Glaciers make a big mark on the landscapes beneath and around them. Both continental glaciation (ice caps, ice sheets) and alpine glaciation (valley glaciers in large mountains) shape the landscape. If you live in northern North America or northern Europe you may find landforms created by glaciation nearby! This is because during the last ice age, ice sheets covered large parts of northern Eurasia and North America. Smaller glaciers were also located (and often still are found) in tall mountain ranges like the Andes and Himalayas. Even thousands of years after a glacier disappears, you can still find evidence of its presence in the glacial landforms left behind!
Before you continue reading: if you need more background info about how glaciers form and why they are important, check out my blog post on glaciers. If you are teaching your students about glaciers, try out my Glaciers: Science on Ice unit.
Formation of glacial landforms
Before we can explore the different types of glacial landforms, we need to understand a little bit more about the forces at play. Glaciers shape the landscape in two main ways: through erosion and deposition. Basically, a glacier picks up materials like rocks and sediments in one place, then later sets them down in a different place. Erosion removes rocks and sediments, leaving behind scarred landscapes. The removed rocks and sediments are then deposited in different locations. Deposition builds up rocks and sediments on the landscape, creating a gently rolling or bumpy-looking terrain. Even after glaciers melt away, we can still see the unique landforms they leave behind.
Let’s take a look at a few common glacial landforms types and how they form.
1. Cirque
A steep-walled mountain basin with one open side, located at the upper end of a glacial valley. Sometimes, you will find a small pond (called a tarn) in the bottom of a cirque.
Formation: Cirques become carved into the landscape at the start of valley glaciers’ paths. A cirque opens to a valley on one side, in the direction that the glacier moved.
Example: Cirque Meadows in northern Colorado, USA (seen from a distance)
2. Arête
A sharp, spiny mountain ridge separating two glacial valleys.
Formation: An arête forms through glacial erosion by two valley glaciers, one on either side of the ridge.
Example: The Carn Mor Dearg arête of Ben Nevis, Scotland
3. Horn
A sharp, pointy mountain peak. Horns are places where three or more arêtes meet. At the base of a horn, you will find three or more cirques.
Formation: A horn forms through erosion on all sides by three or more glaciers.
Example: Multiple glacial horns near Laguna Parón, Peru
4. U-shaped valley
A gently sloping valley carved out by a glacier that looks like a U from a profile view. In contrast, a valley carved out by running water will have a V-shape on profile.
Formation: U-shaped valleys become eroded into the landscape by valley glaciers.
Example: Lötschental Valley, Kippel, Switzerland
5. Moraine
Long mounds of unsorted glacial till that are deposited onto the landscape along the borders of glaciers. There are several different types of moraines including lateral moraines, end moraines, and medial moraines.
Formation: Moraines form as a glacier deposits till along its sides and front.
Example: Kettle Moraine State Forest, Wisconsin, USA (moraines create the gently hilly landscape)
6. Drumlin
A low, streamlined hill made of glacial till with one steep end and one smooth, elongated end pointing in the direction that the glacier moved.
Formation: Drumlins are depositional landforms that form beneath ice sheets. If the area around a drumlin later becomes flooded with water, the drumlin can become an island.
Example: There are many drowned (island) drumlins in the Clew Bay, Ireland
7. Esker
A long, winding ridge made of sand and gravel.
Formation: Eskers form in the outwash from ice sheets. They form as sand and gravel settle out of meltwater flowing in streams underneath and in front of receding glaciers. If the area around the esker later becomes flooded with water, the esker can become an isthmus.
Example: Eskers Provincial Park in Alberta, Canada (look for subtle, s-shaped ridges in the landscape)
8. Kettle
A depression in the earth where a buried ice block melted. Kettles are often filled with water (e.g., a kettle lake).
Formation: A kettle forms when a large chunk of ice is deposited and buried in glacial outwash. As the buried ice melts, a depression forms and often fills with water.
Example: Devil’s Lake, Wisconsin, USA
9. Fjord
A fjord is a deep, narrow inlet found along a coast.
Formation: Fjords are carved out by valley glaciers, then fill in with ocean water when the sea level rises.
Example: Eyjafjörður near Dalvik, Iceland
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References and Further Reading
- Bendle, J. (2020). Moraine Types. AntarcticGlaciers.org. Available: https://www.antarcticglaciers.org/glacial-geology/glacial-landforms/glacial-depositional-landforms/moraine-types/
- Bluemle, J. P. (2007). Eskers in North Dakota. North Dakota Dept. of Mineral Resources. Available: https://www.dmr.nd.gov/ndgs/ndnotes/Eskers/Eskers.asp
- Mervine, E. (2012). Geology Word of the Week: D is for Drumlin. American Geophysical Union. Available: https://blogs.agu.org/georneys/2012/11/23/geology-word-of-the-week-d-is-for-drumlin/
- National Park Service (2018). U-Shaped Valleys, Fjords, and Hanging Valleys. Available: https://www.nps.gov/articles/ushapedvalleysfjordshangingvalleys.htm
- Plummer, C. C., Carlson, D. H., & Hammersley L. (2019). Physical Geology. Sixteenth edition. New York, NY: McGraw-Hill Education. Chapter 17: Glaciation.
- Rose, W. (n.d.). Glaciers. Available: https://www.geo.mtu.edu/KeweenawGeoheritage/Glaciers/Welcome.html