Discovering evidence for past events

In this video, Dr Dan Hobley explains the story of how evidence for the Missoula megaflood was discovered.

J Harlen Bretz became interested in Eastern Washington State in 1910 when a new map was published showing its natural, physical features, and in particularly some large potholes. He began visiting and conducting field research in the area some years later.

What he observed was remarkable and unusual.

He observed evidence for waterfalls at the cliffs of Dry Falls but of a scale and size much larger than had been seen previously.

Dry Falls is estimated to be 3.5 miles wide, which is five times the width of Niagara falls in North America. It drops 400 to 600 vertical feet compared with 165 vertical feet of Niagara Falls.

This historical waterfall would have had torrents of water flowing through it, at scale that is hard for us to fully appreciate.

This and other observations, led him to the conclusion that these landscapes could only have been created by an extreme event of a megaflood.

But as we heard in the video, going from these observations to providing convincing evidence, and that evidence being accepted was challenging.

In the next step we’ll discuss this.