Message #188660

[Atlas]

CLUES AND TIMELINES

While there are other archaeological sites around the mountain – 95 at last count –Buck Lake is unique because of the lake itself. The lake is fed by melt water and has no outlet stream, so anything that has fallen into the lake has settled to the bottom, including pollen from plants that grew in the area over the ages.

Examining lake bottom core samples almost 15.5 feet deep, Burtchard and his crew have tracked environmental changes that might have affected human use of the area. After two major volcanic eruptions, the core samples show pollen levels dropped immediately afterwards as plants were smothered in ash.

“You can tell when there were fires and changes in vegetation,” Burtchard said.

Seeing the volcanic history unfold as archaeologists dug deeper adds to the site’s unique character.

Looking at the pit walls, one can see layers of dirt interspersed with six lighter layers, markers as if the wall were a timeline.

One near the surface is the volcanic deposit left behind when Mount St. Helens erupted about 4,200 years ago. Until three years ago, all the artifacts found at Buck Lake were above this layer.

A deeper layer was created by the eruption of ancient Mount Mazama in Oregon, the event that led to the creation of Crater Lake about 7,400 years ago.