What Are Glaciers?

• Glaciers are masses of ice that move slowly over land due to gravity.
• Types based on location and scale:
  • Continental Glaciers: Large ice sheets covering vast areas.
  • Piedmont Glaciers: Spread at the foot of mountains across plains.
  • Mountain/Valley Glaciers: Flow down mountain slopes in trough-like valleys.

Movement of Glaciers

• Movement is slow, ranging from a few centimeters to several meters per day.
• Driven by gravity and the weight of ice.
• Movement causes erosion, transportation, and deposition of large rock materials.

Glaciers in India

• Found in the Himalayas.
• Key regions: Uttarakhand (Uttaranchal), Himachal Pradesh, Jammu & Kashmir.
• Gangotri Glacier feeds Bhagirathi River at Gaumukh.
• Alkapuri Glacier feeds Alakananda River.
• Bhagirathi + Alakananda = Ganga River (joins at Devprayag).

Erosion by Glaciers

• Erosion is tremendous due to:
  • Friction from the massive weight of moving ice.
  • Plucking and abrasion of rocks.
• Can reduce high mountains to low hills and plains.
• Glaciers scrape, polish, and gouge out landforms formed.

Erosional Landforms

a) Cirques (Corries)

• Found at the heads of glacial valleys.
• Bowl-shaped, deep, long basins with steep walls.
• Created by accumulated ice eroding the mountain.
• Often contain lakes after glacier melts – called Cirque or Tarn lakes.
• May appear in stepped sequences down a slope.

b) Horns and Serrated Ridges

• Horns: Sharp, steep peaks formed by headward erosion where 3 or more cirques meet.
  • Example: Matterhorn (Alps), Mount Everest (Himalayas).
• Serrated Ridges/Arêtes:
  • Narrow, saw-toothed ridges formed between adjacent cirques.
  • Created by erosion along the sides of cirques.

c) Glacial Valleys/Troughs

• U-shaped, wide, and broad-floored valleys with steep sides.
• Formed by glacier movement along mountain valleys.
• Features:
  • Littered debris or moraines (unsorted deposits).
  • Lakes formed by gouging or debris blockage.
  • Hanging valleys: Elevated tributary valleys; create waterfalls.
  • Truncated spurs: Triangular-shaped valley sides.
  • Fjords/Fiords: Deep glacial troughs filled with seawater in coastal regions (high latitudes).

Difference Between River and Glacial Valleys

Depositional Work of Glaciers

• Glaciers deposit unsorted, coarse and fine debris during melting.
• Glacial Till: Unsorted, angular debris left behind by glaciers.
• Glacial Outwash: Sorted, stratified deposits carried by glacial meltwater.

Depositional Landforms

a) Moraines

• Ridges made of glacial till (unsorted debris).

Types:

1. Terminal Moraine:
   • Found at the end (toe) of a glacier.
   • Formed when glacier deposits debris during retreat.
2. Lateral Moraine:
   • Found along the sides of a glacier.
   • Formed by debris falling from valley walls or pushed by glacial movement.
3. Medial Moraine:
   • Found in the center of a glacier, where two lateral moraines meet.
   • Often less distinct than lateral moraines.
4. Ground Moraine:
   • Irregular sheets of till left under the glacier.
   • Varies in thickness and topography.
5. Combined Moraines:
   • Lateral + Terminal moraines can form horse-shoe shaped ridges.

b) Eskers

• Sinuous (winding) ridges of stratified sand and gravel.
• Formed when meltwater streams flow in sub-glacial tunnels.
• After glacier melts, the deposits remain as raised ridges.

c) Outwash Plains

• Found beyond glacier’s terminal point.
• Created by meltwater streams depositing gravel, sand, silt, clay.
• Resemble alluvial fans that coalesce into broad plains.

d) Drumlins

• Oval-shaped hills made of glacial till (sometimes with sand and gravel).
• Aligned parallel to glacier movement.
• Structure:
  • Stoss End: Steeper, faces glacier.
  • Tail End: Tapering, away from glacier.
• Size:
  • Length: up to 1 km
  • Height: up to 30 m
• Formed when heavily loaded ice dumps debris, shaped by glacial push.

Source: NCERT