Oregon State University researchers linked recent eruptions at Sumatra’s Mt. Sinabung to the last supervolcano eruption on Earth, which took place 74,000 years ago at the Toba Caldera some 25 miles away.
When Toba erupted, it emitted a volume of magma 28,000 times greater than that of the 1980 eruption of Mount St. Helens in Washington state. It was so massive, it is thought to have created a volcanic winter on Earth lasting years, and possibly triggered a bottleneck in human evolution.
To qualify as a supervolcano, the eruption must reach at least magnitude 8 on the Volcano Explosivity Index, which means the measured deposits for that eruption are greater than 1,000 cubic kilometers, or 240 cubic miles.
This short video explains how Lake Toba was formed.
“Supervolcanoes have lifetimes of millions of years during which there can be several supereruptions,” said Shanaka “Shan” de Silva, an Oregon State University volcanologist and co-author on the study. “Between those eruptions, they don’t die. Scientists have long suspected that eruptions continue after the initial eruption, but this is the first time we’ve been able to put accurate ages with those eruptions.”
The study also found that the magma in Toba’s system has an identical chemical fingerprint and zircon crystallization history to Mt. Sinabung, which is currently erupting and is distinct from other volcanoes in Sumatra. This suggests that the Toba system may be larger and more widespread than previously thought, de Silva noted.
“Our data suggest that the recent and ongoing eruptions of Mt. Sinabung are part of the Toba system’s recovery process from the supereruption,” he said.
The discovery of the connection does not suggest that the Toba Caldera is in danger of erupting on a catastrophic scale any time soon, the researchers emphasized. “This is probably ‘business as usual’ for a recovering supervolcano,” de Silva said.
“The hazards from a supervolcano don’t stop after the initial eruption,” de Silva said. “They change to more local and regional hazards from eruptions, earthquakes, landslides and tsunamis that may continue regularly for several tens of thousands of years.
“Toba remains alive and active today.”
As large as the Toba eruption was, the reservoir of magma below the caldera is much, much greater, the researchers say. Studies at other calderas around Earth, such as Yellowstone, have estimated that there is between 10 and 50 times as much magma than is erupted during a supereruption.
Other well-known supervolcano sites include Yellowstone Park in the United States, Taupo Caldera in New Zealand, and Campi Flegrei in Italy.
Mucek and de Silva are affiliated with OSU’s College of Earth, Ocean, and Atmospheric Sciences. The study was supported by the National Science Foundation.
The above info came from a news release issued by Oregon State University on May 16th of this year. See entire news release:
Thanks to John of Cloverdale, WA, Australia, for this link