What is a Glacier? REVIEW = An accumulation of compacted snow & ice that moves slowly under the force of gravity 2 types of glaciers: Valley glacier = wedge-shaped stream of ice in a valley Continental glacier = sheet of ice over all/part of a continent (Ice caps are small ice sheets)

Valley Glacier

Valley Glacier

Continental Glacier

It is snow “on the way” to becoming glacial ice.   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

= the lowest level that permanent snow reaches in the summer   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 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

crevasse = large fissure/crack in ice Glacier movement can cause crevasses to form crevasse = large fissure/crack in ice

icebergs = chunks of glacier broken off into water 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: 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   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: Cirque lakes Kettle lakes Moraine dammed lakes Task : Do 1 – 5 (Pg 328)

Moraine

Glacial Milk

Kames

Kettle

15.4 : Ice Ages Evidence of ice ages: It began 2 million years ago + 4 advances of ice Interglacial periods between advances Many ice ages in the past Advances + retreats occurred at the same time in both hemisphere   Hypothesis of causes of ice ages: Change in the sun energy Volcanic dust in the atmosphere Continents blocking ocean mixing Changes in earth axis & orbits    Task : Do 1 – 5 (Pg 333)

Ice Age

Ice Age