The Hole in the Ground: The Science behind the Beauty

Located in Eastern Washington, a part of the Channeled Scablands, lies an interesting land feature with even a more interesting story. Carved out by the Missoula Floods, the Hole in the Ground is a place that has fascinating geologic attributes and scenic views.

15,000 years ago at the end of the last age, Glacial Lake Missoula’s dam failed causing a series of 40 to 90 floods (Allen et al., 2009). The massive amounts of water and debris created what is known as The Hole in the Ground. The repetitive process of the floods created high, steep walls, or coulees. A coulee develops when mass amounts of water and debris flow over a cliff, creating a plunge pool (Bretz, 1956). The water crashing over the cliff is similar to that of a waterfall. Over the course of several floods this process of erosion causes the waterfall to recede, forming a recessional cataract, or coulee (Bretz, 1956).

The steep walls of the Hole in the Ground have interesting markings. These markings look as though something had clawed the massive walls of basaltic rock. How did these particular markings get there? The answer lies in the formation of columnar basalts. Prior to the Missoula Floods columnar basalts were formed through a series of 300 plus effusive volcanic eruptions (Allen et al., 2009). The columns on the walls of the coulee are considered columnade, as they are well defined in their shape (Long and Wood, 1986) The shape of the columns are created in the way the lava cools. When lava cools, it contracts. The contracting of lava in turn causes fractures or cracks (Mervine, 2012). Typically the fractures create a hexagonal shape (Mervine, 2012). The arrangement of these columnade basalts can be thought of as a honeycomb from a beehive.

Through geological processes columnar basalts and coulees formed, making the Hole in the Ground a massive landmark with incredible views. Even more fascinating is to take a look back in time at the series of floods that are responsible for the landforms widely viewed today. The Missoula Floods will forever be remembered as the event that shaped Eastern Washington and its unique land features.

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