We arrived a few days early for a backpacking trip in the Sierra’s so we could see Devils Postpile.
Approximately 100,000 years ago a lave flow created the columns. Estimates of the formations thickness range from 400 to 600 feet. The exposed part we see now was at the bottom of the mass. Due to the large mass of material the lava cooled slowly resulting in the columns we see today.
The grooves were caused by a glacier that polished the surfce.
HAPPY TRAILS, STEVE