Depositional landforms created by glaciers result from the accumulation of sediments transported and deposited by glacial ice. These landforms provide valuable insights into the dynamics of past glacial movements and the environments in which they formed.
Moraines
Moraines are accumulations of glacial debris (till) that have been transported and deposited by a glacier. They are classified into several types based on their location relative to the glacier.
Formation Process:
- Transport: Glaciers pick up and transport debris from the valley walls and floor.
- Deposition: When the glacier retreats, it leaves behind these sediments, forming various types of moraines.
Types of Moraines:
- Terminal Moraines: Form at the snout (end) of a glacier, marking its furthest advance.
- Lateral Moraines: Form along the sides of a glacier.
- Medial Moraines: Form where two glaciers converge, and their lateral moraines combine.
- Ground Moraines: Form as an irregular blanket of till deposited beneath a glacier.
Examples:
- India: Gangotri Glacier, Uttarakhand
- The terminal moraine of the Gangotri Glacier is a prominent feature, marking the furthest advance of the glacier.
- World: Long Island, USA
- Long Island was formed by terminal moraines from the Laurentide Ice Sheet during the last Ice Age.
Drumlins
Drumlins are streamlined, elongated hills formed by glacial action, often found in clusters known as drumlin fields.
Formation Process:
- Till Deposition: Glaciers deposit till as they advance and retreat.
- Reshaping: The movement of the glacier reshapes the deposited till into an elongated hill with a steep stoss side (facing the direction from which the glacier came) and a gentle lee side.
Examples:
- India: Kangra Valley, Himachal Pradesh
- Drumlins can be found in this region, formed by past glacial activity in the Himalayas.
- World: Central New York, USA
- The region is known for its extensive drumlin fields, formed during the last glacial period.
Eskers
Eskers are long, winding ridges of sand and gravel deposited by meltwater streams flowing beneath a glacier.
Formation Process:
- Subglacial Streams: Meltwater streams flow beneath a glacier, carrying sediments.
- Deposition: As the glacier retreats, these streams deposit sediments along their path, forming ridges.
Examples:
- India: Thar Desert, Rajasthan
- Although primarily a desert, some eskers can be found in regions that were once glaciated.
- World: Maine, USA
- The state has several prominent eskers formed during the last glacial period.
Glacial Tills
Glacial Tills are unsorted sediments deposited directly by glacial ice. Till can include a range of particle sizes, from clay to boulders.
Formation Process:
- Plucking and Abrasion: Glaciers pick up debris from the ground through processes of plucking and abrasion.
- Deposition: As glaciers advance and retreat, they deposit this unsorted material directly onto the landscape.
Examples:
- India: Spiti Valley, Himachal Pradesh
- Glacial tills are evident in the Spiti Valley, indicating past glacial activity.
- World: Northern Europe
- Extensive till deposits are found across northern Europe, left behind by the retreating ice sheets of the last Ice Age.
Additional Depositional Landforms
Kettle Lakes:
- Description: Kettle lakes are depressions left behind after partially buried ice blocks melt, filling with water to form a lake.
- Formation Process: Kettle lakes are formed when chunks of ice calve off the front of a retreating glacier and become buried in glacial till. When the ice melts, it leaves behind a depression that fills with water.
- Example:
- Minnesota, USA: Known as the “Land of 10,000 Lakes,” many of which are kettle lakes.
- Tso Kar, India: Located in Ladakh, it is an example of a kettle lake formed by glacial activity.
Outwash Plains:
- Description: Outwash plains are flat areas of land formed by meltwater flowing from the glacier, depositing sediments.
- Formation Process: As glaciers melt, the meltwater carries sediments away from the glacier’s snout, depositing them over a wide area.
- Example:
- Great Plains, USA: Formed by sediments deposited by meltwater from glaciers during the last Ice Age.
- Terai Region, India: Formed by meltwater from the Himalayan glaciers.
Summary
Depositional landforms created by glaciers, such as moraines, drumlins, eskers, and glacial tills, provide significant evidence of past glacial activity and offer insights into the processes of sediment transport and deposition by glaciers. These landforms are found in glaciated regions worldwide, from the Himalayas to North America, and from Europe to New Zealand, highlighting the extensive and powerful impact of glaciers on shaping the Earth’s surface. Understanding these landforms helps geologists reconstruct past glacial environments and climate conditions, contributing to our knowledge of Earth’s geologic history.
