 As much as plate tectonics builds up the Earth’s surface, forces in nature are also working to wear it down. One major force of erosion happens due the incredible power of continental glaciers that cover entire landmasses and alpine glaciers that erode mountain valleys.

 Size They are not as large as Continental glaciers. Location:  These glaciers are found in mountainous regions (think Alpine skiing = downhill skiing!). They flow through mountain valleys such as The Rockies, The Alps and The Himalayas.

 Alpine glaciers move downhill due primarily to force of gravity.

 They erode the sides of mountains making the peaks sharper, and the valley bottoms wider and deeper.  Alpine glaciers turn V-shaped valleys into U-shaped valleys as they move through them. V – Shaped Valley BEFORE Glaciation U – Shaped Valley AFTER Glaciation

V-Shaped Valley BEFORE glaciation U-Shaped Valley AFTER glaciation

 Size  They are much bigger compared to Alpine glaciers!  Location  Huge ice sheets that cover large continental landmasses,  Greenland and Antarctica.

 They flow out of a “zone of accumulation”. Snow accumulates in the middle of the flat glacier and flows outwards from it in all direction. Zone of Accumulation

 They give the land a smoother, more rounded appearance. They erode higher areas and fill in lower areas with eroded rock material such as till. 1.End morraine 2.Drumlin hill 3.Kettle Lake 4.Esker 5.Till 6.Outwash plain 7.Glacial lake bed

 - End Moraine: A ridge of eroded rock material deposited by the snout of a glacier

 - Till: Eroded rock material deposited under the glacier, made up of various sizes (from gravel to sand size or even clay sized sediment particles).

 Kettle Lakes: Round, depressions filled by glacial melt-water. They are created by retreating glaciers that leave huge ice blocks behind, causing a depression in the earth below.

 Kettle Lake

 - Drumlin: An egg or tear shaped hill made up of eroded till material. They are steep on one side with a gentle slope on the other.

 Drumlin Hill

 - Esker: A long ridge of material deposited by glacial meltwater rivers that flow beneath a glacier as it melts and retreats.

 Esker

 Some glaciers have been known to be thousands of feet high and continental glaciers can spread across thousands of kilometers in area.

 The surface of glaciers often have deep cracks in them called crevasses. These can be quite deep and wide (refer to cross-section of a glacier diagram in your notes!).

 Most of the glaciers in the world today are retreating (melting) due to warmer average global temperatures

 The Collapse of the Larson B Ice Shelf in Antarctica:

 Icebergs are not glaciers! They are chunks of ice and snow that break off of the edge of glaciers, where a glacier meets a body of water. The chunk of ice then floats in the water until it eventually melts. The part of the iceberg that we see above the water is only a small part of a much larger piece of ice. Due to buoyancy most of the iceberg is under water!

 Video Clip:  (8 minutes)  Amazing Planet – Destructive Forces (water)   (50 min)