#sheep rock

[rabbitcruiser]

La Sal Mountains Viewpoint, Arches National Park (No. 3)

Humans have occupied the region since the last ice age 10,000 years ago. Fremont people and Ancestral Puebloans lived in the area until about 700 years ago. Spanish missionaries encountered Ute and Paiute tribes in the area when they first came through in 1775, but the first European-Americans to attempt settlement in the area were the Mormon Elk Mountain Mission in 1855, who soon abandoned the area. Ranchers, farmers, and prospectors later settled Moab in the neighboring Riverine Valley in the late 1870s. Word of the beauty of the surrounding rock formations spread beyond the settlement as a possible tourist destination.

The Arches area was first brought to the attention of the National Park Service by Frank A. Wadleigh, passenger traffic manager of the Denver and Rio Grande Western Railroad. Wadleigh, accompanied by railroad photographer George L. Beam, visited the area in September 1923 at the invitation of Alexander Ringhoffer, a Hungarian-born prospector living in Salt Valley. Ringhoffer had written to the railroad to interest them in the tourist potential of a scenic area he had discovered the previous year with his two sons and a son-in-law, which he called the Devils Garden (known today as the Klondike Bluffs). Wadleigh was impressed by what Ringhoffer showed him, and suggested to Park Service director Stephen T. Mather that the area be made a national monument.

The following year, additional support for the monument idea came from Laurence Gould, a University of Michigan graduate student (and future polar explorer) studying the geology of the nearby La Sal Mountains, who was shown the scenic area by local physician Dr. J. W. "Doc" Williams.

Source: Wikipedia

[johnhopkinsphotography]

Highway 402 to 19 to US 26

June 11, 2021

South of Pendleton, past Pilot Rock and Ukiah one finds Oregon 402. Head west and then Oregon 19 and you will be transiting through the heart of the John Day Fossil Beds. If you like these pictures and you find yourself visiting Oregon, consider taking the time to drive these roads. These pictures hardly do the drive much justice.

Highway 402

Highway 402 heading towards Monument

As seen from the road

Cathedral Rock--according to the sign

View from the Condon Paleontolgy Center

Sheep Rock

Burnt Branch Road, off US 26, just west of Mitchell, Oregon

Painted Hills

[the-rediscovery-corps]

Arches National Park, Moab, Utah

This place is a rock enthusiasts playground. Absolutely gorgeous examples of different formations of rock. Particularly noticeable on Balanced Rock, the base is Dewey Bridge (Carmel formation) sandstone which is water deposited, and the cap is Slick Rock (Entrada formation) which is wind deposited (eolian). But the entire park is stunning exposed Jurassic (mainly) rock.

A fun fact about Dewey Bridge sandstone, it’s very convoluted in the area. There are large waves and deformations in it. There are a few explanations for this, but my favorite is that in the late Jurassic, just after the Dewey Bridge sand had been set down, a meteor struck (forming Upheaval Dome) and the shockwaves forced the still pliable sand into the strange wavy shapes before it hardened into rock. Apparently the convolutions get worse and more drastic the closer you get to Upheaval Dome (we didn’t go there, so I can’t say for sure)

Rock formations are named in the captions.

[stillebesat]

[pisaliv08]

[rabbitcruiser]

Clouds (No. 969)

Arches National Park, UT

[rabbitcruiser]

Great Wall, Arches National Park (No. 6)

The entire region began to rise 15 million years ago, and increasing erosion caused removal of the sedimentary rocks above the Entrada Sandstone. Once at the surface, erosional forces began to act upon the sandstone layers creating the famous arches with the national park.

Today many of the rocks in Arches National Park and throughout the southwestern United States are coated by a thin red-to-black coating called desert varnish. It is found mainly in arid environments and is thought to be formed from atmospheric dust and surface runoff. The color of desert varnish depends on its chemistry. More manganese-rich desert varnish is black, while more iron-rich desert varnish is red or orange. Black streaks of desert varnish can be seen in Arches National Park after rain events as pictured below.

Arch Formation

In order for sandstone arches to form several conditions need to be met. These conditions are brittle sandstone that has been jointed due to faulting activity, a dry climate and adjacent to salt anticlines that are undergoing dissolution. The vast majority of arches in Arches National Park are within the Entrada Sandstone, including at Devils Garden and Klondike bluffs.

Source  

[rabbitcruiser]

Great Wall, Arches National Park (No. 5)

Tectonic collision increased off the western coast during the Middle Jurassic and the rock layers were warped upward. The sea came onto the continent from the north and  sandstone formations were deposited in an extensive dune field. During the Upper Jurassic Period, the sea level rose and fell multiple times, destroying the vast aolian sand seas that once covered the area. An epicontinental sea, one that is large, shallow, and extends inland upon the continental shelf, once again covered Utah during the Cretaceous Period and rising mountains in Utah stopped the inundation of marine water to the west. This shallow sea redistributed the sediments that had been deposited from river systems, and it advanced, retreated and  advanced many times during the Cretaceous depositing additional sediments. This process created many different environments including incised river valley systems, estuaries, coal swamps, lagoons, delta systems, beach and offshore marine deposits.  

Approximately 70 to 35 million years ago the Laramide Orogeny, an event in which oceanic crust slipped under the North American Plate, deformed rocks throughout Utah. The tectonic forces warped the entire geologic column in the area of Arches National Park creating anticlines and synclines. An anticline is a folded structure with an arch-like shape. In an anticline the oldest beds are at the core, while a syncline is the opposite. One way to visualize this process is to think of a rug where the ends are pushed toward one another. Folds form across the middle of the rug creating a series of U-shapes (synclines) and inverted U- shapes (anticline). When these folds were forming, cracks also formed in the sandstone deep beneath the surface. These anticlines create a favorable environment for arch formation because many of the rock layers are not lying flat.

Source