Thanks for asking such a great question! The
Earth has many different types of layers. It has
thin layers on the surface, which we call
strata. These thin layers are made of
different types of rocks and are deposited one at
a time over very long periods (sometimes millions
of years!) Because these layers are not actually
living, we don’t say that they ever die.
Sometimes these layers are made by living
things, for example small creatures in the ocean
make shells and when they die their shells fall to
the sea-floor and become part of Earth’s layers.
Although some types of rocks are made by living
things, the rocks themselves are not living. Even
though Earth’s layers are not living and can’t
die, they can go through transformations into
other types of rocks through a process we call
metamorphism. Perhaps you’ve heard of
metamorphic rocks? These are types of
rocks that changed into another rock type
because it was heated to very high temperatures or
because it was under a lot of pressure (from
overlying layers or in places where mountains are
being pushed upwards). Deep under the Earth’s
surface, the layers may be heated enough that they
completely melt and turn into magma. In this case,
the layers no longer exist and the magma that
formed from the melted rocks can come out in
volcanic eruptions or cool to form a type of rock
called an igneous rock.
The Earth also has four major layers: The
crust, the mantle, the outer core, and the inner
core. Each of these layers acts differently.
For example, the crust is on the Earth’s surface
and is solid, but the mantle, which is right
beneath the crust, flows very slowly through time.
It flows so slowly that if you could look at it
you wouldn’t notice, but over hundreds or
thousands of years it will have moved. Because
Earth has a rigid crust, and because the mantle
moves slowly through time, we have something
called plate tectonics. You may have
learned about plate tectonics in class. The
surface of the earth is broken into several major
tectonic plates and many more small tectonic
plates. These plates move through time meaning
that in some places plates are moving past each
other, in some places they are moving away from
each other, and in some places they are colliding
with each other. In places where they are
colliding with each other, one of the tectonic
plates gets “recycled” back into the mantle. The
way this happens is one plate goes underneath the
other and it sinks down into the hot mantle. The
hot mantle then eventually melts the plate and it
becomes part of the mantle. This is one way
that tectonic plates “die,” but because it was
never actually alive we instead think of it as
recycling of the material that made up the plates.
I hope this answered your question!
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