Chapter 3 Changing Climates The Big Freeze A cooling trend began in the Cretaceous Period and continued throughout the Tertiary Period By the end of the Tertiary Period 17 mya the climate became so cold that snow began o accumulate year after year in the Polar regions ID: 311369
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Slide1
3.2 The Icy Epoch
Chapter 3: Changing ClimatesSlide2
The Big Freeze
A cooling trend began in the Cretaceous Period and continued throughout the Tertiary Period
By the end of the Tertiary Period (1.7
mya
) the climate became so cold that snow began o accumulate year after year in the Polar regions
This marked the beginning of the icy Pleistocene EpochSlide3
The Big Freeze
The weight of the snow caused the lower layers of snow to become compacted into ice which formed glaciers
Glacier
– a large river of ice that forms on land and moves under the influence of gravitySlide4
COntinental
Glaciers
Very large glacier often more than 1 km thick, forms in polar regions
During the Pleistocene Epoch when these ice sheets reached a critical mass, they began to slowly flow outward toward the equator like a viscous fluid
Current continental glaciers cover nearly all of Antarctic and GreenlandSlide5
As
a continental glacier flows
outward it eventually reaches the sea, where
calving
occursSlide6
Alpine Glaciers
Snow accumulated in mountainous regions
As these glaciers flow to lower altitudes the temperature increases causing ice to melt and flow into streams
In Alberta chances are good that the water coming out of your tap is glacial melt waterSlide7
Alpine Glaciers
As the ice slowly flows it scrapes and gouges the rock below it
The original v-shaped valleys became u-shaped
The original dome shaped mountains became jaggedSlide8
Are we in an Ice Age Right Now?
An ICE AGE is a period which ice sheets cover parts of the Northern and Southern hemisphere
Glaciation is a period during which polar ice sheets advance to cover large regions of North America and northern EuropeSlide9
Ice Core Samples
Ice cores contain bubbles of gases from the past
Similar to deep sea sediment cores
The ratio of oxygen-18 to oxygen-16 is calculated and the average temperature change can be chartedSlide10Slide11
Glacial Evidence
As a continental ice sheet advances and then retreats, it leaves behind characteristic landforms
KAMES
– created as glacier chunks fallen off the larger ice mass are left to melt in place
Found between Slave Lake and Fort VermillionSlide12
Glacial Evidence
Drumlins
As the ice sheet flow, till is sometimes deposited in streamlined shapes called drumlins
The tapered ends of the drumlins point in the direction the ice sheet flows
Found in Morley FlatsSlide13
Glacial Evidence
Sand Dunes
The advancing ice sheet plucked up enormous amounts of fine, clean sand, as it scraped and gouged its way across rocks
When the ice sheet melted, sandy water poured into a glacial lake
The glacial lake drained and left a huge deposit of sandSlide14
Glacial Evidence
Athabasca Sand Dunes
Field of sand piled in the middle of green forests
7 km long, 1.5 km wide and up to 35 m deep
Migrates southward at a rate of 1.5 m per year!Slide15
Glaciers and Freshwater
Mountain glaciers and ice sheets have been melting
A warming trend has been linked to the burning of fossil fuels which is increasing the
G
reenhouse effect
As glaciers become obsolete so does our fresh water supplySlide16
Giants of the
Pleistocene Epoch
LARGE mammals thrived
Fossils have been collected near Medicine Hat, Alberta and in the Walsh Valley, Saskatchewan