Evolution of Mountains and Continents: Geology 230 Study Guide - Prof. Lynn Fichter, Study notes of Theory of Evolution

Download Evolution of Mountains and Continents: Geology 230 Study Guide - Prof. Lynn Fichter and more Study notes Theory of Evolution in PDF only on Docsity! Study Guide #3 Geology 230 - Evolution of the Earth THE EVOLUTION OF MOUNTAIN RANGES AND THE ORIGIN AND EVOLUTION OF THE CONTINENTS (Archean, Proterozoic, Phanerozoic) Lynn S. Fichter James Madison University Topics to Be Covered and General Objectives: During this period, we will cover the following topics in lecture: ( The geology of TRANSFORM, DIVERGENT and CONVERGENT plate tectonic boundaries and their bearing on the history and geology of mountain ranges. ( The various mechanisms of plate tectonic mountain building. ( The WILSON CYCLE. ( The question of the origin of the continents, the Archean and Proterozoic history of the continents, and the processes responsible for the origin of the North American craton. ( A plate tectonic rock cycle and a hypothesis for the origin of all rocks from a parent mafic magma. ( The principles used to interpret cratonic geologic records. ( The sequential evolution of the North American continent beginning with the latest Precambrian, and getting as far as we can before the semester runs out. When we examine the oldest rocks on the earth we observe that most are not significantly different from rocks forming today. The implications are that the processes operating on this planet have not changed significantly since the earth's formation. This is the core of Charles Lyell’s comment that the earth had “no vestige of a beginning, no prospect of an end.” It was just the same processes cycling over and over endlessly, but getting nowhere in particular. STUDY GUIDE: EVOLUTION OF MOUNTAIN RANGES GEOLOGY 230: EVOLUTION OF THE EARTH AND THE EVOLUTION OF THE EARTH 2 What has changed through the earth's history, however, and Lyell was not aware of, is the relative abundances of different rocks. Some rocks form in much greater abundance today than in the past, others have declined in importance, while a few have ceased forming altogether. The implication is that the frequency and intensity of the earth's processes have changed through time, leading to the conclusion that the earth has evolved. But, as we shall see, the earth's processes can interact in an almost unlimited variety of combinations, and the resulting evolution of the earth has been a continuously unique and changing scene. Thus what we observe in the Evolution of the Earth (the course title) are fundamental processes, but changing patterns of response. On an exam, you should be able to demonstrate your knowledge and comprehension of the principles and processes behind the Earth's evolution, and the ways they have interacted to create the Earth in general and North American in particular, by specifically answering the questions below: THE EVOLUTION OF MOUNTAIN RANGES Introduction and Background Knowledge Plate Tectonic Theory is an integral part of this subject. In Geology 110 you have learned the basic concepts of plate tectonics, its historical development from continental drift theory, and the basic physical geology needed to understand it. I will not repeat this in this class. Yet that knowledge is essential to what we will discuss, and the importance of many ideas we discuss may be unclear or lost to you without this background knowledge. Review the list of terms and concepts below. If any are unfamiliar to you look them up in your physical geology textbook or lab manual. Your historical textbook by Stanley, Exploring Earth and Life Through Time, also has a very good chapter on plate tectonic theory (chapter 6, p 130-155), although it will not cover all the concepts below. If you still have problems come see me. Alfred Wegner and Continental Drift Theory $ The Origin of Continents and Oceans $ Pangaea $ Panthalassa $ Laurasia $ Gondwana $ Tethys sea $ Wegner's evidence for continental drift $ Wegner's mechanism for continental drift STUDY GUIDE: EVOLUTION OF MOUNTAIN RANGES GEOLOGY 230: EVOLUTION OF THE EARTH AND THE EVOLUTION OF THE EARTH 5 2 Explain the processes by which Hot Spots are responsible for the bimodal igneous suite associated with them. 3 Describe and illustrate what is meant by a TRIPLE JUNCTION, " Explain how they form, " The processes and rocks formed in them, and " Give a modern example. 4 Define what an AULACOGEN is (i.e., how they are recognized), . . . " List a few examples, and . . . " Explain their relationships to triple junctions, rifting events, continents, and the conditions under which they form. B. Describe how PLATE ACCRETION creates new oceanic crust by doing the following: 1 Describe what an OPHIOLITE SUITE is. 2 Draw a fully labeled cross section of a typical oceanic rift where plate accretion is occurring: include: " The location, composition, and/or characteristics of Layers 1-4, " Positions of the Moho, crust, mantle, asthenosphere, and " The origin, composition and position of all rocks associated with rifting processes. C. Describe the characteristics of a DIVERGENT (Atlantic-type, passive, or trailing edge) CONTINENTAL MARGIN by doing the following: 1 Draw a sequence of fully labeled cross-sections showing the timing and development of a typical divergent continental margin including: # Axial rift # Continental terrace # Continental crust # Transition crust # Oceanic crust # Bimodal association # Listric faults # Plateau (flood) basalts # Slope/rise # Rift graben clastics # Continental margin deposits # Transgressive quartz arenite # Axial graben # Ophiolite suite # Aulacogen # Lateral graben 4. For the closing stages of the Wilson cycle, PLATE CONVERGENCE, SUBDUCTION, EARLY MOUNTAIN BUILDING: A Understand the complex geology of Subduction Zones and associated Mobile Belts, by doing the following: STUDY GUIDE: EVOLUTION OF MOUNTAIN RANGES GEOLOGY 230: EVOLUTION OF THE EARTH AND THE EVOLUTION OF THE EARTH 6 1 List the variety of CORDILLERAN TYPE and COLLISION TYPE mobile belts including a simple cross section of each, a modern example, and how they are driven (i.e., their major sources of energy). 2 Draw a detailed, fully labeled cross section of a typical Cordilleran Mobile Belt of the ISLAND ARC TRENCH type, including the location of the following: ( Alkaline suite ( Backarc ( Blueschist metamorphism ( Calc-alkaline suite ( Flysch ( Forearc ( Island (volcanic, magmatic) arc ( Marginal (backarc) spreading center ( Mobile core ( Outer arc trough ( Outerarc ridge ( Regional metamorphism ( Subduction zone ( Tholeiite suite ( Trench ( Volcanic front ( Zone of fractionation 3 Describe and/or clearly explain the formation of the following: k Alkaline suite k Blueschist metamorphism k Calc-alkaline suite k Flysch k Marginal (backarc) spreading k Melange k Subduction zone k Tholeiite suite 5. For PLATE COLLISION AND MOUNTAIN BUILDING: A Draw fully labeled, simplified cross sections illustrating the plate relationships in an "Island Arc Trench type" collision and a "Continental Trench type" collision, (show the position of major lithologic units). B List and illustrate several ways in which mobile belt mountain building may become more complex than that presented in the simple models. 6. Draw a detailed, fully labeled cross section of a CONTINENT-CONTINENT collision mountain building episode including the location of the following: " Allochthons " Backarc (marginal) basin " Divergent margin sedimentary wedges " Foreland " Foreland basin " Flysch " Hinterland " Klippe " Melange belt " Molasse " Obduction " Oceanic crust " Paired metamorphic belts " Remnant ocean basin " Subduction zone " Suture zone " Volcanic front " Wildflysch STUDY GUIDE: EVOLUTION OF MOUNTAIN RANGES GEOLOGY 230: EVOLUTION OF THE EARTH AND THE EVOLUTION OF THE EARTH 7 7. For STAGE I, the last stage, of the Wilson Cycle: " Take the last stage and be able to deconstruct it, identifying the processes or stages in the cycle where each rock unit formed, and/or identifying each rock type in the cross section and the processes by which it formed (see http://geollab.jmu.edu/Fichter/Wilson/StageI.html#How Much 8. List the complications of mountain building models, and explain each of their effects. THE ORIGIN AND EVOLUTION OF THE CONTINENTS Fundamental Processes But Changing Patterns of Response Historical Background 9. Draw a time line of earth history showing the timing of the Archean, Proterozoic, and Phanerozoic Eras. For each Era give a succinct description of the significant rock record or geological processes occurring. 10. Given a chart showing the distribution of major rock types through time (see “Major Divisions in Earth History” in notebook) be able to explain or answer questions about why the abundances of rock types are changing with time. These explanations may include tectonic evolution of the earth, changing processes in earth history, the influence of life processes, or any others responsible for the generation of specific rock types. For the Archean Geological Record 11. Describe the nature of the Archean rock record, including a listing of the major rock complexes, groups, or associations and their characteristics for both granulite- gneiss belts and greenstone belts. L With the use of fully labeled diagrams, charts, or cross sections completely explain, describe, or understand the processes by which each of the complexes or rocks are formed.