Nye bevis tyder på at Chicxulub-asteroiden utløste et jordskjelv så monstrøst at det rystet planeten i uker til måneder etter kollisjonen.
En 6 mil (10 kilometer) asteroide traff jorden for 66 millioner år siden, og utløste utryddelsen av dinosaurene. Ifølge nye bevis utløste Chicxulub-påvirkningen også et jordskjelv som var så massivt at det rystet planeten i uker til måneder etter kollisjonen. Dette “mega-jordskjelvet” frigjorde en utrolig mengde energi, anslått til 1023 joule, som er omtrent 50 000 ganger mer energi enn det som ble frigjort i jordskjelvet på Sumatra på 9,1 i 2004.
Bevis på dette “mega-jordskjelvet” vil bli presentert på det kommende GSA Connects-møtet i Denver denne søndagen, 9. oktober, av Hermann Bermúdez, en doktorgradsstudent i programmet for miljøvitenskap og ledelse ved Montclair State University. Tidligere i år, med støtte fra et GSA Graduate Student Research Grant, besøkte Bermúdez utmarkene av det beryktede[{” attribute=””>Cretaceous-Paleogene (K-Pg) mass extinction event boundary in Texas, Alabama, and Mississippi to collect data. This supplemented his previous work in Colombia and Mexico documenting evidence of the catastrophic impact.
Artwork by Hermann Bermúdez depicting one dinosaur’s experience of the Chicxulub impact. Credit: Hermann Bermúdez
While doing fieldwork on Colombia’s Gorgonilla Island in 2014, Bermúdez found spherule deposits. These are layers of sediment filled with small glass beads (as large as 0.04 inches / 1.1 mm) and shards known as ‘tektites’ and ‘microtektites’ that were ejected into the atmosphere during an asteroid impact. These glass beads were created when the heat and pressure of the impact melted and dispersed the crust of the Earth, ejecting small, melted blobs up into the atmosphere, which then fall back to the surface under the influence of gravity, cooling to glass along the way.
Deformed spherule-rich layer at Gorgonilla Island (Colombia) showing that seismic activity persisted for weeks or months after impact. Credit: Hermann Bermúdez
The rocks exposed on the coast of Gorgonilla Island tell a story from the bottom of the ocean—roughly 1.2 miles (2 km) down. There, about 2,000 miles (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 35-50 feet (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. This suggests that the shaking must have continued for the weeks and months it took for these finer-grained deposits to reach the ocean floor. Preserved fern spores just above those spherule deposits signal the first recovery of plant life after the impact.
Spherule deposits on Gorgonilla Island. Credit: Hermann Bermúdez.
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, October 9, 2022. He will also present a poster about his observations of tsunami deposits and earthquake-related deformation on Monday, October 10, which will be available in English, Spanish, French, Italian, 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
https://gsa.confex.com/gsa/2022AM/meetingapp.cgi/Paper/377578
Sunday, 9 October 2022, 3:45 PM-4:00 PM
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