How Broken Rocks Can Flow Like Liquid When A Dinosaur Killing Asteroid Strikes

“For a while, the broken rock behaves as a fluid,” said Jay Melosh, a professor of earth, atmospheric and planetary sciences at Purdue University. “There have been a lot of theories proposed about what mechanism allows this fluidization to happen, and now we know it’s really strong vibrations shaking the rock constantly enough to allow it to flow.”

This mechanism, known as “acoustic fluidization,” is the process that allows the ring of mountains in the crater’s center to rise within minutes of the asteroid’s strike. (This idea was first proposed by Melosh in 1979). Craters are essentially the same on all the terrestrial planets (Earth, Mercury, Venus, Mars and our moon), but they’re hard to study in space for obvious reasons: We can’t look at them with the same detail we can on Earth.

The Chicxulub crater isn’t easily accessible by traditional standards either; it’s been buried throughout the last 66 million years. So the International Ocean Discovery Program (a group within the International Continental Scientific Drilling Program), did the only thing they could – they dug. The team drilled a core roughly six inches in diameter and a mile into the Earth, collecting rock that was shattered and partly melted by the impact that wiped out the dinosaurs.

In examining fracture zones and patterns in the core, the international research team found an evolution in the vibration sequence that would allow debris to flow.

“These findings help us understand how impact craters collapse and how large masses of rock behave in a fluid-like manner in other circumstances, such as landslides and earthquakes,” Melosh said. “Towns have been wiped out by enormous landslides, where people thought they were safe but then discovered that rock will flow like liquid when some disturbance sets a big enough mass in motion.”