Some details of the geologic origin of the Devils Postpile are not completely clear, but enough is known to reconstruct much of the story. Until relatively recently, it was thought to have formed about one million years ago. Current studies suggest that the Postpile was formed less than 100,000 years ago when a cooling lava flow cracked into multi-sided columns. However, to fully understand the geologic setting of the Postpile we must go back millions of years to a time when there was no Sierra Nevada and California was a shallow sea.