Chalk reveals greatest underwater landslide

Column of sediment from 637 to 639 meters below the ocean floor shows layers of chalk (white) deposited during underwater landslides 65 million years ago. Norris, et al./Geology

The cataclysmic event that wiped out the last dinosaurs also triggered the greatest underwater landslides ever, scientists report.

A chunk of a giant comet or asteroid slammed into Mexico’s Yucatan peninsula about 65 million years ago, setting off earthquakes with magnitudes estimated at 10 to 13.