Earth on the Move
Earth Structure & Plate
Tectonics Notes
Baker 7th grade science 20032004
Earth, Inside & Out

1.
2.
3.
The Earth is divided
into three layers
Crust
Mantle
Core
Baker 7th grade science 20032004
Crust





(1) This is the outermost layer
of the Earth.
(2) This is the layer we walk on.
(3) It is a thick, rocky skin.
(4) If we think of the Earth as
a billiard ball, this crust is as
thin as a postage stamp stuck on
a billiard ball.
(5) At its thickest, which is
under mountain ranges, the
crust is only about 35km (22mi)
thick.
Baker 7th grade science 20032004
And what type of crust would
you like with your Earth?

There are two types of
crust
Baker 7th grade science 20032004
Continental Crust:



1. Makes up the
continents
2. Contains light
colored rocks such as
granite.
3. Floats high on the
mantle
Baker 7th grade science 20032004
(i)
Oceanic Crust



1.
Makes up the
ocean floor
2. Contains the
dense rocks such as
basalt
Thinner than the
continental crust
Baker 7th grade science 20032004
Mantle



(1) Hotter and denser
than the crust because
the deeper you go
inside the earth, the
temperature &
pressure increases.
(2) Made of solid rock.
The Mantle is made of
two zones
Baker 7th grade science 20032004
Mantle Zones



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(a) Lithosphere
(i) Thin, uppermost part
of the mantle; cooler & less
rigid
(ii) Floats on the
athenosphere, and slides
around very slowly.
(iii) The upper part of the
lithosphere melts rocks,
forming a substance called
magma.
Baker 7th grade science 20032004
Magma



1. Magma (melted rock)
moves like hot oatmeal.
Uneven heating causes
material in the mantle to
constantly and slowly rise &
fall in convection currents.
Convection Current:
process by which hot fluid
rises to the surface, and
then sinks again, like soup
being heated in a saucepan
Baker 7th grade science 20032004
(a) Asthenosphere


Hot, weak zone
directly under the
lithosphere
Flows at a very slow
rate
Baker 7th grade science 20032004
Core




i)
Deep within the
Earth is the core
ii) The core is made
mostly of nickel & iron
iii) Twice as dense as
the mantle.
Main source of heat
that triggers the
convection currents
Baker 7th grade science 20032004
The core is made of two layers


(1) Outer core:
molten & is responsible
for the Earth’s
magnetic field.
Inner core: solid
Baker 7th grade science 20032004