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How to Determine a Glacier's Direction of Flow

Glaciers are enormous bodies of frozen water, usually located in polar or alpine settings. Like all bodies of water, glaciers flow downhill. It seems counterintuitive, but the solid ice will flow like a liquid. You can see this effect by watching time-lapse video of a glacier, since it takes months, and sometimes years, to see any noticeable change. Despite the slow speed of flow, however, there are ways to determine both the rate and direction of glacial movement.

Things You'll Need

Topographic map of glacial area
Aerial photo of glacier

Instructions

- 1
  Find the glacier on the aerial photo. This allows you to see the whole glacier on a large scale, which will help you to determine its location on the topographic map. Glaciers often appear as long, curving streaks on a map which might converge as you follow them.
- 2
  Choose specific features on your aerial photo. Make sure you choose features that are topographically based, such as mountain peaks, valleys and rivers. Do not choose a feature on the glacier's surface, because the glacier is flowing downhill, and it will not be present on the topographic map.
- 3
  Locate the same features on the topographic map. Elevations are shown on topographic maps as contour lines with associated elevation numbers, usually in feet or meters above sea level. Mountain peaks will appear as tightly enclosed areas with high numbers. Valleys will appear as elongated areas with relatively low numbers.
- 4
  Determine the location of the glacier's terminus (or front face) on the topographic map. To do this, find the end of the glacier on the aerial photo, then match that location to the appropriate point on the topographic map. The terminus should be at a lower elevation (a lower line number) than the accumulation area, or top, of the glacier.
- 5
  Use the compass on the topographic map to find the direction of north. It's a good idea to mark this direction on the map near the middle of the glacier. If you can't draw on the map, use a toothpick or a small piece of paper to make a point.
- 6
  Follow the glacier from high to low elevation on the topographic map. Compare the direction of this flow to the north direction you marked near the glacier's path. Glaciers always flow downhill, so be sure your flow ends at the terminus.

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