GlaciersOctober 21st, 2009

Pre - Activity Knowledge Check

on the note sheet provided, answer the true or false questions

Glacial Power

http://www.youtube.com/watch?v=cIBFAke90SI

Glaciation of Canada

at one time, ice sheets covered much of North America

the last ice age ended approximately 10, 000 years ago, at which time 30% of the land was covered and glaciers were up to 1000 km wide (about the distance from Montreal to Windsor) and 100m thick

today only about 10% (mostly Antarctica) of the earth is covered by ice sheets

What is a glacier?

a large mass of ice and snow that moves over the earth's landscapes

generally formed by the continual accumulation (continuously building up) of snow that compacts into ice

formed in areas where temperatures are so low that snowfall does not melt entirely during the summer

today, such conditions are found only at high latitudes (North / South poles) or high altitudes (the Alps, Rockies, Himalayas)

Konkordia, Switzerland

QuickTime™ and aMPEG-4 Video decompressor

are needed to see this picture.

Types of Glaciers

Continental glaciers (high latitudes)

cover large areas of land

found in areas of high latitude (North / South poles)

in their most extensive form are referred to as ice sheets

example: Greenland

Alpine glaciers (high altitude)

found in he mountainous regions (high altitudes)

located in bowl-shaped hollows or valleys on the mountains

continually grow from a collection of snow (snowfield) near the top

Movement

glaciers are constantly advancing and retreating, despite the movement not always being visible to the naked eye

glaciers shape land through scraping and depositing material (deposition)

as the snow and ice buildup continues, glaciers move

thicker continental glaciers move outward from the centers of accumulation (think of a mound of play-doh being squished down)

smaller alpine glaciers aided by gravity, move downhill

Glacier Advance / Retreat Model

http://www.uky.edu/AS/Geology/howell/goodies/elearning/module13swf.swf

There are 3 main mechanisms by which glaciers are thought to move:

Creep

Basal Slip

Shearing

Creep

the pressure of the overlaying ice causes the crystals to be crushed and produced and an outward or downward movement under the influence of gravity

creep occurs very gradually and seldom amounts to more than a few centimeters per day

Basal Slip

occurs when there is a thin film (layer) of water between the ice and rock

movement is more rapid than creep (up to 1 meter per day)

Shearing

process is similar to faulting

usually occurs when glaciers are moving down slope

sometimes ice in glaciers cannot adjust to the pressures produced by creep and basal slip

so the ice shears as it moves forward, producing deep cracks in the ice called crevasses

Shearing / Crevasse Model

http://highered.mcgraw-hill.com/sites/0072402466/student_view0/chapter12/animations_andmovies.html#

True / False

answer the same true / false questions on the note sheet from the beginning of the lesson

Glaciers and Climate Change

www.youtube.com/watch?v=M3g1iZn95sc

Exit Card

pull out a sheet of lined paper

on that sheet of paper, WRITE DOWN AS MUCH AS YOU KNOW ABOUT GLACIERS

you have 2 minutes

Homework

use your textbook pages 118 - 125 for this work (you can also use an atlas)

do questions 1, 2, 4, 5, 7 and 8