Sumatra faces yet another risk -- major volcanic eruptions

May 16, 2012

The early April earthquake of magnitude 8.6 that shook Sumatra was a grim reminder of the devastating earthquakes and tsunami that killed tens of thousands of people in 2004 and 2005.

Now a new study, funded by the National Science Foundation, shows that the residents of that region are at risk from yet another potentially deadly – major .

Researchers from Oregon State University working with colleagues in Indonesia have documented six major volcanic eruptions in over the past 35,000 years – most equaling or surpassing in explosive intensity the eruption of Washington's Mount St. Helens in 1980.

Results of the research have just been published in the Journal of Volcanology and Geothermal Research.

"Sumatra has a number of active and potentially explosive volcanoes and many show evidence of recent activity," said Morgan Salisbury, lead author on the study, who recently completed his doctoral studies in OSU's College of Earth, Ocean, and Atmospheric Sciences. "Most of the eruptions are small, so little attention has been paid to the potential for a catastrophic eruption.

"But our study found some of the first evidence that the region has a much more explosive history than perhaps has been appreciated," he added.

Until this study, little was known about Sumatra's volcanic history – in part because few western scientists have been allowed access to the region. The most visible evidence of recent volcanic activity among the estimated 33-35 potentially active volcanoes are their steep-sided cones and lack of vegetation, indicating at least some minor eruptive processes.

But in 2007, an expedition led by OSU's Chris Goldfinger was permitted into the region and the Oregon State researchers and their Indonesian colleagues set out to explore the history of the region by studying sediment cores from the Indian Ocean. Funded by the National Science Foundation, it was the first research ship from the United States allowed into Indonesia/Sumatran waters in nearly 30 years.

While searching the deep-sea sediment cores for "turbidites" – coarse gravel deposits that can act as a signature for earthquakes – they noticed unmistakable evidence of volcanic ash and began conducting a parallel investigation into the region's volcanic history.

"The ash was located only in certain cores, so the activity was localized," said Adam Kent, a professor of geosciences at OSU and an author on the study. "Yet the eruptions still were capable of spreading the ash for 300 kilometers or more, which gave us an indication of how powerful the explosive activity might have been."

Salisbury and his colleagues found evidence of six major eruptions and estimated them to be at least from 3.0 to 5.0 on the Volcanic Explosivity Index. Mount St. Helens, by comparison, was 5.0.

The Indian Ocean region is certainly known to have a violent volcanic history. The 1883 eruption of Krakatoa between Sumatra and Java is perhaps the most violent volcanic explosion in recorded history, measuring 6.0 on the VEI and generating what many scientists believe to have been one of the loudest noises ever heard on Earth.

Sumatra's own Toba volcano exploded about 74,000 years ago, generating a major lake – not unlike Oregon's own Crater Lake, but much larger. "It looks like a giant doughnut in the middle of Sumatra," said Jason "Jay" Patton, another OSU doctoral student and author on the study.

Sumatra's volcanoes occasionally belch some ash and smoke, and provide comparatively minor eruptions, but residents there may not be fully aware of the potential catastrophic nature of some of its resident volcanoes, Goldfinger said.

"Prior to 2004, the risk from a major earthquake were not widely appreciated except, perhaps, in some of the more rural areas," Goldfinger said. "And earthquakes happen more frequently than major volcanic eruptions. If it hasn't happened in recent memory…"

Kent said the next step in the research is to work with scientists from the region to collect ash and volcanic rock from the island's volcanoes, and then match their chemical signature to the ash they discovered in the sediment cores.

"Each volcano has a subtly different fingerprint," Kent said, "so if we can get the terrestrial data, we should be able to link the six major eruptions to individual volcanoes to determine the ones that provide the greatest risk factors."

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

add to favorites email to friend print save as pdf

Related Stories

Possible trigger for volcanic 'super-eruptions' found

Oct 12, 2011

The "super-eruption" of a major volcanic system occurs about every 100,000 years and is considered one of the most catastrophic natural events on Earth, yet scientists have long been unsure about what triggers ...

Eruptive characteristics of Oregon's Mount Hood analyzed

Aug 02, 2010

A new study has found that a mixing of two different types of magma is the key to the historic eruptions of Mount Hood, Oregon's tallest mountain, and that eruptions often happen in a relatively short time ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

LindaPP
5 / 5 (1) May 18, 2012
This is news?

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...