Thursday, 30 May 2019


Had you been swimming with the marine fossils that were laid down in the Eocene Epoch in Oregon, some 55 to 38 million years ago, you'd be treading water right up to where the Cascade Mountains are today.

The Farallon Plate took a turn north some 57 million years ago, sweeping much of western coastal Oregon along with it. The Cascades were beginning to uplift and acting as the breakwater for a retreating Pacific Ocean. By the middle Oligocene, the Cascadia Subduction Zone was in full force. The growing pressure fracturing our magma shield and causing volcanic eruptions along the Western Cascades. Lassen Peak erupted twice in fairly recent history, 1914 and 1921. Mount St. Helens has had a long history of minor eruptions but there was a massive eruption as recently as 1980.

We see a fair bit of volcanic action in Oregon right through to the Miocene. We also see lovely marine fossils from this same era. The soft ocean sediments of Oregon contain beautifully preserved gastropods, bivalves, wood, bone and cephalopods that range in age from 15 to 30 million years old.