SLO 1: The Theory of Plate Tectonics

Plate Boundaries

There are three different types of plate boundaries: Divergent, Convergent, and Transform. Each type describes how two plates react with each other whether moving apart, coming together, or sliding against one another.

(There are also two types of plates: Oceanic or Continental)

Divergent

This occurs when two plates are being pulled away from each other.

Convergent

This occurs when two plates are being pushed together, causing subduction.

Transform

This occurs when two plates are sliding in opposite directions against one another.

Oceanic-Oceanic Divergent: When both plates are ocean crust, this is when a mid-ocean ridge will form along with undersea mountain ranges. Effects from this collision can be shallow earthquakes and volcanos.

Continental-Continental Divergent: When both plates are continental crust, this is when volcanic mountain ranges with rift valleys will form. Sometimes this will create new oceanic crust. Effects of this collision are volcanic activity and shall earthquakes.

Examples of Divergent Boundaries:

-Mid-Atlantic Ridge

-East African Rift

Continent-Continent Convergent: When both plates that come together are continental crust, this is when large mountain features form. Effects from the collision are highly deformed rocks, but no volcanos, and usually extensive earthquakes.

Oceanic-Continent Convergent: When the one oceanic crust and one continental crust come together, this is when deep ocean trenches will form, along with mountain ranges. Effects include: explosive volcanism, deep earthquake activity, and subduction.

Oceanic-Oceanic Convergent: When both plates that come together are oceans, this is when even deeper ocean trenches form, also with volcanic arcs. Effects of this collision are explosive volcanism, deep earthquake activity, and subduction.

Examples of Convergent Boundaries:

-Himalayas

-Andes Mountains

-Mariana Trench

Continent-Continent Transform: When both plates sliding past one another are continental, this is when thin valleys can form and river beds to split, and fault lines will appear. Effects of this collision will be major earthquakes and breakage due to the rough and uneven passing of plates. Things such as fence lines or trees can be moved and be off because of these boundaries.

Examples of Transform Boundaries:

-San Andres Fault

-Alpine Fault

Why are Plate Tectonics Important?

Well, without plate tectonics we would not have the world we know today. They are the reason for how everything is the way it is, without it our continents may be gone and under the ocean.

-Earthquakes, volcanos, mountain ranges, rift valleys, trenches, and fault lines are all formed from the different movement of plates.

Earthquakes

Earthquakes are simply caused by plate tectonics. We also have learned how to predict these earthquakes and prepare for disaster.

Volcanos

Volcanos are formed from plate tectonics! They form new land and have also been said to act as a global thermostat, producing CO2.

Mountain Ranges

When plates come together they form these big mountain ranges. Some common ones are the Himalayas and Andes.

Rift Valleys

Rift valleys form when plates move apart or rift. They can also be found at the bottom of the ocean where the seafloor spreads.

Trenches

Deep ocean trenches, like the Mariana Trench, are formed when two plates meet and subduction occurs. These are known as the deepest places in the world.

Fault Lines

Fault lines form when plates have a transform boundary. The line is a fracture in a rock where it has been displaced. Our San Andres Fault is a great example.

Pangea:

Without plate tectonics, we also would not have the separate continents we have and live on now.

Pangea was a supercontinent believed to exist in the early Mesozoic era. It connected all the major land mass on Earth into one. It was not until about 200 million years ago when plate tectonics began to shift these land masses. This is what we call continental drift. Over millions of years these pieces split apart further and further until they become what we know today. These plates are still moving, and theoretically could come together again in a different way, millions of years from now.

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