The structure of the earthStructure
Part
Crust
(oceanic
7km thick,
continental
up to 70
km thick)
Mantle
(700 km to
2890 km
deep)
Temperature
Density
Composition
Surface
temperature
to about
400°C
Less dense
(continental= 2.7
g/cm³
oceanic= 3.3
g/cm³)
Granite
(continental)
and basalt
(oceanic)
870°C
Less dense to
medium density
(3.3 to 5.4 g/cm³)
Outer core
(2890 km
to 5150 km
deep)
Inner core
(5150 km
deep to
center)
4400 to
6100°C
Dense (9.9 to
12.3 g/cm³)
Peridotite
Upper = olivine
Lower =
magnesium
silicate
12% Sulphur
88% iron
7000°C
(radioactive
decay)
Very dense (13.5
g/cm³)
20% nickel
80% iron
Physical
state
Solid
Earthquake (seismic) waves
Phases of
liquid and
solid in
layers
Body waves pass through at
variable rates due to density
changes
Liquid (+
generates
magnetic
field)
Solid (+
radiates
heat),
maybe
two parts
with
huge
crystals
aligned in
opposite
directions
Only P waves able to pass
through, an S wave ‘shadow
zone’ is created from about
105° from the focal point
Only P waves read the inner
core and pass through, but
their refraction at the coremantle boundary creates a
ring ‘shadow zone’ between
105° and 140° from the focal
point
Surface and body waves able
to pass through