"From one pole to the other, from the wide-open spaces of our
West to the Far East, this courtly gentleman is represented. Oddly
enough, though more geographical sites probably have been named
after him than any other man, you may never have heard of him.
This lean, erect man is Gilbert Grosvenor. He never led an army
or held political office, but giant mountains, crystal lakes, and
mighty glaciers have been named after him. Even forms of animal
life, mollusks from Greenland and a species of fish from Peru, bear
his name. The latest discovery named after him is Grosvenor Arch, A
towering mass of sandstone that rises above the floor of an almost
inaccessible valley in Utah.
Dr. Grosvenor is the leading figure and spirit behind the
National Geographic Society. For almost half a century he was
editor of the National Geographic Magazine, the best-known
publication in its field. For many decades he served as the
Society's president, and today he is chairman of the Society's
board..."
The Palm Beach Post - March 9, 1958
Rare and beautiful, Grosvenor Arch is one of nature's unequaled
masterpieces. Wind and water persistently carved away at the
landscape to reveal this magnificent double arch set high atop the
majestic cliffs.
The arch is formed at the contact of two rock formations where
the Upper Jurassic and Lower Cretaceous rocks were removed from the
area by erosion prior to deposition of the Dakota Formation.
Natural arches can form in many ways, and do not always form in all
rock and landscape types, but it is most definitely an erosional
process. The first thing that must happen is cracks or fissures in
the ground surface open up, sometimes through catastrophic
processes. Once this occurs, the openings are widened through a
variety of erosional processes (chemical
exfoliation & freeze
expansion among them). This leads to isolation of narrow walls
or fins of rock.
Over time, erosional processes work more rapidly on the layers
of rock that are softer or more easily eroded. If these layers lie
beneath harder or more erosion-resistant layers, the materials
beneath are weathered and eroded away. If this process happens for
a long enough time and the conditions are right, the narrow wall or
fin can be completely eroded through, forming a natural arch of
rock above. See the image for a graphic representation of this
process (image courtesy of the National Park Service).
This arch has not always been known by its current name - early
settlers to the area referred to it differently. The arch was
renamed in 1947 by a National Geographic Society expedition in
honor of their founder, Dr. Gilbert Grosvenor. Then and now,
adventurers find this remote wonder awe-inspiring and a true work
of natural art.
In order to log this cache, please email me with the answers to
the following questions:
- How tall would you estimate the height of the arch from the
ground (in feet or meters)?
- Estimate the ratio of the arch span to it's overall height from
the ground.
- How many big boulders are arranged in formation near the end of
the cement path?
- The arch is formed at the contact of which two rock
layers?
- What was the original name of the arch?
- How many people in your group?
Also, please submit a photo of your party holding a GPS unit at
the site.