Composition and Physical Layers of the Earth

Plate tectonics

Composition

The Earth is composed of three main layers based on the differences in chemical make up

1. the crust 2. the mantle 3. the core

Composition of the Earth’s crust Continental crust (found

on land) is made up mostly of granite rock.

Oceanic crust (found under the oceans) is made up mostly of basalt rock

Basalt rock is more dense than Granite rock

The crust is less than 1% of the Earth’s total mass

Composition of the Earth’s mantle

The Earth has an upper mantle and a lower mantle.

The upper mantle is partially melted (molten) and contains iron and silicon metal compounds

The lower mantle is completely molten and also contains iron. Magnesium, silicon and oxygen are also present.

Composition of the earths core

The Earth has an inner core and an outer core

They both contain large quantities of the element iron and small amounts of the elements nickel, sulfur and oxygen

Cool fact!

The solid inner core of the Earth spins faster than the rest of the planet.

The Earth’s outer core is hot liquid iron and other minerals that conduct electricity .

The combination of the spinning inner core and the electrical moving outer core generates the Earth’s magnetic field!

Physical layers

The earth is also separated into 5 physical layers based on differences in temperature and pressure

1. Lithosphere 2. Asthenosphere 3. Mesosphere 4. Outer core 5. Inner core

Earth Physical Layers

* Differences in pressure and temperature cause STRESS which separates the Earth into physical layers.

For example if rock gets hot enough it will melt and become a liquid but if we put enough pressure on the liquid rock it can be come a solid again

Lithosphere

Outermost physical layer of the earth

Called the Rock sphere Consists of the crust

and the upper part of the mantle

This layer makes up the “Tectonic Plates”!

15 – 300 km thick Why do you think the

thickness varies?

Asthenosphere

Called the weak sphere

It is the “soft” layer of the mantle

The “tectonic plates” move on top of this layer

250 km thick

Mesosphere

Strong lower part of the mantle

2,550 km thick

Outer Core

Liquid molten iron Conducts

electricity Continuously

moving by convection.

- remember studying convection in weather?

• 2,200 km thick

Inner core

Solid iron Spins faster than

the rest of the planet

Why is the inner core solid and the outer core liquid when they are both made up of the same element iron?

How do we know about these Layers?

Seismic waves (vibrations) created by earthquakes travel at different speeds depending on the density of each layer

The denser the material the faster the waves travel

Let’s review!!

What are the layers of the earth that are described by their composition?

What are the two types of crust? What type of rock is found on each

type of crust? Which type of rock is most dense?

Review continued!

What causes stress in the Earth’s layers?

What are the five physical layers of the earth?

Which physical layer makes up the tectonic plates?

Which layer is soft and the plates move on top of it?

Which layer is liquid, has strong magnetism and conducts electricity?

Pictures cited

http://www.yorku.ca/esse/veo/earth/image/1-2-10.JPG http://www.ncad.net/GP/Erla/EarthCore.gif http://www.geocities.com/cdegonia/Picture5.gif http://upload.wikimedia.org/wikipedia/en/7/7a/EarthCrustMantleCo

re.png http://anshsmagnetism.files.wordpress.com/2009/01/earth-magfie

ld.jpg http://www.plate-tectonics.org/Lithosphere%20and%20Asthenosp

here.gif http://www.architectjaved.com/earthquakes/crust1.jpg http://www.geography.info/images/interior.gif http://bprc.osu.edu/education/rr/layers_of_the_earth/layers_of_the

_earth_diagram.jpg http://students.usiouxfalls.edu/mologan/Earths%20structure_files/

slide0004_image035.gif http://www.lbl.gov/Science-Articles/Archive/assets/images/2003/M

ay-09-2003/Earth_cutaway.jpg