Chapter 1 the Tectonic Cycle

Glaciation 5th year Geography Ms Carr Learning Intention Visualise what glaciation is. Name and briefly explain the formation of

glacial landforms. Recognise the landforms on a diagram, OS map and Aerial photograph. Glaciation

Earth once covered with glaciers Last glaciation ended around 10,000 years ago Current interglacial period Holocene Two major glaciations have affected Ireland:

i. ii. The Munsterian, 300,000 to 132,000 years ago The Midlandian, 79,000 to 13,000 years ago Glaciers

Rivers of ice that move slowly. Move downslope under the influence of gravity and the pressure of own weight. Form where rate of accumulation of snow and ice is greater than rate of melting. Largest reservoir of fresh water on Earth.

Types of Glaciers 1. Valley glaciers: form in mountainous locations and move down valleys. 2. Continental ice sheets/glaciers: enormous areas of glacial ice and snow. Chapter 13: Glacial Processes, Patterns & Associated Landforms

Causes of an Ice Age Change in the Earths orbit around the sun Change in the angle of the Earths axis Processes of Glacial Erosion Glaciers erode the landscape they

travel over in two ways: 1.Plucking 2.Abrasion Textbook page 146 Plucking

Most effective where: Rock is well jointed Rock has already been weakened by freeze-thaw action Bottom of glaciers scrape along valley floors creates friction causing melting around the base of the glacier Meltwater refreezes Freezes around the rocks on the valley floor

and these become part of the glacier Glacier advances Newly trapped rock is plucked out of the valley floor New material is then used in process of abrasion

Abrasion

Occurs when the bedrock beneath the glacier is eroded by the debris/material embedded in the sides and bottom of the glacier Sandpaper effect scrapes the rock over which it is travelling and leaves scratches or grooves in the rock

Striations show the direction of the ice flow Processes of Glacial Transportation 1.

Basal sliding Friction between the base of the glacier and the valley floor Meltwater acts as a lubricant Glacier slides downslope under the influence of gravity

2. Internal flow Ice crystals react to pressure and gravity Melting and refreezing Ice changes internally over time

without completely melting or breaking Material transported by the glacier is called moraine. Chapter 13: Glacial Processes, Patterns & Associated Landforms

Factors affecting the rate of glacial erosion Thickness of ice Topography Geology Gradient Accumulation and ablation

Landforms of Glacial Erosion

Cirque / Corrie Arete Pyramidal Peak U-Shaped Valley Ribbon Lake Fjords

Landforms of Glacial Erosion 1. Cirque Birthplace of a glacier Depression in a mountain Three steep sides Also called a corrie or coom

2. Arte Narrow ridge Formed when two cirques formed side-by-side or back-to-back Pyramidal Peak Formed when three or more cirques are eroded back-to-back or side-to-side around

the sides of a mountain. Isolated peak in the centre. Chapter 13: Glacial Processes, Patterns & Associated Landforms U-Shaped

Valley Glaciers take the easiest route as they move from upland areas down through their valleys Route is often a pre-existing V-shaped river valley Glacier moves through this valley, changing the shape from a V-shape to a U-shape

Erode vertically and laterally Valleys have steep sides and flat floors Glacier cuts off interlocking spurs of the V-shaped valley leaving truncated spurs Ribbon Lakes Long, narrow lakes found in glaciated U-shaped valleys

As a glacier advances through its valley it abrades the landscape Soft rock is abraded faster and easier than the harder resistant rock forming basins Within the rock basin meltwater and rainwater accumulates forming a ribbon lake

Fjords Drowned U-shaped valleys Result of melting glaciers OS Map Textbook page 149

Pairwork Quick Questions Name two processes of glacial erosion. What is the name given to material that is transported by the glacier? Name the landform that is said to be the birthplace of a glacier. How is an arete formed?

Explain the formation of a ribbon lake. Homework Textbook page 159 Questions 1-4 Landforms of Glacial Deposition

Moraines Drumlins Erratics Glacial Deposition Dropping or laying down of sediment that was once transported by a glacier

Lowland areas Deposited material is called glacial drift Material deposited directly by ice is called till or boulder clay Material deposited by glacial meltwater is known as fluvio-glacial deposits Chapter 13: Glacial Processes, Patterns & Associated Landforms

Examples of landforms of fluvio-glacial deposition Eskers Outwash plains Kames and kettle holes

Moraine Deposited debris Various sizes ranging from large boulders to fine rock flour Material may be angular or rounded in shape

Chapter 13: Glacial Processes, Patterns & Associated Landforms Five types of moraine i. Lateral moraine ii. Medial moraine

iii. End/terminal moraine iv. Ground moraine v. Englacial moraine Drumlins

Oval-shaped hills consisting of boulder clay Show direction of glacier movement

Occur in swarms or cluster Basket of eggs topography Drowned drumlins as the ice melted sea levels rose and the drumlins appear as islands in the sea OS Map Textbook page 155

Erratics Material transported by the glacier and are said to be out of place when deposited Provide information about the direction of the glacier and how far it has travelled crag and tail Esker long winding ridges of stratified sand and gravel that wind its way

across lowland areas Chapter 13: Glacial Processes, Patterns & Associated Landforms Examples of landforms of fluvio-glacial deposition Eskers

Outwash plains Kames and kettle holes Eskers Long winding ridges of stratified sand and gravel.

Outwash Plains Outwash Plains Glaciers melt Release vast amounts of water Spreads outwards beyond the end/terminal moraine Carries large volumes of rock and gravels and sands

Kames Piles of sediment consisting of gravels and sand Deposited along the front of a retreating glacier Kettle Holes

Blocks of ice separate from the main glacier Buried partly in meltwater sediments Blocks of ice melt leaving depressions or holes Fill with water form kettle hole lakes Landform

Processes Description involved 1 other fact Example

Homework Textbook page 160 Questions 7 - 12 Exam Questions Long Qs;Choice between fluvial / coastal /

mass movement / glacial... Long Qs; OS Map / Aerial Photograph Short Qs; Variety of questions on glacial landforms. Exam Questions

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