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?

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

Continental-Oceanic Crust

Subduction
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 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 has a divergent plate boundary running through its middle
Iceland http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-
Margins/Divergent/Mid-Atlantic-Ridge

Transform Boundaries http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-
Margins/Conservative/San-Andreas-Fault
Above: View of the San Andreas transform 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