Photos

Photographer's Note

The eruption of Mount St. Helens in Washington State on May 18, 1980, is certain to be remembered as one of the most significant geologic events in the United States of the 20th century. The explosion, on May 18, was initiated by an earthquake and rockslide involving one-half cubic mile of rock. As the summit and north slope slid off the volcano that morning, pressure was released inside the volcano - where super hot liquid water immediately flashed to steam. The northward-directed steam explosion released energy equivalent to 20 million tons of TNT, which toppled 150 square miles of forest in six minutes. In Spirit lake, north of the volcano, an enormous water wave, initiated by one-eighth cubic mile of rockslide debris, stripped trees from slopes as high as 850 feet above the pre-eruption water level. The total energy output, on May 18, was equivalent to 400 million tons of TNT - approximately 20,000 Hiroshima-size atomic bombs. 57 people died as a direct result of the blast.

The landslide generated waves on Spirit Lake stripped the forests from the slopes adjacent to the lake and created an enormous log mat, made up of millions of prone floating trunks that occupy about two square miles of the lake surface. These logs float freely as the wind blows them, and the decreasing size of the log mat indicates that the trees are gradually sinking to the lake floor. Careful observation of the floating log mat indicates that many trees float in upright position, with a root ball submerging the root end of the trunk, while the opposite end floats out of the water. Hundreds of upright floated and deposited logs have been grounded in shallow water along the shore of the lake. These trees, if buried in sediment, would appear to have been a forest which grew in place over hundreds of years, which is the standard geological interpretation for the upright petrified "forests" at Yellowstone National Park.

The gray area you see in my photo is this log mat. It isn't a great photo since it was really foggy this day but the fog moved away just long enough to get a couple of photos.

tomaszmarcinek, delaufer, alvaraalto, LCannon has marked this note useful

Photo Information
Viewed: 1522
Points: 2
Discussions
Additional Photos by Julie Wyatt (j_wyatt) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 113 W: 55 N: 131] (685)
View More Pictures
explore TREKEARTH