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Weathering and Erosion
 
Quick Erosion: Flash Flood &
Avalanche
Slow erosion over long period of time
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Weathering and Erosion (e-row-shun)
In order to understand how the major landforms around Grand Junction were formed, it is very important to know how weathering and erosion work. In both processes rock and dirt are broken down by water, wind, ice, or gravity. But, with weathering the rock simply breaks apart and stays almost in the same place. The roots of plants and chemicals in the air can also cause weathering. Erosion is where rock breaks apart and is carried away by wind, water, or ice to a different place.
Weathering and erosion can take place quickly or slowly. Flash floods, avalanches, and mudslides may break down and move rock and dirt quickly. On the other hand, rivers, streams, rain, wind, glaciers (large sheets of ice), and gravity may slowly carve down the earth around them over millions of years. Whether fast or slow, weathering and erosion can form beautiful cliffs, canyons, mesas, and other landforms.
In the paragraphs below you will learn more about weathering and erosion.
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Grand Mesa and Colorado River
Top of the Grand Mesa
Edge of the Grand Mesa in the Fall
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Grand Mesa
The Grand Mesa is east of Grand Junction. It was formed by lava and erosion. A long long time ago, lava slowly oozed out of the earth into a low valley. It cooled down and turned into a hard rocky surface. Believe it or not, it was once the lowest point for many miles around. Now it is one of the highest landforms in the area.
Since the other types of rock around it like sandstone were easier to break apart than the volcanic rock, the sandstone started getting eroded away quicker by water, wind, and ice. Where ever the volcanic rock covered the ground, it was more protected from erosion. Over millions of years, the softer rocks and dirt on the sides of the mesa were washed away making the Grand Mesa that much higher than the land around it. Next time you are on the Grand Mesa, see if you can spot some of the volcanic rock.
Today, the Grand Mesa stands over 10,000 feet above sea level. It is the largest flat-top mountiain or mesa in North America. In the winter lots of snow falls on the top and sides of it. During the winter, many people snowmobile, ski, snowboard, and sled on it. During the summer, many people go hiking, camping, four wheeling, and fishing around the many lakes on top of it. The water that comes down the Grand Mesa from rain and snow is another important water source for the people that live in Grand Junction.
Click here to see more information
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Bookcliffs and Mt. Garfield
Roan Plateau
Layer of Oil Shale
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Bookcliffs and Roan Plateau
The Bookcliffs are located north of Grand Junction. They were named the Bookcliffs because at the very top part of the cliffs they look like a bunch of books all lined up in a row. The Bookcliffs go from East to West and continue way into Utah.
The Bookcliffs were formed by erosion from water wind, and gravity. In order to understand how they were formed, it is important to think about different kinds of glue. Super glue sticks things together much stronger than a paste stick. Similarly, some types of sandstone rock were formed with better "glue" or minerals, which make them tougher to break down (the top of the Bookcliffs). The sandstone formed with weaker "glue" or minerals break down easier (the lower part of the Bookcliffs). Water, wind, gravity, eroded away the bottom part faster making tall cliffs.
If you climb up to the top of the Bookcliffs you will see a large raised area of land with many hills and canyons. This is called the Roan Plateau. It is an important wild area for many animals and plants.
It also has lots of oil stuck in the rock underneath it called oil shale. With people using so much oil for cars and other things, companies want to get the oil out. However, many people are concerned about the oil companies ruining and polluting the wild environment for the animals and plants. We want the oil; but, we also want to protect the environment.
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Colorado National Monument
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Uncompahgre Plateau
Ice Weathering and Erosion
Colorado National Monument
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Colorado National Monument and
Uncompahgre Plateau (Un-com-pah-gray)
The Colorado National Monument and the Uncompahgre Plateau are south of Grand Junction. The Colorado National Monument is part of a much larger landform called the Uncompahgre Plateau. A long time ago strong forces in the crust of the Earth forced the land to lift up forming the Uncompahgre Plateau. It rises from dry desert canyons (like the Colorado National Monument) to much higher aspen and pine forests. Many different kinds of animals and plants live there.
The many canyons, cliffs, and monoliths (large towers of rock standing on their own like Independence Monument) in the Colorado National Monument were formed by the process of erosion over millions of years. Wind, rain, streams, rivers, ice, and gravity have carved out the rugged desert landscape.
Ice can put cracks in rocks and cause them to fall apart (weathering). What happens is that water soaks into the cracks in the sandstone rock and then the water freezes into ice on cold winter days and nights. When water freezes, it expands or gets larger. The ice pushes against the rock causing it to crack further and fall apart. If it ends up falling down from gravity, then it is called erosion. Click on the link How Ice Crack Rocks: Harcourt Schools to get a better visual idea of how it works.
Similar to the Bookcliffs, the different layers of sandstone in the Colorado National Monument are glued together with different minerals. The layers that are stuck together with weaker minerals erode quicker. If you look at the top of the cliffs and monoliths, you will see a layer of harder sandstone protecting the softer stone underneath it. Once the top hard layer wears away, the softer layers erode away quickly.
Look at the rock layers at the top of these cliffs on the picture to the left. Can you guess which layers are harder and softer? How do you think the hole between the rocks formed?
Click here to visit CNM's website
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Colorado River running through
Grand Junction
A canal in Grand Junction
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Colorado River
The Colorado River starts way up high in the Rocky Mountains. The rain that falls and the snow that melts from the mountains forms into streams. The streams travel down hill and connect together forming into the Colorado River. The Colorado River travels out of Colorado, through other states, and eventually heads towards the ocean in the Gulf of California. It is an important river for the southwestern United States.
Over millions of years, the Colorado River has eroded the dirt and rocks and formed the Grand Valley. It is one of the reasons why many of the rocks around Grand Junction have their unique shapes today.
The Colorado River is the main reason why many people can live in Grand Junction. During the spring, summer, and fall, some water is taken from the river by the roller dam above Palisade and put into canals. The canals go all around town providing water for fruit orchards, farms, trees, and grass. This process is called irrigation (ear-i-gay-shun). Without the water, most of Grand Junction would be dry dirt with a few desert plants on it. Also, we clean and use the water for drinking, bathing, and cooking.
Click here for more information
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Gunnison River
Black Canyon and Gunnison River
Blue Mesa Dam and Reservoir
Blue Mesa Reservoir
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Gunnison River
Similar to the Colorado River, the Gunnison River starts way up high in the Rocky Mountains. The rain that falls and the snow that melts from the mountains forms into streams. The streams travel down hill and connect together forming into the Gunnison River. The Gunnison River flows by the cities of Montrose and Delta. Finally it connects into the Colorado River in Grand Junction by the 5th Street Bridge.
As the Gunnison flows down from the mountains it goes through two major landforms, one natural and one man-made.
Black Canyon of the Gunnsion
Imagine traveling west across for miles of rolling hills with open shrublands. Then out of nowhere in front of you is a narrow 1,500 feet deep canyon stopping you from going any further west. That is the Black Canyon of the Gunnison. Over millions of years, the Gunnison River has cut a very steep and narrow canyon called the Black Canyon. Its steepest point is 2722 feet deep at Warner Point. The Black Canyon is fairly close to Montrose, Colorado. If you ever get to visit, you will be amazed by the rugged and beautiful canyon and river.
For more information click here.
Blue Mesa Reservoir (Res-er-vo-ir)
The man-made landform is the Blue Mesa Reservoir. It is located about 30 miles west of the city of Montrose and is the largest body of water (lake or reservoir) in Colorado. In 1965 people built the Blue Mesa Dam across the Gunnison River. The water backed up forming a reservoir about 20 miles long. By controlling the water that flows out of the dam, people can control against floods. The reservoir also provides lots of water for farming, for making electricity, for ranching, and for people to use in cities like Montrose. Many people go fishing, boating, tubing, camping, and hiking at the reservoir.
Click here for more information
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