The planet we live on: The beginnings of the Earth Sciences

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Figure 3.32: A photograph of James Lovelock,taken recently.Figure 3.33: One of James Lovelock’s‘Daisyworld’ simulations, showing that lifecould maintain a steady temperature on a<strong>planet</strong>, as solar radiation increases.One of the most highly debated hypotheses of the climate change debate is the ‘GaiaHypothesis’ proposed by James Lovelock in the 1970s. Lovelock, working with LynnMargulis, proposed that the Earth works like an organism in that it has many negativefeedback systems that maintain the conditions needed for life on Earth, and that thesefeedback systems are related to life. So the hypothesis proposes that life itself regulatesthe <strong>planet</strong>ary conditions of the Earth to keep them suitable for life. Before Lovelock’sproposal, most scientists thought that it was coincidence that the conditions on Earth<strong>we</strong>re suitable for life, which is why the ‘Gaia Hypothesis’ is such a revolutionary idea andhas promoted such scientific discussion.When Lovelock found that many scientists disagreed with his ideas, he devised a computersimulation to demonstrate how the ‘self-regulation’ of the Earth suggested by the ‘GaiaHypothesis’ could work. He called this simulation ‘Daisyworld’ which is based on a <strong>planet</strong>like a cloudless version of the Earth, with a Sun, like our Sun, where solar radiationincreases over time. His ‘Daisyworld’ had only two organisms, a white daisy and a blackdaisy. In the early days of ‘Daisyworld’ the Sun was fairly cool and there was littlesolar radiation. At this stage, ‘Daisyworld’ was almost completely colonised by blackdaisies that could absorb all the radiation available and survive. As the temperatureof ‘Daisyworld’ increases, the black daisies near the equator absorb too much radiation,become too hot and die, and so are replaced by the white daisies that reflect radiationand stay cool. As ‘Daisyworld’ becomes still warmer, white daisies replace back daisiesmore and more until the <strong>planet</strong> is completely covered by white daisies that keep it ascool as possible. Through this interaction of life with solar radiation, conditions suitablefor ‘daisylife’ <strong>we</strong>re maintained much longer than they would have been if the negativefeedback caused by the change in the colour of the daisies had not taken place, as shownin Figure 3.33. Later Lovelock extended these computer simulations by incorporatingdaisies of other colours and later, rabbits to eat the daisies and foxes to eat the rabbits.Despite the increasing complexity, the results <strong>we</strong>re always the same, that the life on the95
<strong>planet</strong> extended the time when the conditions suitable for life <strong>we</strong>re maintained as thesolar radiation increased.Lovelock extended his ‘Gaia Hypothesis’ to include all the natural systems active onEarth, arguing that all of these must be moderated by the effects of life, since not onlydoes life need an optimum temperature to survive, but it also needs optimum salinity inthe oceans, optimum percentages of gases in the atmosphere (including carbon dioxide),optimum levels of trace elements in soils, etc. He argued that, since life on the <strong>planet</strong>moderated these conditions, like organisms moderate conditions in their own bodies (suchnegative feedback conditions in organisms are called homeostasis) then the <strong>planet</strong> itselfalso has a form of homeostasis, and can be likened to a ‘superorganism’. It was whenLovelock suggested that the Earth itself acts like a living organism in some ways thatmany scientists disagreed with him, and many do to this day. Ho<strong>we</strong>ver, his ideas havebeen taken seriously and tested by many scientists across the <strong>planet</strong> and, whilst theydon’t all fully support the ‘Gaia Hypothesis’ their studies have developed a new branchof science called ‘Earth System Science’. ‘Earth system science’ investigates the Earthas a series of systems that interact with one another and seeks to discover how theseinteractions can have both positive and negative feedback effects in certain conditions.It has helped us to generate computer climate models of increasing complexity, that willenable us to predict, with increasing certainly, how the global climate might change inthe future.At the moment, James Lovelock is just seen as a very important scientist in the climatedebate. In future he might be considered to be one of the ‘giants’ of ‘Earth science’, likeHutton, Darwin, Wegener and Tuzo Wilson.96
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Basic Books in ScienceBook 6<strong
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BASIC BOOKS IN SCIENCE- a Series of
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BASIC BOOKS IN SCIENCE- a Series of
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Looking ahead - If you came across
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3.2 Plate tectonics (20th Century)
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1.30 Coal seams in an opencast coal
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3.4 Alfred Wegener, the polar explo
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5.14 A GPS remote volcano monitorin
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Figure 1.2:minerals.A sandstone roc
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Even diamond can have different col
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Figure 1.8: A red garnet crystal in
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Figure 1.12: Crystals of minerals i
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Hematite, Fe 2 O 3 - earthy red, me
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Figure 1.17: Sedimentary rocks show
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Figure 1.20: A close up view of a p
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Figure 1.26: Ancient wave ripple ma
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Figure 1.30: Coal seams in an openc
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Figure 1.32: Close up view of a pie
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Figure 1.35: A fossil colonial cora
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Figure 1.38: Fossil ammonites, indi
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Figure 1.39: ‘Massive’ igneous
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Figure 1.41: A close up view of a p
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Figure 1.44: A basalt flow that coo
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Figure 1.47: Deposit of volcanic as
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Figure 1.49: An old slate quarry, s
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Figure 1.51: Slate, a low-grade met
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Figure 1.53: Schist, a medium-grade
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Figure 1.56: Metaquartzite, produce
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Figure 1.58: A region of folded roc
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Page 71 and 72: Chapter 2Reading landscapes: how la
Page 73 and 74: Figure 2.3: Rock fragments loosened
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Page 87 and 88: found evidence that the Earth was a
Page 89 and 90: Figure 3.3: James Hutton, the ‘Fo
Page 91 and 92: Figure 3.5: A page of Wegener’s 1
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Figure 6.10: A slab foundation, bui
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An example of this is investigation
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GlossaryAbsolute age The</s
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Carbon capture The
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Crustal shortening This results of
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Evaporite deposits (or evaporites)
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Geophysical survey Using the method
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“Integrated waste management” <
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Metamorphism The r
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Pore spaces (or pores) Gaps bet<str
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Saltation Sediment movement by flui
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Suspension Sediment movement by flu
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AcknowledgementsPermission to repri
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Figure 2.3 A scree slope. Photo ID:
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Figure 1.15a Hematite.Figure 1.15b
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Figure 1.28 Dune cross bedding in s
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Figure 3.18 An island arc volcano,
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Figure 5.21 Excavations at the dino
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