Welcome to our Earthcache at Cedar Breaks National Monument. Before you try to visit Cedar Breaks check the website if it's open. Due to high elevation (10300 ft) the opening season is really short.
This EarthCache is set on a ViewPoint in the near of the Cedar Breaks Scenic Drive (Highway 148).
During the Cretaceous period, 144-65 million years ago, the North American continent was slowly drifting towards the southwest, driven by the spreading of the ocean floor. A shallow arm of the sea stretched across most of what is now Texas, Oklahoma, Kansas, Nebraska, North and South Dakota, Colorado, Utah, Arizona and New Mexico. About 105 million years ago, the plates of earth’s crust changed direction and speed. As the heavy Pacific plate plunged under the lighter continental plate at a more rapid rate, it compressed the western margin of the continent. Massive sections of the earth’s crust slowly moved eastward along low-angle “thrust faults.” This period of faulting, known as the Sevier Orogeny, formed a chain of mountains to the west of what is now Cedar Breaks.
The Laramide Orogeny lasted 40 million years, causing the Cretaceous seabed to lift and drain, and leaving the Rocky Mountains and such features as the San Raphael Swell, the Waterpocket Fold of Capitol Reef, and the Monument Upwarp in its wake. The only traces of the Cretaceous seaway that remain in the area today are the marine sandstones and shales of the Straight Cliffs Formation found in the canyon below Cedar Breaks.
Deposition
Deposition at Cedar Breaks started about 60 million years ago. The plateau that Cedar Breaks is currently located on was much lower than it is today. During this time, the area was completely covered by a lake. This lake became known as Lake Claron. The lake was 70 miles wide and 250 miles long.
Starting about 60 million years ago, streams flowing from the surrounding highlands washed sand, silt and mud into the basin. Algae living in the lake incorporated calcium carbonate (CaCO2) into their body structures. When they died, their remains left thick deposits of carbonate mud on the lake bottom. Freshwater snails fed in the muddy ooze. Periodically, the lake would dry up, leaving a level plain where soils formed, plants grew, and insects such as ants and wasps burrowed into the dry sediments. Streams ran across the basin, leaving lens-shaped sand and gravel deposits. Then the lake would fill with water and deposition would begin again, adding more layers of sediments.
Deposition continued for 20 to 25 million years, gradually filling up the basin as the surrounding highlands wore down. Trace amounts of iron derived from the source rocks combined with oxygen and water, “ rusting” the sediments into warm red, orange, and yellow hues. Oxidized manganese stained some sediments purple. These sediments eventually hardened, becoming the siltstones, sandstones, and limestones of the Claron Formation.
About 30 million years ago, volcanoes erupted first to the west and then to the north of Cedar Breaks, spewing ash into the atmosphere. Some of this ash settled into the dwindling basin left by the Claron lake. The rocks of the Brian Head Formation are distinguished from the Claron Formation by their volcanic ash content.
Further volcanic eruptions sent hot ash flows racing across the landscape; the ash welded together and then cooled to become the Isom Formation.
Uplift
On the rim of Cedar Breaks you stand at the western edge of the Colorado Plateau geologic province. Farther west you can see the flat valleys and the sharp north-south running mountain ranges that characterize the Basin and Range province.
Between Cedar Breaks and the valley below, the Hurricane Fault divides the two provinces. Although movement has occurred along the Hurricane Fault for as long as 30 million years, the most dramatic episode of
movement began 10 million years ago. This period of faulting caused a massive block of the earth’s crust to drop to the west, forming the level valley far below. It also raised the Markagunt Plateau to its present altitude and exposed the edge of the Claron Formation to the elements. The tension that resulted from this movement caused the rock to crack; these cracks are known as joints.
Erosion
Ever since the rocks were uplifted, they became exposed to the various erosion elements. There are three types of erosion apparent at Cedar Breaks: chemical, water, and wind erosion.
Chemical: When it rains or snows, it combines with carbon dioxide in the atmosphere to form a weak carbonic acid. Although the acid is weak, it reacts with the limestone, dissolving the rock creating shallow caves, cracks, and fissures.
Water: At Cedar Breaks, there are two forms of water erosion: running water and frost-wedging. Running water is caused by the rain and snow. At Cedar Breaks it snows about 15 feet during the winter and rains almost every day in July. These run down the amphitheater carrying away loose sediments and rock down into the valley at the bottom. Frost-wedging is the more interesting type of erosion at Cedar Breaks. Out of the year, Cedar Breaks gets about 250 days worth of freezing temperatures. The water gets in the cracks during the day, freezes at night and expands. This expanding process eventually causes the rock to break away from the main bedrock. Eventually erosion wears through the sides of the fins leaving isolated pillars or “hoodoos.” Undercutting of cliffs and fins forms shallow caves and arches.
Wind: On a very windy day, loose sediments can be carried away with the wind and deposited in a new location elsewhere.
All of these erosion elements create the various features one can see looking down into the amphitheater. All the hoodoos, arches, fins, and shallow caves are created from these various forms of erosion.
Visit the Viewpoint of the EarthCache-Location. From this point you have a fantastic view about the amphitheater that spans some three miles, and is more than 2,000 feet deep.
Going to the viewpoint your way is bordered by a small stone wall. What stone type could this be? Why do you think so?
Look into the amphittheater. There you can see a thick layer of a light colored stone. Which type is this?
Feel free to take a picture of you at the location. We would be pleased if you upload a picture to your log. Please pay attention not showing the solutions on a picture.