Gel1503 Summary Study Notes

GEL1503 SUMMARY STUDY NOTES GEL1503 - Environmental Geology The planet Earth, which we study in Geology today, came into existence in some manner together with other planets and stars and has developed into its current composition and structure. However, the limitations of science have thus far only allowed us to form hypotheses (conjectures) about the originating processes of the universe. • After reading chapter 1 in UE-6, which is about the origin of our system of planets, you should, for instance, know what a dense point mass is, what planetesimals are, and that the Earth might be 4,5 billion years old. • Use the above concepts to form your own opinion about the Big Bang theory and the nebular hypothesis. 1.1.2 Early Earth: formation of a layered planet 201Read the text under the first three subheadings about the early formation of the Earth on pages 7–12 in UE-6 very carefully, and take note of the following: 202 4GEL1503/1 35 203 1. Earth heats up and melts. 204 2. Differentiation begins. Take note of figure 1.9 in UE-6 (cross section of the Earth) and make sure that you can depict the information given in the figure in a simple diagram. 205 3. Earth's continents, oceans, and atmospheric form. Take note of the Earth processes that formed the Earth's atmosphere, as portrayed in figure 1.14 in UE-6. 206 In your own words, summarise the most important aspects of what you have read. Use the three headings given above as a structure for your summary. 207 Compare your summary with the example below: 208 1. The Earth heats up and melts. • Kinetic energy: planetesimals and larger bodies crash into the Earth • Radioactive elements disintegrate (decay) into the Earth and emit heat 209 2. Differentiation starts – an impact with the Earth causes exterior layer to melt, interior soft. • Heavy materials sink to the interior, light materials (and heat) float to the surface • Solidify into heavy/light zones during cooling » Core of heavy iron; molten on the outside, solid on the inside; depths » Crust of light elements (O, Si, Al, Fe, Mg, Ca, K, Na); depths » Mantle of intermediate densities (compounds of O, Mg, Fe, Si) 210 3. Continents, oceans and atmosphere form. • Repetitive melting/solidifying, erosion; comets and volcanoes produce gas and water 211 Exercise 212Answer the following questions in writing. 213 1. What caused Earth to differentiate, and what was the result? 214 2. How does the chemical composition of Earth's crust differ from that of its deeper interior? And from that of its core? 16 2ENVIRONMENTAL GEOLOGY 215 The answers to the questions above can be found in the following references: 216 1. See the summary "How did Earth form and evolve over time?" on page 21 in UE-6. 217 2. Figure 1.12 ("The relative abundance of elements") on page 12 in UE-6 and the related paragraph give percentages of the relative abundance of elements (chemistry) in the whole Earth and the crust. You can compare differences in the quantities of the four most common elements. 1.1.3 Earth as a system of interacting components 218 Carefully read the section "Earth as a system of interacting components" on pages 13–17 in UE-6 and figure 1.14. 219 Exercise 220Answer the following questions: 221 1. Write down the components of the climate system, the plate tectonic system and the geodynamic system. Describe each component in one sentence and state which source of energy drives each. 222 2. Describe/define the following terms in your own words: 223 (a) Plate tectonics 224 (b) Lithosphere 225 (c) Asthenosphere 226 (d) Convection 227 Compare your definitions with the definitions given where the terms are printed in bold in the text, or with those in the "Glossary" at the back of UE-6. Adjust your answers, if necessary. Also refer to the following: 228 1. Table 1.2, which contains the system names, and figure 1.10 on pages 12–13 in UE-6 229 2. (a) UE-6, page 15 230 (b) UE-6, page 16 231 (c) UE-6, page 14 232 (d) UE-6, page 16, together with figure 1.15 4GEL1503/1 37 1.1.4 Revision and application 233 Revision 234 1. The most important aspects of this study section are covered in the summary on page 21 in UE-6. Read it again. Make your own summary with which you are comfortable to use when revising for the examination. 235 2. Make sure that you can define the key terms below, and that you can use them in the context of the composition of the Earth and the theory of plate tectonics as described in chapter 1 of UE-6. 236 237Key terms and concepts 238 239UE-6, page 240 asthenosphere 241 14 242 climate system 243 15 244 core 245 12 246 crust 247 11 248 lithosphere 249 16 250mantle 251 10 252 plate tectonics 253 15 255 Application 256Start developing your own code of ethical scientific conduct. Read page 2 in UE-6 for background knowledge on "the scientific method" and the paradigm within which the theory of plate tectonics was developed, and give your own opinion about the credibility of the theory. 257 18 2ENVIRONMENTAL GEOLOGY 258Study section 1.2 Plate tectonics – the unifying theory 259 The time scheduled for this study section is 10 hours. Learning outcomes 260On completion of this study section, you should be able to • explain the theory of plate tectonics in broad terms • describe the geological features of the different plate boundaries • describe how the age of the seafloor is determined • demonstrate background knowledge on the reconstruction of Pangaea • give a broad outline of the mechanism(s) that cause(s) the formation and motion of lithosphere plates • read up (as application of your knowledge) how modern technology such as seismic tomography can help detect and explain geological phenomena, and communicate your knowledge in the form of a report (using standard conventions and methods) 261 General overview of learning content ª This study section is based on parts of chapter 2 of UE-6, pages 25–53. • We will cover the following themes referred to in the scheme on page 25: the mosaic of plates, plate motions and mantle convection. Apply your knowledge by using the scientific method you studied in study section 1.1 (formulating the problem and hypotheses, doing research by reading, and drawing a conclusion) to develop a model of mantle convection. • The outcome of this study section is to study the theory of plate tectonics and to relate it to the mantle convection system (UE-6, p 25, text printed in blue). 4GEL1503/1 39 Page quickly through chapter 2 of UE-6, using the scheme on page 25, and look at some of the figures and their captions, in order to acquaint yourself with the themes. The most important issues covered in this study section have been summarised on page 52 of UE-6. Read this summary to get an overview of these issues in a nutshell. 1.2.1 The discovery of plate tectonics 262 Read pages 26–27 in UE-6 cursorily, from the development of the hypothesis on continental drift to the theory of plate tectonics. This will provide you with a brief overview of the development of this theory. 263 Overview of the theory of plate tectonics 264Geologists suggest that the crust of the Earth is divided into about 12 lithosphere plates, and that these plates slide past one another, converge with one another, or diverge as they move over the interior of the Earth. New plate material is formed at diverging points and material is reabsorbed into the mantle where plates converge in a continuous process of formation and destruction. Continents embedded in the lithosphere plates drift with the moving plates. The theory of plate tectonics describes the movement of the plates and the forces between them. It also explains the distribution of large-scale geological features – mountain chains, collections of rocks, structures on the seafloor, volcanoes and earthquakes – which are the result of movement along the plate boundaries. Plate tectonics provides a conceptual framework for a large part of geology, as will be evident in the following study sections. 1.2.2 The plates and their boundaries 265 Carefully read the parts under the blue subheadings ("The plates and their boundaries") on pages 29–36 in UE-6, that is, the descriptions of the different plate boundaries.