The concept of glacial landforms and their identification on maps

Glacial landforms are distinctive features in the landscape created by the action of glaciers over thousands of years.

These landforms can be identified on ordnance survey (OS) maps by interpreting specific patterns and symbols that indicate their unique shapes and characteristics.

Using contour lines to spot corries and arêtes

Contour lines are essential tools on OS maps, represented as orange lines that indicate the height and shape of the land. They provide critical information about elevation and steepness, which helps in identifying specific glacial features like corries and arêtes.

Understanding contour lines for glacial identification

• Height indication - Numbers on contour lines show the elevation of the land above sea level.
• Steepness of slopes - The closer the contour lines are to each other, the steeper the terrain, which is a key clue for spotting glacial features.

Identifying arêtes on maps

• Narrow ridge feature - Arêtes appear as a thin, elongated hill with closely spaced, parallel contour lines on both sides, indicating steep slopes.
• Associated features - They are often flanked by corries or tarns (small lakes) on either side.
• Naming conventions - Footpaths along arêtes may have names that suggest sharpness or height, such as "Something Edge" (e.g., "Knife Edge").

Identifying corries on maps

• Distinctive U-shape - Corries are shown by tightly bunched contour lines forming a U-shaped pattern.
• Presence of tarns - Many corries contain a small lake or tarn within the basin.

Recognising glacial troughs on maps

Glacial troughs are another prominent glacial landform, easily identifiable on OS maps due to their unique characteristics.

Features of glacial troughs on maps

• Flat valley floor - The bottom of a glacial trough shows few or no contour lines, indicating a level surface.
• Steep valley sides - Closely packed contour lines along the sides of the valley highlight the steep slopes created by glacial erosion.
• Wide and straight appearance - These valleys often appear broad and linear, typically located in mountainous regions.
• Mismatch with river size - A river running through the trough often seems too small to have eroded such a large valley.
• Presence of ribbon lakes - Many troughs contain long, narrow lakes, known as ribbon lakes.