You’d think a 10km-wide asteroid hitting earth would be eventful enough, but now scientists have discovered this asteroid, which wiped out the entire dinosaur population, triggered a huge earthquake lasting up to several months.
These findings were presented at the Geological Society of America (GSA) on Sunday, with researchers dishing up gory details on what they dubbed the “mega-earthquake”.
The events took place 66-million years ago and the asteroid collision — known as the Chicxulub impact — triggered the mega-earthquake, releasing about 10²³ joules of energy.
To put that into perspective, this is about 50,000 times more energy than was released in the Sumatra earthquake of 2004.
That earthquake, by modern standards, was almost beyond comprehension. It had a magnitude of 9.1 and, lasting eight to 10 minutes, is the longest recorded. It triggered what became known as the Boxing Day tsunami that killed about 250,000 people.
The findings on the mega-earthquake from 66-million years ago are thanks to the hard work of lead researcher Hermann Bermúdez from Montclair State University in New Jersey.
Like an investigator sweeping a gargantuan crime scene, Bermúdez made his way through evidence as far afield as Columbia and Mexico, to the boundary between Texas, Alabama and Mississippi.
According to the GSA: “In 2014, while doing fieldwork on Colombia’s Gorgonilla Island, Bermúdez found spherule deposits — layers of sediment filled with small glass beads [as large as 1.1mm] and shards known as ‘tektites’ and ‘microtektites’ that were ejected into the atmosphere during an asteroid impact. These glass beads formed when the heat and pressure of the impact melted and scattered the crust of the Earth, ejecting small, melted blobs up into the atmosphere to then fall back to the surface as glass under the influence of gravity.”
The rocks exposed on the coast of Gorgonilla Island tell a story from the bottom of the ocean — about 2km down.
There — about 3,000km southwest from the site of the impact — sand, mud and small creatures were accumulating on the ocean floor when the asteroid hit.
“Layers of mud and sandstone as far as 10 to 15 metres below the sea floor experienced soft sediment deformation that is preserved in the outcrops today, which Bermúdez attributes to the shaking from the impact. Faults and deformation due to shaking continue up through the spherule-rich layer that was deposited post-impact, indicating that the shaking must have continued for the weeks and months it took for these finer-grained deposits to reach the ocean floor. Just above those spherule deposits, preserved fern spores signal the first recovery of plant life after the impact,” according to the GSA.
Bermúdez explains: “The section I discovered on Gorgonilla Island is a fantastic place to study the K-Pg boundary, because it is one of the best preserved and was located deep in the ocean, so it was not affected by tsunamis.”
Evidence of deformation from the mega-earthquake is also preserved in Mexico and the US.
At the El Papalote exposure in Mexico, Bermúdez observed evidence of liquefaction — when strong shaking causes water-saturated sediments to flow like liquid.
In Mississippi, Alabama, and Texas, Bermúdez documented faults and cracks likely associated with the megaquake.
He also documents tsunami deposits at several outcrops left by an enormous wave that was part of the cascading catastrophes resulting from the asteroid hit.
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