Transcript C1b 6.1 Structure of the Earth

The Changing World
Structure of the Earth
The Earth’s Structure
Bristol
New York
If you start on the Earth’s
surface how far down would
you go if you travelled the
same distance as the distance
between London and:
Barcelona
Paris
The distance from London to:
Bristol =
200 km
New York =
5586 km
Barcelona =
1183 km
Paris =
343 km
Structure of the Earth
• Deepest mines in the world = 3 500 m
• Deepest geological survey = 12 000 m
• The Earth is 12 800 000 m in diameter
– 1000 x deeper than our deepest hole
• The Earth is made of many layers
• Formed millions of years ago
– Heavy matter sank to middle
– Lighter matter floated on top
The Earth’s Structure
Beneath the atmosphere the Earth consists of 3 main layers:
The core
The core extends to about half the radius of
the Earth.
It is made mostly from iron and nickel and is
where the Earth’s magnetic field comes from.
It is very dense.
5500 C
The temperature is high and the outer
core is molten.
Towards the centre high pressure
makes the inner core solid.
1300 km
Intense heat is generated in the inner
core by decay of radioactive elements
like uranium.
1110 km
3000 km
Inner
Outercore
core
• How many parts make up the Earths core?
What are they?
• Challenge: Why is the hotter part of the core
solid, while the cooler part is liquid?
The mantle
The mantle extends outwards from
the core to the crust: a distance of
about 2,900 km.
It is mostly a semi-molten liquid
upon which the Earth’s crust floats.
The heat coming from the core
generates convection currents in
the viscous mantle that cause the
crust above to move.
2900km
Mantle
• What is the layer of our planet surrounding the
core called?
• Challenge: This layer is not a liquid, but is
often described as ‘syrupy’. Why is this?
The crust
The crust is the thin layer of rock at
the surface upon which we live.
Eight elements make up over 98%
of the Earth’s Crust – although
they are virtually entirely in the
form of compounds.
50
% 45
40
35
30
25
20
15
10
5
0
20-60 km
O
Si
Al
Fe
Ca
Na
K
Mg
Crust
• What is the outer layer of the Earth known as?
• Challenge: Why do scientists think that the
core is made of much denser material than the
crust?
How do we know?
• By studying earthquakes
– Seismic waves travel through the Earth
• The way the waves travel tells us what they’re
travelling through
• Features on the surface
– Cooling of the crust – cracking
– Actually movement of plates
Layer
Crust
Mantle
Core
Location
Outer
surface of
planet
6 km
(ocean)
35 km (land)
‘Skin’ of the
planet
Below the
crust
Centre of the
planet
3000 km
below
surface
3500 km
radius
Behaves like
a solid, is
actually
slow flowing
liquid
Nickel and
Iron, outer is
liquid, centre
is solid
Thickness
Description
What am I?
•
I am dense, very hot, made mostly of solid iron
and nickel.
Inner core
•
I’m iron and nickel too, but I’m liquid.
Outer core
•
I’m really very thin and am mostly silicon,
Crust
oxygen and aluminium
•
I’m a viscous semi-solid with convection
Mantle
currents circulating in me.
•
I just hang around on the outside.
Atmosphere
Attach labels to the correct part of the diagram.
Atmosphere
Outer core
Crust
Mantle
Inner core