The Shaping of Glacial Landscapes
GEO101 Earth Science
Colorado State University Global
For millions of years, glaciers have been shaping the earth in dramatic ways. Glaciers are a formation of dense ice that moves under its own weight (Downs & Day, 2005). As glaciers move, they carve their way through the landscape leaving behind a lot of land we recognize as home.
WEATHERING AND EROSION
When it comes to weathering and erosion, both play a major role in glacial processes. Both weathering and erosion work in different ways, just like glaciers work in their own way. Weathering is the physical breakdown of bedrock into smaller pieces (Johnson, Affolter, Inkenbrandt & Mosher, 2017). Weathering is either “mechanical” or “chemical”. Mechanical and chemical weathering are both natural processes; mechanical weathering happens through pressure, changing temperatures, water cycles, plant and animal activity and salt evaporation (Johnson, et. al., 2017); chemical weathering occurs primarily in humid areas, “when water, oxygen and other reactants” degrade the minerals in the bedrock and “turn them into water-soluble ions” (Johnson, et. al., 2017).
Erosion is similar to weathering in that it is a natural process. Known as a “mechanical process”, erosion occurs when water, gravity, wind, or ice removes any sediment left in areas of weathering (Johnson, et. al., 2017). Water does the most when it comes to erosion. Erosion and weathering work together to change and shape the world around us. In addition to the movement of glaciers, we can gather a better understanding of how many places around the world got their shape.
Around the world, many different kinds of glaciers exist. There are two main types of glaciers that are seen most commonly: ice sheets and alpine glaciers. Ice sheets are very large, flat bodies of ice that can cover vast areas of land (Berends, Boer & Wal, 2020). There are two main ice sheets and they are located in Greenland and Antarctica (Johnson, et. at., 2017). Alpine glaciers form in mountainous areas (Johnson, et. al., 2017). Alpine glaciers are commonly found in narrow mountain valleys. These are known as valley glaciers. These glaciers have taken the place of rivers that once flowed through the valley. They “flow” downstream, just like the river would have, but because they are made of dense ice they move very slowly (Kenner, 2019). Ice sheets are larger than alpine glaciers; the two aforementioned ice sheets make up about 99% of all of the glacial ice on the planet (Earle, 2015).
WEATHERING, EROSION AND GLACIERS
Mechanical and chemical weathering can occur due to glaciers. As the glacier moves it cuts through the landscape, breaking it down. Even as they move past mountains, glaciers can reshape the sides of the mountain as it moves. The most common way that this occurs is through frost wedging. Also known as ice wedging, this process involves the expanding of ice to break away the rock and sediment around it (Johnson, et. al., 2017). As water freezes, it can expand with intense force, taking advantage of any weak spots (Johnson, et. al., 2017). As the ice melts, the water carries away more of the loose rock and sediment, furthering the process of erosion.
This type of weathering can be seen in the Sierra Nevada Mountain Range in Yosemite National Park. The Sierra Nevada Mountain Range already existed prior to the formation of glaciers. When alpine glaciers began to form and move, they carved through the range creating U shaped valleys as they went (Duggan-Haas & Ross, 2014). The rock and sediment that made up the sides of the mountains broke down, allowing for chemical weathering to run its course.
There have always been questions about how the land around us came to be the way that it is. Thanks to geology and the understanding of weathering, erosion and even glaciers many of these questions have been answered. This doesn’t make any of these formations any less awe-inspiring. Over millions of years, ice has slowly moved past mountains changing the earth as it went. Even though all of this happened hundreds of thousands, even millions of years ago the processes of weathering and erosion can still be seen today and they will continue to occur and change the world around us.
Berends, T., Boer, B. D., & Wal, R. V. D. (2020). Reconstructing the evolution of ice sheets, sea level and atmospheric CO2 during the past 3.6 million years. Climate of the Past. doi: 10.5194/egusphere-egu2020-8762
Duggan-Haas, D., & Ross, R. (2014, December). The Cascade-Sierra Mountains. Retrieved May 31, 2020, from http://geology.teacherfriendlyguide.org/index.php/rocks-w/rocks-region4-w
Downs, R. M., Day, F. A. (2005). National Geographic Almanac of Geography. United States: National Geographic.
Earle, S. (2015, September 1). Physical Geology. Retrieved May 31, 2020, from https://opentextbc.ca/geology/
Johnson, C., Affolter, M., Inkenbrandt, P., & Mosher, C. (2017). An Introduction to Geology. Retrieved May 31, 2020, from https://opengeology.org/textbook/
Kenner, R. (2019). Geomorphological analysis on the interaction of Alpine glaciers and rock glaciers since the Little Ice Age. Land Degradation & Development, 30(5), 580–591. https://doi.org/10.1002/ldr.3238