Plate tectonics

PLATE TECTONICS STUDY GUIDE

1. CONTINENTAL DRIFT

Main idea – Pangea once existed, a super-continent where all the continents were one, until something happened to make them crack and drift apart.

Evidence – Mountain ranges, volcano chains, similar plant and animal fossils, “jigsaw-like fit” of continents, weather patterns (history of erosion and opposite weathering from the current ie. Glacier erosion in a tropical place)

Why was Alfred Wegener laughed at ? He proposed the idea of continental drift without much evidence, other than the “jigsaw-like fit” of all the continents. The argument against Wegener was that it was not “possible for some of the earths crust to be solid, and some to be liquid, or molten.”

2. PLATE MOVEMENT

What is the lithosphere ? The hard and rigid outer layer of the earth. The upper mantle and crust.

Explain the differences between a oceanic plate and a continental plate

An oceanic plate is the plate underneath the water, and a continental plate is one of which is exposed above the water. The continental plate is much thicker and made of granite, and they have also been around for much longer. Whereas the oceanic plate is composed of mainly basalt, making them thinner.

What is the asthenosphere ? The asthenosphere is a molten zone located beneath the lithosphere and is composed of plastic properties.

How does it make plates move ? Convection currents make the plates move, where the molten earth is moving in such a way that it makes the lithosphere on top roll along (very slowly.)

How fast do the plates move ? Very slowly, some plates only move two centimeters per year. In some cases, when there is pressure built up between two subducting plates, when the pressure is released, it results in an earthquake.

Name two natural disasters/phenomenon associated with plate boundaries and movement.

Subduction plate boundaries result in earthquakes, whereas diverging plate boundaries result in volcanoes and trenches.

3. Evidence of plate movement

coastline fit – West coast of Africa and East Coast of South America seem to fit together.

geologic fit – The Himalayas continue from one continent to another in a broken mountain chain range.

Paleoclimatology – The climate change on the continent. A once polar place ( complete with glacier and ice erosion from millions of years ago) can now be a tropical place. This can also deal with tree rings, ocean sediments, radiocarbons in organic material...etc.

fossil correlation – Fossils of plants and animals have been discovered oceans away from eachother.

age of sea floor – the different rock minerals and compositions and changes due to the magnetic polar shifts throughout time.

paleomagnetism – The polar shifts create a pattern along the sea floor, in the magnetic minerals.

What was PANGAEA ? - A super continent millions of years ago, before it split and the continents moved.

4. TYPES OF PLATE BOUNDARIES - labeled diagrams - NAME AN EXAMPLE

Divergent boundaries -

a) seafloor spreading: hot spots

b) continental rifting: Great East African Rift Valley, the Nubian Plate and Somali Plate

Convergent Boundaries -

a) continent/continent: The Juan De Fuca plate beneath the North American plate is an example. This is a transfom boundary, where one continental plate grinds against another and pushes the crust upwards. This creates mountain chains and volcanoes.

b) ocean/continent: This is where an ocean plate submerges beneath a continental plate, creating trenches and such.

c) ocean/ocean: This is where one of the oceanic plates submerges under the other and creates deep trenches.

Big Important summary question - How has plate tectonics affected Canada and its landforms ?

Plate tectonics are affecting Canada and other countries massively. In Canada, there are many mountains and volcanoes that are the result of moving plate tectonics. Although dormant, Mount Garibaldi and Mount Meager are caused by a subduction zone. There is a spreading ridge just off the coast of Vancouver Island (The Juan De Fuca Plate). The Northwestern corner of Canada is going through some stretching due to a spreading ridge as well. This is weakening the earths crust. There are also hot spots along the coast of Canada- such as the Nazko Cone in British Columbia.