Scientists have no idea how powerful is the Earth's crust

A powerful earthquake that killed almost 100 people in Mexico last year.

The magnitude 8.2 struck in September 2017 just off the coast of the state of Chiapas, near Guatemala. Mexican President Enrique Peña Nieto called it "the biggest country has seen in a century."

It's now emerging the quake was so strong, it broke the 60km-thick tectonic plate completely in two in a matter of seconds.

"We do not yet have an explanation on how this was possible," said Diego Melgar of the University of Oregon, who is studying the quake.

"We can only say that it contradicts the models that we have so far

The quake's epicenter was 46km deep in the Cocos ocean plate, which is diving under the North American plate. Quakes are known to be in the world, they are on their journey to the underworld.

"If you bend an eraser, you can see the top half being extended and stretched," Melgar told Dr. Melgar. National Geographic.

It 's understood that stretching at the top can trigger a quake, the flat splits apart – but never before have seen a quake split right in the middle, right down through the compressed part at the bottom.

"These kinds of cracks, we're all over the world but we're not propagating them all the way through the tectonic plate," Dr. Melgar told IFL Science.

The Cocos is also geologically very young, at only about 25 million years old, and warm. Scientists believe these types of quakes only, and more prone to snapping.

One theory is that seawater seeped into the plate, accelerating its cooling and making it more prone to breaking. If this is true, Dr. Melgar says the whole coast of the US and Canada is at risk.

"Our knowledge of these places where large earthquakes happen is still imperfect," Dr. Melgar said.

"We can still be surprised." We are still in the process of becoming more informed than we are. in terms of tsunami hazard. "

The study was published in journal Nature Geoscience.

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