Pillow Basalt, Lopez Island, Washington.

Pillow basalt, named because individual blocks resemble pillows, form underwater. Along the west coast of North America, there are many exposures of pillow basalt, because they formed in a marine environment and were subsequently accreted to the continent.

On to the next slide: Aerial view of Mt. Rainier , Washington
Back to the last slide: Photomicrograph of basalt

Back to photos of volcanic rocks and features
Back to Geology photos