The Arches Of Zion National Park

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Kolob Arch
Zions National Park
Photo Courtesy NPS

Hoodoo Arch
Zions National Park
Photo Courtesy NPS

Historic Crawford Arch
Zions National Park
Photo Courtesy NPS

Hidden Arch
Zions National Park
Photo Courtesy NPS


Though another national park in Utah is famous for arches, Zion National Park has more than you might imagine.

Doubt it? Next time you visit the park, take a good look around. All the elements for arch building are readily on hand in Zion.

A natural arch is formed when deep cracks penetrate into a sandstone layer. Erosion wears away the exposed rock layers and the surface cracks expand, isolating narrow sandstone walls, or fins. Water, frost, and the release of tensions in the rock cause crumbling and flaking of the porous sandstone and eventually cut through some of the fins. The resulting holes become enlarged to arch proportions by rockfalls and weathering.

Worldwide, arches number in the tens of thousands, and probably no place is more suited for their creation than the Colorado Plateau, home of Zion National Park. The vast geology of Zion has created environments as widespread and varied as the topography of the park itself.

Hidden in its geologic grandeur are dozens, perhaps hundreds, of freestanding arches of all shapes and sizes. Although freestanding arches may be found in many different types of geologic formations, the Navajo Sandstone formation, which makes up the magnificent cliffs of Zion, provides a fertile setting for the creation of these ribbons of rock.

Among the many arches in Zion, two stand out: Crawford Arch and Kolob Arch. Crawford Arch is the most visible, clinging to the base of Bridge Mountain a thousand feet above the Zion Canyon floor. It’s frequently pointed out to casual observers by an interpretive sign located on the front patio of the Human History Museum.

The other famous arch in Zion is not so easily seen. Located deep in the backcountry of the national park’s Kolob Canyons District — it takes a seven-mile hike in to reach– Kolob Arch is hidden in a small side canyon, perched high on the canyon wall.

For most of the 20th century, many believed that Kolob was in fact the world’s largest freestanding arch, leading to years of debate and the motivation for various parties of adventurous thrill seekers to climb on and around the massive span in hopes of securing a defensible measurement.

The Natural Arch and Bridge Society long has pondered this question, and using lasers and an agreed upon definition of what should be measured says Landscape Arch is the world’s longest stone arch. But don’t be surprised if the debate continues.

The definition used by the society centers on the “maximum horizontal extent of the opening.” That opening beneath Landscape Arch measures right around 290.1 (plus or minus 0.8 feet) feet across.

The opening beneath Zion National Park’sKolob Arch, which long had been in the running for world’s largest, measures 287.4 feet (plus or minus 2 feet), according to the group.

Despite its isolated location, Kolob Arch has become a favorite backcountry destination for thousands of visitors to Zion. They discover what most arch seekers will tell you: while beauty awaits every seeker at the end of the path, the reward begins unfolding at the trailhead.

Anxious to see another arch, but not ready for a 14-mile roundtrip hike? Then head for Double Alcove ARch. A 5-mile roundtrip along the Taylor Creek Trail takes you into a narrow box canyon toward the Double Arch Alcove, where erosion has carved out natural openings in the Navajo sandstone.

For Wild About Utah and National Parks Traveler, I’m Kurt Repanshek.

Credits:
Images: Courtesy and Copyright Kurt Repanshek, www.nationalparkstraveler.com
Text:     Kurt Repanshek/, NationalParksTraveler.com.


Additional Reading:

http://www.nationalparkstraveler.com/browse/Arches%20National%20Park

http://www.nps.gov/zion/index.htm

Gypsum Dreams

Shallow briny lagoon on the
Great Salt Lake where
salt deposits are accumulating
Courtesy and Copyright David Roubik, Photographer

Gypsum deposits seen off the tour route in Lehman Caves, Great Basin National Park (Along the Western Utah/Nevada border)
Courtesy US NPS, NPS Photo

Sheetrock manufactured from Gypsum
near Sigurd, UT by US Gypsum (USG)
Courtesy USG

Gypsum sand from White Sands National Monument, New Mexico
Courtesy
Mark A. Wilson, Photographer,
Department of Geology, The College of Wooster
Public Domain
Courtesy Wikipedia

Many of us slumber nightly amid the mineral sediments of ancient oceans. The Sheetrock walls of your home are made from the marine mineral gypsum. Along with rock salt, gypsum forms as a precipitate from salty brines. In deep stagnant waters, these minerals are concentrated by settling. More commonly, evaporative precipitates accumulate beneath shallow lagoons like those of the Great Salt Lake. Long ago, under a shrinking Lake Bonneville, such evaporates produced the Bonneville Salt Flats.

Gypsum is a pale, soft mineral composed of hydrous calcium sulfate. Both gypsum and rock salt, or halite, are geologically peculiar. Pressed under the weight of overlying rock strata, they become plastic and mobile. Gypsum and halite are light compared to other rock layers and so are squeezed upward to form massive salt domes. The arches of Arches National Park were molded by an underlying gypsum salt dome that bowed the sandstone layers above.

Gypsum can be found in diverse forms. Glass Mountain in Capitol Reef National Park consists of massive translucent slabs of crystalline gypsum, called selenite. As alabaster, it is readily sculpted and carved. Gypsum sand comprises the white dunes southwest of Fillmore Utah, as well as those of White Sands Missile Range in New Mexico. Dehydrated in kilns, gypsum becomes plaster of Paris. Most gypsum is quarried, however, to make wallboard.

Near Sigurd, gypsum-bearing strata are mined and made into Sheetrock. These strata were laid down in the Jurassic when dinosaurs roamed. You can see a surface quarry of gypsum on a hillside just east of Nephi. Precipitated in briny lagoons, buried under rocks, squeezed upward into salt domes, perhaps blown about and sculpted by wind, the gypsum in your Sheetrock walls had a long and active history whose transformative stages you can witness right here in Utah.

Credits:

Images: Courtesy David Roubik
            Courtesy US NPS
            Courtesy USG, Usg.com
            Courtesy Mark A. Wilson
Text: Jim Cane, Bridgerland Audubon Society http://www.bridgerlandaudubon.org

Additional Reading:

Ralph Walter Stone. 1920. Gypsum deposits of the United States – Issues 697-701, pages 261-283, http://books.google.com/books?id=k1CsW4ux0-kC

Ege, Carl, The amazing monoliths and “mountain” of gypsum at Lower Cathedral Valley, Capitol Reef National Park, Wayne County, Utah, Utah Geological Survey http://geology.utah.gov/surveynotes
/geosights/cathedralvalley.htm

Chronic, Halka, Roadside Geology of Utah, http://www.amazon.com/Roadside-Geology-Utah-Series/dp/0878422285

The Dynamic History of Arches

The Dynamic History of Arches: Utah's Delicate Arch, Photo Courtesy and Copyright Mark Larese-Casanova
Utah’s Delicate Arch
Photo Courtesy & Copyright
Mark Larese-Casanova

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

The Dynamic History of Arches

A “bow-legged pair of petrified cowboy chaps” is how Edward Abbey once described Delicate Arch, that timeless example of Utah’s peculiar geology. In fact, it’s become such an icon that we see it on automobile license plates throughout the state. What we might not realize, though, is that there is nothing ‘timeless’ about Utah’s arches at all.

To help us understand this, let’s go back in time about 300 million years ago. At that time, inland seas routinely flowed into eastern Utah and evaporated, leaving behind a layer of salt that, in some places, is thousands of feet thick. During the next 200 million years, winds, oceans, and rivers deposited a rainbow of sediment layers in southern Utah. These sediments were eventually cemented into sandstones, limestones, and other sedimentary rocks.

Dynamic History of Arches: How nature builds an arch, Graphic Courtesy US National Parks Service
Click Graphic to
Learn How Nature Builds an Arch
Graphic Courtesy
US National Parks Service

Under the weight of all of these rock layers, along with the gradual uplift of the Colorado Plateau around 10 million years ago, the unstable salt layer below flowed like toothpaste. This caused the rock layers above to shift and buckle. Think of it as trying to build a brick house on top of a bed of mud- you would eventually have a house full of cracks.

In some areas, many parallel cracks formed at the surface, and as water flowed into these cracks, the sandstone eroded into tall vertical fins. Some of the fins collapsed over time, and some eroded in just the right way to form an arch. Arches continue to erode and will eventually collapse. But, at the same time, new arches will always form.

There are over 2,000 catalogued arches just within Arches National Park. That’s a lot of arches within such a small area! Within the park, most of the arches have formed in the red, iron-rich Entrada sandstone, however the tan Navajo sandstone also has several. Other rock formations to be seen include spires, mesas, windows, natural bridges, and balanced rocks.

To learn more about Utah’s amazing geologic history, visit Arches National Park’s website at nps.gov/arch or the Utah Geological Survey’s website at geology.utah.gov. And, make sure to visit and explore Utah’s arches as often as you can. After all, they won’t be around forever…

For Wild About Utah, I’m Mark Larese-Casanova.
Credits:

Images: Courtesy US National Parks Service

Delicate Arch, Courtesy & Copyright Mark Larese-Casanova

Text:     Mark Larese-Casanova, Utah Master Naturalist Program at Utah State University Extension.
Additional Reading:

Desert Solitaire, Edward Abbey, http://www.amazon.com/Desert-Solitaire-Edward-Abbey/dp/0671695886

Arches National Park, US National Park Service, US Department of the Interior, www.nps.gov/arch/

Utah Geological Survey, State of Utah, www.geology.utah.gov