Ancient Geology Meets Modern Geology

September 12, 2009

20090912 - Ancient Geology Meets Modern Geology

Photographer: Rebecca Roush
Summary Author: Rebecca Roush

Roughly five million years ago, lava flows covered what is now central and eastern Washington State. Were it not for the catastrophic ice-age floods of 10-15,000 years ago, much of the results of the lava flows would remain hidden. The floods removed the areas topsoil, exposing harder surfaces below. The channeled scablands are a dramatic example of this, clearly showing where the water was forced to flow, due to the unmovable lava. The Potholes of central Washington are locations where water continues to pool, either naturally or as a result of damming. They are often combined with sand dunes. This photograph was taken while hiking through the potholes area, up and down the dunes.

On May 18, 1980, Mount St. Helens erupted. During the early hours of the eruption, much of what was forced out of the volcano was broken rocks and rubble. As the hours passed, this turned to molten magma that turned into ash, blanketing this part of the state with a layer of gray ash. This photograph shows that ash is clearly still part of this environment which has been so dramatically shaped by natural catastrophe. Mount St. Helens' eruption was fairly benign in geologic terms, though for those that witnessed it, or remembered its happening, it may well be the most significant geologic event of a lifetime. Image Date: August 27, 2009.