I have always loved visiting this part of the country. The canyons
and arches offer a multitude of scenic picture options. Everything
you see has been provided by water and is continuing to be changed
by water.
It is apparent to most people that the Colorado River in the
valley below created the canyon in front of you, but water has
played a much greater role in all that you can see. The rock
formations you see around you are here as a result of water.
From 320 Million Years Ago (MYA) until 285 MYA this area was
under sea level. Thick layers of limestone, sandstone, siltstone,
and shale were deposited in shallow marine waters. Many layers of
sediment were deposited which formed the foundation for this area.
Water was obviously a large factor in creating these layers.
Between 285 and 245 MYA the Ancestral Rocky Mountains eroded and
completely covered the Moab area. The area became a region of dunes
very near the ocean. At this time sandstone was deposited in the
area forming many of the sandstone formations you see. Water was
the primary force in the erosion which brought the material, used
to create the sandstone formations, to this area.
Next, from 245 MYA to 205 MYA the oceans washed in and out over
the area which existed primarily as mud flats. This action created
more layers of rock in the area.
During the Jurassic Perios (205-140 MYA) The southern area of
Utah was covered by deep sand dunes which formed the Navajo
sandstone. This is the rock you are standing on. Above this layer,
the Entrada sandstone was formed. This layer is the one in which
the arches of Arches National Park were formed.
More recently, 65 MYA, the western continent was uplifted
creating the Colorado Plateau. This uplift gave the rivers much
more energy causing them to begin cutting the canyons in this part
of the country. One of the most well-known rivers lies not far
below you.
After the uplift event much of the rock was fractured and a large
fault system was created. The Moab valley sits between two faults.
The evidence of the faults is readily visible and very interesting
to study from the entrance area of Arches National Park. The
fracturing caused by the uplift can be seen across the valley in
the Behind the Rocks Wilderness Area. If you examine this area you
can see where the fracturing has occurred. After the rock was
fractured, water wore down the rock along the fractures. This is
evident by the fins present in the wilderness area.
Water has had a significant impact on what you see before you.
This started long before man was around to see the effects and will
continue long after man has left. The people at Arches National
Park have put together an excellent film about the area which you
can view
here.
To claim a find on this cache answer the following questions
about this location.
1. Determine what type of weathering you believe formed this arch?
(Search for weathering)
2. Estimate the height and width of the arch opening. (Arch
location is N38 33.810 W109 35.132. Use this information to
determine your distance to the arch in estimating the size of the
arch.)