Slides in this set
The Theory Of Plate Tectonics
The theory that the Earth's surface is
divided into a series of moving plates.
The Structure Of The Earth:
How Do The Tectonic Plates Move?
1. Magma nearest to the core is heated.
The particles spread out and it becomes
less dense (lighter).
2. The hot magma rises.
3. As it reaches the crust, the magma cools
to become denser (heavier).
4. If other particles are `following' it, then it
can't sink back down. Therefore it is
5. The viscous magma `attaches' itself to
sections of the crust and drags the
6. At a plate boundary, the magma has
nothing to `hold' on to and therefore it
sinks towards the core.
7. It is reheated and the `conveyor-belt
style' cycle repeats.
The Theory Of Plate Tectonics (2)
As the crust is dragged by viscous magma, it rips
and tectonic plates formed. There are four different
types of plate boundary:
There are two types of crust:
Oceanic Crust Continental Crust
Dense Less Dense
Thinner Thicker / Deeper
Younger Oldest Rock On Earth's Surface
Can Be Made & Destroyed Can't Be Made & Destroyed
The main features of a volcano:
Volcanoes form at
through the crust.
Volcanoes can be classified by activity
level (active, dormant, extinct) or by type
(composite cone, shield, super - caldera).
· low and wide with no alternating · Tall & thin with alternating bands
bands @ Constructive PBs. of ash & lava @ Destructive PBs.
· Regular / frequent / constant · Irregular eruptions with long
eruptions where lava `pours' out. periods of being dormant.
· Erupts basic lava which is thin, · Erupts acidic lava (due to oceanic
runny and non-viscous and thus crust melting) which is thick, sticky,
can travel a long way (`spread out'). viscous and contains air bubbles.
· Non-explosive due to lack of · Highly explosive due to
trapped air bubbles. pressurised air bubbles in lava.