A Pile of Magma Pancakes May Help Fuel Super-Eruptions

During super-eruptions, tremendous amounts of lava are spewed from beneath the ground. Yet this lava comes from somewhere--reservoirs of magma that take millions of years to accumulate. Now, scientists have found that these reservoirs consist of magma that intrudes into the crust in the form of numerous horizontally oriented sheets resting on top of each other like a pile of pancakes.

In this latest study, the scientists investigated the question on where the tremendous amounts of material that are ejected to form huge calderas during super-eruptions actually originate. For example, the Toba caldera in the Sumatra subjection zone in Indonesia originated from one of the largest volcanic eruptions in recent history. This event emitted about 2,800 cubic kilometers of volcanic material and had a dramatic global impact on climate and environment.

The scientists installed a seismometer network in the Toba area to investigate further. This allowed them to peek at the internal structure of the magma reservoir beneath the Toba-caldera. In the end, they found that the middle crust below the Tolba supervolcano is horizontally layered.

About seven kilometers below the surface, the deposits of the last eruption formed a zone of low velocities. Below this depth, the seismic anisotropy is caused by horizonatally layered intrusions that structure the reservoirs like a pile of pancakes.

The findings reveal a bit more about the structure of these reservoirs. This, in turn, may allow researchers to better estimate when eruptions may occur and how large they might be. There are supervolcanoes across the world which erupt once every couple of hundred thousand years. This means that understanding the processes that fuel them is crucial for understanding when and how these eruptions may impact our globe.

The findings are published in the journal Science.