What Is Glacial Plucking?

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  • Written By: Andrew Kirmayer
  • Edited By: Shereen Skola
  • Last Modified Date: 10 May 2020
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Climate change generally refers to atmospheric warming and changing weather patterns that may be brought on by man-made processes and emissions. The climate has gone in cycles throughout history and glaciation is typically one example. Large areas of ice have shaped the landscape in many parts of the world, reshaping rock formations by processes such as abrasion and glacial plucking. Pieces of bedrock can break off as a glacier passes, and become frozen within the ice. The rocks typically travel along the base of the ice, and new features in the bedrock are often formed as the ice sometimes repeatedly advances and retreats.

Glacial plucking often occurs as the advancing ice pushes against fractured bedrock. Additional breaks can form as a result of the stress, while warmer temperatures and friction from the movement of the glacier can cause melting. Water can then get into other cracks in the rock, weaken it from force or by re-freezing, and break off more pieces.

Abrasion is another process that affects the bedrock as a glacier passes over it. The ice, as well as debris in it, can erode various surfaces. Small particles can polish bedrock, while large pebbles and boulders typically leave scratch marks that can be examined to determine the motion of a glacier. The concentration and hardness of the entrained rocks as well as the speed of the ice typically influence the degree of erosion. Abrasion and glacial plucking sometimes happen at the same time, and is often identified by a bullet-shaped rock formation.

Glacial plucking can happen in zones, where large amounts of rock are broken away. Nearby is often a lake that is formed when the glacier melts and the water pools in that area. Abrasion is commonly seen on the other side of this lake, while a rock formation called a moraine typically marks the farthest point a glacier has advanced to.

Evidence of glacial plucking and other types of erosion can be found throughout the world. It is often seen in the United States as well as Canada as a result of ice sheets that formed during the last ice age, called the Wisconsin glaciation period. Rock formations produced by glaciers are commonly found in Connecticut and Iowa, while the land in what is now Finland and Sweden was shaped during a previous ice age. Many landscapes have been shaped by glacial plucking and other processes, while some modern day islands were formed by glaciation as well.

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