Devils Postpile National Monument officially opened its gates for the season! The valley came alive as visitors flocked from all over globe to see one of the world’s finest examples of columnar basalt. I was lucky to have good friends from Notre Dame, Alex and Natalie, come visit me!
The hexagonal basalt columns for which the monument is named began as a lake of lava about 82,000 years ago, relatively recent in geologic time. Basalt lava flowed from a volcanic vent a few miles north of the Postpile and began pooling into a lake of lava that was an incredible 400 feet deep. As the homogenous lava cooled slowly at a constant rate the basalt began shrinking and then cracking into hexagonal columns. The cracking started at the top and bottom of the lake and on faces that were exposed to cool air. As the vertical cracks moved inward to meet each other, columns of basalt began to take shape.
Thousands of years later a glacier flowing over the valley carried away much of the basalt formation, exposing and leaving behind the 60-foot high columns we see today. If you hike to the top of Devils Postpile, you can stand on the smooth cross-section of columns that were polished as the glacier passed through. Rocks studded to the bottom of the glacier left behind parallel grooves that indicate the direction in which the glacier flowed.
In 1911 President William Howard Taft granted protected status to Devils Postpile by proclaiming the columnar basalt formation and the 800 acres around it a national monument. The area includes Rainbow Falls, a waterfall dropping 101 feet over a cliff and where visitors can see sparkling rainbows in the cool mist on a clear, sunny day. Come visit some day!