Plate Tectonics

Objectives 1. Know the different tectonic plates

2. Understand how the tectonic plates move

3. Understand what happens at the different plate boundaries

What is a plate?

A plate is a rigid section of the earth’s crust which 'floats' on the

semi molten mantle.

PLATES ARE MADE OF EITHER OCEANIC CRUST OR OCEANIC AND CONTINENTAL CRUST. NO PLATE IS MADE OF ONLY CONTINENTAL CRUST.

How do the plates move?

These plates are moved by the convection currents that

occur within the mantle.

Plate Boundaries / Margins

The plates have recognized boundaries, where they are either moving towards one another, moving away from one another or moving past one another.

Objectives 1. Know the different tectonic plates

2. Understand how the tectonic plates move

3. Understand what happens at the different plate boundaries

Three types of plate boundary Divergent (constructive)

Convergent (destructive)

Transform (conservative)

Convergent Plate Boundary

There are three styles of convergent plate boundaries◦Continental-continental crust◦Continental-oceanic crust ◦Oceanic-oceanic crust

Continental-Continental

Forms Fold mountains, e.g. European Alps, Himalayas

Himalayas

•India used to be an island, but about 15 million years ago it crashed into Asia (see map). •As continental crust was pushing against continental crust the Himalayan mountain belt was pushed up.

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Continental-Collision

Continental-Oceanic Crust

Oceanic crust subducts underneath the continental crust

Oceanic crust heats up as it as it subducts and melts

The moltan rock is magma and rises forming volcanoes

e.g. The Andes in South America

Subduction

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Oceanic-continental

Oceanic-Oceanic Plates

When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone.

The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench.

The worlds deepest parts of the ocean are found along trenches.

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Oceanic-oceanic-collision

The Mariana Trench is 11Km deep!

Divergent Boundaries

Iceland

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Divergent/Mid-Atlantic-Ridge

Iceland has a divergent plate boundary running through its middle

Transform Boundaries

Above: View of the San Andreas transform fault

http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Conservative/San-Andreas-Fault

Summary

The Earth is made up of 3 main layers (core, mantle, crust)

On the surface of the Earth are tectonic plates that slowly move around the globe

Plates are made of crust and upper mantle (lithosphere)

There are 2 types of plate There are 3 types of plate boundaries Volcanoes and Earthquakes are closely linked to the margins of the tectonic plates