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What is indicated by the yellow lines in the image above, which separate flat-lying sedimentary rocks, on top, from slanting sedimentary rocks beneath? A) A great fault, where push-together action shoved the upper rocks over the lower ones. B) A great fault, where pull-apart action slid the upper rocks across the lower ones. C) A great unconformity, with sedimentary rocks above resting on metamorphic rocks below. D) A great unconformity, with sedimentary rocks above resting on older sedimentary rocks below. E) An intrusion, with melted rocks squirted along the yellow line and then hardened. Feedback: John Wesley Powell, of the United States Geological Survey, and the leader of the first boat trip through the Grand Canyon, called the feature marked by the yellow lines “The Great Unconformity”. It separates horizontal Paleozoic sedimentary rocks, above, from inclined Precambrian sedimentary rocks, below. Table for Individual Question Feedback
Points Earned: 1.0/1.0 Correct Answer(s):D 11. In the photograph above, a portion of cliff about 30 feet high is shown. From what location in the Grand Canyon did Dr. Alley take this image? A) Near the top, in sedimentary rocks that slumped downhill when they were soft, folding the rocks. B) About halfway between the top and the river, where a large fault has dragged the rocks and caused the fold. C) Near the bottom, where the river has cut through rocks that were cooked, squeezed, and partially melted deep in an old mountain range.
D) Near the west end, where lava that came up pull-apart faults folded while flowing before hardening fully. E) In the gift shop, where artists have painted the cliff to look like real rocks. Feedback: This is the Vishnu Schist and Zoroaster Granite, rocks from the heart of a mountain range. The river is just barely out of the picture to the bottom. Correct Answer(s):C Table for Individual Question Feedback Points Earned: 1.0/1.0 12.
The picture above shows a very hard piece of rock about six inches across, in the Grand Canyon. The surface of the rock looks rather different from the surfaces of many other rocks. What made this odd-looking surface?
Table for Individual Question Feedback Points Earned: 1.0/1.0