Favorite thing: Arches National Park lies atop an underground salt bed that is basically responsible for the arches, spires, sandstone fins and eroded monoliths found in the Park. Thousands of feet thick in places, this salt bed was deposited across the Colorado Plateau 300 million years ago when a sea actually flowed into the region and eventually evaporated. Over millions of years, residue from floods, winds and the oceans that came and went, blanketed the salt bed. The debris was compressed as rock, at one time possibly a mile thick.
Salt under pressure is unstable and the salt bed lying below Arches was no match for the weight of this thick cover of rock. The salt layer shifted, buckled, liquefied and repositioned itself, thrusting the rock layers upward as domes and whole sections fell into the cavities.
Faults deep in the Earth made the surface even more unstable. You can see the result of one 2,500 foot displacement, THE MOAB FAULT, from the visitor center.
Fault-caused vertical cracks later contributed to the development of Arches. As the salt's subsurface shifting shaped the Earth, surface erosion stripped off younger rock layers. Except for isolated remnants, today's major formations are salmon-colored Entrada Sandstone and buff-colored Navajo Sandstone.
Over time, water seeped into cracks, joints and folds. Ice formed in the fissures, expanding and putting pressure on the rock, breaking off bits and pieces. Wind later cleaned out the loose particles, leaving a series of free-standing fins. Wind and water then attacked these fins until the cementing material in some gave way and chunks of rock tumbled out. Many of these damaged fins collapsed. Others survived despite missing sections. These became the famous Arches.
Updated Dec 6, 2009
Favorite thing: The main question surrounding the collapse of an Arch is WHY?
Erosion and gravity reign supreme over sandstone. For countless eons, rain, ice and groundwater slowly but relentlessly eat away at the natural calcium "cement" holding the Arch's sand grains together. Eventually there isn't enough of the cement left to withstand the forces of gravity and so the entire structure finally comes crashing down, as in the case of Wall Arch, when the remains of the ancient arch were found on the Devil's Garden Hiking Trail on August 5, 2008. Perhaps nature wedged off one piece of rock too many. This was the first major span to fall in 17 years. Wall Arch was 71 feet tall and 33 1/3 feet wide and was ranked 12th largest in size.
Updated Oct 20, 2009
Favorite thing: The last section of Arches is DEVILS GARDEN. Here you will find a varied area of Arches (eight all together) , Fins, Canyons and Slickrock. The Park's Campground is also located here.
Devils Garden Trailhead starts off gravelled, flat and easy. Hans and I did a bit of this trail, until it started to descend into the canyon and besides it was getting near the end of the afternoon.
One of the first arches you come to are Pine Tree, Tunnel Arch and Landscape Arch, the destination for most walkers. The huge 89 meter span is a little more than one meter thick at its narrowest point and has numerous fractures, making it prone to collapse one day.
Beyond this, the trail is rougher though more interesting and have many more arches including Navajo Arch, Partition Arch, Double O Arch, Dark Angel and Private Arch along the Primitive Trail.
Updated Oct 21, 2009
Favorite thing: One of the many interesting Plaques in the Park, explained about the ANCIENT SAND DUNES. I found it fascinating and it read as follows:
"This vast area was once covered by extensive Sand Dunes. Some 200 million years ago, winds from the Northwest carried tons of fine-grained sand into the area, creating an immense desert.
Over time, the sand drifts were covered by other layers of sediment, compressed and cemented by quartz and calcite into Navajo sandstone. erosion has since washed away the overlying layers, exposing the "Petrified" dunes.
Written Oct 21, 2009
Favorite thing: One of the more impressive Arches in the Park, DOUBLE ARCH is a closely set pair of natural arches that share the same stone foundation. The Arches, which is located in the Windows Section, are reached by a short walk from the parking lot. Its massive size does not become apparent until you walk right up to it. Visitors can explore directly beneath and through the Arches.
Double Arch was formed differently than most of the others. It is known as a POTHOLE Arch as it was formed by water erosion from above rather than more typical erosion from the side.
It was one of my favourite Arches and it was easy to get to, even for me.
Updated Oct 21, 2009
Favorite thing: One of the prettiest and easily accessible arches is TURRET ARCH in the Windows Section of the Park. Hans and I parked the Van in the large parking area and then proceeded to walk up the steps to the Arch. Lots of delicate shrubbery, so please stay on the designated trail. Lots of photo opportunities, especially shooting through one of the dead juniper trees to frame your picture. Do watch your step though, as the loose gravel is slippery. I just about fell, when I lost my footing.
This is one of the more popular Arches, because it is so accessible and not a far walk. Lots of families with children were making their way up to the Arch.
Written Oct 22, 2009
Favorite thing: There is a surprising variety of VEGETATION IN ARCHES. Pinon and Utah Juniper trees provide a splash of green, in contrast to the red surroundings. Cacti and yuccas thrive throughout the Park. Other plants such as wildflowers, grasses and mosses come to life from April to July, with the right conditions.
Written Oct 20, 2009
Favorite thing: Located in the Devils Garden Section of Arches, SKYLINE ARCH has a span of 69 feet and is 45 feet high, making it one of the most impressive of the arches.
It is an easy hike to the Arch and is popular with families as it is a great place to experience an Arch up close. I would also imagine it would be a wonderful spot for photographing a sunset photo.
Written Oct 21, 2009
Favorite thing: Like many of the sights in Utah, Arches National Park owes its existence to the work on nature on rock, in this case the sandstone of the Entrada Formation. Water (in the form of ice and rain) and wind have eroded the sandstone into these amazing formations over millions of years. The park today contains the world's largest concentration of natural stone arches – there are over 2,000 catalogued arches, which range in size from a three-foot opening (the minimum considered to be an arch), to Landscape Arch which measures 306 feet from base to base. To be considered an arch there must be a clear hole in the rock, at least three feet across and completely formed by natural forces. The hole has to have been caused by the selective removal of rock by any natural force (whereas in the case of a natural bridge, such as Rainbow Bridge near Lake Powell, it has to have been caused by flowing water).
The Entrada Formation sits on a large salt bed, deposited here 300 million years ago by a long-since dried-up ocean. Over time the salt bed liquefied under pressure from the layers of rocks above it, shifted and tilted those some rocks. The rocks fractured, forming long, parallel cracks, covering many square miles of rock. Over time, water seeped into the cracks and ice formed in the fissures, expanding and cracking the surrounding rock, breaking off bits and pieces. A series of free-standing fins remained, which were attacked by wind and water until, in some, softer rocks gave way and chunks tumbled out. This caused many to collapse, but others, with the right degree of hardness and balance, survived despite their missing sections to become the famous arches.
And of course, just as the arches have formed slowly over time, so time continues to pass and the arches to erode. Since 1970, forty-three arches have toppled because of further erosion. You can read about the collapse of Wall Arch in 2008 on the National Park Service website, from where (with permission) I borrowed these two “before and after” photos.
Updated Mar 26, 2010
Favorite thing: The entrance fee to get into Arches National Park is ten dollars per vehicle payable at the entrance station about a quarter mile from the highway on the main park road. In December of 2003 the main pay station was being reconstructed and all traffic was diverted to the visitors center where payment could be made inside. Several park passes are also available - a Southwest Utah Annual Park pass is available for 25 dollars. A National Park pass is 50 dollars and gets you into any National Park or Monument for one year at no additional cost (camping and tours excluded).
Written Dec 26, 2003
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