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Layers Of the Earth. 1.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
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Layers Of the Earth 1.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?
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.