Post on 13-Dec-2015
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.
GlaciersWhere 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 climateCold polar regions
GlaciersHow do glaciers form?
Snowflakes Granular Snow Firn Glacier Ice
Firn: the transition between snow and glacial ice
Glacial MovementGlaciers 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
Glacial MovementGlacial 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.
Glacial MovementLandforms created from glacial
erosion From Alpine Glaciers
Forms U-Shaped Valleys, tarns, paternoster lakes, horns, arêtes, hanging valleys, fjords (p. 314)
From Continental GlaciersForms vast regions- entire mountain rangesFormed the Great Lakes and the Finger Lakes in
New York
Glacial DepositsDRIFT: 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
Ice AgeSWhat 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.
Ice AgesWhen 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.
Ice AgesWhy 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.
Ice AgesWhat 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_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>.