1. How the last Ice Age shaped Canada
Glaciation & Erosion
How the last Ice Age shaped Canada

2. Ice Ages
We are technically in an ice age since there is ice covering the Poles (this Ice Age is called the Quaternary)
Glacial period = colder time within an ice age
Interglacial = warmer time within an ice age (we’re in one of these)

3. There have been at least 5 major Ice Ages in Earth’s history
Sometimes the entire Earth freezes over (Snowball Earth)
And sometimes all the ice melts at the Poles (Hot House Earth)

4. Ice Ages Cycle

5. Why were there Ice Ages?
Many scientists believe the ice ages were caused by changes in the shape of Earth’s orbit & the tilt of its axis

6. The Pleistocene Epoch
The Pleistocene Epoch is the actual name for the last glacial period
This period is the first in which Homo sapiens evolved, and by the end of the epoch humans could be found in nearly every part of the planet.

7. The Last Ice Age
The world's most recent glacial period lasted from 110, ,500 years ago.

8. Laurentide Ice Sheet
A massive ice sheet that covered most of Canada and a large portion of the northern US
It covered most of northern North America between 95, ,000 years ago.
It created much of the surface geology of the area, leaving behind many glacial landforms

9. Retreat of the Laurentide Ice Sheet
As the ice sheet retreated, it left behind many large glacial lakes

10. How Do Glaciers Form Landscapes?
By scratching the surface like sandpaper
Glaciers can pick up rocks and sand
Then the ice sheet acts like sandpaper and scratches the land underneath
Striation: a scratch mark on a rock
It can also polish the rock smooth

11. How Do Glaciers Form Landscapes
2) The glacier will dump rocks along the way
Glaciers will leave rocks and sediment as it moves
It will leave little mounds and hills along its edges

12. Glacial Landforms Till: the sediments in a glacier
Moraines, Eskers, Drumlins: hills created from the deposit of till from a glacier
Kettle Hole: the hole or lake created from a leftover chunk of glacial ice

13. Toronto Drumlins
Toronto has several drumlins, ridges created by glaciers.
How Drumlins are formed
How glaciers form the landscape 2:30

14. Toronto’s Ice Age

15. Great Lakes and Lowlands
Most of the Great Lakes’ basins were carved out by the moving ice.
Soil and rocks were scooped off the Canadian Shield and deposited over southern parts such as Toronto.

16. Formation of the Great Lakes

17. Don Valley
The deep wide lower Don Valley was formed after the draining of Lake Iroquois (a huge glacial lake)
Many streams, including The Don, cut deep U-shapes ravines through the previously V-shaped valley

18. Toronto’s Lakeshore
Modern Lake Ontario is within the bed of ancient Lake Iroquois, a meltwater lake that rose while Ice Age glaciers blocked the outlet of the Saint Lawrence River to the sea.

19. Old Toronto

20. Oak Ridges Moraine North of the city
The moraine's spongy wetlands and soil were deposited 12,000 years ago from the retreating glacier
Now dozens of streams spring from there and 35 of them pass through the Greater Toronto Area.

21. Weathering & erosion

22. What’s the Difference?
Weathering: the breakdown of rock and the formation of new minerals.
Erosion: the physical removal and transportation of rock particles from the source by water, wind, or ice.

23. 2 Types of Weathering 1) Mechanical weathering
The physical disintegration of rock into smaller pieces.
Facilitated by the action of ice, water, and wind
Can be caused by water, ice, frost, burrowing animals, plant roots

24. 2) Chemical weathering
Chemical decomposition of rock from exposure to atmospheric gases or liquid water (which is often acidic).