Impact that killed the dinosaurs triggered "mega-earthquake" that lasted
weeks to months
Denver, Colo., USA, 66 million years ago, a 10-kilometer asteroid hit
Earth, triggering the extinction of the dinosaurs. New evidence suggests
that the Chicxulub impact also triggered an earthquake so massive that it
shook the planet for weeks to months after the collision. The amount of
energy released in this "mega-earthquake" is estimated at 1023
joules, which is about 50,000 times more energy than was released in the
magnitude 9.1 Sumatra earthquake in 2004.
Hermann Bermúdez will present evidence of this “mega-earthquake” at the
upcoming GSA Connects meeting in Denver this Sunday, 9 October. Earlier
this year, with support from a GSA Graduate Student Research Grant,
Bermúdez visited outcrops of the infamous Cretaceous-Paleogene (K-Pg) mass
extinction event boundary in Texas, Alabama, and Mississippi to collect
data, supplementing his previous work in Colombia and Mexico documenting
evidence of the catastrophic impact.
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 1.1 mm) 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—roughly 2 km down. There, about 3,000-km southwest from
the site of the impact, sand, mud, and small ocean creatures were
accumulating on the ocean floor when the asteroid hit. Layers of mud and
sandstone as far as 10–15 meters 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.
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 it 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 United States. At the El Papalote exposure in Mexico,
Bermúdez observed evidence of liquefaction—when strong shaking causes
water-saturated sediments to flow like a liquid. In Mississippi, Alabama,
and Texas, Bermúdez documented faults and cracks likely associated with the
mega-quake. He also documents tsunami deposits at several outcrops, left by
an enormous wave that was part of the cascading catastrophes resulting from
the asteroid collision.
Bermúdez will deliver a talk about evidence for the mega-earthquake at the
GSA Connects meeting in Denver on Sunday, 9 October. He will also present a
poster about his observations of tsunami deposits and earthquake-related
deformation on Monday, 10 October, which will be available in English,
Spanish, Italian, French, and Chinese. In discussing his research, he
emphasized the important role collaboration has played in visiting and
studying so many outcrops that tell the story of this extreme event in
Earth’s history.
The Chicxulub Mega-Earthquake: Evidence from Colombia, Mexico, and the
United States
Author: Hermann Bermúdez, Montclair State University, hdbermudez@yahoo.com
https://gsa.confex.com/gsa/2022AM/meetingapp.cgi/Paper/377578
Sunday, 9 October 2022, 3:45 PM-4:00 PM
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