[Fig. 42(6)] The Devils Postpile offers visitors an outdoor classroom in volcanic history of the Sierra Nevada. The Postpile basalt has been studied and analyzed for many years by many people because it is such a spectacular sight. Hundreds of individual, vertical basalt columns came together as a single formation. They look as though someone purposely tried to create a bizarre backdrop for a horror movie.
Around the Postpile, visitors can find waterfalls, dense forest, and many other volcanic formations. The 100,000 people who come to this area each year are usually headed for the Postpile to see one of the famous columns.
The columns have an average diameter of about 24 inches and some are as long as 60 feet. They are the remains of a lava flow that probably occurred about 100,000 years ago. For many years, the Postpile was mistakenly dated at 600,000 years old. More recent methods of dating the rock indicate it is much younger.
Though the Postpile began as a molten mass, it shrank as it cooled, and it began to crack. Temperatures inside the lava bed were consistent enough to allow the cooling basalt to form six-sided columns. The Postpile's regularity of shape is probably its most remarkable feature. Temperatures are rarely consistent enough to form the columns seen at the Postpile.
The Postpile is a remnant of a much larger flow. It was perhaps 400 feet deep, emanating from the glaciated valley of the San Joaquin River's Middle Fork. The basalt lava probably filled the valley for about 3 miles, though no one knows for sure. Later glaciers pulverized most of the lava formations and stream erosion carried away other parts of it. There are indications that the smallest of the ice flows was 1,000 feet thick.
In the 10,000 to 12,000 years that have passed since the last glacier, columns have fallen from the formation, creating a heap of broken rock at the base of the Postpile. On top of the formation, visitors will see how the glaciers polished the rock. The top of the Postpile is probably the most spectacular angle for visitors to see.
This striking feature was hardly mentioned in the literature of the late nineteenth century. Little is known about the Postpile before the turn of the century. Miners were active in the area. Red-bearded "Red" Sotcher settled into nearby Reds Meadow in the late 1870s, but history does not connect him with the Postpile.
The feature was known locally in the 1890s as the Devils Woodpile. It was first recognized as the Devils Postpile in 1901 on various maps. The Postpile was part of Yosemite National Park in the late 1800s when Congress designated its boundaries. It was removed from the park in 1905 when Congress removed 500 square miles from the park under pressure from mining and lumber lobbying interests.
By 1910, a proposal was made to dynamite the Postpile and use it dam the San Joaquin River. Members of the Sierra Club and University of California professor Joseph LeConte, who was also a mountaineer, successfully campaigned against the project. On July 6, 1911, President William Howard Taft proclaimed the area a national monument and extended full protection of the federal government.
The typical Eastern Sierra forest greets hikers as they make their way to the Postpile—red fir (Abies magnifica), Jeffrey pine (Pinus jeffreyi), and lodgepole pine (Pinus murrayana). The slender cinquefoil (Potentilla gracilis ssp. nuttalii) is particularly noticeable in this area, along with alpine shooting star (Dodecatheon alpinum) in August. For bird watchers, look for the dark-eyed junco (Junco oreganus) and the white-crowned sparrow (Zonotrichia leucophrys) in the summer months.
Management of the monument can be a bit confusing. It is almost completely surrounded by the Inyo National Forest, yet Inyo officials have nothing to do with the management. Inyo officials can answer any of your questions, but Sequoia National Park on the western slope of the Sierra manages the monument.
To approach the Postpile, visitors need to enter from Inyo National Forest to the east. In the short hike, visitors pass from the arid Eastern Sierra to the lusher western slope. Besides the imposing and irregular outcroppings of granite along the way, the geology includes pumice and some basalt.
[Fig. 42(7)] People stand at Rainbow Falls in summer around the noon hour and just watch the rainbows forming in the constant mist. The San Joaquin River plunges 101 feet down Rainbow Falls in a thundering crescendo all through the summer. There is no shortage of water and, most days, there is no shortage of people. Don't expect to get away from the crowds here.
The hike to the falls from the Devils Postpile takes visitors through the shade of white fir (Abies concolor). Depending on the time of year, the wildflowers can be dazzling in the moist meadows. Look for the broad-seeded rockcress (Arabis platysperma) in the rock crannies. The cutleaf daisy (Erigeron compositus) and the shaggy hawkweed (Hieracium horridum) are also seen in this area.
There's a bonus when you hike into the falls: You'll be going downhill. However, remind the children that they will be gaining about 300 feet in elevation on the way back. Bring the camera and a sandwich, but don't get too close to the falls or the slippery rocks around them.
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