A 25 mile long crater was created nearly 35 million years ago which still lies intact below Chesapeake Bay of North America when an asteroid had hit earth. When the impact was made it led to fires, earthquakes and shower of molten glass droplets followed by a massive air blast and also a devastating tsunami say scientists. Though the crater is now completely buried by sand it was discovered in early 1990’s with scientific drilling which ranks as largest impact crater within United States and the 15th largest one on Earth. When it hit the earth it released an ejecta layer that comprises of natural glass formed from debris that is part of meteorite impact called tektites. The layer is referred to as North American tektite strewn field which comprises of zircon crystals that covers nearly 4 million square miles.
While some of the ejecta material landed on firm land a majority landed in seawater and cooled on contact after sinking to ocean floor. Researchers from Arizona State University’s School of Earth and Space Exploration obtained drilling samples from Ocean Drilling Project site number 1073 after dating them with technique of “uranium-thorium-helium” for first time. They say that mass extinction of dinosaurs 65 million years ago was caused by similar asteroid impact which created the extraordinarily large Chicxulub impact crater.
Key to their investigation was zirconium silicate crystals that are spread across 400 kilometers northeast of the actual impact site in the Atlantic Ocean. The accurate age of impact events was a vital part of their research as it would help in understanding history of earth through impact events on its geological and biological history. They prepared samples for analysis and used the uranium-thorium-helium method to date the zircon crystals. Details of their research were published in international journal of Meteoritics and Planetary Science.