# Tectonics

This is to help you with the location and characteristics of tectonic activity.

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• Created by: Megan
• Created on: 26-04-12 15:58

## Three Plate boundaires

There are 3 plate boundaries called Destructive, Constructive and Conservative.

Destructive (Convergent) is when the plates move towards each and the denser plate subducts in some cases. There are three and they include:

Oceanic- Oceanic- Volcanoes and Earthquakes

Oceanic- Continental- Powerful Earthquakes

Continental- Continental (Colliding Plates)- Fold Mountains.

Conservative (Transform) plate boundary is when two plates slide past each other and only earthquakes occur at this plate boundary.

Constructive (Divergent) plate boundary is when two plates move apart from each other and minor earthquakes and volcanoes occur at this plate boundary.

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## Mercalli and Richter Scales

There are two main types of scales that are used to measure tectonic theory. They are known as the Mercalli and Richter Scales.

Mercalli Scale

The Mercalli scale is determined by the effect of an earthquake. This depends on how much damage has been caused by the earthquake. The scale goes from 1-12 and is rated by descriptive words. This scale is very subjective because many people disagree on what words to use for the damage that has been caused.

Richter Scale

The Richter scale is based on the magnitude of an earthquake. They use a seismograph to check the readings of the earthquake and to determine whether there will be and earthquake in an earthquake prone place. The scales goes from 1-10, 10 being the worst earthquake ever and 1 being that there wasn't much to the earthquake. Using Richter scale and a seismograph you can compare it to other earthquakes from years ago.

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## Focus and Epicentre

The focus and epicentre are an important factor to earthquakes. Here is the definition of each.

Epicentre

The Epicentre is the point which is directly above the focus and this is where the most amount of damage occurs from an earthquake.

Focus

The focus is the point at which the earthquake begins in the earths crust. This can be many kilometers deep.

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## Why are earthquakes and volcanoes found at these d

Earthquakes and volcanoes can be found in any different places which will shown below.

Plate tectonics theory:

The plate tectonics theory is also known as Continental Drift. This is when convection currents in the mantle broke apart the super continent of Pangaea into separate continents over millions of years. Earthquakes are found here because of what happens at the different plate boundaries and also volcanoes.

Hotspots

Volcanoes usually occur at hotspots because where areas which have the greatest pressure, the magma will erupt through the crust. Volcanoes will only be created if the magma rises above the oceans surface.

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