North Dakota killing field offers snapshot of Earth's last mass extinction

For more than half a decade at a North Dakota site called Tanis in the Hell Creek Formation, paleontologist Robert DePalma has worked to unearth evidence of what is believed to be a 'killing field' established shortly after the impact of the asteroid that ushered in Earth's last mass extinction event. The site is home to the fossilized remains of many dead creatures ranging from fish to a dinosaur.

All of the creatures encased in the 66-million-year-old killing field died at the same time on the same day; they represent all stages of life, according to an announcement by UC Berkeley. The mass grave was established during the K-T boundary — that is, the end of the Cretaceous Period and beginning of the Tertiary period. Dinosaurs went extinct during the K-T mass extinction event and 75-percent of life on Earth was destroyed.

The K-T mass extinction event is believed to have resulted from the strike of a large meteorite or small asteroid that made impact near the Yucatan Peninsula around 66 million years ago. A massive impact crater was formed on the ocean floor and a combination of vaporized asteroid dust and molten rocks were blasted into the atmosphere.

A cloud of this particulate spread across Earth, paving the way for the mass extinction event. Melted rock ejected into the atmosphere formed into glass beads called tektites, which then rained down on the creatures below, including ones located at the North Dakota site. At the same time, tsunamis flooded the region likely due to huge earthquakes caused by the impact.

The result is a large killing field set down in layers that exists as something like a snapshot of this cataclysmic moment in Earth's history. Within the killing field lie fish that died with glass beads in their gills, as well as the remains of insects, mammals, burned trees and loose branches, the partial remains of a Triceratops, amber, and more.