Erratic Erosion EarthCache
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In order to count this Earthcache as a find, you must complete the following tasks and email the answer to me.
1. What type of weathering is taking place in this area, chemical or physical?
2. What two things are causing the erosion of the Big Sioux’s banks?
3. Where is the eroded material going?
4. What can be done in order to reduce the amount of erosion?
This Earthcache is located at the local disc golf course. The Big Sioux River flows directly through the park. The bike trail runs on the west side of the park, and the zoo borders the park to the west as well. Also located nearby is a kiddie pond for fishing. Enjoy!
Erosion is the process by which the surface of the Earth gets worn down. Natural elements, such as wind and glacial ice, can both cause erosion. Water is one of nature’s most powerful elements and the most common agent of erosion, simply because there is so much of it on the Earth’s surface. Given enough time, even the greatest works of man will be washed away. The Grand Canyon is one of the best examples of water erosion.
Erosion is happening all around us. Even though you may not recognize it, the forces of erosion are constantly at work shaping our planet. Sometimes, as in a mudslide or avalanche, erosion happens quickly. More often than not, erosion happens so slowly that you can’t even see it. Over time, the simple act of water running downhill can not only carve out a hole the side of the Grand Canyon, but it can literally move mountains. Although erosion is a natural process, it has be increased dramatically by human land use, such as industrial agriculture, deforestation, and the growth of cities.
Before water and wind can carry material away, the sediments, soil, and rocks first need to be broken down through a geological process called weathering. As its name suggests, weathering is controlled by elements things like wind and rain, and it comes in two basic forms.
Chemical weathering happens when substances like water or acids get into the rock and react with the minerals that make up the rock. Think of the process like steel objects rusting when they are left out in the rain. The same thing happens to certain minerals inside rocks. After enough time, these minerals change so much that they simply crumble.
Physical weathering happens when things like ice physically break rock apart. If you have ever left a can of pop in a freezer for too long, you know that when the water freezes to ice, it expands so much that it may actually split the can apart. This same thing happens when rain gets inside rocks and freezes. This process is called “frost wedging.” Through this, solid rock can be reduced to tiny pieces in just a few years.
Once weathering breaks a rock down, it is then moved along by gravity, which leads to the process of erosion.
The banks of the Big Sioux River in Watertown are suffering from weathering and erosion. With the high water events that occur in the area, such as flooding and spring runoff, the river will eventually eat out the bottom of the bank, causing the top to fall down. When you add in the effects of foot travel and snowmobile traffic, nature can’t keep up and the river bank needs a little help. The bend in the river where you currently stand has been helped by the Watertown Middle School Geography Club. In order to lessen the impact of erosion, the once exposed river bank has been covered with topsoil that contains seed and organic matter, which provides a base for new plants to extend their roots to hold the soil together. Students have worked to protect this bend in the river with cranberry and willow tree plantings. Given enough time, the roots of the plants will hold the soil together and keep the water from washing it away. The trees will eventually grow enough to provide a physical barrier to snowmobiles and foot traffic and also provide shade and habitat for beneficial animals and insects.
NOT A LOGGING REQUIREMENT: Feel free to post pictures of your group at the area or the area itself - I love looking at the pictures.
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