Download CompositionoftheEarth

Planets are like Onions… (They have layers)
Our planet, Earth, is made up of ​ 4​ layers.
The inside layers are much ​Hotter/warmer​ than those on the outside.
Each layer is under different levels of pressure and exists at a different temperature.
Inner Core
The inner core is the very center of the Earth.
It is under the ​most/highest​ pressure.
The inner core is made up of 2 metals _​Nickel​and ​Iron​.
In the inner core these metals are totally ​Solid​.
The inner core was identified based on the force of _​gravity​_ on Earth.
The inner core sits at around 5400℃
Outer Core
Again, much like an onion, the outer core is wrapped around the inner core.
The outer core is made of molten, liquid ​metal​. Specifically, iron and nickel just like the inner
core.
The outer core begins about ​3000km​ below the surface of the earth and is around 2000 km thick.
A very wide range of temperatures are estimated for the outer core. They range from 2500℃ on
the cooler end and 7500℃ on the hot side.
The the movement of the outer core is thought to be responsible for the
Magnetic field​ of the earth.
Mantle
The mantle is a little odd. It’s very hot but the rocks are still ​solid​.
This is due to the very high ​pressure​ within the mantle.
Some locations in the mantle have lower pressure and are still _​liquid​_.
This liquid rock is called ​magma​.
The majority of the mantle is made up of Silicone, ​oxygen​ and Magnesium.
The mantle starts at ​50km​ below the earth’s surface.
Crust!
As the only layer we ever see, we know a fair bit about the crust.
The crust is where all our mineral resources are mined and fossil fuels are collected.
Acts like a ​skin​ covering the earth’s insides.
Tectonic Plates
The crust that covers the earth isn’t one complete piece!
The crust is broken into several large slabs of rock called​ tectonic plates​.
These plates float on the asthenosphere, the uppermost part of the ​mantle​.
Where these giant plates of rock meet we get ​plate boundaries​, or ​faults​.
With the most famous of these being the San Andreas Fault, hence the film.
There are three basic types of plate boundaries:
● Convergent (The plates move towards one another, colliding)
● Divergent​ (The plates move away from one another, spreading)
● Transform (The plates ​slide past​ one another)
Convergent Boundaries
These boundaries occur when two plates collide.
If one of them is ocean crust, it subducts (sinks
below).
These boundaries produce
earthquakes​ as well as
Volcanoes.
Divergent Boundaries
In these places plates move away from
one another. This creates new crust as the
magma from the asthenosphere rises to
the surface.
These boundaries produce volcanoes
and ocean ridges, like as the one in the
mid-Atlantic.
Transform Boundaries
Unlike the other boundaries, transform faults do ​NOT​ cause ​volcanoes​.
However, they are responsible for the majority of ​earthquakes​.
As the plates slide past one another, they
can get caught or stuck. Over time
energy is stored in the rocks until they
break releasing energy as an earthquake.
Volcanoes!
A volcano is a rift or ​cut​ in the earth’s crust.
If we think of the crust as a ​skin​ then volcanoes are like ​wounds or cuts, or even pimples​.
Volcanoes can be found at ​convergent​ and ​divergent​ plate boundaries.
They are particularly common in the ​ring of fire​ around the Pacific.
However, some volcanoes can pop up in the middle of nowhere.
This occurs when rising magma punches a hole in the earth’s crust.
We call these ​hot spot​ volcanoes.
Examples include the volcanoes that formed the Hawaiian islands.
Eruptions
Volcanoes erupt when ​gas​ and magma from below the crust get trapped under a layer of solid
rock.
Eventually ​pressure​ builds up and the rock shatters in an eruption.
Shield Volcanoes
Not all volcanoes erupt in violent explosions.
These volcanoes are ​wider/flatter​ and shorter.
They have​ basaltic/runny​ lava that is runny due to
having a lot of iron.
Shield volcanoes don’t build up pressure and tend
to erupt continuously.
Example:​Mauna Loa ​in ​Hawaii
Stratovolcanoes
These are the scary explosive volcanoes we usually think of when we think volcano.
They are tall and ​cone​ shaped with steep sides.
The lava in a stratovolcano is ​sticky/thick/viscous​ and rich in
silicates. This makes the lava thick, sticky and prone to clog up
the vents.
Clogged vents cause pressure to build until… ​BOOM.
Eventually, stratovolcanoes empty their magma chambers.
When this happens they collapse, fill with water forming lakes called ​caldera​.
Pyroclasms or pyroclastic flows​ are avalanches of dust and ash that are faster and more deadly
than any lava flow.
Lava comes in various shapes and sizes including:
● ‘A’a- Sharp-edged lava that is painful to walk on
● Pahoehoe- Basaltic lava that is extremely ​runny​.
● Pillow- Cools underwater forming smooth round shapes.
Earthquakes
Earthquakes occur at ​transform ​plate boundaries.
They can happen elsewhere, but that is fairly rare.
The spot where an earthquake starts is called the ​epicenter​.
Earthquakes form when jagged rocks get caught on one another causing ​pressure/stress​ to build
until the rocks ​break​ and move suddenly.
Think of this like a tug-o-war, but someone runs in and cuts the rope mid-game.
The destructive energy of an earthquake moves through the ground in ​waves​.
The three main types are:
● Primary Waves (P-waves)
● Secondary Waves (S-waves)
● Surface waves
Primary Waves
These waves are
compression/compressive/longitudinal​ waves.
This means they represent constant changes in
pressure throughout a substance.
Sound is an example of a compressive wave.
Some animals can ​hear/sense​ primary waves before we feel them.
P-waves are the ​fastest ​type of wave, they are detected first.
Secondary Waves
These waves are also called ​shear/transverse
waves.
They undulate or oscillate back and forth in a
snaking pattern.
These waves move slower than ​P-waves​ and are
detected later.
Shear waves cannot travel through liquids,
because of this they cannot travel through the
outer core​.
Scientists can use a machine called a ​seismograph​ to compare the arrival times of S and P waves
and determine where the epicenter of an earthquake is.
Surface Waves
The most devastating waves roll along the earth’s surface, lifting, bending and breaking the
crust.
These are the ​slowest​ kind of waves, and arrive/are detected last.
Richter Scale
The Richter scale is an outdated but still sometimes handy way to express the destructive
potential of an earthquake.
The higher the magnitude, the ​more ​destructive the quake.
Magnitude
Energy Example
0.2
Hand Grenade
4.0
Nuclear Power plant meltdown
6.0
Atomic Bomb
8.0
Tsar Bomba
10+
Mega-asteroid impact
Tsunamis
These giant waves are caused when earthquakes happen ​below the ocean/underwater​.
They are often called tidal waves, but they have nothing to do with the tide.
In deep water the tsunami moves ​quickly​_ but is rather small.
In the shallows, the tsunami moves slowly but grows incredibly ​tall/large​.
A tsunami in the open ocean may travel at ​400km/hr​ but be only 1 meter tall.
Whereas once it reaches the shore it slows to just a few kilometers an hour, but may be 30 meters
in height.