Devil's Postpile, a spectacular example of columnar basalt. Once molten and under great pressure underground, the lava that makes up Devil's Postpile cooled evenly and slowly, contracting and fracturing into polygonal-sided columns. The age of the formation is estimated between 100 and 700 thousand years old. Sometime after the basalt columns formed, a glacier passed over the formation, cutting and polishing the tops of the columns. The columns have from three to seven sides, varying because of differences in how quickly portions of the lava cooled.
Location: Devils Postpile National Monument
Image ID: 23266