They were looking for evidence of ancient glacial episodes, which if found would support a model of the planet's early history that included oceans filling the low spots.

The latest work indicates that deposits of three glacial episodes since 150,000 to 200,000 years ago are preserved on the volcano.

The latest glacial episode destroyed much of the evidence for former ones but traces do exist.

Interestingly, another major glacial episode may have ended just a few million years before the Cambrian explosion.

The Late Ordovician is the only glacial episode that appears to have coincided with a major mass extinction of nearly 61% of marine life.

Near the shore, old raised-beach deposits can be observed throughout the region, representing changes in sea levels at about the same time as the glacial episode.

Paleo-Indian period - the first people who entered, and subsequently inhabited, the American continent during the final glacial episodes of the late Pleistocene period.

This high ground is believed to be stabilized sand dunes formed during a high sea level episode prior to the last glacial episode.

The cone has probably suffered through at least one glacial episode.

Starting 2 million years ago, a series of glacial episodes periodically caused much of the valley to become a fresh water lake.