Convection currents in Earth's mantle driven by heat from the core cause the movement of tectonic plates. Denser, cooler material sinks and less dense, warmer material rises in a convection cycle. Earth is composed of layers with increasing density, temperature, and pressure towards the core. The crust and rigid upper mantle form tectonic plates that move due to convection in the soft asthenosphere below.

1. Lithospheric Plates
1. Why is the Earth broken up into
different pieces on the surface?
2. What is making the plates move
relative to one another?

2. Convection Currents
Heat from the Interior creates convection currents slowly
moving rock due to density differences.

3. Convection Currents
Crust
Mantle
Core
Differences in density
displace material
A more dense
material will fall
and replace a
less dense
material making
it rise.
Water = More Dense
Oil = Less Dense
Colder = More Dense
Warmer = Less Dense

4. Two different models of Earth’s Interior
Mechanical Model
 The physical properties
that allow the
movement we observe.
Chemical Model
 The composition of each
layer.

5. Chemical Model
Crust
Mantle
Core
Elements get heavier
Temperature
Increases Pressure Increases
The closer to
the core…
ATM

6. Composition: Layers of Earth
 The crust is the layer of rock that forms Earth’s outer
skin. The crust is a layer of solid rock that includes
both dry land and the ocean floor. CRUST

7. Composition: Layers of Earth
 The crust is the layer of rock that forms Earth’s outer
skin. The crust is a layer of solid rock that includes
both dry land and the ocean floor.
 Oceanic crust consists mostly of rocks such as
basalt – Thinner Crust

8. Composition: Layers of Earth
 The crust is the layer of rock that forms Earth’s outer
skin. The crust is a layer of solid rock that includes
both dry land and the ocean floor.
 Oceanic crust consists mostly of rocks such as
basalt – Thinner Crust
 Continental crust, the crust that forms the continents,
consists mainly of rocks such as granite – Thicker
Crust.

9.  Earth’s mantle is made up of rock that is very
hot, but solid.
Mantle

10.  Earth’s mantle is made up of rock that is very
hot, but solid.
 Scientists divide the mantle into layers based
on the physical characteristics of those layers.

11.  The uppermost part of the mantle and the
crust together form a rigid layer called the
lithosphere

12.  The part of the mantle just beneath the
lithosphere is less rigid than the rock above.
This part of the mantle is somewhat soft—it
can bend like plastic. This soft layer is called
the asthenosphere

13.  The core is made mostly of the metals iron
and nickel. It consists of two parts—a liquid
outer core and a solid inner core.
OUTER
CORE
INNER
CORE

14.  The outer core is a layer of molten metal that
surrounds the inner core. Despite enormous
pressure, the outer core is liquid.

15. The Core and Earth’s Magnetic Field
 Scientists think
that movements in
the liquid outer
core create
Earth’s magnetic
field. Because
Earth has a
magnetic field, the
planet acts like a
giant bar magnet.

16.  The inner core is a dense ball of solid metal.
In the inner core, extreme pressure squeezes
the atoms of iron and nickel so much that they
cannot spread out and become liquid.

18. Mechanical ModelCOREMANTLECRUST
Upper
Lower
Middle
Ocean
Land
Outer
Inner
Solid
Plastic
Molten
Liquid
Solid
Lithosphere
Asthenosphere
Mesosphere
Liquid Fe and Ni
Solid Fe and Ni

19. Let’s put the chemical and
mechanical models together!