Mt. Kelud lava dome seen as warning sign

Indra Harsaputra, The Jakarta Post, Surabaya

Geologists from 10th November Institute of Technology (ITS) in Surabaya on Thursday say the lava dome that has formed on Mount Kelud's lake crater is not a new phenomenon, and could indicate an eruption is imminent.

They said a similar lava dome was reported before the 1919 eruption that claimed more than 5,000 lives.

They also warned the lava dome could amplify the intensity of an eruption and the damage to surrounding areas.

Geologist and head of the School for Disaster Studies at ITS, Amien Widodo, said documents from the Dutch colonial administration described the formation of a lava dome on Kelud.

"The said the lava dome, comprised of andesite lava, disintegrated and was thrown up during the eruption in the form of large rocks and pebbles, followed by a sand shower," he told The Jakarta Post on Thursday.

He added that the depth of the lake crater increased due to the magmatic pressure from the lava pocket. However, the documents did not specify the depth of the lake in detail.

The current depth of the lake crater is 38 meters, holding about 2.5 million cubic meters of water.

"The eruption in 1919 is recorded as the most fatal in the volcano's history, taking a toll of 5,160 lives," said Amien.

He said the presence of the lava dome, along with tremors and discharges of ash up to 120 meters high, must be taken as a serious warning sign.

"In theory Mount Kelud is ready to erupt. The higher the dome grows, the greater the possibility of an eruption," said Amien.

He said it was difficult to gauge the mountain's current Volcanic Explosive Index (VEI), but data from previous eruptions showed Kelud's VEI ranged from three to five.

A magnitude five VEI eruption took place in 1856. The force of that explosion was similar to explosions by the Philippines' Mount Pinatubo in 1991 and Mount St. Helens in the U.S. in 1980.

By comparison, the legendary eruption of Mount Krakatau in 1883 was a magnitude six VEI. The eruption killed more than 36,000 people.

"It's difficult to predict when Mount Kelud will erupt, but a number of theories imply that a full moon could have an influence on volcanic activity," said Amien.

Head of the Volcanology and Geological Disaster Mitigation Center's Volcano Observation Division, Agus Budianto, said there was every possibility Mount Kelud would erupt.

The lava dome is expanding daily and now covers 90 percent of the lake crater, reaching 300 meters in diameter and a height of 120 meters.

"We will constantly monitor Mount Kelud," Amien told the Post.

Sugihwaras village administrative chief in Ngancar district, Kediri regency, Susiadi, said residents were still going about their daily activities, but there had been growing concerning since Kelud was placed on top alert status on Oct. 16.

"Residents have held a traditional jaranan ritual to appease the mountain. They were told that Mount Kelud would erupt before the end of the year," said Susiadi.