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8.1 Earth has several
layers
Learning Goals
• Students will:
-describe the different properties of
Earth’s layers.
-describe the plates that make up
Earth’s outermost layers
8.1 Warm-Up
• Decide if each statement is true. If not,
correct it. Write out every sentence.
1. The rock cycle describes the natural
processes that form, change, break
down and form rocks again.
2. The most common type of rocks in the
Earth’s crust are sedimentary and
igneous.
3. Heat and pressure can change a rock
into another type of rock
8.1 Warm-up answers
• Decide if each statement is true. If not,
correct it.
1. The rock cycle describes the natural
processes that form, change, break down
and form rocks again. true
2. The most common type of rocks in the Earth’s
crust are igneous and metamorphic
3. Heat or pressure can change a rock into
another type of rock. true
Earth is made up of materials
with different densities
• Scientists think that Earth formed 4.6 billion
years ago when bits of material ran into
each other and stuck
• Planet grew larger when intense heat was
produced by impacts, radioactive decay
and Earth’s gravity. It became a glowing
ball of melted rock.
• Dense materials sank toward the center and
less dense moved toward the surface
• Layers were formed—core, mantle, crust
Earth’s layers have different
properties
• inner core—a ball of hot, solid
metals at Earth’s center, under
great pressure.
– The atoms of metals are
squeezed together so
closely due to the pressure.
The core is solid despite the
intense heat.
• outer core—a layer of liquid
metals that surrounds the Earth’s
inner core
– pressure is lower than the
inner core so the metals are
liquid
• mantle—Earth’s thickest layer, made up
of hot rock, surrounding the outer core.
– Very hot, rocks flow like currents
– the very top is cool and hard; just below
that the rock is hot enough to move like
thick paste
• crust—thin layer of cool rock that covers
Earth like the shell of an egg. It includes
dry land and ocean basins.
– Two types of crusts: continental and
oceanic
• lithosphere—cold, brittle layer of Earth
made up of the crust and the very top of
the mantle.
– This layer breaks easily
• asthenosphere—layer of hot, soft rock in
the upper mantle, directly under the
lithosphere.
– This is a layer of hotter, softer rock in the
upper mantle
– Hot enough to flow slowly like hot tar
• Lithosphere is like pavement resting on
hot tar
lithosphere
crust
mantle
outer core
inner core
The lithosphere is made up of many
plates
• As scientists studied Earth’s surface, they
found that the lithosphere is broken up
into many large slabs of rock
• tectonic plates—large moving slabs of rock
on which Earth’s lithosphere is broken,
carrying oceanic and continental crust.
• Tectonic plates fit like a jigsaw puzzle
• Most tectonic plates include both
continental crust and oceanic crust