Download The Structure of The Earth – Revision Pack (C2) The Lithosphere

The Structure of The Earth – Revision Pack (C2)
The Lithosphere and Structure of The Earth:
The outer layer of the earth is called the lithosphere. The layer is relatively cold and
rigid; it is made up of the crust plus the upper mantle. The lithosphere is made up of
tectonic plates which are less dense than the mantle below.
The earth’s crust is far too thick to drill through, so we use information from seismic
waves produced by earthquakes to understand the structure of the earth.
The mantle is the zone between the crust and the outer core; it is cold and rigid but
at greater depths, it is hot, NOT rigid and able to move. The earth’s mantle gets
hotter with depth because the earth’s core transfers energy – the closer you are (the
deeper you are) the more energy transfer and the hotter the area.
The oceanic crust is DENSER than
the continental crust. When they
collide, the oceanic crust sinks and
pulls more of the plate down. The
plate will partly melt when it reaches
the hotter part of the mantle.
This is called subduction.
The plate movement is due to the CONVECTION CURRENT – without this, subduction
wouldn’t happen. NOTE: Collisions create mountains and the place where two
plates meet is known as the plate boundary.
The Structure of The Earth – Revision Pack (C2)
Plate Tectonics Theory:
Most scientists know accept the theory, which suggests that Africa and South
America were once ONE single land mass. This acceptance has come about
because:
-
It explains a wide range of evidence (Africa and South America fit nicely
together)
It has been discussed and tested by a number of scientists
Wegener’s theory was not accepted when it was released in 1914, but in the 1960’s,
new evidence about the sea floor spreading was found. This led to research which
eventually made Wegener’s theory more widely accepted.
Magma and Rocks:
Magma rises up through the earth’s
crust and upper mantle, because
the crust is denser than the magma.
This can cause volcanoes.
Magma may have different
compositions which cause different
types of eruption.
Geologists look at volcanoes in depth so that they can predict eruptions and learn
more about the structure of the earth. Geologists are now better able to make
predictions BUT there is NEVER 100% certainty.
Different types of igneous rocks are formed from lava:
Iron-rich basalt rock
Silica-rich rhyolite rock
This is formed from runny lava in SLOWER
volcanic eruptions.
This comes from thick lava in explosive
volcanic eruptions.
The Structure of The Earth – Revision Pack (C2)
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