Download Layers.of.Earth.part.1

The Differentiated Earth…

Earth shows differentiation
– Separation into layers due to
differing densities
– Just like separation shown
here
How Do We Know What Earth’s
Interior is Like??

Three ways
1. Volcanic activity brings some of the interior up to
us.
2. Density information…



The overall density of the Earth is 5.5 g/cm3
The density of the surface is 2.2 g/cm3
So…..the interior MUST be denser!
3. Seismic (earthquake) waves act like an
“ultrasound” and give a picture of the
interior
How Did Earth Become
Differentiated?

Earth became differentiated
During the Great Bombardment
(around 4.5 billion years ago
when Earth was very young)

As material from space hit the
young Earth, the heat from the
impact melted the Earth leading
to a magma ocean
Demo – How Earth Became
Differentiated??
 Describe
the demonstration you
just saw and heard.
–What position were the marbles in
originally?
–What brought about the change?
–Where did the marbles end up?
Why?
The Iron Catastrophe

The Iron Catastrophe is the name given to
this Layering event
– Heavy elements (iron, nickel) sink to the center
of the Earth
– Lighter elements (silicon, oxygen) rise to the
surface
This
early layering led to the way
our planet functions today AND to
the way life developed!
Earth’s BASIC Layers
– Basic Layers are defined by composition
Core
Mantle
Crust (oceanic and continental)
Composition of Layers
 Core
–Composed of nickel and iron
 Metallic, not rocky like the other layers
–Very dense – more than 6x the
density of the surface
–Makes up more than ½ of the
thickness3480 km thick (of 6400 km
total)
Composition of Layers
 Mantle
– Middle layer of the Earth
– Rocky, rather than metallic like the core
– Composed of mafic minerals (silicates
high in magnesium and iron (Fe)
– Makes up 48% of the thickness and
67% of Earth’s mass
Layers Due to Composition
 The
Crust
– Outermost layer of the Earth
– Rocky, mostly silicates
– Two types
 Oceanic (most of the crust) –
made of mafic rocks – mostly
basalt
 Continental – made of felsic
rocks (feldspars and light
colored minerals)– mostly
granite
Layers Due to Composition
Oceanic crust–
– very thin only
– very young
– Denser than continental rock by about 0.3
g/cm3
Continental crust
– thicker – up to 75 km thick –
– Old - up to 4 billion years old
Question –
since oceanic crust is
denser, what happens
when oceanic and
continental crust
interact?
Summarize…

What does differentiation mean?

Why did Earth become differentiated?

In what two ways are Earth’s
differentiated layers defined?

Identify one property each of the core,
mantle, and crust.