What Triggered The Largest Volcanic Eruption In Human History?

Posted: Jan 29 2017, 7:55am CST | by , Updated: Jan 29 2017, 7:59am CST, in News | Latest Science News

 

What Triggered the Largest Volcanic Eruption in Human History?
Quartz crystals from Toba. Credit: Troll et al
 

Quartz crystals provide more insight into devastating Toba supervolcano eruption

Around 75,000 years ago, Indonesian supervolcano Toba erupted furiously and ejected 2, 800 cubic kilometers of magma and volcanic ash into the atmosphere, which is equivalent in mass to more than 19 million Empire State Buildings. 

The massive volcanic eruption changed the course of human history by reducing the average global temperature by 3 to 3.5 degrees Celsius for several years and possibly triggering an ice age.

Scientists have long debated how this massive volcanic eruption was triggered and what made the magma to erupt so explosively? A team of international researchers has found intriguing clues hidden inside the tiny crystals from the volcanic ash and rocks, also known as quartz. 

“Quartz crystals that grow in the magma register chemical and thermodynamical changes in the magmatic system prior to eruption, similar to how tree rings record climate variations. When the conditions in the magma change, the crystals respond and produce distinct growth zones that record these changes. The problem is that each "tree ring"-analogue is only a few micrometers across, which is why they are extremely challenging to analyze in detail.” Dr. David Budd from Uppsala University’s Department of Earth Sciences said.

Quartz is one of the most common crystalline materials. It is an important rock-forming mineral that is resistant to alteration and retains variable magmatic 180 values post-eruption values. This makes quartz a better candidate to understand magmatic processes compared to other volcanic minerals.

When researchers analyzed quartz crystals from present-day Toba site, they found a distinct shift in the isotopic composition in the outer rim of the crystals. The crystal rims showed a relatively lower proportion of the heavy isotope 18O compared to the lighter 16O. These oversized crystals provide a peek into the events that occurred hundreds of years ago and led to the massive eruption.

“The low ratio of 18O to 16O contents in the crystal rims indicate that something in the magmatic system changed drastically just before the big eruption. The explanation behind these chemical signatures is that the magma melted and assimilated a large volume of a local rock that itself is characterized by a relatively low ratio of 18O to 16O,” explains co-author Dr. Frances Deegan.

“This rock type also often contains a lot of water, which may be released into the magma, producing steam, and thereby an increased gas pressure inside the magma chamber. This rapidly increased gas pressure eventually allowed the magma to rupture the overlying crust, and send thousands of cubic kilometers of magma into the atmosphere.”

Theorists believe that Toba catastrophe nearly driven humanity extinct. Another cataclysmic eruption that could wreak as much havoc as the impact of a giant asteroids, can happen again at Toba or somewhere else. Studies, like this one, can help us better prepare for a catastrophe event in future.

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Hira Bashir covers daily affairs around the world.

 

 

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