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

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)

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)

Ice Ages Cycle

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

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.

The Last Ice Age The world's most recent glacial period lasted from 110,000 - 12,500 years ago.

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 - 20,000 years ago. It created much of the surface geology of the area, leaving behind many glacial landforms

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

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

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

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

Toronto Drumlins Toronto has several drumlins, ridges created by glaciers. https://www.youtube.com/watch?v=677PQitX7Fk How Drumlins are formed https://www.youtube.com/watch?v=loI584OFVpE How glaciers form the landscape 2:30

Toronto’s Ice Age

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.

Formation of the Great Lakes

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

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.

Old Toronto

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.

Weathering & erosion

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.

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

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