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
||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,
|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