Mount Mazama (known today as Crater Lake National Park, Oregon) erupted violently 7,700 years ago leaving an impressive crater where the mountain once stood. A blanket of volcanic ash from the eruption was deposited downwind - a well-known time marker for geologists throughout the Pacific Northwest.

This 3-minute video - Mazama Ash - features a site where the famous ash is exposed in Johnson Canyon, right next to heavily-traveled Interstate 90 in central Washington. No other ash bed - including the 1980 Mt St Helens ash layer - rivals the Mazama for regional thickness. The Mazama is found through the Northwest, including under the waves of the Pacific Ocean. The 7,700 year-old ash layer has been consistently found in submarine canyons beneath 13 underwater landslide deposits created by 13 great earthquakes since the Mazama eruption.

Tom Foster (http://HUGEfloods.com) and Nick Zentner (Central Washington University) have been hiking together in eastern Washington for years. ‘Mazama Ash’ is part of an "I-90 Rocks” geology video series.