The Earth
The Structure
The Earth is the world we live in. It is divided up into
four layers. These layers are called: crust, mantle, outer core and inner core.
These layers are what form the Earth. The crust is made out of basalt and
granite and is in a solid state. The mantle is made out of silicon, oxygen,
magnesium, iron, aluminum and calcium. It is known to be in a plastic state.
The outer core is made out of iron and nickel and it is in a liquid state. The
crust is 38 km in depth whereas the mantle has the biggest depth reaching an
extensive 2840 km. The outer core is 2272 km in depth and finally the inner
core is 1228 km in depth. From the inner core to the crust, the depth is 6378
km. The Tectonic Plates
The Earth's crust is divided into tectonic plates. In the
early 1900s German scientist Alfred Wegener first noticed that the coastlines
of Africa and South America matched coming to a conclusion that the Earth's
plates were together 225 million years ago. He called it Pangaea (in Greek
meaning 'all the Earth'). According to Wegener's theory he said that the
Earth's plate started moving apart. They were different landmasses that moved
apart due to tectonic activity in the Earth. They are now known as continents
and oceans. This is in the Lithosphere of the Earth. The plates move roughly
2-3 cm each year.The Causes of the Tectonic Activity
Tectonic plates 'float' on the molten rock magma. As the
molten magma gets heated up, the heat causes convection currents, a movement of
rising and sinking caused by heat, inside the molten magma. The magma rises and
spreads out across the surface, then cools and sinks, making the plates to
move.
The extensive heat in the core of the earth makes the molten
rock in the mantle layer to move. The movement of plates is divided into
transform, divergent and convergent movements. These often are carried out by
results of earthquakes, tsunamis, volcanoes and mountains.
Types of Tectonic Plates
There are four types of plate boundaries. These are called
Conservative Plate Boundary, Collision zones, Convergent Plate Boundary and
also Divergent Plate Boundary.
In a conservative boundary, the plates slide past each other
in opposite directions or in the same directions but at different speeds. When
this sudden movement happens, it causes an earthquake which has an epicentre
where it focuses on the fault. An example of this is in the San Andreas Fault
in California.
Collision zones happen when two continental or two oceanic
plates collide making both of the plates to force up. Continental layers are
lighter so they rise up whilst oceanic plates are denser making them go down.
When this happens they form Fold Mountains. An example of this is the Andes in
South America. They are formed this way.
When two plates come together, it is known as a convergent
boundary. The impact of the two colliding plates buckles the edge of one or
both plates up into a rugged mountain range. A chain of volcanoes often forms
parallel to the boundary, to the mountain range, and to the trench. Powerful
earthquakes shake a wide area on both sides of the boundary.
A divergent boundary occurs when two tectonic plates move
away from each other. Frequent earthquakes strike along the rift. Beneath the
rift, magma (molten rock) rises from the mantle. It closes up into the gap and
hardens into solid rock, forming new crust on the torn edges of the plates.
Magma from the mantle solidifies into basalt, a dark, dense rock that underlies
the ocean floor. This is why at divergent boundaries, oceanic crust, made of
basalt, is created.
Comparison between two types of Plates
In a convergent boundary, the plates collide together whereas in a divergent boundary, the plate move away from each other. In a convergent boundary, volcanoes and earthquakes are formed whereas in a divergent boundary, volcanoes are formed whilst magma fills up the gaps. This means the convergent boundary is more effective because the collision of the plates have a huge impact since the result is two types of natural disasters, volcanoes and earthquakes. Overall, this means that the convergent boundary is more effective than a divergent boundary because in a divergent boundary earthquakes are created along the rift forming a dark, dense rock called basalt that underlies on the ocean floor.
