Glaciation

Glaciation: Junior Cycle Geography Notes

The Work of Ice

Glaciers shape the landscape through erosion, transportation, and deposition:

1. Erosion: Glaciers wear away the land as they move.

2. Transportation: Glaciers carry eroded material (rocks, stones, soil).

3. Deposition: Material is deposited when the glacier melts or loses energy.

Landforms of Glacial Erosion

1. Cirque (Corrie):

   • Bowl-shaped hollow in a mountain where a glacier begins.

   • Formation:

     1. Snow gathers in a hollow and turns to ice.

     2. Ice erodes the hollow through plucking and abrasion.

   • Example: Lough Tay, Wicklow.

2. Arête:

   • Narrow ridge between two cirques.

   • Formation: Erosion on both sides sharpens the ridge.

   • Example: Striding Edge, Lake District.

3. Pyramidal Peak:

   • Sharp, pointed peak formed by erosion from three or more cirques.

   • Example: Matterhorn, Alps.

4. U-Shaped Valley:

   • Steep sides and flat floor, formed when a glacier moves through a river valley.

   • Formation:

     1. Glacier erodes the sides and floor of the valley.

     2. Valley becomes wider, deeper, and straighter.

   • Example: Glendalough, Wicklow.

5. Hanging Valley:

   • Smaller valley left hanging above the main U-shaped valley.

   • Often has a waterfall.

6. Fjord:

   • Drowned U-shaped valley, where the sea floods the valley after the glacier melts.

   • Example: Killary Harbour, Ireland.

Glacial Transportation

Glaciers carry material in three ways:

1. On the Glacier:

   • Material falls onto the glacier from cliffs above (supra-glacial).

2. In the Glacier:

   • Material is trapped inside the ice (englacial).

3. Under the Glacier:

   • Material carried at the glacier base by moving ice (subglacial).

Landforms of Glacial Deposition

1. Moraine:

   • Piles of material left behind by a glacier.

   • Types:

     • Lateral Moraine: Deposits along the sides of the glacier.

     • Terminal Moraine: Deposits at the glacier's end.

     • Ground Moraine: Deposits spread underneath the glacier.

2. Drumlins:

   • Oval-shaped hills made of boulder clay.

   • Formation:

     • Glacier deposits material.

     • Ice moves over it, smoothing the hill into an oval shape.

   • Example: Clew Bay, Mayo.

3. Erratics:

   • Large rocks transported and deposited by glaciers in areas where they do not naturally occur.

4. Eskers:

   • Long, winding ridges of sand and gravel.

   • Formation: Deposited by meltwater streams flowing under the glacier.

   • Example: Esker Riada, Ireland.

5. Outwash Plains:

   • Flat areas of sand and gravel deposited by meltwater in front of a glacier.

   • Example: Curragh, Kildare.

People and Glaciation

1. Positive Impacts:

   • Tourism: Glacial landscapes attract visitors (e.g., skiing, hiking).

   • Fertile Soil: Outwash plains and glacial deposits improve farmland.

   • Hydroelectric Power (HEP): Meltwater from glaciers powers dams.

2. Negative Impacts:

   • Flooding: Melting glaciers can cause sudden floods.

   • Poor Drainage: Drumlins can lead to poorly drained land.

   • Dangerous Conditions: Avalanches and unstable ice can harm people.

Quick Mnemonics

1. Erosion Landforms:

   • C.A.P.U.H.

     • Cirque

     • Arête

     • Pyramidal Peak

     • U-Shaped Valley

     • Hanging Valley

2. Deposition Landforms:

   • M.E.D.E.O.

     • Moraine

     • Eskers

     • Drumlins

     • Erratics

     • Outwash Plains

feature of deposition (esker) formation

To understand and memorize the formation of an esker (a depositional feature created by glaciers), here's a simplified explanation with easy-to-remember steps:

What is an Esker?

• An esker is a long, winding ridge of sand and gravel deposited by meltwater streams that flow beneath glaciers.

Key Steps of Formation (Simplified):

1. Tunnel Streams: Meltwater streams flow in tunnels beneath the glacier. (Think: a river under ice.)

2. Carrying Sediment: These streams carry sand, gravel, and other debris. (Think: the river carries "stuff.")

3. Deposition: As the glacier melts and water flow slows, the sediment is deposited in the tunnel. (Think: dropping the "stuff.")

4. Ice Melts Away: When the glacier retreats, the sediment ridge is left behind as an esker. (Think: leftover winding road of sand and gravel.)

Mnemonic to Remember:

T - Carry - Drop - Reveal

• Tunnel streams under the glacier

• Carry sediment

• Drop sediment as water flow slows

• Reveal the esker when the glacier melts away

This sequence helps you recall the process step-by-step for your exam

What is a Cirque?

A cirque is a bowl-shaped hollow found on mountains, formed by glacial erosion. It’s the starting point of a glacier.

Key Steps of Formation (Simplified):

1. Snow Collects: Snow gathers in a mountain hollow and compacts into ice over time. (Think: ice factory in the mountains.)

2. Plucking: The glacier pulls rocks away as it moves. (Think: a giant ice "claw" pulling rocks.)

3. Abrasion: Rocks at the glacier's base scrape the hollow deeper and wider. (Think: sandpaper effect, making a deep bowl.)

4. Overdeepening: The hollow gets deeper and steeper, forming a rounded back wall and a flat basin. (Think: carving a bowl shape.)

5. Glacier Melts: When the glacier melts, a cirque is left behind, often with a small lake (tarn). (Think: an ice-made bowl with leftover water.)

Mnemonic to Remember:

Snow - Pluck - Scrape - Deepen - Melt

• Snow collects and compacts into ice.

• Pluck rocks from the mountain walls.

• Scrape the hollow with rocks at the glacier’s base.

• Deepen the bowl shape.

• Melt leaves a cirque behind.

This sequence helps you recall the steps for your exam in a simple, logical order!