Glacial Geology: Understanding Moraines

Study Notes

Moraines

Definition A moraine is a type of glacial landform that consists of a ridge or deposit of rocks, soil, and debris carried by a glacier and deposited at its margin or terminus.

Types of Moraines

Lateral Moraines: Formed by rocks and debris pushed to the sides of a glacier as it moves.
Medial Moraines: Formed when two glaciers merge, and their lateral moraines are pushed together.
Terminal Moraines: Formed at the end of a glacier, marking its maximum extent.
Ground Moraines: Formed by rocks and debris dropped by the glacier as it retreats.

Characteristics

Shape: Moraines can be linear, sinuous, or irregular in shape, depending on the glacier's movement and terrain.
Composition: Moraines are composed of unsorted rocks, soil, and debris, often with a mix of large boulders and fine sediment.
Size: Moraines can range from small, scattered rocks to massive ridges hundreds of meters high and kilometers long.

Formation Process

Glaciers pick up rocks and debris as they move.
The debris is carried along the glacier's margin or base.
As the glacier melts or retreats, the debris is deposited, forming a moraine.

Significance

Moraines provide valuable information about a glacier's history, including its extent, movement, and environmental conditions.
Moraines can be important geological and ecological features, supporting unique habitats and ecosystems.

Examples

The terminal moraines of the Laurentide Ice Sheet in North America.
The lateral moraines of the Glacier Bay National Park in Alaska.
The ground moraines of the Scottish Highlands.

Moraines

Definition: A moraine is a type of glacial landform formed by a ridge or deposit of rocks, soil, and debris carried by a glacier and deposited at its margin or terminus.

Types of Moraines

Lateral moraines: formed by rocks and debris pushed to the sides of a glacier as it moves.
Medial moraines: formed when two glaciers merge, and their lateral moraines are pushed together.
Terminal moraines: formed at the end of a glacier, marking its maximum extent.
Ground moraines: formed by rocks and debris dropped by the glacier as it retreats.

Characteristics

Shape: linear, sinuous, or irregular in shape, depending on the glacier's movement and terrain.
Composition: unsorted rocks, soil, and debris, often with a mix of large boulders and fine sediment.
Size: range from small, scattered rocks to massive ridges hundreds of meters high and kilometers long.

Formation Process

Glaciers pick up rocks and debris as they move.
Debris is carried along the glacier's margin or base.
Debris is deposited, forming a moraine, as the glacier melts or retreats.

Significance

Provide valuable information about a glacier's history, including its extent, movement, and environmental conditions.
Important geological and ecological features, supporting unique habitats and ecosystems.

Examples

Terminal moraines of the Laurentide Ice Sheet in North America.
Lateral moraines of the Glacier Bay National Park in Alaska.
Ground moraines of the Scottish Highlands.

Glacial Erosion Features

Glaciers form U-shaped valleys characterized by steep sides and a flat or rounded bottom through erosion
Fjords are long, narrow inlets of the sea formed by glacial erosion
Glacial troughs are elongated depressions carved out by glaciers
Hanging valleys form when a tributary glacier erodes a smaller valley that is not as deep as the main valley, resulting in a smaller valley suspended above the main valley floor

Glacial Deposition Features

Moraines are ridges of sediment deposited by glaciers, found at the glacier's terminus or along its sides
Drumlins are elongated, teardrop-shaped hills formed by the deposition of sediment beneath a glacier
Kames are small, rounded hills formed by the deposition of sediment in a glacial lake or meltwater channel
Eskers are long, narrow ridges of sediment deposited by meltwater streams flowing beneath a glacier

Glacial Erosional and Depositional Features

Glacial lakes form when a glacier carves out a depression and then melts, leaving a lake behind
Glacial erratics are rocks transported by a glacier and deposited in a new location, often of different geological composition than the surrounding area
Glacial striations are scratches and grooves carved into the bedrock by the movement of a glacier

Other Glacial Features

Cirques are circular or semicircular valleys formed by glacial erosion at the head of a glacier
Arenas are flat areas of sediment deposited by a glacier, often found at the glacier's terminus
Glacial plucks are large rocks plucked from the bedrock by the movement of a glacier