You can easily spot a steep mountain when you are standing in front of it, but how do you recognise one when it is just a flat piece of paper? The secret lies in reading map scales and interpreting the spacing of brown contour lines.
Before identifying specific landforms, you must understand how different Ordnance Survey (OS) map scales display information. The distance between adjacent contour lines is known as the vertical interval, which helps indicate the steepness of the terrain.
Mountain peaks are often marked by a spot height (a black dot with a number indicating exact height) or a trigonometrical station (a small blue triangle representing a surveying pillar).
Glacial erosion leaves highly distinctive marks on the landscape. Follow these steps to describe and identify them using contour patterns:
Step 1: Locate a corrie / cwm. First, scan the map for a distinctive horseshoe-shaped or armchair-shaped contour pattern. The contours will be closely packed on three sides (indicating a steep back wall) but wider at the front lip. In the UK, most face North or North-East, and they often contain a small circular lake called a tarn. They are approximately 1 km wide and 1 km long, and may be named "Corrie" (England), "Cwm" (Wales), or "Coire" (Scotland).
Step 2: Trace the ridges to find an arête. Next, look for a narrow, knife-edged ridge between two back-to-back corries. The contours will appear as narrow bands of very close, parallel lines on either side of a central crest, often named "Edge" (e.g., Striding Edge) on the map.
Step 3: Pinpoint a pyramidal peak. Finally, look for an intersection where three or more corries and arêtes meet at a central high point. The contours will radiate sharply outwards from the peak. Importantly, the shape must be angular; if the contours at the top are circular and widely spaced, it is a rounded hill, NOT a pyramidal peak.
A glacial trough (or U-shaped valley) has a completely different contour signature to a typical river valley. The map will show a wide, flat valley floor where contours are widely spaced or completely absent.
The valley sides will be marked by tightly packed, parallel contours indicating extreme steepness. Furthermore, a glacial trough is noticeably straighter than a winding V-shaped river valley. Within or alongside these troughs, you can identify several other features:
Examiners may ask you to calculate the gradient of a glaciated slope using map evidence.
Worked Example:
Calculate the gradient of a corrie backwall that rises from a 200 m contour to a 700 m peak over a distance of 4 cm on a 1:50,000 map.
Step 1: Write down what you know.
Step 2: Convert map distance to real-world horizontal distance.
Step 3: Substitute into the equation and calculate.
Students often confuse V-shaped river valleys with U-shaped glacial troughs. Remember that glacial troughs have wide, flat floors with widely spaced contours, whereas V-shaped valleys have narrow floors where contours meet in a sharp 'V'.
In 'describe the relief' questions, you must provide specific map evidence to gain full marks. State what the contours are doing (e.g., 'contours are very close together indicating steep land') and use a 6-figure grid reference to pinpoint small, specific features like a tarn or waterfall. In contrast, use 4-figure grid references for larger, general areas such as a glacial trough.
Hanging valleys are usually the hardest feature to spot; look specifically for the word 'Waterfall' or blue dash symbols right where a small stream meets the tight contours of the main, steep valley wall.
Vertical interval
The height difference between two adjacent contour lines on a map.
Scree
A mass of loose rock fragments on a mountain side, represented on 1:25,000 OS maps by stippled dots.
Spot height
A black dot on an OS map with a number next to it, indicating the exact height of the land in metres.
Trigonometrical station
A concrete surveying pillar marking the highest point of a peak, shown on an OS map as a small blue triangle.
Contour pattern
The arrangement and spacing of brown lines on an OS map that indicate the shape and steepness of the terrain.
Corrie / Cwm
An armchair-shaped hollow high on a mountain with a steep back wall and a raised lip, identifiable on a map by horseshoe-shaped contours.
Tarn
A small, circular mountain lake that forms in the basin of a corrie after the glacier has melted.
Arête
A narrow, knife-edged ridge separating two adjacent corries, shown by closely packed, parallel contour lines.
Pyramidal peak
A sharp, three-sided mountain peak formed where three or more corries meet, indicated by angular, radiating contour lines.
Glacial trough
A steep-sided, flat-bottomed valley formed by a glacier, also known as a U-shaped valley.
Ribbon lake
A long, narrow lake found occupying the flat floor of a glacial trough.
Misfit stream
A river that is too small to have eroded the wide glacial trough in which it currently flows.
Hanging valley
A tributary valley that ends abruptly high above the floor of a main glacial trough, often featuring a waterfall.
Truncated spur
A steep, cliff-like valley side where the original interlocking spurs were eroded away by a moving glacier.
Put your knowledge into practice — try past paper questions for Geography A
Vertical interval
The height difference between two adjacent contour lines on a map.
Scree
A mass of loose rock fragments on a mountain side, represented on 1:25,000 OS maps by stippled dots.
Spot height
A black dot on an OS map with a number next to it, indicating the exact height of the land in metres.
Trigonometrical station
A concrete surveying pillar marking the highest point of a peak, shown on an OS map as a small blue triangle.
Contour pattern
The arrangement and spacing of brown lines on an OS map that indicate the shape and steepness of the terrain.
Corrie / Cwm
An armchair-shaped hollow high on a mountain with a steep back wall and a raised lip, identifiable on a map by horseshoe-shaped contours.
Tarn
A small, circular mountain lake that forms in the basin of a corrie after the glacier has melted.
Arête
A narrow, knife-edged ridge separating two adjacent corries, shown by closely packed, parallel contour lines.
Pyramidal peak
A sharp, three-sided mountain peak formed where three or more corries meet, indicated by angular, radiating contour lines.
Glacial trough
A steep-sided, flat-bottomed valley formed by a glacier, also known as a U-shaped valley.
Ribbon lake
A long, narrow lake found occupying the flat floor of a glacial trough.
Misfit stream
A river that is too small to have eroded the wide glacial trough in which it currently flows.
Hanging valley
A tributary valley that ends abruptly high above the floor of a main glacial trough, often featuring a waterfall.
Truncated spur
A steep, cliff-like valley side where the original interlocking spurs were eroded away by a moving glacier.