Glacier Features

• Glaciers are formed when snow accumulates over many years, compressing it into ice.
• Plucking- Removal of entire chunks of rock; a process of erosion that that occurs during glaciation
• How does Plucking Occur?

  As glaciers move across rocks, friction causes it to heat up and melt. The water seeps into the cracks and when it re-freezes, it causes larger chunks to be separated and be 'plucked' into the glacier, leaving behind protrusions of cracked rock.

  
• Striations- a number of parallel linear marks, gouges or scratches on a rock

  A) The scratches from the plucking

  
• How do striations form?

  The glaciers move over the rocks and sediment leaving grooves, showing the direction the glacier was flowing. Ex: Devils Postpile
• Cirque- a bowl shaped, amphitheatre like depression; tarns are usually left once the glacier retreats. Ex: Granite Creek Tarn

  
• How do cirques form?

  Formed when glaciers carve out from mountains and valley sidewalls; plucking and erosion are factors in it.
• Tarn- Lakes that form in glacially carved cirques once the glaciers retreat; often dammed by moraines; if they are associated with moving glaciers the tarns are full of small glacially-ground sediment
• Horn-A sharp promontory peak on top of a mountain. They typically have three flat faces that give them their point triangle shape and distinct edges.
• How do Horns form?

  When at least three sides of the mountain has been carved out by glaciers, leaving behind a pointy, triangular peak. EX: Matterhorn in the Alps in Switzerland
• U-shaped Valley- u-shaped valleys also known as valley troughs have flat and/or round bottoms and straight sides
• How do U-shaped Valley's form?

  They form through glacial erosion. Glaciation develops in an established v-shaped river valleys where the ice erodes the surrounding rock. EX: Avalanche Lake
• Arete- A thing jagged crest that separates or did separate two glaciers next to each other

  
• How do Aretes form?

  Forms when two glaciers erode U-shaped valleys parallel to each other, leaving a crest in between. Ex: Garden Wall
• Hanging Valley- A valley that connects to the main valley
• How do hanging valleys form?

  A small mountain glacier may join a larger valley glacier, just as a stream may join a larger river. The Hanging Valley is higher than the main valley. The melting and freezing of glacier create the valley and also the stream
• Moraine- A mass of rocks and sediment carried down and deposited by the glacier, typically as ridges at its edges or extremity.

  
• How do moraines form?

  Medial: When two glaciers meet Two lateral: The sides glaciers pushing against the rock and soil Ground: Tiny sediment that is built up over time underneath the glacier by tiny streams
• Erratic- A rock of unspecified shape and size, transported a significant distance from its origin by a glacier or iceberg and deposited by melting of the ice.
• How do Erratics form?

  Glaciers can pick up chunks of rocks and transport them over long distances. When they drop these rocks, they are often far from their origin—the outcrop or bedrock from which they were plucked. These rocks are known as glacial erratics.

  
• Pluvial lakes - A pluvial lake is a type of lake that forms as a result of increased precipitation or changes in climate, leading to higher water levels
• How do pluvial lakes form?

  Pluvial lakes typically develop during times of climate change, such as during ice ages or other shifts in global weather patterns. Increased precipitation can lead to the accumulation of water in basins, creating larger and deeper lakes. Conversely, decreased evaporation can also contribute to the persistence and growth of pluvial lakes.

  EX: Lake Bonneville (ice age one)