Plate Tectonics Project.

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Plate Tectonics Project

PLATE TECTONICS

CONTENTS

1. Introduction

2. Earthquakes and Volcanoes

2.1 Earthquakes

2.2 Ocean Trenches

2.3 Volcanoes

3. Plate Movements

3.1 Europe

3.2 Far east, Australia and the Pacific

3.3 North America

3.4 Nazca and South America

4. References

1. INTRODUCTION

In this report I am going to study the Earth's plates (see fig. 1) and how they move and behave in different areas around the world. The Earth's crust is made up by a number of rigid plates, these plates move in relation to one another. They may move apart, together, or along side each other. The plates FLOAT on a hot liquid called the mantle beneath the crust of the Earth, the movement of the plates is caused by rising hot currents within the mantel, these are known as convection currents. The mantle is made up of hot liquid rocks. Mountain ranges, earthquakes, volcanoes and deep ocean trenches are all caused by the processes that take place along the boundaries between the plates of the earth. This report is divided into a number of sections. First of all I will write about earthquakes and volcanoes and how they occur. This will cover convection currents and deep sea ocean trenches. It will also look into the case of Mount St. Helens. Then in a number of different sections I will write about the different plates in different parts of the world and how different forces change the way the land lies and why every part of the earth's landscape is unique. The first of these sections will be about Europe and its plates. The next section will be about the far east, Australia and the pacific. The next section will be about South America. The final section before the references will include North America and Nazca. The last section is the references which shows my information sources. See my internet home page for a full copy of the project (at http://www.corbishley.co.uk).

2. EARTHQUAKES AND VOLCANOES

2.1 EARTHQUAKESAn earthquake is a violent or gentle movement of the ground, it moves like a wave or a ripple across the ground. There are many different velocities of earthquake and they are measured on a seismometer. The earthquake is given a number on a scale, either the Richter scale or the Mercalli scale (see fig 2 for the two scales). An earthquake occurs where a fault between two plates is situated, and when two plates move against each other and become jammed together. Behind each of the plates pressure builds up. Then the plates slip past each other releasing vast amounts of energy which move outwards that can travel over 100 miles from the origin of the earthquake. The epicentre is where the earthquake starts, the focus is where the earthquake hits hardest and the shock waves are the ripples of energy that travel across the surface of the earth (see fig. 3). It can take just a few seconds for an earthquake to travel hundreds and hundreds of miles. Plates move in three ways, towards each other, away from each other and alongside each other. Depending which way the plates travel decides the different waves on an earthquake. Earthquakes are extremely destructive for example San Francisco was hit by and earthquake in 1906 and was totally devastated. There are two main causes of distruction: 1. Liquefaction, this is when the land shakes so violently that the soil acts like quick sand and large structures sink into the ground. 2. The extreem shaking of the ground which causes structures to collapse. In an earthquake gas and fuel pipes rupture and start fires. It is imppssible to stop the fire as the water pipes are broken too. The devastation of an earthquake is enormous, although they only last a few seconds.

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3.2 OCEAN TRENCHES

A trench is formed where two converging plates meet and one slides under the other. The area where the two plates meet is know as the subduction zone. The diagram below shows the two plates meeting, the currents under the plates and the trench being formed.

3.3 VOLCANOES

There are two movements of plates that volcanoes can be formed by, Converging plates and Diverging plates. Here are two examples of converging plates and then two examples of diverging plates.

Here is a diagram of how an Island arc is created. As the downward moving plate sinks deeper ...

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