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The extinction of the dinosaurs was triggered when a 10 km wide asteroid hit Earth about 66 million years ago. Scientists find new evidence that the Chicxulub impact triggered “a megaquake releasing about 100 billion joules of energy, or about 50,000 times the energy of the 2004 Sumatra earthquake of magnitude 9.1 on the Richter scale.”
Evidence of this “megaquake” was presented by GSA researcher Hermann Bermudez at his GSA Connects conference in Denver on Sunday, October 9. This year, Bermudez visited outcrops of the Cretaceous-Palaeogene mass extinction frontiers in Texas, Alabama and Mississippi to provide data that complement previous studies documenting evidence of impacts in Colombia and Mexico.
In 2014, Bermudez discovered bullet deposits during field research on Colombia’s Gorgonilla Island. Spherical sediments are layers of sediments filled with tiny glass beads less than 1.1 mm and debris known as ‘tektites’ and ‘microtektites’. These fragments and glass beads were thrown into the atmosphere during the asteroid impact. They formed when the heat and pressure of the collision melted and dispersed the Earth’s crust.
Globule and tektites found off the coast of Gorgonilla Island provide clues about what happened on the seafloor about 2 km (1.2 miles) underwater during the collision. The impact of the asteroid Chicxulub on Earth deformed layers of mud and sandstone up to 15 meters below the seafloor. This was obtained in an impact-induced seismic outcrop. The shaking-induced disturbances and deformations propagate through the bead-packed layer deposited after the collision. This indicates that tremors must have lasted for weeks to months before these finer sediments reached the seafloor. And fern spores preserved on spherical sediments show an early recovery of plant life after impact.
Evidence of deformation from this great earthquake is also found in Mexico and the United States. Bermudez documented faults and fissures likely associated with the great earthquakes in Mississippi, Alabama, and Texas. He also documented that some of these outcrops had tsunami debris, left behind by the huge waves created by the impact.