Geology 101 Study Guide – Test #2 Chapter 5 Know how sedimentary rocks are classified based on texture (clastic rocks, Figure 5.4) and chemical composition (chemical/organic rocks). Be able to identify a sedimentary rock if given a description (i.e., if I give you grain size, you should be able to tell me the type of clastic rock). Understand how grain size relates to the energy of the depositional system. Understand transgression and regression. Given a stratigraphic sequence of sedimentary rocks, be able to determine whether that sequence is a record of transgression or regression. FIGURE 5.26 Be able to define/identify these sedimentary structures: stratification, cross bedding, graded bedding, ripple marks, mud cracks. Know how these structures relate to the depositional environment (e.g., how/where they form). FIGURE 5.2, FIGURE 5.9 Cross-bedding, Figure 5.10 Graded bedding The type of rock and its structures are important records of past depositional environments. Know the major sedimentary systems, their important characteristics and types of sediments that accumulate in them (Figures 5.13; and 5.14-5.25; are key). In other words, know how sedimentary rocks form and how their formation and structural features relate to depositional environments. Chapter 6 Know the rock cycle – this links all the various rock types to plate tectonics and surface processes. Know how metamorphic rocks form, including the processes of recrystalization, plastic deformation. Know how metamorphism occurs under pressure, temperature, and composition changes; understand where these conditions take place in relation to plate tectonics (figures 6.4 (Where), 6.6, 6.19 are a good place to start). The driving forces for metamorphism are changes in temperature, pressure, and composition of the environment or strong deformation.These changes cause recrystallization in the solid state as the rock changes toward equilibrium with the new environment. Understand stability diagrams and be able to use them to predict what mineral would be stable under given environmental conditions. Figure 6.5 Know how metamorphic rocks are classified; be able to identify the common metamorphic rocks presented in class and lab (and in the chapter). Understand why some rocks are foliated and some are not. Know figure 13. Foliation is caused by differential stress and shearing. Usually occurs during the recrystallization step. Understand figure 6.16. Be able to use information about metamorphic facies to identify metamorphic grade in relation to plate tectonics (again, figure 6.19 will help with this). Where and why… In other words, know how and under what conditions rocks are metamorphosed, what a given rock metamorphoses into for a given set of conditions (high temperature metamorphism of sandstone equals quartzite), where those conditions and their associated metamorphic rocks occur. Chapter 7 Now that we’ve created rocks in chapters 3-6, chapter 7 discusses how we modify their structure. Be able to identify the types of folds, geometries of folds, and types of faults that can occur. Be able to link the types of stress and types of deformation that give rise to these structures. Know what factors influence how a given rock body deforms in response to a given stress. Figure 7.4 Know the terminology associated with folds and faults (limb, hinge, hanging wall, etc.). Be able to identify folds and faults given a description of the dip of limbs, ages of rocks as you walk from the limb to the hinge axis, direction of movement of the hanging wall, etc. We did a large number of examples of this in class. Hanging wall, footwall, forelimb, back limb, top limb. Figure 7.11. Rule of v’s (Figure 7.15) Eroded V’s point the direction the bed dips Be able to identify a plunging fold, whether it is an anticline or syncline, and its major features (direction the “v” points, dip of the limbs, etc). Age of rock (syncline and anticline) Know the large scale features that result from regional stress – fold and thrust belts, horst and graben, shortening and thickening of the crust, etc. Be able to identify the type of plate margin given a description (or figure) of the dominant structural features. And be able to do the reverse (give the most likely structural features that would occur at a given plate boundary). In other words, be able to use the information above to relate structural features to plate tectonics. In other words, know how rocks are deformed, the processes that influence that deformation, the types of structures that result, and where those structures occur with respect to tectonic setting. Chapter 8 Know the difference and importance of both relative and absolute dating. Know the relative dating tools (principles) and unconformities. Be able to identify examples of each. Be able to use these to place a sequence of events in relative order (given a description or a cross section). (Major Concepts #2) Understand the principle of absolute dating. Know how elements radioactively decay, how this relates to half-life (and whether radioactive decay occurs linearly or exponentially), and how geologists use unstable (radioactive) isotopes to date a sample. Be able to determine the number of half-lives required to remove a given fraction of radioactive atoms (or the reverse: what fraction of radioactive atoms remain after a given number of half-lives). Figure 8.11 Know how absolute ages of crust relate to the major features of the continents. Know what evidence geologists use to determine the age of the earth. Potassium-Argon Dating Understand how the standard geologic column was first developed (the relative dating tools), and how absolute dating has improved our understanding of the time divisions within that column. FIGURE 8.8 (caption) The original order of the units in the geologic column was based on the sequence of rock formations in their superposed order as they are found in Europe. In other words, know the difference between relative and absolute dating, how we date rock sequences using both methods, and why both methods are important. Chapter 18 Understand elastic rebound and how it relates to earthquakes. Figure 1.8 Know the difference between P, S, and surface waves (in terms of motion, speed, etc.) Figure 18.3. Know the differences between the schemes used to determine the intensity(measured in relation to effects on humans)/magnitude(objective scale of energy released) of an earthquake moment magnitude is the most widely used today. Know how we use the properties and energy of the waves to locate the epicenter and focus of an earthquake (figure 18.4) Understand how the distribution of focal depths around the world relates to plate boundaries. Know how material properties affect how/whether the different seismic waves are transmitted through the earth. Be able to describe how this is evidence that the earth is a differentiated planet (figures 18.15-18.22 will help a lot). Also, be able to relate material properties at the surface to the level of “property” damage that occurs due to an earthquake of a given magnitude. Chapter 17 Understand the theories of continental drift and plate tectonics, the difference between the two, and the evidences for each. Understand paleomagnetism, how it is recorded in the rock record (both on continents and in the seafloor), and why it is important. Know the major plates and types of plate boundaries. Know how we determine plate boundaries. Know the processes that occur at convergent and divergent plate boundaries (e.g., seismicity, magmatism, metamorphism, structural features, etc). Know how magmatism occurs at divergent and convergent plate margins. In other words, understand how plate tectonics explains the dynamic evolution of the earth evident at the surface. Chapter 23 Understand the relationship between tectonism, the hydrologic cycle, differential erosion, and climate in the production of landforms. Know the relationship between elevation, erosion, and isostasy. Figure 23.4, 5 Know the primary geomorphic landscapes that occur on all continents (there are three of them Shield, stable platform, folded mountain belt). Also know these geomorphic landscapes that occur on some continents: rift systems and magmatic arcs. Know how these geomorphic provinces form and the distinctive landforms that develop for each – pay special attention to the examples from the US. The production of landforms play a key role in determining the rock types exposed at the surface. Know how the basic rock types exposed at the surface of the continent relate to geomorphic landscapes. In other words, understand the processes that influence the evolution of landforms and how these landforms relate to tectonic setting.