Layers Of the Earth1.Mantle

2.

Lithosphere

3. Outer Core

4. Inner Core

How compressional forces are caused.

• Compressional / Destructive (subduction zones) plate boundaries occur when an oceanic plate is forced under (or subducts) a continental plate

• What do you think could be the result of this type of force?

Compression at Work:

Earth Quakes

Relate selected plate movements to compressional and tensional forces • An earthquake is a sudden

movement of the earth's surface. • Earthquakes are caused by the

movement of the earth's tectonic plates. – Earthquakes occur where the earth's

plates meet along plate boundaries

An example of the cause of an Earthquake

– For example as two plates move towards each other, one can be pushed down under the other one into the mantle.

– If this plate gets stuck it causes a lot of pressure on surrounding rocks.

– When this pressure is released it produces shock waves. These are called seismic waves. This is an earthquake.

– The waves spread out from the point where the earthquake started - the focus. More damage is done near the focus.

– The point on the earth's surface directly above the focus is the epicentre.

How tensional forces are caused • Tensional / Constructive (divergent ) plate boundaries occur when two plates move away from each other

• What do you think could be the result of this type of force?

Volcanoes• A volcano is a conical hill or mountain

formed by material from the mantle being forced through an opening or vent in the Earth's crust.Volcanoes are found in three states - extinct, dormant and active. – An extinct volcano will never erupt again. – A dormant volcano has not erupted in 2000

years. – An active volcano has erupted recently and is

likely to erupt again.

• Volcanoes are found along destructive (subducting) plate boundaries, constructive (divergent) plate boundaries and at hot spots in the earth's surface.

What are the three main volcanoes? • There are three main types of volcano -

composite or strato, shield and Ash and Cinder.

– Composite volcanoes, sometimes known as strato volcanoes, are between the steep sided ash and cinder cones and the low-lying shield cones.

– They are formed from layers of ash and [lava] flows. When composite volcanoes erupt they are sometimes explosive and sometimes less violent.

– Shield Shield volcanoes have gently sloping sides and are formed from layers of lava. Eruptions are typically non-explosive. Shield volcanoes produce fast flowing fluid [lava] that can flow for many miles.  

– Ash and Cinder volcanoes are typically violent and destructive, characterized by narrow tall cones.