Over 800 miles from the affect web site, large ripples buried deep underground document the devastation wrought by an asteroid. The Chicxulub impact, the possible smoking gun for the extinction of the dinosaurs on the finish of the Cretaceous, despatched tsunamis tearing throughout the Gulf of Mexico. These big waves left ripples within the undersea sediments as they handed and a brand new examine has discovered what is likely to be the most important “megaripples” on the planet.
The Darkest Day
Let’s step again a second. It has been round 40 years because the Chicxulub affect, situated on the northern shores of the Yucatan Peninsula, was recognized because the potential reason behind the famed Cretaceous-Tertiary extinction (a.ok.a., the K-t boundary). Since then, indicators of this large collision have been discovered throughout the planet. These embody a layer of iridium from the asteroid, droplets of molten rock that rained down after the affect, wave deposits as far away as North Dakota and the charred remains of forest burned by the warmth of the blast.
The Cretaceous-Tertiary boundary (marked) from southern Alberta in Canada. Credit score: Mike Beauregard, Flickr.
And we’re nonetheless discovering the outcomes of that bleak day 66 million years in the past. A new study in Earth and Planetary Science Letters by Gary Kinsland and others might have revealed the deposits left by the large tsunamis created by the affect. When the asteroid, thought to have been 6 miles throughout, blasted into the shallow proto-Gulf of Mexico, it unleashed waves that raced throughout the ocean.
At the moment, the shoreline alongside the north of the gulf was a lot additional north due to excessive sea ranges, so the fashionable state of Louisiana was beneath 100 or so toes of sea water. The tsunamis that sloshed throughout the gulf carried sediment and deposited it within the type of large ripples throughout what’s now dry land in central Louisiana.
Seismic picture of the buried megaripples in central Louisiana. Credit score: Kinsland and others, EPSL (2021)
Large Waves Create Large Ripples
These megaripples are the primary to be recognized from the Chicxulub affect. Now, these ripples are, on one hand, very similar to you would possibly see on a seaside. Then again, they had been enormous. The common peak of the ripples is 50 toes and their wavelength is over a 3rd of a mile. The megaripples had been so effectively preserved as a result of the ocean was deep sufficient that later storms did not disturb the options.
These megaripples aren’t seen on the Earth’s floor right this moment. They have been buried by later sediments however they present up in seismic information that has been collected over the many years by petroleum corporations. Seismic data like these present modifications within the layers of rock and sediment primarily based on their traits like composition and density by utilizing how the pace of seismic waves change as they cross by. Consider it considerably like sonar for underground.
There’s a huge trove of geophysical information about our planet locked away in propertiary information units like these (and one can hope it could actually see the sunshine of day once we transfer away from fossil fuels). Till then, these Louisiana megaripples are a tantalizing clue into what it might need been like for days after the Chicxulub affect, the place large tsunamis rolls forwards and backwards throughout the Gulf of Mexico.