A long time ago they thought
I was flat but came to find
out they were wrong about
that. My shape is not a circle
but a sphere. The blue and
green that you see is only the
top but underneath lies three
layers that you cannot spot.
Who Am I?
At close to 3,000 kilometers (1,865
miles) thick, this is Earth’s thickest
layer. It starts a mere 30 kilometers
(18.6 miles) beneath the surface.
Made mostly of iron, magnesium
and silicon, it is dense, hot and
semi-solid (think caramel candy).
Like the layer below it, this one also
circulates. It just does so far more
Near its upper edges, somewhere
between about 100 and 200 kilometers
(62 to 124 miles) underground, the
mantle’s temperature reaches the
melting point of rock. Indeed, it forms
a layer of partially melted rock known
as the
(As-THEEN-ohsfeer). Geologists believe this weak,
hot, slippery part of the mantle is what
Earth’s tectonic plates ride upon and
slide across.
Answer: Lithosphere
The mantle’s outermost zone
is relatively cool and rigid. It
behaves more like the crust
above it. Together, this
uppermost part of the mantle
layer and the crust are known
as the
.
Earth’s crust is like the shell of a
hard-boiled egg. It is extremely
thin, cold and brittle compared to
what lies below it. The crust is
made of relatively light elements,
especially silica, aluminum and
oxygen.
Continental Crust VS Oceanic Crust
✓ The oceanic crust is relatively younger than the continental
crust.
✓ The oceanic lithosphere is thinner than the continental
lithosphere
✓ The oceanic lithosphere is denser as compared to the
continental lithosphere.
✓ The oceanic crust is primarily composed of basaltic rocks
while the continental crust is primarily composed of granitic
rocks.