What is a Glacier?

= An accumulation of compacted snow & ice that moves slowly under the force of gravity

2 types of glaciers:

1. Valley glacier = wedge-shaped stream of ice in a valley

2. Continental glacier = sheet of ice over all/part of a continent

(Ice caps are small ice sheets)

REVIEW

Valley Glacier

Valley Glacier

Continental Glacier

 • Firn/ Neve

= snow compressed from being buried, which has taken on a rough, granular ice form. It is in a state between snow and ice.It is snow “on the way” to becoming glacial ice.

 

Firn / Neve

 • Snow line

= the lowest level that permanent snow reaches in the summer

• Lowest snow line near poles

• Highest snow line near equator

  Banff Snowline

Glacial Movement & Erosion

1) Movement of glaciers:

• Glaciers move due to their great weight under the force of gravity

fastest movement at the surface and

in the centre

glaciers melt at lower elevations where it’s

warmer

• The melting end of a glacier is called the ice front or terminus

• Glacier movement can cause crevasses to form

• crevasse = large fissure/crack in ice

• Calving = when the ice front meets a sea, and chunks of glaciers break off into the water

• icebergs = chunks of glacier broken off into water

 

2) Weathering and Erosion from glaciers:

• As glaciers move, they pick up and move rock

• Rock of all sizes is moved, from powder to house-sized boulders

• Glaciers move rock in different ways:• rock drops on top of a glacier• rock is incorporated into a glacier• rock is dragged at the bottom of a glacier

• Plucking = a glacier “freezes around” a large rock, picking it out of the ground and carrying it away

• Glaciers can leave striations ( = parallel scratches on bedrock) because the rock material being dragged at the bottom of the glacier scratches the rock beneath it• Striations show the direction a glacier moved

• Rock flour = fine sediment formed by the crushing of rock beneath a glacier

3) Landforms caused by glacial erosion:• U-shaped Valley = a valley with a U-shape

• Hanging Valley = where a shallow U-shaped valley (caused by a small glacier) is intersected by a deep U-shaped valley (caused by a large glacier)

• Cirque = a semicircular basin formed at the head of a glacial valley

 • Arete = a sharp divide between 2 cirques  • Horn = a peak formed from 3 or more cirques 

3) Landforms caused by glacial erosion:• U-shaped Valley = a valley with a U-shape

• Hanging Valley = where a shallow U-shaped valley (caused by a small glaceir) is intersected by a deep U-shaped valley (caused by a large glacier)

• Cirque = a semicircular basin formed at the head of a glacial valley

 • Arete = a sharp divide between 2 cirques  • Horn = a peak formed from 3 or more cirques 

3) Landforms caused by glacial erosion:

• Cirque = a semicircular basin formed at the head of a glacier 

3) Landforms caused by glacial erosion: • Arete = a sharp divide between 2 cirques  

3) Landforms caused by glacial erosion:

• Horn = a peak formed from 3 or more cirques 

*Assignment 1: Draw a “before glacier erosion” and “after glacier erosion” picture of mountains, using

the diagrams on p.325 to help you.

*Assignment 2: Do 1 – 5 (Pg 325)

3) Deposition by glaciers:• When glacial ice melts (e.g., at the bottom or sides of a glacier),

the rock it carries gets deposited• Glacial deposits are called till

• Till is unsorted (rock of all sizes is jumbled together)• Moraine = a long pile of glacial till, formed at the end

or sides of a glacier• End moraine (end)• Lateral moraine (sides)

 Cirque = a semicircular basin formed at the head of a glacial valley • Arete = a divide between 2 cirques • Horn = a peak formed from 3 or more cirques Task 1 : Do 1 – 5 (Pg 325)

15.3 : Glacial Deposits• Glaciers carry & deposit drift ( = foreign rock material – eg: boulders, bedrock)

• There are 2 types of drift:

1.Till = unsorted, unstratified rock deposited directly by ice

Ex: Moraines are rock deposits of till when the glacier retreats

Ex: Drumlins are canoe-shaped hills made of till found in swarms when advancing glaciers ran over a moraine

 

2.Outwash = sorted, stratified rock deposited by streams of glacial melt-water

Ex: Eskers are winding ridges formed when sand & gravel fill melt-water tunnels beneath a glacier.

 

Drift

Till

Outwash

• Moraines = accumulations of glacial till

• Rock flour = mixture of sand & silt formed by crushing rock under a glacier

• Glacial milk = milky, white melt-water due to suspended rock flour. • Kames = cone-shaped hills of stratified sand/gravel

• Kettles = circular hollows formed on moraines & outwash plains • There are 3 types of lake formed from glaciation:

1. Cirque lakes2. Kettle lakes3. Moraine dammed lakes

 

Task : Do 1 – 5 (Pg 328)

Moraine

Glacial Milk

Kames

Kettle

15.4 : Ice Ages• Evidence of ice ages:

1. It began 2 million years ago + 4 advances of ice

2. Interglacial periods between advances

3. Many ice ages in the past

4. Advances + retreats occurred at the same time in both hemisphere

 

• Hypothesis of causes of ice ages:

1. Change in the sun energy

2. Volcanic dust in the atmosphere

3. Continents blocking ocean mixing

4. Changes in earth axis & orbits

  

Task : Do 1 – 5 (Pg 333)

Ice Age

Ice Age