Social StudiesUnit 2Canada’s Physical Landscape

Introduction Canada’s geography – its landforms

and climate - has a great impact on Canadians’ sense of identity.

Planet Earth

Movement of the Crust In 1915, the German geologist and meteorologist

Alfred Wegener first proposed the theory of continental drift

The theory of Continental Drift: states that parts of the Earth's crust slowly drift

atop a liquid core. The fossil record supports and gives credibility to

the theories of continental drift and plate tectonics.

Wegener hypothesized that there was a gigantic supercontinent 200 million years ago, which he named Pangaea, meaning "All-earth".

The Earth's crust is divided into huge, thick plates that drift atop the soft mantle.

The plates are made of rock and are from 80 to 400 km (50 to 250 miles) thick.

They move both horizontally and vertically. Over long periods of time, the plates also

change in size as their margins are added to, crushed together, or pushed back into the Earth's mantle.

PLATE TECTONICS The theory of plate tectonics (meaning

"plate structure") was developed in the 1960's.

This theory explains the movement of the Earth's plates (which has since been documented scientifically) and also explains the cause of earthquakes, volcanoes, oceanic trenches, mountain range formation, and other geologic phenomenon.

The top layers of the plates are called the crust.

Oceanic crust (the crust under the oceans) is thinner and denser than continental crust.

Crust is constantly being created and destroyed; oceanic crust is more active than continental crust.

TYPES OF PLATE MOVEMENT: Divergence, Convergence, and Lateral

Slipping At the boundaries of the plates, various

deformations occur as the plates interact; they separate from one another (seafloor

spreading), collide (forming mountain ranges), slip past one another (subduction zones, in which

plates undergo destruction and remelting), and slip laterally.

Canada’s Crust Canada’s Pacific coast is the western

edge of the North American Plate. The Pacific Plate moves in a north-easterly direction, creating a subduction zone.

A subduction zone is an area of the earth’s crust where one plate slides beneath another, creating volcanoes and potential earthquakes.

http://www.youtube.com/watch?v=6OHRb_ODo-Q&feature=related

British Columbia experiences approximately one-fifth of Canada’s thousand or so earthquakes.

What are Landforms? Land forms are the topography, or

natural features, of the land’s surface. A landscape is an area’s landforms

together with its cover of vegetation, water, ice, and rock.

Landscape also includes the activities of humans and other animals.

There are urban and rural landscapes. Landscapes directly affect people’s

lives, influencing what they eat, how they earn a living, and many other factors of daily life.

Topography can be described using the following terms:

Elevation – height of land above sea level. Relief – difference in elevation between

two points on the earth’s surface. Gradient – refers to the steepness of

slopes. Geology – the types of rocks and the

history of those rocks. General appearance – Is the description

of landforms.

How are Landforms Built?

The earth’s surface is built of material that comes from beneath the crust, or it is formed by the movement of the earth’s crust itself.

The heat of the earth’s interior creates convection currents in the mantle.

These convection currents sometimes cause the magma in the mantle to break through the crust of the earth as lava and volcanic ash.

At other times, moving magma may cause the plates to separate or collide at their boundaries, resulting in parts of the crust moving upward or downward to trenches and rift valleys.

When continental plates collide, they can push up mountains.

When undersea plates collide, the plate edges are pulled down in a subduction zone, and deep trenches and valleys are produced.

Similarly, when plates separate, different landforms can be created depending on whether the plates are continental or undersea.

When continental plates separate along a fault, or break in the earth’s crust, the movement of magma can either raise or lower the blocks of the crust depending on the direction of the forces (see figure 2.7 on page 24).

How Are Landforms Shaped?Canada’s topography is the result of four forces: The building-up forces of mountain

building The wearing-down forces of weathering,

or exposure to the atmosphere The wearing-down forces of erosion The build-up forces of deposition, where

eroded materials add new shapes

Canada’s Landform Regions Canada is so large that geographers

divide it into regions to make it easier to study.

A region is an area that is defined on the basis of the presence or absence of certain characteristics.

Geographers classify landform regions based on a combination of characteristics: Age of rock Type of rock Relief Gradient Process that has shaped the area

It is difficult to limit the number of Canadian landform regions. However, there is general agreement about the eight major regions shown in figure 2.11

Canadian Shield