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Is the region from the northwest corner to the Potomac River strongly folded or strongly faulted? Is the region from the southeast corner to Harrison Island along the Potomac strongly folded or strongly faulted? In the eastern part of the map, along the Shenandoah River, the sediments are only quaternary in age, yet they are surrounded by much older Cambrian sediments. How do you explain this? In the southeastern corner of the map, locate Montrose and Glen Hills. Notice that they are separated by a fault. Is Montrose moving atop Glen Hills or is Glen Hills moving atop Montrose? How old are the rocks around Martinsburg, WV, in the upper northwest corner? What about Martinsburg, MD, in the south-central portion of the map? Which Martinsburg is associated with older sediments? Locate Dru Run in the far northwestern corner of the map. Which way is it flowing? How many different ages of rock would you encounter along its course? Would the area in the northwest be considered an anticline, syncline, dome, or basin? In the middle image at the bottom, to the far right, you see that the younger Prettyboy Schist lies beneath the older Mather Gorge Formation. How can older rock be found atop younger rock? Would the rocks to the east and west of this map area be younger or older? Why? Make a geologic profile of the area between the Monocacy River and the Hyattstown fault. Start at the word “Monocacy,” just north of the junction of the Monocacy and Potomac Rivers and draw your profile line to the east to connect with Thompson’s corner, just east of the fault. It might be easiest if you print out this portion of the map. In the previous exercise, you used contour lines for contouring. This time, use rock ages. Before you can finalize your profile, you must answer the next question as it is essential to determine your next step. What type of geologic formation did you just map? Now you can finish your profile. How do the contour lines relate to the geologic ages in the east versus the way they relate in the west? Why do you think that the rock on the western side of the map flows north-south, while the rivers on the eastern side flow west-east? Which river system would be best to walk along to study a large number of geologic ages? In the west-central region of the map there are numerous red lines. What do you think that they indicate?