Photo Gallery of
      Some of My Favorite Geological Localities in the American Southwest III

All photos by Jim Reynolds

The Jurassic Navajo Sandstone forms the high cliffs of the Zion Valley in Zion National Park, Utah. The sandstone represents a large erg (sandy desert) one of many that occupied the southwestern states during the late Paleozoic and Mesozoic eras.

Climbing 3000' above the valley floor, the East Rim Trail provides a spectacular view of the canyon cut by the Virgin River in Zion National Park, Utah. These Mesozoic rocks in Zion would stratigraphically overlie the Paleozoic strata exposed in the Grand Canyon.

The strata in Bryce Canyon National Park, Utah were deposited in the Cretaceous and Teriary periods. spanning the transition from the Mesozoic to the Cenozoic. The same strata seen in the foreground are exposed in the distant Aquarius Plateau in the background but are 2000' higher on the plateau due to uplift along a fault between the two sites. These rocks stratigraphically overlie those exposed at Zion, completing a visit through the geologic record of the western part of the Colorado Plateau.

The ornate exposures in the Claron Formation of Bryce Canyon resulted from erosion of strata that possess a high angle of repose. Even though they erode relatively easily, the remnents do not collapse after lateral support is removed.

To the northeast of Bryce Canyon, the Navajo Sandstone is once again exposed at Capitol Reef National Park, Utah. The Navajo and other Mesozoic strata re-emerge along the Waterpocket Fold--a classic Colorado Plateau monocline.

The red strata in the foreground are part of the Triassic Moenkopi Formation. These strata are also seen at the northeastern corner of the Grand Canyon near Lee's Ferry. The cliffs in the background are the Navajo Sandstone. Capitol Reef received its name because the Navajo sandstone presents such an impressive barrier. One of the peaks in the formation is reminiscent of the dome of the U.S. Capitol building in Washington, DC.

Delicate Arch in Arches National Park, Utah connotes Utah. It appears on the license plates and in numerous official and promotional documents. The arch formed in the Jurassic Entrada Sandstone. In the background are the snow-covered peaks of the La Sal Mountains--Tertiary stocks that intruded into the Mesozoic strata. The park is located outside of Moab, Utah in the east-central part of the state.

The numerous arches seen at Arches National Park resulted from upwelling of salt from the Paradox Formation. The rising salt bowed the Entrada Sandstone causing it to split along parallel lines into numerous "fins" like the one seen here. Over time, the central portions of some of these fins calved away leaving arches.

Arches are distinct from natural bridges. Gravity and weathering cause the central parts of some fins to fall away leaving an arch. Natural bridges are formed when two meanders of a stream erode through a rock wall.

Landscape Arch on the Devil's Garden Trail is the longest arch in the world. This graceful structure will probably not be around much longer (tens to hundreds of years).

The Colorado River meanders past Dead Horse Point State Park, Utah , near Moab, before entering Canyonlands National Park. The muddiness of the river is typical. In Spanish, Colorado means "reddish".

This view to the east from Dead Horse Point State Park shows two of the turquoise-colored evaporation ponds that are part of a large potash mining operation outside of Moab. Potassium is mined from the potassium salt sylvite (KCl). Colorado River water is pumped deep underground into the Paradox Formation. The water dissolves the salt and is pumped to the surface where it is left in the evaporation ponds. After all the water evaporates, the reprecipitated sylvite is collected (along with other salts). The La Sal mountains rise in the background.

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Last updated February 21, 2006