1. Canada’s Geologic History
Chapter 11

2. Plates
The structure of the earth is similar to that of a frozen lake; however, there a three important differences.
Earth’s plates (i.e. the ice on the lake) are made up of solid rock.
The “water” beneath the earth is actually very dense liquid rock that is heated by the earth’s core.
The movement of ice on the water is generally caused by wind, but the movement of Earth’s plates is due to heat currents that start in the core.

3. There are TWO types of plates:
Oceanic (water surface)
Continental (Land surface)
Uneven temperatures within the earth cause convection currents to move the plates

5. Earthquakes and Volcanoes
These natural disasters occur where there is movement of Earth’s plates
Picture the ice of the frozen lake is now broken up into huge plates that can be moved by wind and by currents in the water below.
In some places ice plates (just like Earth’s plates) are pulled apart, while in others they are smashed together.

6. The Theory of Continental Drift
First proposed by Alfred Wegener in 1912
His theory Stated:
A super continent called Pangaea (meaning “all land”) once existed. Pangaea started breaking up into smaller continents about 200 million years ago and ‘drifted’ into their present positions.

7. Evidence to support his theory…
Fit of the continents – they fit like a puzzle.
Fossil Evidence
Identical fossil evidence was found on different continents. Therefore, the landmasses must have been joined together at some point.
Rock type similarities
The exact same age and type of rocks were found on various continents.
The issue was he couldn’t explain HOW the plates were moving and was ridiculed by many colleagues.

8. The Theory of Plate Tectonics
Proposed by J. Tuzo Wilson in 1968
His Theory states:
The outer crust consists of several individual segments called ‘plates’, they are moving over a weak layer of hot rock
Movement is caused by energy created beneath the Earth’s surface because of uneven temperatures.

9. PLATE MOVEMENT
transverse
divergence
convergence

10. DIVERGENCE - plates move apart from one another
- creates seafloor spreading
- located along the Mid-Atlantic Ridge

11. SEAFLOOR SPREADING
oceanic plate
oceanic plate

12. CONVERGENCE - plates move towards one another
- creates mountains, or subduction
- located in the Pacific Ocean

14. TRANSVERSE - Plates move past or beside one another, causing friction
- Located along the San Andres Fault
line in California