Download How do the Tectonic Plates on the Earth`s crust move ? The crust of

How do the Tectonic Plates on the Earth’s crust move ?
The crust of planet Earth is split into seven main sections which are known as
tectonic plates. These tectonic plates are constantly moving in relation to each
other but at a very slow rate. Earthquakes are very sudden movements of the
Earth’s crust which provide evidence of plate movement such as the earthquake
in the Indian Ocean which caused the devastating Tsunami of 2004. The edges
of each tectonic plate are referred to as plate boundaries or plate margins. The
majority of plate movement occurs along these plate margins.
The 3 main causes of plate movement are
1. Convection Currents
2. Sea Floor Spreading
3. Subduction
1. Convection Currents
Beneath the crust of planet Earth lies a layer called the mantle. The very top of
this layer which is called the asthenosphere contains molten rock called magma.
Heat from the core travels up through the mantle and causes the magma to rise
towards the crust. As the magma rises, it looses some heat and eventually sinks
back down into the mantle. It heats up and rises again in a continuous cycle.
The tectonic plates that float on top of these currents of magma get dragged in
whatever direction they are travelling. See diagram 1. These convection
currents of magma are the main cause of tectonic plate movement.
Diagram 1. Convection Currents.
Hotter
Magma
Rising
Cooler
Magma
Sinking
2. Sea Floor Spreading
The process of sea floor spreading is caused by hot magma rising through the
mantle towards the crust. In some parts of the world the tectonic plates are
separating such as the along the Mid Atlantic Ridge deep in the Atlantic Ocean.
Where this happens, magma rises through the gap between the separating plates
then cools and hardens. See diagram 2. The hardening magma pushes the
plates apart. This cycle continues and keeps forcing the ocean floor apart in a
process known as sea floor spreading.
Diagram 2 Sea Floor Spreading
3. Subduction.
The crust of planet Earth is made from 2 main types of rock. Oceanic crust
which is mainly found beneath the oceans is made mostly from heavy basalt
rock. Continental crust which is mainly dry land is formed predominantly from
a lighter granite rock. Where both of these types of crust meet and push against
each other, the heavier oceanic crust sinks underneath the lighter continental
crust. See diagram 3. As the oceanic crust sinks back down into the mantle, it
begins to melt. This process is known as subduction. Examples of where this
takes place is along the west coast of South America where the Nazca plate
converges is the South American plate and results in the formation of the Andes
mountains.
Diagram 3 Subduction