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How is the local hydrologic cycle affected by the practice of drawing drinking water from a river and then returning sewage to the same river? Is water in the unsaturated zone called groundwater? Why or why not? In an aquifer, if the water table next to a stream is lower than the water level in the stream, does groundwater flow into the stream or does stream water flow into the ground? Explain. In a confined aquifer, water in a well can rise above the top of the aquifer. What is this system called? In an unconfined aquifer, how high can water rise in a well that is not pumped? Which is better for transmitting fluid: quartz sandstone or quartzite? Explain. What are low-permeability rocks? Do they make good aquifers? What is a perched water table? What is a sinkhole? What factors contribute to its formation? Are underground rivers ever found in nature? Defend your answer. Cite two examples of sedimentary rocks that provide information about past geologic events at Earths surface. How is foliation different from sedimentary layering? Why do we find folded and fractured rock layers in zones of regional metamorphism? How does rainwater naturally become acidic? How does this affect limestone? Describe the formation of stalactites. Removal of groundwater can cause subsidence. If removal of groundwater is stopped, is the land likely to rise again to its original level? Defend your answer. As runoff into streams increases, which variables of stream flow increase? What is channel geometry? What happens to stream speed if the discharge in a stream doubles while the channel remains the same size and shape? If discharge is held constant and the width of the stream channel decreases, what happens to stream speed? What effect will this have on the stream channels depth? Must a streams speed increase in order for it to carry more sediment? Explain. In the United States, the Continental Divide follows the spine of the Rocky Mountains through five states: Montana, Idaho, Wyoming, Colorado, and New Mexico. Which basinPacific or Atlanticreceives... Generally speaking, where is streamflow fastest: in a rounded and deep channel, or in a wide and shallow channel? What three variables influence the speed of stream flow? What are some possible sources of stream flow? Why do point bars form on the inside bends of meandering streams? In the formation of a river delta, why are larger particles deposited first, followed by smaller particles farther out? Defend your answer. What causes the formation of distributaries off the main channel of a river delta? Do you think a stream with laminar flow can become turbulent without the volume of water increasing in the stream? Defend your answer. Why is surface water both a creator and a destroyer of sediments and sedimentary rocks? Streams transport great amounts of sediment. Then as stream flow slows, these sediments are deposited. What are these deposited sediments called, and how are they laid out? How does frictional drag play a role in the external movement of a glacier? How does this drag affect the internal movement? What distinguishes a huge block of ice from a glacier? Why do crevasses form on the surfaces of glaciers? Does all the ice in a glacier move at the same speed? Explain. What is a glacial surge, and how does it happen? What is basal sliding? How does a glacier grow in size? How does a glacier decrease in size? How is a roche moutonne different from a drumlin? What well-known landscapes have been carved by glaciers? How do deposits from glacial ice differ from rocks deposited by rivers? The Paleozoic era experienced several fluctuations in sea level. What effect did this have on life forms? Name the periods of the Paleozoic era. What life form emerged in the Silurian period? What life forms are associated with the Devonian period? Why are internal nostrils in the lobe-finned fishes an important step in the evolution of life on Earth? Why do many geologists consider the lobe-finned fishes especially significant? During what time period were most coal deposits laid down? Why was this period unique? In what area of the United States do we find rich coal deposits? Which epochs make up the Tertiary period? The Quaternary period? How is the element iridium related to the time of dinosaur extinction? What effect did the breakup of Pangaea have on sea level? What is the most likely cause of the Cretaceous extinction that wiped out the dinosaurs? By what informal name is the Mesozoic era known? What group evolved from the amphibians with the arrival of the amniote egg? What evidence do we have of Precambrian life? What key developments in life occurred during Precambrian time? How old is Earth? Which of the geologic time units spans the greatest length of time? What isotope is commonly used for dating sediments or organic material from the late Pleistocene? What isotope is preferred for use in dating very old rocks? What are the half-lives of uranium-238, potassium-40, and carbon-14? What is radioactive half-life? Explain how fossils of fishes and other marine animals are found at high elevations, such as the Himalayas. How are fossils used in determining geologic time? Why dont all rock formations show a continuous sequence from the beginning of time to the present? What six principles are used in relative dating? Describe each one. A granitic dike is found across a sandstone layer. What can be said about the relative ages of the dike and the sandstone? What principle applies here? What is relative dating? With increased development and the growth of cities, the natural landscape is replaced by roads, buildings, housing developments, and parking lots. What overall effect can this have on a river and... With global warming and melting of the polar ice caps, how will sea level be affected? Fresh drinking water is a precious resource. As water is depleted from the ground and from streams and rivers, what other resources can be tapped to get fresh water? How does an increase in stream gradient and discharge affect a streams sediment load? Which agents of erosion are assisted by the force of gravity? Give examples. Wind erosion is more likely in an arid environment than in a more humid environment. What other factors might impede wind erosion? How are sand dunes formed? Which of the three agents of transportationwater, ice, and windtransports only small rocks? Which of the three agents of transportationwind, water, and icetransports the largest boulders? Why? What are glacial striations? In the continental United States, what type of glacier is more common: alpine or continental? What is the significance of the large, out-of-place boulders that are sometimes found in glacial deposits? What important life forms evolved during the Cenozoic era? How did the Precambrian atmosphere become nitrogen-enriched? Name the eons in Precambrian time. Describe each eon, using no more than three words. Before entering the atmosphere, where did much of the newly released oxygen end up during the Precambrian? What factors are believed to have contributed to the generation of free oxygen during the late Precambrian? In what way did the increase in oxygen affect our planet? What is the basis for the divisions of the geologic time scale? In the geologic time scale, which time division represents the greatest span of time? Before the discovery of radioactivity, how did geologists estimate the age of rock layers? Has the amount of uranium in Earth increased over geologic time? Has the amount of lead in Earth increased? Which isotopes are most appropriate for dating rocks from the following ages: (a) early Precambrian time, (b) the Mesozoic era, and (c) the late Pleistocene epoch? If we divide a number by 2, and then divide the result by 2, and so on indefinitely, the answer will never be zero. Why, then, is carbon dating useful only for materials that are no older than about... Two isolated rock outcrops that share similar characteristicssequence of layers and fossil communitiesare separated by 50 km. Could these two outcrops be related? What principle helps to confirm... What is the difference between a nonconformity and an angular unconformity? In a sequence of sedimentary rock layers, the youngest layer is found at the bottom and the oldest layer at the top. What does this type of layering signify? Two isolated rock outcrops share a few similar characteristicssequence of layers, mineralogy, and certain fossil communitiesbut not all layers are present. The rocks are separated by 300 km. Could... Granitic pebbles within a sedimentary rock have a radiometric age of 300 million years. What can you say about the age of the sedimentary rock? Nearby, a dike having a radiometric age of 200 million... If a sedimentary rock contains inclusions of metamorphic rock, which rock is older? Defend your answer. The Precambrian spans a huge amount of time. List the following highlights of the Precambrian from first to last: (a) stromatolites, (b) formation of the Moon, (c) appearance of primitive ozone...
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