Ice Ages
- Earth has had several ice ages
- Ice ages are periods of time when freezing temperatures created massive sheets of ice that covered continents
- The last ice age ended between 6000 and 10,000 years ago
- During the last ice age, glaciers covered most of Canada and the Northern US
How Ice Ages Occur
- An ice age occurs when the earth’s climate cools, and snow falling in winter does not all melt in summer
- Over 1000s of years, the snow builds up and gets so deep it turns to ice- a glacier
- Glaciers can move very slowly, like a very thick liquid
Types of Glaciers – Alpine and Continental
Alpine Glaciers are smaller glaciers found on mountains
- They move down valleys because of gravity
- There are still alpine glaciers in Canada today in the Arctic and in the West Coast Mountains
Continental Glaciers (or ice sheets) are much bigger than alpine glaciers – they can cover entire continent
- These glaciers move because of their own weight (like pancake batter spreading over the pan)
- Today, there are only two continental glaciers – over Greenland and Antarctica
Continental Glaciers – Landforms
- Continental Glaciers make the land smoother by eroding some areas and depositing sediments in others
- Striations are grooves scraped in rock by rocks frozen in the glacial ice
- Moraines are large rocks that have been picked up by a glacier and dropped 100s of kilometers away from where they belong
- Moraines are ridges of sediments and rocks (till) that are pushed along by a glacier and then left behind when it melts
- Drumlins are egg shaped hills with a steep side and a gentle side
- The steep side points in the direction the glacier came from
Humans and Glacial Features
- We use glacial landforms in a number of ways
- Gravel extraction – we use gravel from glacial till for construction
- Moraines tend to be used for grazing, forestry
- Drumlins have deep soil, good for farming
