Co-author of extinction study looks ahead

Walter Alvarez and Mark Richards

Geophysicists Walter Alvarez (at left) and Mark Richards (in the background) examine a piece of impact ejecta at the North Dakota fossil site. (Jackson Leibach Photo via University of Kansas)

After days of puzzling over secondhand reports, anyone with an internet connection can now read a research paper about a fossil graveyard in North Dakota that appears to document the day nearly 66 million years ago when an asteroid pushed the dinosaurs and many other species into extinction.

Even scientists who criticized the way the news about the site came out on March 29 acknowledged that the discovery, as described in the Proceedings of the National Academy of Sciences, was astounding.

“I am very much looking forward to the crowd-sourced opinions of everyone,” University of Edinburgh paleontologist Steve Brusatte said in a tweet. “There is a real thrill and a real mystery around this discovery, and it is EXCITING! Let’s see where the evidence leads.”

The study documents fossil evidence for a catastrophic fish kill that did in many other organisms as well. Intermixed with the fossilized remains were tiny beads of glass that had turned to clay. Some of those beads were found embedded in the gills of the fish.

The evidence led the research team, headed by paleontologist Robert DePalma, to conclude that the Cretaceous creatures were washed up onto a sandbar by a giant wave of water. Then they were pelted by hot droplets of molten rock, known as tektites, which were thrown up into the stratosphere by an asteroid impact thousands of miles away.

In the paper, the research team lays out a scenario suggesting that the impact produced a magnitude 10 to 11 earthquake, which sparked a standing wave in the body of water where the fish had lived. Such a wave, known more scientifically as a seiche (pronounced like “saysh”), could have done as much damage as a tsunami within an hour after the asteroid hit. That scenario would leave enough time for the tektites to deliver the coup de grace.

One of the study authors who came up with that scenario is Mark Richards, a geophysicist who left the University of California at Berkeley last July to become the University of Washington’s provost and executive vice president for academic affairs.

Today, Richards said the seiche scenario isn’t the only possibility for explaining what happened in North Dakota during what’s known as the Cretaceous-Paleogene or Cretaceous-Tertiary extinction.

“I think that the surge, unless it was some freak coincidence with something else, was likely seismically induced,” Richards told GeekWire. “Now, it could have been from a seiche. Also, for example, you could have had a local landslide that was triggered by seismic waves. We have to be pretty cautious.”

Get the full story on GeekWire.

About Alan Boyle

Award-winning science writer, creator of Cosmic Log, author of "The Case for Pluto: How a Little Planet Made a Big Difference," president of the Council for the Advancement of Science Writing. Check out "About Alan Boyle" for more fun facts.
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