Devil's Postpile
Devil's Postpile, an example of columnar jointing in basalt. These unusual, symmetrical columns were formed by joints that developed when a river of molten lava contracted as it cooled slowly and evenly. The flow occurred nearly 100,000 years ago. The formation was exposed through erosion by glaciers and San Joaquin River. Devil's Postpile National Monument. Madera Co., Calif.
Devil's Postpile
Devil's Postpile, an example of columnar jointing in basalt. These unusual, symmetrical columns were formed by joints that developed when a river of molten lava contracted as it cooled slowly and evenly. The flow occurred nearly 100,000 years ago. The formation was exposed through erosion by glaciers and San Joaquin River. Devil's Postpile National Monument. Madera Co., Calif.