TPO25阅读(全·托福).doc

The surface of MarsThe surface of Mars shows a wide range of geologic features, including huge volcanoes-the largest known in the solar system-and extensive impact cratering. Three very large volcanoes are found on the Tharsis bulge, an enormous geologic area near Marss equator. Northwest of Tharsis is the largest volcano of all: Olympus Mons, with a height of 25 kilometers and measuring some 700 kilometers in diameter at its base. The three large volcanoes on the Tharsis bulge are a little smaller-a “mere” 18 kilometers high.None of these volcanoes was formed as a result of collisions between plates of the Martian crust-there is no plate motion on Mars. Instead, they are shield volcanoes-volcanoes with broad, sloping slides formed by molten rock. All four show distinctive lava channels and other flow features similar to those found on shield volcanoes on Earth. Images of the Martian surface reveal many hundreds of volcanoes. Most of the largest volcanoes are associated with the Tharsis bulge, but many smaller ones are found in the northern plains.The great height of Martian volcanoes is a direct consequence of the planets low surface gravity. As lava flows and spreads to form a shield volcano, the volcanos eventual height depends on the new mountains ability to support its own weight. The lower the gravity, the lesser the weight and the greater the height of the mountain. It is no accident that Maxwell Mons on Venus and the Hawaiian shield volcanoes on Earth rise to about the same height (about 10 kilometers) above their respective bases-Earth and Venus have similar surface gravity. Marss surface gravity is only 40 percent that of Earth, so volcanoes rise roughly2.5 times as high. Are the Martian shield volcanoes still active? Scientists have no direct evidence for recent or ongoing eruptions, but if these volcanoes were active as recently as 100 million years ago (an estimate of the time of last eruption based on the extent of impact cratering on their slopes), some of them may still be at least intermittently active. Millions of years, though, may pass between eruptions.Another prominent feature of Marss surface is cratering. The Mariner spacecraft found that the surface of Mars, as well as that of its two moons, is pitted with impact craters formed by meteoroids falling in from space. As on our Moon, the smaller craters are often filled with surface matter-mostly dust-confirming that Mars is a dry desert world. However, Martian craters get filled in considerably faster than their lunar counterparts. On the Moon, ancient craters less than 100 meters across (corresponding to depths of about 20 meters) have been obliterated, primarily by meteoritic erosion. On Mars, there are relatively few craters less than 5 kilometers in diameter. The Martian atmosphere is an efficient erosive agent, with Martian winds transporting dust from place to place and erasing surface features much faster than meteoritic impacts alone can obliterate them. As on the Moon, the extent of large impact cratering (i.e. craters too big to have been filled in by erosion since they were formed) serves as an age indicator for the Martian surface. Age estimates ranging from four billion years for Marss southern highlands to a few hundred million years in the youngest volcanic areas were obtained in this way.The detailed appearance of Martian impact craters provides an important piece of information about conditions just below the planets surface. Martian craters are surrounded by ejecta (debris formed as a result of an impact) that looks quite different from its lunar counterparts. A comparison of the Copernicus crater on the Moon with the (fairly typical) crater Yuty on Mars demonstrates the differences. The ejecta surrounding the lunar crater is just what one would expect from an explosion ejecting a large volume of dust, soil, and boulders. However, the ejecta on Mars gives the distinct impression of a liquid that has splashed or flowed out of crater. Geologists think that this fluidized ejecta crater indicates that a layer of permafrost, or water ice, lies just a few meters under the surface. Explosive impacts heated and liquefied the ice, resulting in the fluid appearance of the ejecta. Q1 The word “enormous” in the passage is closest in meaning to A. ImportantB. Extremely largeC. Highly unusualD. ActiveQ2 According to paragraph 1, Olympus Mons differs from volcanoes on the Tharsis bulge in that Olympus MonsA. Has more complex geologic featuresB. Shows less impact crateringC. Is tallerD. Was formed at a later timeParagraph 1 Q3 The word “distinctive” in the passage is closest in meaning to A. DeepB. ComplexC. CharacteristicD. AncientQ4 According to paragraphs 1 and 2, which of the following is NOT true of the shield volcanoes on the Tharsis bulge?A. They have broad, sloping sides.B. They are smaller than the largest volcano on Mars.C. They have channels that resemble the lava channels of volcanoes on Earth.D. They are over 25 kilometers tall.Paragraph 1 and 2 Q5 The word “roughly” in the passage is closest in meaning toA. TypicallyB. FrequentlyC. ActuallyD. ApproximatelyQ6 In paragraph 3, why does the author compare Maxwell Mons on Venus to the Hawaiian shield volcanoes on Earth?A. To help explain the relationship between surface gravity and volcano heightB. To explain why Marss surface gravity is only 40 percent of EarthsC. To point out differences between the surface gravity of Earth and the surface gravity of VenusD. To argue that there are more similarities than differences between volcanoes on different planetsParagraph 3 Q7 Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.A. Although direct evidence of recent eruptions is lacking, scientists believe that these volcanoes were active as recently as 100 million years ago.B. Scientists estimate that volcanoes active more recently than 100 years ago will still have extensive impact cratering on their slopes.C. If, as some evidence suggests, these volcanoes erupted as recently as 100 million years ago, they may continue to be intermittently active.D. Although these volcanoes were active as recently as 100 million years ago, there is no direct evidence of recent or ongoing eruptions.Q8 The word “considerably” in the passage is closest in meaning to A. FrequentlyB. SignificantlyC. ClearlyD. SurprisinglyQ9 According to paragraph 4, what is demonstrated by the fact that craters fill in much faster on Mars than on the Moon?A. Erosion from meteoritic impacts takes place more quickly on Mars than on the Moon.B. There is more dust on Mars than on the Moon.C. The surface of Mars is a dry desert.D. Wind is a powerful eroding force on Mars.Paragraph 4 Q10 In paragraph 4, why does the author point out that Mars has few ancient craters that are less than 5 kilometers in diameter?A. To explain why scientists believe that the surface matter filling Martian craters is mostly dustB. To explain why scientists believe that the impact craters on Mars were created by meteoroidsC. To support the claim that the Martian atmosphere is an efficient erosive agentD. To argue that Mars experienced fewer ancient impacts than the Moon didParagraph 4Q11 According to paragraph 5, what have scientists been able to determine from studies of large impact cratering on Mars?A. Some Martian volcanoes are much older than was once thought.B. The age of Marss surface can vary from area to area.C. Large impact craters are not reliable indicators of age in areas with high volcanic activity.D. Some areas of the Martian surface appear to be older than they actually are.Paragraph 5Q12 According to paragraph 6, the ejecta of Marss crater Yuty differs from the ejecta of the Moons Copernicus crater in that the ejecta of the Yuty craterA. Has now become part of a permafrost layerB. Contains a large volume of dust, soil and bouldersC. Suggests that liquid once came out of the surface at the crater siteD. Was thrown a comparatively long distance from the center of the craterParagraph 6 is marked with an arrowQ13 Look at the four squares【】that indicate where the following sentence could be added to the passage.This surface feature has led to speculation about what may lie under Marss surface.Where would the sentence best fit? Click on a square to add the sentence to the passage.Q14 Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it. To review the passage, click VIEW NEXT. Volcanoes and impact craters are major features of Martian geology.A. Plate motion on Mars, once considered to have played no role in shaping the planets surface, is now seen as being directly associated with the planets earliest volcanoes.B. Mars has shield volcanoes, some of which are extremely tall because of the planets low surface gravity.C. Although the erosive power of the Martian atmosphere ensures that Mars has fewer craters than the Moon does, impact craters are prominent on Mars s surface.D. Scientists cannot yet reliably estimate the age of the Martian surface because there has been too much erosion of it.E. Scientists have been surprised to discover that conditions just below the surface of Mars are very similar to conditions just below the surface of the MoonF. Studies of crater ejecta have revealed the possibility of a layer of permafrost below the surface of Mars.The Decline of Venetian ShippingIn the late thirteenth century, northern Italian cities such as Genoa, Florence, and Venice began an economic resurgence that made them into the most important economic centers of Europe. By the seventeenth century, however, other European powers had taken over, as the Italian cities lost much of their economic might.This decline can be seen clearly in the changes that affected Venetian shipping and trade. First, Venics intermediary functions in the Adriatic Sea, where it had dominated the business of shipping for other parties, were lost to direct trading. In the fifteenth century there was little problem recruiting sailors to row the galleys (large ships propelled by oars): guilds (business associations) were required to provide rowers, and through a draft system free citizens served compulsorily when called for. In the early sixteenth century the shortage of rowers was not serious because the demand for galleys was limited by a move to round ships (round-hulled ships with more cargo space), with required fewer rowers. But the shortage of crews proved to be a greater and greater problem, despite continuous appeal to Venic s tradition of maritime greatness. Even though sailors wages doubled among the northern Italian cities from 1550 to 1590, this did not elicit an increased supply. The problem in shipping extended to the Arsenale, Venices huge and powerful shipyard. Timber ran short, and it was necessary to procure it from father and father away. In ancient Roman times, the Italian peninsula had great forest of fir preferred for warships, but scarcity was apparent as early as the early fourteenth century. Arsenale officers first brought timber from the foothills of the Alps, then from north toward Trieste, and finally from across the Adriatic. Private shipbuilders were required to buy their oak abroad. As the costs of shipbuilding rose, Venice clung to its outdated standard while the Dutch were innovation in the lighter and more easily handled ships. The step from buying foreign timber to buying foreign ships was regarded as a short one, especially when complaints were heard in the latter sixteenth century that the standards and traditions of the Arsenale were running down. Work was stretched out and done poorly. Older workers had been allowed to stop work a half hour before the regular time, and in 1601 younger works left with them. Merchants complained that the privileges reserved for Venetian-built and owned ships were first extended to those Venetians who bought ships from abroad and then to foreign-built and owned vessels. Historian Frederic Lane observes that after the loss of ships in battle in the late sixteenth century, the shipbuilding industry no long had the capacity to recover that it had displayed at the start of the century.The conventional explanation for the loss of Venetian dominance in trade is establishment of the Portuguese direct sea route to the East, replacing the overland Silk Road from the Black sea and the highly profitable Indian Ocean-caravan-eastern Mediterranean route to Venice. The Portuguese Vasco da Gamas Voyaga around southern Africa to India took place at the end of the fifteenth century, and by 1502 the trans- Abrabian caravan route had been cut off by political unrest.The Venetian Council finally allowed round ships to enter the trade that was previously reserved for merchant galleys, thus reducing transport cost by one third. Prices of spices delivered by ship from the eastern Mediterranean came to equal those of spices transported by Paortuguese vessels, but the increase in quantity with both routes in operation drove the price far down. Gradually, Venices role as a storage and distribution center for spices and silk, dyes cotton, and gold decayed, and by the early seventeenth century Venice had lost its monopoly in markets such as France and southern Germany. Venetian shipping had started to decline from about 1530-before the entry into the Mediterranean of large volumes of Dutch and British shipping-and was clearly outclassed by the end of the century. A contemporary of Shakespeare (1564-1616) observed that the productivity of Italian shipping had declined, compared with that of the British, because of conservatism and loss of expertise. Moreover, Italian sailors were deserting and emigrating, and captains, no longer recruited from the ranks of nobles, were weak on navigations. This decline can be seen clearly in the changes that affected Venetian shipping and trade. First, Venics intermediary functions in the Adriatic Sea, where it had dominated the business of shipping for other parties, were lost to direct trading. In the fifteenth century there was little problem recruiting sailors to row the galleys (large ships propelled by oars): guilds (business associations) were required to prov