Geography of Canada

Physical Geography

Geologic History

•  The surface of the earth is a thin layer of moving plates that float on the mantle.

•  Each earthquake is an indication of the movement of the earth’s upper layer called the crust.

•  Seismologists (scientists who study earthquakes) have discovered that earthquakes occur more frequently in specific areas.

•  Earthquakes and volcanoes frequently occur where the edges of the earth’s plates are spreading, colliding, or sliding from one another.

Types of Plate Behaviour

Spreading

Colliding

Sliding

The Earth’s Interior

Major Earthquakes and Volcanoes

Red dots represent active sites where major volcanoes or earthquakes have occurred in the twentieth century. The sites outline vast "plates" that drift around on the surface of our planet.

Alfred Wegener’s Theory of Continental Drift

①  He saw the jigsaw fit between South America and Africa.

�  He found fossils of the same plants and animals on different continents.

Alfred Wegener’s Theory of Continental Drift

�  There are mountains similar in age and structure on both sides of the Atlantic Ocean the Appalachian Mountains in North America were similar to the Caledonian Mountains in Europe.

�  Glaciers once covered southern Africa, India, Australia and South America.

Alfred Wegener’s Theory of Continental Drift

Why did most scientists disagree with Wegener?

  Wegener could not explain what mechanism was powerful enough to move huge continents.

Mount Kilauea, Hawaii / Kobe, Japan

[A] An active volcano on Mount Kilauea in Hawaii. Kilauea seems to be a virtually ongoing eruption. [B] The aftermath of the earthquake that claimed more than 5000 lives and caused billions of dollars' worth of damage in Kobe, Japan in January 1995.

San Andreas Fault

The San Andreas and associated faults in California result from the North American and Pacific plates sliding past one another. (a) A small part of the fault line separating the two plates. (b) A satellite photo of the San Francisco Bay area, showing the location of two fault lines. (c) A larger-scale view of the fault system.

Plate Tectonics

•  About 300 million years ago all the earth’s land masses were joined together into one supercontinent called Pangaea

•  About 200 million years ago Pangaea began to break up, with each tectonic plate moving in a different direction.

Theory of Plate Tectonics

•  The earth’s crust is made up of about 20 plates.

  With the help of satellites, scientists have discovered that the plates move between 1-2 cm every year.

•  These plates are moving over a layer of molten rock known as the mantle.

•  It is believed that the unequal distribution of heat within the earth causes convection currents to move the plates.

Pangaea

Given the currently estimated drift rates and directions of the plates, we can trace their movements back into the past. About 200 million years ago, they would have been at the approximate positions shown in (a). The continents' current positions are shown in (d)

Earthquakes in Canada

Significant Earthquakes in Canada Homework

•  Handout: The Earth’s Interior – Questions #1-8.

•  Blank Map: Copy page 112 from your textbook onto your blank map.

•  Textbook: Read pages 110-117; Questions #1-5 on page 118.