1 / 20

Glaciers

Glaciers. Erosive forces . Glacier. persistent body of dense ice that is constantly moving under its own weight. It forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years. Glacier formation . Snowfall

karma
Download Presentation

Glaciers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Glaciers Erosive forces

  2. Glacier • persistent body of dense ice that is constantly moving under its own weight. • It forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years.

  3. Glacier formation Snowfall • Glaciers form where the accumulation of snow and ice exceeds ablation. • This snow collects and is compacted by the weight of the snow falling above it, crushing the individual snowflakes and squeezing the air from the snow Firn • left over from past seasons and has been recrystallized into a denser substance • snow repeatedly freezes and thaws, changing into granular ice Glacial Ice • Once all air has been squeezed from it, the snow is turned into extremely dense glacial ice • When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure.

  4. Clicker • What is ablation? • Melting and sublimation • Melting and evaporation • Freezing and evaporating • Melting and precipitation Times up! Timer

  5. Explain what the growth of a glacier depends on • The balance between snow fall received and the amount of ice lost be melting and sublimation(evaporation)

  6. Advance v. Retreat • Advance • Snow accumulation is greater than ablation • Retreat • Ablation is greater than snow accumulation

  7. Glacier Types Alpine (Valley) Continental Long, narrow wedge shaped form on the crests and slopes of mountains. Ex. Alaska, Himalayas, Alps, Andes Wide, very large millions of km2 Polar regions Only found in two places Greenland and Antarctica

  8. Clicker • Today a continental ice sheet is located in? • Eastern Europe • New Zealand • Alaska • Greenland Times up! Timer

  9. Glacial Movement Basal Slip Internal Plastic Flow glacier slides over the terrain on which it sits, lubricated by the presence of liquid water. Refreezes as pressure removed Solid ice crystals slip over each other, causing slow forward motion. Slope Thickness Temperature (of Ice) Surface faster Friction

  10. Erosion • Plucking/ Ice wedging : Plucking: “pluck” material from V sides makes a U shaped valley Ice wedging: water seeps into cracks and expands leaving larger cracks.

  11. Erosion • Abrasion: • Mechanical erosion of rocks (think sand paper) as glacier scrapes over the landscape/ bedrock below

  12. Features caused by Erosion • Cirques: • start of a classic valley glacier is a bowl-shaped • Horns: • 3 or more cirques thatencirclea single mountain (looks like a pyramid) • Arêtes: • Two glacial cirques may form back to back and erode their backwalls until only a narrow ridge or “spine” is formed • U-shaped valley: • widened, deepened, and smoothed, by a glacier forming a "U"-shaped glacial valley

  13. Features caused by Erosion • Hanging valleys: • when glaciers recede, the valleys of the tributary glaciers remain above the main glacier's depression ( water falls often) • Striations: • Grooves from plucking/ and abrasion • Kettle lake • shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters.

  14. Clicker Cirques are best described as • rounded knobs of rock. • bowl-shaped depressions. • sharp, curved peaks. • sharp and jagged ridges. Times up! Timer

  15. Deposition (homework) • Kames: • an irregularly shaped hill composed of sand, gravel and till that accumulates in a depression on a retreating glacier.

  16. Michigan’s Glacial History

  17. Big idea Great lakes Each of the Great Lakes began as a river. Image from Earth Science, Tarbuck and Lutgens, 2003

  18. As the climate cooled… • The rivers froze. • Glaciers moved through them – widening and deepening them to form today’s “U” shaped lake bottoms.

  19. Why do scientists believe that glaciers once covered Michigan? • The unsorted moraine deposits follow the outline of Great Lakes. • Other depositional features such as drumlins and kettle lakes are found throughout Michigan. • Erosional features like striations are found in Michigan as well.

  20. Explain what happens to Earth’s crust when a glacier is removed. • Isostatic Rebound • The upward movement of the Earth’s crust

More Related