Glaciers and Ice Ages By Liz Alessi Brittany

Glaciers and Ice Ages By: Liz Alessi Brittany Spalding Megan Timmers

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

Glaciers l 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 l Cold polar regions l

Glaciers l How do glaciers form? ¡ Snowflakes Granular Snow Firn Glacier Ice ¡ Firn: the transition between snow and glacial ice

Glacial Movement l Glaciers begin to move when there is an increase in pressure. l 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

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

Glacial Movement l Landforms ¡ From l created from glacial erosion 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 l Formed the Great Lakes and the Finger Lakes in New York l

Glacial Deposits l DRIFT: all rock or sediment transported and deposited by a glacier ¡ 2 types of drift: l Till: deposited directly by glacial ice • Landforms composed of till: Moraines and drumlins l 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

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

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

Ice Ages l Why do Ice Ages occur? ¡ Because of the change of continental positions. ¡ Because of the uplift of continental blocks. ¡ Because of the reduction of CO 2 in the atmosphere. ¡ Because of changes in the Earth’s orbit.

Ice Ages l 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

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