A Rare Geologic Site ~ Devil’s Postpile National Monument, CA

“Keep close to Nature’s heart…and break clear away, once in a while, and climb a mountain or spend a week in the woods.  Wash your spirit clean.” ~ John Muir

Horizontal to vertical columns

In early October, while “washing our spirits clean” in the Eastern Sierras we decided a visit to Devil’s Postpile National Monument was in order.  On an overcast, chilly day we headed up the mountain with friends Nina, Paul and their lovely pooch Polly to see this rare geologic site, about 40 minutes outside Mammoth Lakes.

Lovely fall colors against a tumbled stack of basalt

The lighting that day did not allow for this novice photographer to take photos that were very exciting so I quickly set them aside and decided to pass on writing a post.  Today, whether because my spirit longed to walk in the woods again or because I took the time to read a little more about this unusual basalt formation, I decided to dust off the photos and give it another go.

Some say that volcanic lava flow dating back over 100,000 years caused this basalt formation, while other dating methods set the flow as far back as 700,000 years.  Suffice to say that Devil’s Postpile has been here a long time.  The lava flowing to this site became confined within glacial debris and the thickness of the formations was so great, from 400 to 600 feet, that the lava cooled slowly, with the result being long symmetrical columns.  A subsequent glacier polished the surface on the top of the Postpile to a smooth-as-glass finish.

Glacier polished cap
Gray day at the Postpile

Devil’s Postpile columns range from 2 to 3.5 feet in diameter and many reach up to 60 feet in height. Most stand vertically but some are almost horizontal, quite an unusual sight. All the columns would be 6-sided (hexagonal) if the cooling of the lava had occurred perfectly evenly, an impossible feat it would seem.  What makes this basalt formation unique is that 60% of its columns are hexagonal, more than most, designating it one of the world’s finest examples of columnar basalt.  Sadly each year’s freezes and thaws bring down more of the outer columns.

Rainbow Falls
Nina, me, Paul, & Polly at the falls

Talks of building a hydroelectric dam at this very site threatened to collapse this unique spectacle into the San Joaquin River.  In 1911, before this fateful event could take place, an order by President William H. Taft granted Devil’s Postpile the status of National Monument.

If you venture into the Ansel Adams Wilderness near Mammoth Lakes, where the John Muir and Pacific Crest Trails merge together on the monument land, Devil’s Postpile awaits you along a 2-mile hike that eventually leads to Rainbow Falls, a 101-foot drop into the San Joaquin River, named for its many rainbows appearing where the pounding waters flow into the river.  Although no rainbows greeted us on this gray overcast day, Rainbow Falls was an added little bonus at this rare geologic site.

Strong vertical columns falling away

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