Geology Mod 1

Which of the following is TRUE regarding convection (transfer of heat by movement) and conduction (transfer of heat between atoms)? Select one: a. Rock is such a poor conductor of heat, that convection is the most important method of heat transfer in the mantle. CorrectThis is the correct answer as it is true that rock is such a poor conductor of heat that convection ends up being the most effective method of heat transport through the Earth's mantle. Despite that convection taking place in solid rock and hence being very slow. Rocks are just remarkably bad at conduction, which is why they are such good insulating or heat-blocking materials. b. Convection is far more effective in solids than in liquids, so solid rock can transfer heat more easily than magma. c. Convection only occurs in liquids and gases; solids can only gain or lose heat through conduction. d. Since mantle rock is solid, conduction is a more effective method of heat transport in the mantle than convection. e. Regardless of their physical state, rocks tend to be more effective at conduction than metals are.

A

Which of the following statements concerning rock magnetism, paleomagnetic signatures, and apparent polar wandering is FALSE? Select one: a. As iron-bearing rocks form from cooling magma or settling fine particles, they can be aligned with the Earth's magnetic field. b. Once formed, the paleomagnetic signature of a rock is not altered as the Earth's magnetic field changes, unless the rock is reheated. c. A rock's paleomagnetic signature reflects the rock's position relative to the Earth's magnetic pole at the time when the rock formed. d. If rocks are heated high enough, they lose their paleomagnetism and will then become aligned to the current magnetic field as they cool. e. Rock records on each continent show different apparent polar wandering paths, which proves that the Earth's magnetic poles have moved. CorrectThis is the correct answer, because it is a false statement. The fact that each continent has its own apparent polar wandering paths is proof that the continents themselves are moving, not the Earth's magnetic pole. If it was only the poles that shifted, the apparent polar wandering paths of each continent would still match one another.

E

Which of the following statements concerning paleomagnetism or the Earth's magnetic field is FALSE? Select one: a. Magnetic records show that in the past the Earth has had multiple co-existing magnetic fields. CorrectThis is the correct answer, because it is a false statement. The Earth only has one core, hence it can only have one magnetic field. The fact that each continent has its own apparent polar wandering paths was proof that the continents moved, not that each continent had its own magnetic field that was somehow invisible to the other continents. b. Multiple magnetic reversals have occurred due to changes in the flow of the Earth's liquid outer core. c. Magnetism can record both the direction and distance to the magnetic pole at the time the rock formed. d. The magnetic axis of the Earth has shifted slightly through time, but tends to remain close to its axis of rotation. e. The paleomagnetic signature of a rock can be reset if that rock is heated to a high enough temperature.

A

Which of the following statements concerning hot spots and their role in determining plate motions is FALSE? Select one: a. Hot spots are areas of volcanic activity that do not necessarily occur along active plate boundaries. b. Hot spots form from rising plumes of hot mantle rock that generate magma which then rises into the overlying plate. c. We can use hot spots to determine plate motions because they do not move at all and always stay in the exact same spot. CorrectThis is the correct answer because it is a false statement. Although hot spots are relatively immobile compared to the much faster moving overlying plates, they still move. They just move so much more slowly that we can still use scars from past hot spot volcanic activity to estimate the plate's absolute motion relative to that much more slowly moving hot spot. d. The scars from volcanic activity at hot spots can be used to determine the absolute motion of a plate. e. Only the most recent volcano(s) over a hot spot are active, the other mountains in the chain are no longer active volcanoes.

Answer: C

Which of the following statements concerning past or present plate tectonic processes is FALSE? Select one: a. New lithosphere is created at divergent plate boundaries, while older lithosphere is recycled at convergent plate boundaries. b. Divergent boundaries often begin in continental settings, but as they continue to spread many will become oceanic spreading zones. c. Transform boundaries are places where plates slide by one another without lithosphere being either created or destroyed. d. Continent collision zones tend to evolve into a subduction zones as the weight of their mountains causes the plates to sink. CorrectThis is the correct answer, because it does not take place. Continental crust is less dense than oceanic crust, so it will seldom subduct. Instead as two plate segments capped by continental crust come together they crumple up to form mountain ranges, like the Himalayas. e. Subduction of the seafloor can result in island arcs being welded onto the margins of continents as exotic terranes.

Answer: D

Which of the following factors did NOT significantly contribute to the 1889 South Fork Dam collapse and Johnstown Flood? Select one: a. The owners had spread fish nets across the spillway which trapped debris that blocked much of the spillway. b. The owners had lowered the dam's height, which decreased its ability to hold excess water during heavy rains. c. The owners had allowed the center of the dam to sag, increasing the chance of a catastrophic dam collapse. d. The owners did not replace the safety release pipes sold as scrap iron by a previous owner. e. The owners built the dam out of mud, rather than gravel or coarse sand which would have been harder to erode. CorrectThis is the correct answer as mud is actually the preferred material for earth dams. Properly-constructed mud earth dams are far harder to erode than gravel or coarse sand and are far more impervious to water seepage. The problem with the South Fork dam is that the dam owners did not construct it of pure mud, but also included straw, brush, and manure, all organic materials that are subject to decay. If the dam had been constructed of mud alone, it would have been safer.

Answer: E

Which of the following statements concerning the impact of plate tectonic processes on Earth's life and climate is FALSE? Select one: a. Plate tectonics could change the Earth's climate by altering the shape of ocean basins and hence the pattern of ocean currents. b. The breakup of a supercontinent into separate continents could increase the global diversity of land animals. c. Collision of two continental masses can lead to changes in predation and competition that can cause some species to go extinct. d. Changes in continent position can result in changes in local climate, forcing animals and plants to adapt to new conditions. e. Slower plate tectonic motion could warm the Earth by dropping sea level to expose more of the land surface to sunlight. Correct This is the correct answer as it is a false statement. Although a global change toward slower plate motions will result in a lower sea level (because the ocean ridges will be cooler and have less volume), exposing more of the land surface to sunlight will actually cool the climate rather than warm it. Most of the sunlight that hits the land is reflected back into space without being absorbed and re-emitted as heat. In contrast, most of the sunlight that hits the water is absorbed and re-emitted as heat. So to warm the Earth, you would need to raise sea level so that water covered more of the Earth's surface, rather than lower it.

Answer: E

Which of the following statements concerning the ways scientists consider past and present Earth processes is FALSE? Select one: a. In general, most rocks in the geologic record formed from processes similar to earth processes that are still active today. b. Geology is a science, so a person's personal experiences have almost no influence on their ability to interpret the rock record. CorrectThis is the correct choice. Despite being a scientific process, geology (and all of science for that matter) is not unaffected by personal experiences. How extensively a person has traveled or their familiarity with different processes and environments helps determine their ability to recognize new features in the rock record. After all, if you had never encountered a living stromatolite, it would be unlikely you would have been the first person to recognize their presence in the fossil record. c. Events that are rare even on a geological time frame (like large meteorite impacts) may still be geologically significant. d. Living organisms have changed over time and the evolution of life can have a significant impact on the geological record. e. Over long periods of time, slow processes and small changes can result in dramatic alterations to the Earth's surface.

B

Which of the following statements concerning ancient Alexandria and Erastothenes' investigation of the Earth is FALSE? Select one: a. Even by the 3rd century BC, humans were actively modifying the landscape to make it better suited for their purposes. b. Erastothenes had access to records that told him that at noon on the summer solstice the sun was directly over the town of Syene. c. Erastothenes used his reports and personal observations to become the first known person to prove that the Earth was round. Correct This is the correct answer as it is a completely false statement. Erastothenes already knew, as most ancient scholars did, that the Earth was round. His goal was to determine its size. At the time a spherical Earth was not only a well-established fact, but was an underlying assumption of the geometric reasoning Erastothenes used to determine the Earth's size. d. Erastothenes recognized that the Earth was tilted and even made a reasonable estimate of the Sun's distance from the Earth. e. To complete his work, Erastothenes needed to determine the solstice noon shadows cast at Alexandria and the distance to Syene.

C

Which of the following statements concerning the evidence for an impact origin for the Moon is FALSE? Select one: a. The Moon's metallic core is much smaller than the Earth's suggesting that the two had somewhat different origins. b. The Moon is much larger than would be expected for a planet the size of the Earth. c. The Earth's rotation is much slower than would be expected if it had not been hit by a large object early in its history. CorrectThis is the correct answer, as it is a false statement. Although tides have slowed down the Earth's rotation a bit over billions of years, our Earth still rotates far more quickly than would be expected if it had not been struck by another large object relatively early in its history. d. The Earth's tilt is much greater than would be expected if it had not been hit by a large object early in its history. e. The Moon and Earth's mantles have slight differences in composition, which suggest the two had somewhat different origins.

C

Which of the following was NOT used by Wegener himself in support of Continental Drift? Select one: a. The past distribution of glacial deposits and tropical swamp coals during the Carboniferous period. b. Fossils of land animals and plants that are only found on the southern continents and India. c. The patterns of magnetic reversals recorded in the rocks that make up the sea floor. CorrectThis is the correct answer because although the seafloor pattern of magnetic reversals later became crucial evidence for the theory of Plate Tectonics, it was unknown in Wegener's time. So these patterns were not part of the suite of evidence he compiled in favor of Continental Drift. d. The trends of ancient mountain belts that only match up if the continents are moved to fit together. e. The presence of tropical fossils in areas that are now in high latitude positions.

C

If all of the Earth's core had the same composition as its present mantle, then: Select one: a. The Earth's total mass would be greater and its climate warmer. However, it would not have an active magnetic field. b. The Earth's total mass would be greater and its climate warmer. It would also generate a stronger magnetic field. c. The Earth's total mass would be greater and its climate warmer. However, there would be no change in its magnetic field. d. The Earth's total mass would be less and its climate cooler. It would also not have an active magnetic field. Correct This is the correct answer, as having a core composed of rock rather than metal would not only mean that the Earth had less mass and a thinner atmosphere (hence less greenhouse warming and a cooler climate), but it would also lack the field of relatively-freely moving electrons that a partially molten metallic core provides. Which is the basis for the Earth's magnetic field. This is the correct answer, as having a core composed of rock rather than metal would not only mean that the Earth had less mass and a thinner atmosphere (hence less greenhouse warming and a cooler climate), but it would also lack the field of relatively-freely moving electrons that a partially molten metallic core provides. Which is the basis for the Earth's magnetic field. e. The Earth's total mass would be less and its climate cooler. It would also generate a stronger magnetic field.

D