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Structure of the Earth
Geology 12
Ms. Pushie
CHS - 2010
Structure of the Earth
• Earth was formed roughly 4.6 billion ears
ago and for a long time was entirely
molten.
• The various materials (elements) that
make up the earth were stratified
(separated) according to their density.
• The densest elements formed the core
and the lighter elements floated to the
surface.
Structure of the Earth
• As the Earth gradually cooled the surface
solidified (became solid) to form a crust.
• Scientists are not 100% sure of the origin
of the water, one theory is the steam from
volcanoes cooled and became the water
of the Earth
The Earth – top layer
• 1. Crust - thin and light layer, made
up of Tectonic Plates composed of
basalt and granite. The crust is where
we live! 5-40 km thick.
• Continental crust- Where we are everyday!
Is made up of less dense granite.
• Oceanic crust -The bottom of the ocean floor.
Is thinner more dense basaltic material.
Why are the Continents
above the Ocean floor?
• Because of density - The layering of the
earth based on differing density.
• Land with greater density will sink, those that are
lighter float. Continental crust is lighter approx
2.7 g/cm3. Oceanic crust is heavier at 2.9 g/cm3
• Continents are 100m above sea level, Ocean
floor are about 4000m below sea level.
The Earth – middle layer
• 2. Mantle -located beneath the crust.
The mantle is more dense and rigid
than the crust, a rocky layer. 2885 km
thick.
The mantle has 2 parts, upper and lower.
- upper mantle- slow convection
currents of magma causes Continental
Drift.
The Earth – inner
• 3. Core- located beneath the mantle. Is
very hot and dense. Composed of iron and
nickel. This is the hottest and heaviest
layer. 2270 km thick, there are 2 parts:
– The outer core is liquid capable of flow and
source of the Earth's magnetic field.
– The inner core is solid Iron Nickel.
Animation of earth structure
http://scign.jpl.nasa.gov/learn/plate1.htm
Earth’s Crust – draw me!
Earth's Internal Structure
• The Earth's interior is characterized by a
gradual increase in temperature, pressure
and density with depth.
• At 100 km depth, the temp is ~1300°C.
• At the Earth's center, the temperature is
>6700°C.