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According to the guidebooks, Arches National Park has “the greatest density of natural stone arches in the world.” A “natural stone arch” is, essentially, a rock formation with a hole in it.
If you aren’t now wondering how the rocks got their holes, and why there are so many of them in the park, you probably won’t be able to avoid asking those questions if you visit Arches National Park. Indeed, if you take trip to southern Utah you’re likely to discover a fascination with geology you never knew you had!
So here’s the thirty-second geology lesson: Underneath the park is a bed of salt several kilometers thick, the remnant of an ancient ocean. Over time, sediment from later (but still ancient) rivers, floods, and a lake covered the salt and became rock. Since salt isn’t a very strong material, the weight of the accumulated rock made it shift, forming cracks in the rock layer. Erosion and further shifting enlarged the cracks, leaving long, narrow strips of rock called “fins.” The weathering of wind, rain, and changing seasons ate holes into the middle of some of the fins, creating arches.
The arches come in all sizes. Some are enormous, such as the
South Window (top left), with an opening 32 meters wide and 20 meters
high; and Turret Arch (top right), with an opening 12 meters wide and 20
meters high. Others are small, such as Jug Handle Arch (bottom left).
This one is a mere baby, and will eventually either grow into a large arch or
lose its “handle.” Double Arch (bottom right) is an unusual pair of
arches set at an angle to each other.
When “Arch in the Making” was originally discovered and named, it was a fin with a small opening near its top. A large piece of rock under that opening suddenly collapsed in November 1940, creating a hole 14 meters high and 21 meters wide. The new arch was renamed Skyline Arch because it’s visible on the skyline from many places in the park. The red sandstone glows with particular intensity at sunset. It’s in the “Devil’s Garden” section of the park.
Arches are rather unusual creatures in the bestiary of rock formations. They can only form in rock fins that are soft enough for weathering to create a substantial hole, but hard enough to remain stable— at least for a while— once the hole develops. Most of the fins in the park lack that elusive quality, and end up as undistinguished rock piles.
In the Courthouse Towers section of the park are large sections of fins, made
of harder rock than what once surrounded it. The Organ (left) is a
prominent formation that suggested a large pipe organ to whoever named it. In
Devil’s Garden, not far from Skylight Arch, is a collection of small fins
(right). Some of them may be future arches.
Some fins became spires and balancing rocks that seem to defy gravity.
Balanced Rock is an Arches landmark. A 17-meter-high boulder, often said to be the size of three school buses, balances precariously atop a 22-meter tapered pedestal.
The formation looks fragile, but the boulder is actually “cemented” quite firmly in place, at least for now. Eventually, however, the “neck” will erode enough so that a good wind gust or burst of rain will be enough to topple it. Or perhaps it will just spontaneously collapse. A smaller companion balanced rock formation called “Chip off the Old Block” stood next to Balanced Rock— on the pedestal in the center of the picture at right— until it collapsed in 1976.
An easy half-kilometer loop trail around Balanced Rock provides changing views at any time of day.
Balanced Rock isn’t the only precarious formation in Arches National Park.
Here are two more in the section called Park Avenue, presumably named for
the resemblance of its sandstone spires to New York skyscrapers.
Dead Horse Point is an essential side trip from Arches. This Utah state park is on a promontory surrounded by very steep cliffs overlooking the Colorado River, some 600 meters below. Cowboys once used the promontory to corral wild mustangs so they could select those that were suitable for sale. The story goes that someone forgot to open the gate to let the unsuitable ones go, so the horses died of thirst in full view of the river.
Dead Horse Point offers a spectacular aerial view of Canyonlands National Park, a “second Grand Canyon” reputedly every bit as stunning as the famous one in Arizona. Only a small section of Canyonlands has paved roads, so most of this remote park is accessible only to back-country hikers and high-clearance, 4-wheel-drive vehicles.
Other parks in southern Utah: