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Glaciers and Ice Ages

Glaciers and Ice Ages. By: Liz Alessi Brittany Spalding Megan Timmers. What is a glacier?. Glacier : a massive, long-lasting, moving mass of compacted snow and ice 2 types: Alpine Glacier Continental Glacier Glaciers covered the land 10,000 to 20,000 years ago. Glaciers.

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Glaciers and Ice Ages

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  1. Glaciers andIce Ages By: Liz Alessi Brittany Spalding Megan Timmers

  2. What is a glacier? • Glacier: a massive, long-lasting, moving mass of compacted snow and ice • 2 types: • Alpine Glacier • Continental Glacier • Glaciers covered the land 10,000 to 20,000 years ago.

  3. Glaciers • Where do they form? • On land where the amount of snow that falls in the winter exceeds the amount that melts in summer • They form in 2 types of environments: • High, snowy mountains in any climate • Cold polar regions

  4. Glaciers • How do glaciers form? • Snowflakes  Granular Snow  Firn  Glacier Ice • Firn: the transition between snow and glacial ice

  5. Glacial Movement • Glaciers begin to move when there is an increase in pressure. • 2 Types: • Basal slip: movement of the entire mass of a glacier along the bedrock • Plastic flow: ice flows as a thick fluid because of an increase in pressure

  6. Glacial Movement • Glacial Erosion: • Glacial Striations: parallel grooves and scratches in bedrock that form as rocks are dragged along at the base of a glacier • These markings show the direction of ice movement and are used to map the flow directions of glaciers.

  7. Glacial Movement • Landforms created from glacial erosion • From Alpine Glaciers • Forms U-Shaped Valleys, tarns, paternoster lakes, horns, arêtes, hanging valleys, fjords (p. 314) • From Continental Glaciers • Forms vast regions- entire mountain ranges • Formed the Great Lakes and the Finger Lakes in New York

  8. Glacial Deposits • DRIFT: all rock or sediment transported and deposited by a glacier • 2 types of drift: • Till: deposited directly by glacial ice • Landforms composed of till: Moraines and drumlins • Stratified drift: was first carried by a glacier and then transported and deposited by a stream • Landforms composed of stratified drift: outwashes, valley trains, outwash plains, kames, eskers, kettle lakes

  9. Ice AgeS • What are ice ages? • Ice Ages: intervals of time when large areas of the surface of the globe are covered with ice sheets • The most recent ice age is the Pleistocene Ice Age • This occurred 2 million years ago in the Northern Hemisphere.

  10. Ice Ages • When did ice ages occur? • Glaciations are concentrated into 4 time intervals. • Proterozoic Age (between 800 and 600 million years ago) • Pennsylvanian and Permian Age (between 350 and 250 million years ago) • Late Neogene to Quaternary Age (the last 4 million years) • Ordovician and Silurian Age (between 460 and 430 million years ago) • Less extensive glaciations.

  11. Ice Ages • Why do Ice Ages occur? • Because of the change of continental positions. • Because of the uplift of continental blocks. • Because of the reduction of CO2 in the atmosphere. • Because of changes in the Earth’s orbit.

  12. Ice Ages • What controls the advance and retreat of glaciers? • Changes in the eccentricity of the Earth’s orbit • Changes in the tilt of the Earth’s axis • The precession of the equinoxes

  13. Works’ Cited • Ice Ages. 2003. Illinois State Museum. 5 November 2005. <http://www.museum.state.il.us/exhibits/ice_ages/index.html>. • Thompson, Gary and Jon Turk. Earth Science and the Environment. 3rd ed. Canada: Brooks/Cole Thompson Learning, 2005. • United Streaming. 2005. Discovery Education. 5 November 2005. <http://www.unitedstreaming.com/index.com>.

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