Glacial landforms are unique landforms that are created by various glacial processes. Most of today's landforms were created by glacial action during the quaternary period, which consists of the Pleistocene and Holocene Epoch.
How are glacial landforms categorised?
There are many ways by which geographers categorise the large amounts of glacial landforms. The most popular ones categorise with respect to the processes that form the landscape.
Erosional landforms
Erosional landforms are the features that are formed by erosional glacial processes e.g.:
- Abrasion: an erosional process where rocks or stones come into contact with another body of matter, and wear away at it through movement. These rocks or stones act like sandpaper against worn-away surfaces. Landscapes affected by abrasion often have smooth/polished surfaces whilst also containing scratch-like marks known as striations. In the context of glaciation, the way in which these rocks and stones wear away at the surfaces happens due to them being picked up by glaciers and embedded in the base or sides of the glacier.
- Plucking: when either rocks or stones become frozen to a glacier (often in subglacial and lateral glacial areas) and due to the glacier’s movement, are forced out of their original source (plucked out). Plucking results in glacial landscapes with jagged and rough characteristics.
Some examples of erosional landforms include glacial troughs, corries, and roche moutonnees.
An example of a corrie lake. Verdi Lake: Jrmichae. CC BY-SA 4
Depositional landforms
Depositional landforms are features of land that are formed by the deposition of glacial matter. The majority of deposition occurs during glacier retreat in both ice sheets and alpine glaciers. During periods of glacial retreat, ablative processes (e.g. snow loss) occur at a faster rate than accumulation, and glacial debris is left behind as a result. One reason for this is that much of glacial matter is entrained in the glacial ice (if you recall plucking) and the rapid ablation of glacial ice disengages the entrained matter and causes it to be deposited in areas of glacial retreat.
Some examples of depositional landscapes are drumlins, terminal moraines, and erratics.
Drumlins around Horicon Marsh. Image: Doc Searls. CC BY 2.0
Fluvioglacial landforms
Fluvioglacial landforms are those that are formed as a direct result of glacial meltwater rather than the glacier itself. The processes that form fluvioglacial landforms may include processes that could be broadly categorised as erosional or depositional processes, however, we set fluvioglacial processes apart. This is due to the fact that in meltwater environments, the same processes cause very different results compared to erosional/depositional processes in non-meltwater glaciation. This is evident when we explore the specific topics of erosional, depositional and fluvioglacial landforms.
Examples of fluvioglacial landforms include eskers, kame terraces, and outwash plains.
A kame terrace in Yellowstone National Park.
The significance of glacial landforms
Glacial landforms are the key to understanding the Earth's historical climate and its variation, which in turn informs our understanding of the modern-day climate. By combining different analysis techniques onto a varied set of glacial landforms we can potentially reconstruct past glacial ice extent as well as its movement. Glacial movement and extent (especially during the Pleistocene) is largely what has determined the topography of the Earth’s modern-day landscapes and may show us what the Earth’s landscapes looked like thousands of years ago.
Combining information on the Earth’s historical climate, glacial cycles, glacial processes, etc. against our modern-day observations allows us to gather a broad understanding of the Earth’s cryosphere and its relationship to the atmosphere and geosphere. As a result of this gathered data, we can both extrapolate and interpolate it in order to understand why our climate is the way it is currently and how it may change.
Glaciated landforms also contribute to glacial landscapes by their aesthetics alone. Due to the uniqueness of the landscapes formed via glaciation, people are attracted to visit these sites which lays the groundwork for a tourist economy in the area e.g. the Lake District brings in 15.8 million visitors per year.
The scientific value of certain glaciated landscapes is invaluable. We are able to reconstruct and understand the Earth’s climate by analysing ice cores to determine the concentration of specific gasses over the past 800,000 years.
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