Basics of Environmental Science

By Michael Allaby | Go to book overview

2

Earth Sciences
When you have read this chapter you will have been introduced to:
• the formation and structure of the Earth
• rocks, minerals, and geologic structures
• weathering
• how landforms evolve
• coasts, estuaries, and changing sea levels
• solar energy
• albedo and heat capacity
• the greenhouse effect
• evolution, composition, and structure of the atmosphere
• general circulation of the atmosphere
• ocean currents and gyres
• weather and climate
• ice ages and interglacials
• climate change
• climatic regions and plants

6

Formation and structure of the Earth

Among the nine planets in the solar system, Earth is the only one which is known to support life. All the materials we use are taken from the Earth and it supplies us with everything we eat and drink. It receives energy from the Sun, which drives its climates and biological systems, but materially it is self-contained, apart from the dust particles and occasional meteorites that reach it from space (ADAMS, 1977, pp. 35-36). These may amount to 10000 tonnes a year, but most are vaporized by the heat of friction as they enter the upper atmosphere and we see them as ‘shooting stars’. At the most fundamental level, the Earth is our environment.

The oldest rocks, found on the Moon, are about 4.6 billion years old and this is generally accepted to be the approximate age of the Earth and the solar system generally. There are several rival theories describing the process by which the solar system may have formed. 1 The most widely accepted theory, first proposed in 1644 by René Descartes (1596-1650), proposes that the system formed from the condensation of a cloud of gas and dust, called the ‘primitive solar nebula’ (PSN). It is now thought this cloud may have been perturbed by material from a supernova explosion. Fusion processes within stars convert hydrogen to helium and in larger stars go on to form all the heavier elements up to iron. Elements heavier than iron can be produced only under the extreme conditions of the supernova explosion of a very massive star, and the presence of such elements (including zinc, gold, mercury, and uranium) on Earth indicates a supernova source.

As the cloud condensed, its mass was greatest near the centre. This concentration of matter comprised the Sun, the planets forming from the remaining material in a disc surrounding the star, and the whole system rotated. The inner planets formed by accretion. Small particles moved close to one another, were drawn together by their mutual gravitational attraction, and as their

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Basics of Environmental Science
Table of contents

Table of contents

  • Title Page iii
  • Contents v
  • Figures vii
  • Tables xi
  • Preface to the Second Edition xiii
  • How to Use This Book xv
  • 1 - Introduction 1
  • 2 - Earth Sciences 19
  • 3 - Physical Resources 90
  • 4 - Biosphere 137
  • 5 - Biological Resources 200
  • References 258
  • 6 - Environmental Management 261
  • Further Reading 296
  • Glossary 300
  • Bibliography 307
  • Index 316
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