I remember well a day 2 years ago when we visited Arches National Park in Utah. It was an extraordinary day. It was one of those travel days that I will never forget. It was not a long day. Sadly, our visit was all too brief.
The Geology of Arches National Parkis as fascinating as the arches. It is history told in the language of stone and rock. The story of the area now contained with Arches National Park (“Arches”) began approximately 65 million years ago. At that time this area was a most improbable sight for what we see today. At that time it was a dry seabed that spread from one horizon to the other. For example, if you stood in Devils Garden 65 million years (‘mya’) ago the red rock features that make up this fantastic landscape would not have been visible at all. Everything would have been buried thousands of feet below the surface. Like the marble that lay in front of Michelangelo, all would have been uncarved raw material.
65 mya geological forces started to work on this rough landscape. The first geological step was for geological forces to wrinkle and fold the buried sandstone. This process has been compared to a person with a giant rug gathering the two edges toward each other. Such a process would make lumps across the middle. Geologists call these lumps Anticlines. As the sandstone warped, fractures tore through it establishing the patterns for rock sculptures of the future.
The great uplift of the Colorado Plateau occurred about 200 million years after that some 40 million years ago. The entire region began to rise thousands of feet above sea level. That happened for much of the American Southwest. As the Colorado Plateau rose up, layers of sedimentary rock were presereved in tact. Now, as a result, scientists can read those rocks like a geological book. The Grand Canyon is one of the places where this geological book is most readable. The entire region, though particularly the Grand Canyon of course, is famous for its multicolored layer cake geology where each layer tells a distinctive story about a particular historical epoch that began in the Precambrian nearly 2 billion years ago and ended 570 million years ago.
Our first stop in the park was near to Park Avenue. There is a short trail that is referred to as Park Avenue because of the many rocks that resemble city skyscrapers. We also saw some rocks that appeared to be balancing on pillars. These were starkly unlike. We did not walk far down the trail as we had little time for hiking. That was a shame. Next time I hope we have more time. Nearby I also stopped for some photos of the wonderful snowcapped La Sal Mountains to the east
We next drove around the trail and stopped at the rock that is referred to as Courthouse Towersbecause it does look like a classic American courthouse. These reminded me of some of the rock formations I had seen a few years ago in Monument Valley, still my favorite place in the American Southwest. Of course, I was compelled to take some more shots with my camera.
Of course, nothing ever stays the same in geological terms. What was lifted up fell subject to the forces of erosion over long periods of time. Specifically, the forces of erosion carved layer after layer of rock away from the surface. One it was exposed, the deeply buried sandstone layers rebounded and expanded, like a sponge expands after it is squeezed. Of course this process takes a very long time. This created even more fractures in the rock and that permitted water to seep into the rock and break it down even further.
It seems odd because this region is so dry, but today water is the force that shapes the environment here more than any other force. Rain erodes rock and carries sediment down and washes that sediment down washes and canyons into the Colorado River. In winter snowmelt pools in fractures and other cavities and often it freezes and then it expands as all water does when it freezes. This breaks off chunks of sandstone. Small recesses develop and grow bigger with each storm. Little by little over thousands of years, this process turns fractured rock layers into fins and in time, fins turn into arches.
Over very long periods of time the forces that created these arches will continue to widen them to such an extent that they become unstable and collapse. That happened just a few years ago. In 2008, Wall Arch collapsed reminding us that these rock forms are not permanent. Noting is permanent, except change. Someday Delicate Arch will collapse too. Of course most of these arches will remain much longer than I will. After all this landscape took 65 million years to be sculpted. It really is an improbable landscape.
Like a fingerprint, every arch in the park is unique. Each arch tells its own distinct story of rock, water, erosion, time and change. Yet there are some interesting categories of arches. The free-standing arch is the most obvious type of arch. It stands alone, independent of other rock walls or fins. It seems to stand proud spanning an opening. Some arches of this kind have been called Windows. Often they frame a scenic view. Of course, in Arches,everyopening frames a scenic sight. It is entirely unavoidable. The most popular arches in the park, such as Delicate Arch belong in this category of arches.
Chris and I both saw Delicate Archfrom the lower viewpoint area. She stayed behind while I walked to the Upper Arch viewpoint, but I did not walk all the way up to the Arch. It would have taken me about 45 minutes to walk up to it but I felt we did not have enough time. This is the most famous of the park’s arches.
More than 2,000 arches have been identified in the park. That is an astounding number. Arches National Park has the densest concentrations of natural stone arches in the world ranging in size from sliver thin cracks to spans of more than 300 feet.
The rock layers that are frequently visible in the park today, were once buried by over a mile of other rock. This overlying rock first had to erode to expose the sandstone beneath, for arches to have formed. Arches National Park is a wonder of nature. It truly is. I am convinced there can’t be anything like it anywhere else in the world. Wall Arch, the 12thlargest arch in the park, completely collapsed overnight in August 2008. Wall Arch fell on August 4, 2008 while people were sleeping at Devil’s Garden Campground not far away. Many reporting hearing the sound of thunder, but the skies overhead were clear. Yet thousands of tons of sandstone came crashing to the ground. The sound was deafening.
For most of the history of what we now call Arches National Park there were no red rocks here at all. Salty inland seas, braided river systems, coastal plains, and sand dunes were what we would have found during most of the history of this park. Geologists know this because they are smart and they know what to look for. The clues are there for the discerning eye to see and interpret. Geologists interpret clues such as fossils, ripple marks and cross bedding to understand the history of each geological layer to compose their picture of what happened here.
It is worth remembering that every arch, spire or other rock shape for that matter is a remnant of ancient massive layers of rock that once covered the entire region. Over time the layers of rock bulged, cracked, and then began to erode. Of course, over time every arch will collapse and crumble. That is entirely inevitable. Although every arch will fall, collapses are actual rare occurrences. I was surprised to learn that there is no good way to predict when an arch will be pulled to its grave by the irresistible force of gravity.
On our too brief drive through the park, we stopped at Balanced Rock with the La Sal Mountains in the background. This was an improbably and acutely precarious balanced boulder sitting on top of a sandstone spire. Together with the arches this is one of the signature rock formations of the park. It looks like it is ready to fall off at the next summer breeze. It has been estimated to weight 3,577 tons, the weight of an ice-breaker ship or 27 blue whales.
We had spent about 4 hours in the park and travelled right to the end of the self-guide tour. Not nearly enough time, yet this concluded one of my best days sight seeing ever! This was right up there with my experiences at Monument Valley, Yellowstone National Park, Sedona, Canyon de Chelly, Plitvice Lakes Croatia, Saguaro National Park, Churchill, and a few others. My camera shutter got hot from over use. I used the word “Wow” far too often to count. If I had shot film images at the rate I shot digital images, I would have had to declare personal bankruptcy. Thank goodness digital “film” is “free.” Long live digital photography.
I still have one of Utah’s 5 National Parks to see–Canyonlands. Next year I hope to see it.