aware of what could happen," said Sigurdsson.

The eruption of Mount Tambora on Sumbawa island blew 200 times more magma and pulverized rock into the air than Mount St. Helen's in the U.S. state of Washington in 1980, according to Sigurdsson.

Tambora's blast also sent sulfur dioxide 43 km (27 miles) into the air, creating a chemical chain reaction in the atmosphere that caused a year of global cooling that made 1816 "the year without a summer."

Scientists located Tambora with help from a local guide, who told them that pottery fragments and human bones had been found in a gully. In the mid-2004 dig, scientists discovered an entombed house with two people inside.

One woman was found in the kitchen, her hand next to glass bottles that had been melted by the ash flow. The house, on wooden stilts with bamboo siding and a thatched roof, had been incinerated into charcoal by the fiery ash that Sigurdsson believes was at least 1,000 degrees Fahrenheit (538 degrees Celsius).

The finding is significant, Sigurdsson said, because "it means that we know that in an eruption such as that in 1815, that pyroclastic flows extend from the volcano in all directions to a distance of at least 40 km (25 miles) radially and within that zone ... there is an extinction of all life."

Scientists also studied the deposits of volcanic ash and documented the size of the particles and their distance from the volcano, said Steven Carey, a University of Rhode Island professor with a background in physical volcanology.

The data can be plugged into computer models that will simulate volcano blasts and their potential fallout, Carey added.

The deposits are one factor used to determine Tambora's eruption rate, or how much content was spewed out of the volcano and how quickly. That, said Sigurdsson, will determine when relatively harmless fallout turns into to the deadly ash flow.