Restless earth

The structure of the earth:

The inner core of the earth is made of metals like iron and nickel. It solid because its under pressure but is very hot, over 5000 degrees, because it has alot of radioactive elements (such as uranium) which are decaying and giving off heat.

This heat creates massive currents of heat called convection currents' in the liquid outer core and mantle. These convection currents bring molten (liquid) rock called magma towards the earths surface.

The earths crust:

The earths crust is split into 7 large nd 12 smaller tectonic plates whihc float on the asthenosphere. There are two types; contental and oceanic.

- Contental crust...

• holds the contentants
• is made of granite
• it isn't destroyed so is very old
• It is between 25 and 50km thick
• is very light so does not sink

- Oceanic crust...

• holds oceans on it
• is made of basalt
• is constantly being destroyed and replaced so is therefore younger
• is 5-10km thick
• is heavy (dense) so sinks under contental crust when the two meet

Contental drift= the concept that earths contenants have drifted over time (Alfred wegnar)#

What are the types of plate boundaries are there?

1. Destructive (subduduction zone). This occurs when an oceanic plate moves towards a contental plate. The denser ocenic crust is forced beneaf the contental rust and destroyed. Fold mountains are formed here. Here there is violent earthquake and volcanic activity.For example, the Andes formed by Nazca plate being forced under the South American plate.

2. Destructive (collision zone). This occurs when two continental plates are forced nto each other and then both are forced upwards as they are too light tio be forced down. Fold mountains are also formed. Some earthquake but no volcanoes as the crust is too thick. For example, the Himalayas formed by the Indo-Australian plate hitting the Eurasian plate.

3. Constructive. This occurs when two oceanic or contenental plates move away from each other. New crust is formed creating mid ocean ridges or rift valleys with volcanoes. Earthquakes and gentle volcanic activity. For example, Iceland fromed ontop of the ridge where the Eurasian and North American plate move away from each other.

4.Conservative. This occurs when two plates move sidways past each other, sometimes in the same direction at opposite speeds, sometimes in opposite directions. Land is neither created nor destroyed. Earthquakes can be violent but no volcanic activity. For example, the San Andreas Fault formed as the Pacific plate moved past the North Amercan plate.

What is an earthquake and how do they occur???

An earthquake is the shaking or trembling of the earths crust. It consists of shock waves generated by rock breaking deep within the earths crust usually linked to tectonic plate movements. These shock waves move outwards. The source of the shock is called the focus (hypercenter) and directly abouve that point on the earths surface is called the epicenter.

They occur when two tectonic plates converge due to convection currents. As presure builds the rock…