Earth structure

Hafeet mountain

What is the earth structure ?

• The earth structure has been classified according to two main criteria's

• 1- the chemical composition • 2- the physical properties

Earth structure based on chemical composition

• The earth structure divided in to 3 main layers 1. Crust : the outer layer of earth which it has 2

main types ( continental and oceanic crusts ) The continental is less dense than the oceanic .

2- mantel

The mantel has more magnesium but less aluminium than crust

They figure out the chemical composition of mantel by : 1- studying the melted rock which pushed up in to the surface 2- by the active volcanoes eruptions under the ocean

3- The core

• The core is the centre of earth and its full of nickel and iron elements which generate the electromagnetic field of earth which protect earth from the sun storms.

Earth physical structure

1. Lithosphere. (this part make the plate tectonics which flows over the asthenosphere )

2. Asthenisphere (the rocks flows over each other )3. Mesosphere4. Outer core (liquid)5. Inner core. (solid )They study the earth interiors by interpretation of the

seismic waves that comes with earth quakes

Wegener continental drift hypothesis

• The main 3 factors that led wegener to create his theory about continental drift are :

1. The shape of the plates boundaries.( they looks like a puzzle they can come over each other)

2. The fossil records. (same animals lived in a different continents)

3. The types of rock formations in the different continents .

Now what is the meaning of continental draft ? is the hypothesis that states that the continents once

formed a single landmass, broke up, and drifted to their present locations

Break up of pangea

How pangea brocks up

• By a process called (sea floor spreading ) • A process by which new oceanic lithosphere

forms as magma rises toward the surface and solidifies.

• when the tectonic plates move away from each other, the sea floor spreads apart and magma fills in the gap. As this new crust forms, the older crust gets pushed away from the mid-ocean ridge.

What is the evidence of sea floor spreading ?

• The magnetic reversal . But how ? 1. The molten rock at the mid-ocean ridges

contains tiny grains of magnetic minerals.2. These mineral grains contain iron and are like

compasses. 3. They align with the magnetic field of the Earth.

When the molten rock cools, the record of these tiny compasses remains in the rock.

4. This record is then carried slowly away from the spreading center of the ridge as sea-floor spreading occurs.

Plates Tectonics

Plate boundaries

1. Convergent : where plates moves towards each other.

2. Divergent : where plates moves far away from each other.

3. Transform : where the plate moves past each other horizontally.

1- Convergent boundaries

The three types of convergent boundaries are:

1. Continental-continental boundaries, as a result mountain chains will be formed in addition for the earth quakes.

2. Continental-oceanic boundaries: the oceanic crust will sink under the continental because it has more dense than the continental the result ( volcanoes – earth quakes )

3. Oceanic-oceanic boundaries. As a result under water volcanic chains will forms .

2- Divergent boundaries

• When two tectonic plates separate, the boundary between them is called a divergent boundary. New sea floor forms at divergent boundaries. Mid-ocean ridges are the most common type of divergent boundary.

Divergent boundaries

3- Transform boundaries

• When two tectonic plates slide past each other horizontally, the boundary between them is a transform boundary. The San Andreas Fault in California is a good example of a transform boundary.

Transform boundaries

What cause plates to move

What are earth quakes?

How earth quakes happen?

Earth quakes happen in the plate boundaries , but how ?

Pressure starts to build up in to the earth crust.

Because of the pressure the rocks starts to be deformed.

The deformation could be even plastic or elastic (in plastic the rocks stay deformed with out any break)

In the elastic deformation the rocks starts to deformed until they reach to the point all the rocks brooked up on it and they returned to their original shape ( this point called elastic rebound ) and releas energy waves as earth quakes

Faults at Tectonic Plate Boundaries

• A specific type of plate motion takes place at different tectonic plate boundaries. Each type of motion creates a particular kind of fault that can produce earthquakes.

Earthquake Zones

• Earthquakes can happen both near Earth’s surface or far below it. Most earthquakes happen in the earthquake zones along tectonic plate boundaries. Earthquake zones are places where a large number of faults are located. The San Andreas Fault Zone in California is an example of an earthquake zone. But not all faults are located at tectonic plate boundaries. Sometimes, earthquakes happen along faults in the middle of tectonic plates.

Earth quakes waves

Earth quakes waves

Body waves

P waves

Called primary waves, moves thrugh solid liquid and gas , the fastes waves

S waves

Shear waves rocks moves side by side , cannot travel

through liquid

Surface waves

surface wave produces motion up,

down, and aroundback-and-forth motion

Body waves

Surface waves

• Surface waves move along the Earth’s surface and produce motion mostly in the upper few kilometers of Earth’s crust. There are two types of surface waves. One type of surface wave produces motion up, down, and around, as shown in . The other type produces back-and-forth motion like the motion produced by S waves. Surface waves are different from body waves in that surface waves travel more slowly and are more destructive.