Something’s brewing in America that could devastate mankind—and we aren’t talking about Trump.
There’s no single natural disaster quite as destructive as a volcanic eruption.
Fortunately, how these eruptions happen is well understood. Scientists know exactly what makes a supervolcano such as America’s Yellowstone blow its top.
At least… they thought they did. But a recent paper by volcanologist Agust Gudmundsson has suggested that everything we thought we knew about how the largest eruptions happen is wrong.
Giant Pimples: The Structure of a Volcano
A volcano is a little like a nasty zit.
At the centre of every volcano is a magma chamber. This is a hollow ‘bubble’ deep under the ground, filled with molten rock that’s forced up from the Earth’s mantle.
As the chamber fills, the pressure inside it increases. And when that pressure becomes too much for the rock surrounding it, that rock breaks, and magma comes shooting out—much like a popping pimple.
This ‘zit’ model, called the poroelastic model of eruption, is the accepted explanation for smaller eruptions. However, when it comes to large eruptions, this model has a big problem.
In the poroelastic model, only about 4% of the total magma in the chamber erupts.
However, the biggest eruptions can produce over 170km3 of ash, equivalent to about 50km3 of magma. This was the case in the 1815 Eruption of Mt. Tamboro. Under the poroelastic model, this means the magma chamber would have had to be 1250km3 large.
But Mt. Tamboro’s magma chamber was only 33km2 wide. For the 1815 eruption to be possible, then, the magma chamber would have to be 38km thick—thicker than the Earth’s crust!
So how are large eruptions possible?
Popping the Pimple
A caldera is a crater formed when a magma chamber totally empties. The rock above the chamber sinks down into the space previously occupied by lava, leaving an indent. Think of the bowl commonly seen at the top of a volcano.
Gudmundsson has suggested that these calderas aren’t the result of large eruptions. They’re the cause.
According to Gudmundsson, large eruptions like that of Mt. Tamboro could happen when a caldera sinks onto a still-full magma chamber. Like a zit being squeezed, the caldera pressing down on the magma chamber raises the pressure… until it pops, and ruins civilizations like a zit ruins prom.
Knowing this is all well and good. But what’s the point?
Gudmundsson claims that understanding large eruptions is the first step towards preventing them. Large eruptions are one of few natural disasters which could wipe mankind off of the planet. Therefore, it’s of utmost importance to learn how to prevent them.
… We’ll get back to you once we find out how.