3 Theories of Glaciation Orbit Change Earth’s orbit changes gradually, turning more elliptical over a cycle that takes years. Mid- cycle is the coldest, which is the time when glaciers form. Axis Change It takes over years for the Earth to change the tilt of its axis. The North Pole receives less light, the temperature drops, and glacial ice begins accumulating Blocked Sun The sun gets blocked by dust in the atmosphere caused by volcanoes or giant asteroids. This prolonged cooling causes and ice age to occur.
Types of Glaciers Alpine Glaciers These glaciers move from mountains to lowland areas following river valleys. Tributary glaciers flow into a single main river of ice, where the sides and bottom layers move the slowest, while the top and middle layers move the fastest. Continental Glaciers Continental glaciers are large ice sheets on flat lowland areas. The ice can be about one kilometer thick, and moves very slowly, sometimes as a result of moving alpine glaciers. They leave behind hilly deposits of debris or scoured bedrock. These giant ice sheets weight down on the continent, and after retreating, the continent moves back up (also known as isostatic rebounding)
Glacial Erosion Plucking Rocks attach to the glacier and get ripped away. This process speeds up when melt-water seeps into cracks, freezes, and cracks the rock. Abrasion Plucked rocks that are attached to the glacier scrape at rock surfaces as the glacier moves. Rock flour: Fine powdery rock material left behind as a result.
Depositional Material Drift Any deposits left behind by a glacier, often as a result of ice melt, are known as drift. Till The unsorted and unstratified material left when glacial ice melts is known as till. This includes rock flour, sand, gravel, and boulders. Outwash The well-sorted and stratified material left from running glacial melt-water is known as outwash. The heaviest material deposits first, followed by lighter.
Features 1 Horn 2 Cirque 3 Arête 4 Medial Moraine 5 Lateral Moraine 6 Crevasses 7 Col 8 Snout 9 U-Shaped Valley
Features 1 Tarn 2 Cirque 3 Striations 4 Truncated Spur 5 Hanging Valley 6 Bridal Veil Falls
Glaciated Definitions Horn: A pyramidal peak that occurs when cirque glaciers erode a mountain on multiple sides Cirque: Hillside hollow made from the erosional activity of glaciers Arête: Two cirques that erode the mountain between them, forming a sharp ridge Crevasse: Deep cracks on the glacier’s surface, formed when the glacier moves over uneven rocks Col: A mountain pass that is formed when two cirques erode the arête between them Snout: Glacier’s leading edge U-Shaped Valley: Shape of a glacial valley; flat bottom and steep sides
Post-Glaciated Definitions Medial Moraine: A strand of debris going through the middle of a valley because of joining tributary glaciers Lateral Moraine: Rock material attached along the glacier’s side that has been ripped from the valley walls Truncated Spurs: The area where the V-shaped valley cuts off into a U-shaped valley Tarn: Lake that comes about when a cirque gets filled with water Hanging Valleys: Tributary glacial valleys that joined with the main valley glacier, melted away, and were left hanging high at the side of U-shaped valleys Striations: Grooves made in bedrock by abrasion
Features 1 Ground Moraine 2 Recessional Moraine 3 Terminal Moraine 4 Esker 5 Drumlin 6 Outwash Plain 7 Kettle 8 Finger Lake 9 Pro-Glacial Lake 10 Erratic 11 Braided Stream
Glaciated Definitions Ground Moraine: Debris deposits that were carried by the glacier in its lower ice layers Terminal Moraine: Debris left at the farthest advance of the glacier Recessional Moraine: Debris deposited at the snout when ablation and accumulation are happening at the same time Outwash Plains: Area where ice melts and the melt-water deposits stratified debris Crag & Tail: Created when a glacier hits a very hard rock (igneous) and gets stuck on one side of the rock (tail) while the rest of it moves on
Post-Glaciated Definitions Pro-Glacial Lake: Lake formed when the terminal moraine acts as a natural dam and is filled with melt-water Esker: Stratified deposits left behind from melt-water Ribbon Lakes: After glaciation, long, narrow gouges fill up with glacial melt- water Kettle Lakes: A chunk of the glacier gets left behind, eventually melts, and fills in its hole to make a lake Drumlins: Deposits left behind that are hill-like Erratic: A large boulder that is deposited far from where it originated from
Benefits of Glaciers Freshwater Melt-water is freshwater and is left in large quantities. It is drinkable and also provides animals with habitats. Hydroelectricity Damming tarns allows for a renewable source of energy. Tourism Glaciers attract people for sight-seeing and recreation, which earns the economy some revenue. Construction Large deposits of sand and gravel are left behind by glaciers which can be used to build roads. Farming Glaciers leave behind minerals and rich soil for farming and grazing (Prairies).
Disadvantages of Glaciers Flooding When glaciers melt, they can cause floods. Excessive melting can lead to the ocean level rising and coastal cities getting submerged. Temperature Glaciers make global temperatures more extreme. Also, the sun reflects off of the ice, which heats the planet Freshwater in Oceans Some animals are unable to survive in freshwater when it melts off a glacier and enters the ocean Crevasses Humans and animals can fall into and become trapped in crevasses Loss of Freshwater Clean drinking water goes to waste when glaciers melt into the ocean. Projects Teachers have reason to give their poor students more projects to work on (although this was a good project!)