Student Name Robert Trommer Prof. Robert J. Sager GEOLOGY 100 – MIDTERM EXAM (20% of course grade) PART A: INTERPRETATON OF A STRATIGRAPHY CROSS-SECTION (10%) Purpose: Apply the scientific method to interpret geologic data/information in this exercise. The student should review the topics covered on rocks (igneous, sedimentary, and metamorphic rocks) and geologic time from your previous assignments, the online textbook, course “Webliography” (Content tab), and online geologic research sources. Your research sources must be listed in proper APA-style citations at the end of the questions. 1 Figure 1. Answer the following questions based on your interpretation of the geologic cross-section (Figure 1) on Page 1. 1) How would you apply the “principle of original horizontality” to the layers (strata) in Fig. 1? Use the strata from B to M (includes B-K-N-J-D-M). Explain. The principle of original horizontality states that under gravity, sediment layers are always deposited horizontally. Therefore, the layers in the figure being horizontal in nature must have been subjected to horizontal deposition. According to the principle of original horizontality, the older beds lie under younger bed. Youngest formation exists above all the beds. Oldest exists below all horizontal beds. Hence, youngest beds exist at top and oldest exists at bottom of horizontal beds. From the statement, you have given that how to apply the principle of original horizontality to the beds B-K-N-J-D-M. In that above rock sequence, the bed B lies above all the horizontal beds. Hence, it will be youngest of all the given rock beds. K is older than B because it lies below the rock bed B. N is older than K because it lies below the rock bed K. J is older than N because it lies below the rock bed N. D is older than J because it lies below the rock bed J. M is the oldest bed of all the given beds in B-K-N-J-D-M, because it is existed at bottom of all horizontal beds 2) How would you apply the “principle of superposition” to the layers (strata) in Fig. 1? Use the strata from B to M (includes B-K-N-J-D-M). Identify by letter the oldest strata and the youngest strata ? Explain. The principle of superposition expresses that older rock is always overlaid by the younger rock. From the strata rock M is overlaid by every other rock in the B,K,N,J,D,M strata and along these lines, rock M is the oldest, then D, J, N, K, and B being the youngest. 3) Which is the surface cover (identify by letter)? What would this be composed of? What are the possible sources of this surface material? Why is this not considered part of the sedimentary rock strata? Explain. The surface cover is letter F and would be composed if loose sediments called soil. Deposition is still present in this layer and it is not bounded by strati-graphic columns. 4) What is a geologic “unconformity”? Are there any unconformities in this strata sequence? If so, what type of unconformity are they? Describe in the stratigraphy (between letters) where at least two (2) unconformities are located, if any. 2 Geologic Unconformity is discontinuity in rock sequence indicating interruption of sedimentation, commonly accompanied by erosion of rocks below the break. The 2 types of nonconformities in the is a nonconformity between A and N and a disconformity below the layer N and above the layer J 5) If rock region A is composed of igneous rock, would it be intrusive or extrusive igneous rock? What type of common igneous rock would it most likely be composed of? What is this large igneous feature called? It would be an intrusive igneous rock. The type of common igneous rock it would be composed of is granite. This large Igneous feature would be called a Batholith 6) If the sedimentary strata from B to M had some metamorphic rock in it, which strata (identify by letter) would most likely have had the most “contact” metamorphism with A? Explain. D, N and K. The reason is that metamorphism occurs due to natural agencies, heat and pressure and affects the adjacent pre-existing rocks. APA citations: PART B. SEISMIC PROFILE AND TECTONIC PLATE BOUNDARY EXERCISE (10%) Purpose: Apply the scientific method to interpret geologic data/information in this exercise. The student should review the topics covered on Plate Tectonics from your previous assignments, the online textbook, course “Webliography” (Content tab), and other online geologic research sources that cover plate tectonics and earthquake distribution. Your research sources must be listed in proper APA-style citations, including any websites you used. Earthquake data has been collected over a 32-month period from a local seismograph network. A total of 2,476 seismic events were recorded, you will be plotting and interpreting 30 of the earthquakes with the most reliable locations. The master data set is provided in Table 2, shows only the earthquake foci locations that occur within the line of the cross-section in Figure 1 at latitude 20ºS. The focus (pl. foci), or hypocenter, of an earthquake is the point of the earthquake location be

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