Day 6: Devil’s Postpile

A National Park Service ranger leads a walk at 11am daily to the Devils Postpile from the Ranger Station and today is the day we’re going along too.

But first, we’re moving from our lovely but sunny site next to the hikers for one under more pines and along the creek. Once we’re somewhat established, and have stashed some drinks and a watermelon in the creek, we make the 1.2 mile dash along the mostly level trail, crossing creeks, spying fish, towing the boy, and passing by the Postpile to make the 11am walk and talk.

About a dozen people join us, including a family covered in mosquito bites. They’d been backpacking with their 6 year old daughter and 10 year old son in the lakes basin and the mosquitoes sent them packing, literally. You could have quite an entertaining game of connect the dots on their poor legs!

While most of us were there to hear about the Devil’s Postpile, the Ranger took the opportunity to talk about water since most of our hike followed the banks of the Middle Fork of the San Joaquin River. While glaciation was most instrumental in the creation of this valley, the river is what provides for the amazing diversity of species found here in this small monument (under 1000 acres). For example, there are 5 more species of bats living here than in the much much larger Yosemite National Park next door to the north! The extremities in elevation also contribute as well as the location between northern and southern sierra.

But it is the Devil’s Postpile which strikes us with awe: a 60′ sheer wall of basaltic blocks looking like a vertical stack of charcoaled french fries. Some of them lean a bit down stream, but most look like their namesake–a pile of posts for someone the size of a mythical creature (and I’m not talking blogging posts either!)

This area, including the Devil’s Postpile and Rainbow Falls, originally belonged to Yosemite National Park under an act of Congress. Somehow, mining interests shook it loose into the Inyo National Forest. But when they applied to blow up the Postpile to make a dam and hydroelectric power, conservationists like John Muir were able to get President Taft to name the area a Monument in 1911 and ensure suitable protection. Since 1984, the Monument and surrounding roadless areas have been protected by Congress as the Ansel Adams wilderness.

Devil’s Postpile (the geologic feature as opposed to the cultural one) was formed 100,000 years or so ago when lava erupted from two miles upstream and was stopped in its flow by a glacial morraine. More recently (12,000-20,000 years ago), another glacier moved down valley and scraped away at them, removing the basaltic pillars and polishing the tops of them so they now look like polished hexagonal floor tiles with parallel striations. Someone actually counted the tops of all the piles found here and discovered that 55% of them are hexagonal (one is 3 sided and the rest are 4, 5, 7, 8 or 9).

Ranger Eric was genial and generous with the children, and the hour with him was well spent. He even made some fishing suggestions: off-duty rangers caught their limit the other day at the picnic area by the river here so off we go!