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  可汗SAT阅读解析答案:Part 1 Level 4 Passage5内容介绍详见下文。

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  Questions 1-11 are based on the following passage.

  Passage 1 is adapted from Eugene C. Robertson, “The Interior of the Earth” ©2011 by U.S. Geological Surve Passage 2 is adapted from USGS, "Hotspots: Mantle Thermal Plumes." ©1999 by U.S. Geological Survey.

  Passage 1

  The planet Earth is made up of three main shells: the very thin, brittle crust, the mantle, and the core; the mantle and core are each divided into two parts. Although the core and mantle are about equal in thickness, the core actually forms only 15 percent of the Earth's volume, whereas the mantle occupies 84 percent. The crust makes up the remaining 1 percent. Our knowledge of the layering and chemical composition of the Earth is steadily being improved by earth scientists doing laboratory experiments on rocks at high pressure and analyzing earthquake records on computers.

  Because the crust is accessible to us, its geology has been extensively studied, and therefore much more information is known about its structure and composition than about the structure and composition of the mantle and core. Within the crust, intricate patterns are created when rocks are redistributed and deposited in layers through the geologic processes of eruption and intrusion of lava, erosion, and consolidation of rock particles, and solidification and recrystallization of porous rock.

  By the large-scale process of plate tectonics, about twelve plates, which contain combinations of continents and ocean basins, have moved around on the Earth's surface through much of geologic time. The edges of th plates are marked by concentrations of earthquakes and volcanoes. Collisions of plates can produce mountains like the Himalayas, the tallest range in the world. The plates include the crust and part of the upper mantle, and they move over a hot, yielding upper mantle zone at very slow rates of a few centimeters per year, slower than the rate at which fingernails grow. The crust is much thinner under the oceans than under continents.

  Passage 2

  The vast majority of earthquakes and volcanic eruptions occur near plate boundaries, but there are some exceptions. For example, the Hawaiian Islands, which are entirely of volcanic origin, have formed in the middle of the Pacific Ocean more than 3,200 km from the nearest plate boundary. How do the Hawaiian Islands and other volcanoes that form in the interior of plates fit into the plate-tectonics picture?

  In 1963, J. Tuzo Wilson, the Canadian geophysicist who discovered transform faults, came up with an ingenious idea that became known as the "hotspot" theory. Wilson noted that in certain locations around the world, such as Hawaii, volcanism has been active for very long periods of time. This could only happen, he reasoned, if relatively small, long-lasting, and exceptionally hot regions -- called hotspots -- existed below the plates that would provide localized sources of high heat energy (thermal plumes) to sustain volcanism. Specifically, Wilson hypothesized that the distinctive linear shape of the Hawaiian Island-Emperor Seamounts chain resulted from the Pacific Plate moving over a deep, stationary hotspot in the mantle, located beneath the present-day position of the Island of Hawaii. Heat from this hotspot produced a persistent source of magma by partly melting the overriding Pacific Plate. The magma, which is lighter than the surrounding solid rock, then rises through the mantle and crust to erupt onto the seafloor, forming an active seamount.

  According to Wilson's hotspot theory, the volcanoes of the Hawaiian chain should get progressively older and become more eroded the farther they travel beyond the hotspot. The oldest volcanic rocks on Kauai, the northwesternmost inhabited Hawaiian island, are about 5.5 million years old and are deeply eroded. By comparison, on the "Big Island" of Hawaii -- southeasternmost in the chain and presumably still positioned over the hotspot -- the oldest exposed rocks are less than 0.7 million years old and new volcanic rock is continually being formed.

  1 The main purpose of Passage 1 is to

  A) highlight the research being done on the Earth’s geological variations

  B) introduce now findings regarding the effect of plate collisions in different locations

  C) discuss the impact of earthquakes and volcanoes on the Earth’s geological structure

  D) provide basic information about the Earth’s layers and the process of plate tectonic

  2 Which statement about the Earth’s crust accurately reflects the point of view of the author of Passage 1?

  A) It is too intricate and complicated in its geological makeup to be studied in-depth

  B) It is the best-understood layer of the Earth’s shell, despite making up a small portion of it

  C) It is easily reachable, easy to study, and makes up the most stable part of the Earth’s shell

  D) It is brittle, complex and equal in thickness to the Earth’s layers of mantle and core

  3 Which idea is presented in Passage 1 but NOT in Passage 2?

  A) Our knowledge of the Earth’s crust is increasing, thanks to the ongoing work of scientists

  B) The Earth’s plates have shifted a great deal over millions of years

  C) Some earthquakes and volcanoes happen in the interiors of plates

  D) Some of the Earth’s most prominent geological features result from plates colliding

  4 In explaining plate tectonics, both passages make use of which kind of evidence?

  A) Geological records

  B) Expert testimony

  C) Long-running experiments

  D) Hypothetical scenarios

  5 Both passages make the point that plate boundaries

  A) move at a rapid pace due to frequent collisions

  B) are the location of many global "hotspots."

  C) are the site of most earthquakes and volcanoes

  D) explain how Hawaii has so many volcanoes

  6 In line 9, “steadily” most nearly means

  A) consistently

  B) evenly

  C) calmly

  D) faithfully

  7. By referring to Wilson’s idea as “ingenious” (line 43), the author of Passage 2 signifies that the idea was

  A) creative and well-researched

  B) inventive and compelling

  C) imaginative but impractical

  D) shrewd but misleading

  8 It can reasonably be inferred from Passage 2 that the hotspot theory

  A) can be supported by comparing the volcanic rocks of two different islands

  B) has yet to be proved due in part to a lack of evidence from multiple locations

  C) has been recently altered after a thorough study of Hawaiian volcano sites

  D) won’t be able to be confirmed with certainty until volcanoes get older and erode

  9 Which choice provides the best evidence for the answer to the precious question?

  A) lines 44-46(“Wilson…time”)

  B) lines 46-51(“This…volcanism”)

  C) lines 62-65(“According…hotspot”)

  D) lines 68-72(“By…formed”)

  10 How would the author of Passage 1 most likely respond to the hotspot theory in Passage 2?

  A) With approval, because it helps refine scientists’ knowledge of the composition of the Earth

  B) With disapproval, because it contradicts the idea that volcanoes generally occur at plate edges

  C) With caution, because the plates move so slowly that there is not yet evidence to support it

  D) With support, because it may help explain the formation of the Himalayas

  11 Which choice provides the best evidence for the answer to the previous question?

  A) lines 7-11 (“Our…computers”)

  B) lines 12-16 (“Because…core”)

  C) lines 22-27 (“By…volcanoes”)

  D) lines 27-32 (“Collisions…grow”)

  以上为可汗SAT阅读解析答案:Part 1 Level 4 Passage5内容介绍,欢迎考生下载可汗SAT阅读新增23套。

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