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Subduction Zones & Sea-Floor Spreading


elisha fox

on 11 June 2012

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Transcript of Subduction Zones & Sea-Floor Spreading

WHAT HAVE WE LEARNT SO FAR? What are the three main
layers of the earth? Earthquakes and Volcanoes
are closely related with the
edges of what? Heat and pressure rises from
the core and upwards through
the mantle. This heat causes what
phenomenon? Name two natural disasters the sudden movement of plates can cause? The movement of plates has been
happening for years. This is known
as what theory? TODAY...
We will be looking closer at

SEA FLOOR SPREADING SUBDUCTION ZONES SEA-FLOOR SPREADING 2. As magma meets the water, it cools and solidifies, adding to the edges of the sideways-moving plates. 3. The ocean floor gradually extends and the size of these plates increases. List two important points you learned from the you tube clip. 2. The older, heavier plate bends and plunges steeply through the asthenosphere, descending into the earth.

It forms a trench that can be as much as 110 kilometres wide, more than a 1600 kilometres long, and several kilometres deep. 1. When two oceanic plates collide, the younger of the two plates, because it is less dense, will ride over the edge of the older plate. 3. Source of magma is the molten rock formed from the friction between the two plates during collision. 4. Magma is low in iron minerals and rich in silicates. What kind of volcanoes are created at subduction zones?

We know there is....

* Powerful frictional force between plates
* Low in iron minerals and high in silicates Composite Cones are created Composite Volcanoes are: Spectacular and Violent Producing large amounts of hot ash,
yet a very little amount of lava. 4. Source of magma is the hot, molten material from the Earth's core coming out through convection currents 5. Magma is rich in iron minerals and low in silicates What kind of volcanoes are created during sea-floor spreading?

We know there is....

* Source is convection currents
* Rich in iron minerals and low in silicates
Extreme heat created Shield Volcano Less Violent and Spectacular Large amounts of lava spread out
over many kilometers 1. Sea-floor spreading is when two plates move apart. As the plates move apart, the rocks break and form a crack between the plates.
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