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Points Earned:1.0/1.0Correct Answer(s):C12.The above picture is from the Escalante-Grand Staircase National Monument. The pink arrows point along some interesting features. What are they?A) Faults, where rocks were moved in earthquakes.B) Mud cracks, formed when a flash flood roared down the road (which is under the lower-right pink arrow), spread mud onto the desert surface, and then the mud dried.C) Joints, formed when the sedimentary rocks were broken by physical-weathering or other processes.
D) Unconformities, formed by erosion in the past.E) Sand-dune cross beds, formed when the wind deposited sand.Feedback: This is the Navajo Sandstone, and it is a sand-dune deposit, but you can’t really see that in this picture. Almost all rocks have joints. Joints channel water, and make space for roots, so plants often grow along joints, as you see here. The change from red to white along the upper-left arrow is probably a record of places in the past where fluids carrying oil met fluids carrying water—the water rusted the iron and made red; the oil left the iron reduced and carried it away.Points Earned:1.0/1.0Correct Answer(s):C13.Can a good geologist ever find a material that is somewhere between sedimentary rock and sediment, loose stuff somewhat stuck together but not really hard?A) No, because sediment and sedimentary rock were formed when the Earthformed, and intermediates cannot be formed.B) Yes, because sediment is changed to sedimentary rock by people with glue guns, and intermediates exist. C) No, because nature lacks intermediates between the things we have named. D) Yes, because sediment is changed to sedimentary rock by people with Diet Pepsi bottles, and intermediates exist.E) Yes, because sediment is changed to sedimentary rock by heat, pressure, and hard-water deposits, and intermediates exist.Feedback: A little squeezing, or heating to cause recrystallization, or “glueing” by hard-water deposits, and sediment gradually becomes sedimentary rock. Where we change the name says a lot about us, and less about nature.Points Earned:1.0/1.0Correct Answer(s):E14.Geologic history involves learning the order of events in the past (which came first?), and, what happened. Part of “what happened” is reconstructing what the environment was like in the past. What is accurate about the human effort to learn about past environments?A) Sediments and sedimentary rocks include almost no clues about past environments.B) Sediments and sedimentary rocks provide no information whatsoever about the past.C) Sediments and sedimentary rocks provide much information about whether they were deposited in the ocean or on land, whether the climate was hot or cold and wet or dry, and more.D) Sediments and sedimentary rocks reveal that our primitive ancestors of previous millennia survived on pizza and Pepsi.
E) Sediments and sedimentary rocks tell us a little bit about whether the past environment was a lakeor desert, but not much else.