January 21, 2011

 Glaciers act as agents of erosion and deposition to help to create unique landforms which you will study in this unit  Glacier: A large mass of ice resting on land or floating as an ice shelf in the sea adjacent to land

 Ice: An Agent of Erosion  as permanent snow cover increases in thickness, the underlying layers of snow are transformed into ice by tremendous pressure exerted by snow on top

 large volumes of ice behave like plastic and under great pressure they begin to flow out in tongues  the weight and abrasive power of these glaciers changes the landscape

 during last years, scientists estimate that there have been four glacial advances with the last one ending approximately years ago

 Volcanic eruptions send a layer of ash and dust around the earth in the atmosphere. Solar radiation from the sun is partially blocked resulting in cooling

 A reduction in the amount of carbon dioxide in the atmosphere reduces the earth's ability to absorb long wave radiation being emitted by the surface. Therefore, not as much heat is trapped by the atmosphere

 The amount of energy emitted by the sun has cyclic variations. Glaciation coincides with periods of reduced solar activity.

 Changes in the tilt of the earth's axis as well as changes in its orbit

 Glacial flow is caused by glacial creep and basal sliding.

 Glacial Creep  due to the tremendous weight and pressure of the glacier, the ice becomes pliable and flows - it flows fastest in the middle of the glacier where it is thickest (i.e. internal flow)

 Basal Sliding - movement along the bottom of the glacier due to the warmth of the earth and internal streams  This generally only happens in temperate based glaciers, such as in the Alps, where the ground is warmer, allowing the ice to melt

 The rapid, lurching, unexpected forward movement of a glacier.  A build up of water pressure under the glacier is a cause

Accumulation and ablation Ablation is the wasting or loss of material from a glacier. If accumulation > ablation, the tip of the glacier advances If accumulation = ablation, the tip of the glacier is stationary If accumulation < ablation, the tip of the glacier retreats

 Abrasion: is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosionfrictionwind glacierwavesgravitywater  Striations: a scratch or groove cut into the surfaces of bedrock by boulders and pebbles frozen into the bottom of a glacier.

 Glacial Plucking: a process by which sections of the rock, frozen to the bottom of the glacier, are pulled out of place and carried away as ice advances.

 Sheer Weight of the Ice

 A major sheet of ice or an continues mass of ice.  Cover the plains and low land areas  81% of Greenland  90% of Antarctica

 Form in upland and mountainous regions, within larger valleys and basins.  Smaller in Size  Valley Glacier is a common subtype

 A scooped out, amphitheatre-shaped basin at the head of a alpine glacier valley

 Page 280: 5A, 6A. B and 7

 Cold Temperatures  Summer blanket of snow  Glaciers can only form where snowfalls exceed the annual melting over long periods of time  Compacted ice crystals that have not yet been pressed into solid mass form what is called a firn

 Features Produced by Alpine Glaciation  Cirques  Cirque Mountain, Labrador

A lake occupying the bottom of a cirque eroded by a glacier that has since completely melted

 A rectangular, sharp- pointed peak formed where several glacial cirques erode back into a single mountain

 A knife-edged ridge formed between the steep walls of two or more adjacent glacial cirques

 A cirque which breaks the space in a continues ridge forms a col.

 A wide, deep valley with a U-shaped cross- section, formed by glacial erosion in a mountainous region.  V shaped river valleys after being occupied by a glacier becomes U- shaped due to erosion

 A U-Shaped valley cut by a smaller tributary glacier that lies at a higher elevation then the deeper U-shaped valley eroded by the main glacier.

 A stream that occupies a hanging valley will enter the main valley as a waterfall

 Triangular faces on the vertical walls of the u- shaped valley.  Ex. Upper Kananaskis River, Alberta

 The result of the drowning of a u-shaped valley by the sea  Fiord coasts are found in Norway, BC, Labrador, New Zealand, Southern Chile and Baffin Islands

 Till  Talus  Moraine  Drumlins  Kettle hole

 Unsorted glacial sediment deposited from a melting glacier.  Vary from clays to mixtures of clay, sand, gravel and boulders.  Usually form plains.

 Shattered bedrock fragments that accumulate at the bottom of rock slopes.  Often form a second slope at the bottom of a steep slope.

 An accumulation of unconsolidated material deposited by glaciers.  They tend to have many different sized particles, ranging from fine silt to large boulders.

 Elongated, streamlined hill deposits of till.  Its long axis is parallel with the movement of the ice, with the blunter end facing into the glacial movement.

 Created from ice melt from a chunk of glacier that was left behind from a retreating glacier.  The sides are built up by glacial drift from the melting ice.

 Alps are high altitude pastures ex: Swiss Alps

 Cracks that occur as a glacier moves into a wider part of the valley or encounters a change in slope.  Eastern Baffin Island, Nunavut

Current Glaciers on Earth Greenland Ice Sheet Antarctic Ice Sheet

 PLEASE WATCH