Transcript Earth`s Frozen Water

Earth’s Frozen Water
Unit E: Topic 2
Glaciers
• Are large bodies of slow moving ice and
snow.
• An ice cap is a glacier that forms on level
land.
• An ice-field is an upland (mountainous)
area of ice that feeds two or more glaciers.
Eg. Columbia ice-field.
How do Glaciers Form?
• As snow falls it gradually adds to the
weight of the snow on the ground and
gradually causes the snow on the ground
to pressurize into ice.
• This is similar to how carbon is hardened
into diamonds under extreme pressure.
Valley and Continental Glaciers
• Valley glaciers – form high in the
mountains and move through valleys b/w
mountain peaks.
• Continental glaciers – Cover large areas of
land like Greenland and Antarctica. Also
called icecaps.
Glacial Features
• - Icefall – is a waterfall for glaciers. When
a glacier flows over a steep cliff and
breaks up under gravity.
• - Crevasse – A large fissure or crack in the
glacier’s ice.
Ice in the Oceans
• Continental glaciers have pieces that
break off and move off into the ocean as
warm air and water weaken the ice. This
breaking up process is called calving.
• If a flat piece falls off and forms a broken
sheet on the water, it’s called pack ice.
• If a large chunk breaks off and floats off
into the ocean, it’s called an iceberg.
Pack Ice
How Glaciers Shape the Land
• As glaciers advance or retreat they affect
the environment and leave landmarks.
• Cirques, aretes, moraines, horns, eskers
striations, erratics, and tills are all
examples of evidence of past glaciers.
• HW: Define the above terms, and
complete the vocabulary worksheet.
Meltwater
• Water formed by melting snow and ice
from glaciers carves channels into the
glacier.
• Meltwater acts as a reservoir of fresh
water feeding rivers, powering
hydroelectric power-plants, supplying
drinking water.
• Glaciers, and meltwater affect climate and
slow the water cycle.
Ice Ages
• The Earth has had 7 ice ages in its recent
history (millions of years)
• During an ice age, glaciers cover up to
28% of the Earth’s surface including all of
Canada.
• Average temperatures on the Earth are
five degrees cooler than they are now
(around 15°C)
How an Ice Age Might Start
• Temporary reduction of the sun’s energy
reaching the Earth.
• More mountain snow reflecting more of the
sun’s energy away from the Earth.
• Volcanic activity spewing a cloud of ash
and dust which blocks the sun’s light (what
might have happened to the dinosaurs).
• Change in Earth’s tectonic plates.
• Change in Earth’s axis of rotation.
Greenhouse Effect and Global
Warming
• Greenhouse Effect – A natural
phenomenon which keeps the Earth
warmer than it should be.
• Global Warming – A possibly man-made
phenomenon which amplifies the natural
Greenhouse Effect and, if continued, will
cause glaciers to melt causing widespread
flooding.