Standing on the rim of the Grand Canyon, gazing across this giant wound in the Earth’s surface, a visitor might assume that the canyon had been caused by some ancient convulsion. In fact the events that produced the canyon, far from being sudden and cataclysmic, simply add up to the slow and orderly process of erosion.
Many millions of years ago the Colorado Plateau in the Grand Canyon area contained 10,000 more feet of rock than it does today and was relatively level. The additional material consisted of some 14layered formations of rock. In the Grand Canyon region these layers were largely worn away over the course of millions of years.
Approximately 65 million years ago the plateau’s flat surface in the Grand Canyon area bulged upward from internal pressure; geologists refer to his bulging action as up warping; it was followed by a general elevation of the whole Colorado Plateau, a process that is still going on. As the plateau gradually rose, shallow rivers that meandered across it began to run more swiftly and cut more definite courses. One of these rivers, located east of the upwarp, was the ancestor of the Colorado. Another river system called the Hualapai, flowing west of the upwarp, extended itself eastward by cutting back into the upwarp; it eventually connected with the ancient Colorado and captured its waters. The new river then began to carve out the 277-mile-long trench that eventually became the Grand Canyon. Geologists estimate that this initial cutting action began no earlier than 10 million years ago.
Since then, the canyon forming has been cumulative. To the corrosive force of the river itself have been added other factors. Heat and cold, rain and snow, along with the varying resistance of the rocks, increase the opportunities for erosion. The canyon walls crumble; the river acquires a cutting tool, tons of debris, rainfall running off the high plateau creates feeder streams that carve side canyons. Pushing slowly backward into the plateau, the side canyons expose new rocks, and the pattern of erosion continues.
1.What does the passage mainly discuss?
2.According to the passage, the first phenomenon to contribute to the formation of the Grand Canyon was（ ）.
3.Which of the following conclusions about the Grand Canyon can be drawn from the passage?
4.The passage would most likely be found in a textbook on which of the following subjects?
问题1选项
A.Patterns of erosion in different mountain ranges.
B.Forces that made the Grand Canyon.
C.The increasing pollution of the Colorado River.
D.The sudden appearance of the Grand Canyon.
问题2选项
A.a series of volcanic eruptions
B.the collapse of rock formations in the Colorado Plateau
C.a succession of floods from the Hualapai River and what is now the Colorado River
D.the Earth’s internal pressure lifting the Colorado Plateau region
问题3选项
A.Its contours are constantly changing.
B.It contains approximately 14 million tons of rock.
C.Its eruptions have increased in recent years.
D.It is being eroded by toxic waste and pollutants.
问题4选项
A.Astronomy.
B.Botany.
C.Geology.
D.Chemistry.
第1题:
1.【选项释义】
1. What does the passage mainly discuss? 1. 这篇文章主要讨论什么？
A. Patterns of erosion in different mountain ranges. A. 不同山脉的侵蚀模式。
B. Forces that made the Grand Canyon. B. 形成大峡谷的因素。
C. The increasing pollution of the Colorado River. C. 科罗拉多河日益严重的污染。
D. The sudden appearance of the Grand Canyon. D. 大峡谷的突然出现。
【考查点】主旨大意题。
【解题思路】首先，根据首段第二句“事实上，形成峡谷的事件远不是突然的、灾难性的，而是缓慢而有序的侵蚀过程”，和末段第一句“从那时起，峡谷的形成是累积的”可知，本文关注的话题是峡谷的形成；然后，结合文章的行文结构，文章的后面三段都是在论述峡谷形成的一些因素；综合理解可推断，文章主要讨论的是形成大峡谷的因素，B项正确。
【干扰项排除】
A项“不同山脉的侵蚀模式”只是在文章中部分提及，属于以偏概全；
C项“科罗拉多河日益严重的污染”在文中并没有提到，属于无中生有；
D项“大峡谷的突然出现”根据原文可知，峡谷的形成是一个缓慢的过程，所以该项属于反向干扰。
第2题:
2.【选项释义】
2. According to the passage, the first phenomenon to contribute to the formation of the Grand Canyon was ______. 2. 根据这篇文章，第一个促成大峡谷形成的现象是______。
A. a series of volcanic eruptions A. 一连串的火山爆发
B. the collapse of rock formations in the Colorado Plateau B. 科罗拉多高原岩层的崩塌
C. a succession of floods from the Hualapai River and what is now the Colorado River C. 来自瓦拉派河和现在的科罗拉多河的一连串洪水
D. the Earth’s internal pressure lifting the Colorado Plateau region D. 地球内部的压力抬升了科罗拉多高原地区
【考查点】推理判断题。
【解题思路】根据题干可定位至文章第三段对大峡谷促成因素的描述：大约6500万年前，大峡谷地区高原的平坦表面由于内部压力而隆起；……接下来是整个科罗拉多高原的整体提升，……随着高原逐渐升高，蜿蜒流过高原的浅水河流开始变得更加湍急，水流的方向也更加明确。……它最终连接了古老的科罗拉多河并获得了它的水。这条新河流随后开始挖出长达277英里的海沟，最终形成了大峡谷。”从中可知，最初促成大峡谷形成的现象是地球内部压力抬升了整个科罗拉多高原，D项“地球内部的压力抬升了科罗拉多高原地区”符合原文。因此，该题选择D项。
【干扰项排除】
A项“一连串的火山爆发”和C项“来自瓦拉派河和现在的科罗拉多河的一连串洪水”在文中没有提及，属于无中生有；
B项“科罗拉多高原岩层的崩塌”是其他的累积因素，并不是最初造成大峡谷的现象，属于本末倒置。
第3题:
3.【选项释义】
3. Which of the following conclusions about the Grand Canyon can be drawn from the passage? 3. 下面哪个关于大峡谷的结论可以从这篇文章中得出？
A. Its contours are constantly changing. A. 它的轮廓在不断变化。
B. It contains approximately 14 million tons of rock. B. 它含有大约1400万吨的岩石。
C. Its eruptions have increased in recent years. C. 近年来，火山喷发次数有所增加。
D. It is being eroded by toxic waste and pollutants. D. 它正受到有毒废物和污染物的侵蚀。
【考查点】推理判断题。
【解题思路】根据第三段第一句中的“……这个过程仍在继续（a process that is still going on）”，和第四段最后一句中的“……侵蚀的模式仍在继续（the pattern of erosion continues）”可推测，大峡谷的轮廓还在持续地变化，所以A项“它的轮廓在不断变化”符合原文。
【干扰项排除】B项“它含有大约1400万吨的岩石”、C项“近年来，火山喷发次数有所增加”和D项“它正受到有毒废物和污染物的侵蚀”在原文中没有依据，属于无中生有。
第4题:
4.【选项释义】
4. The passage would most likely be found in a textbook on which of the following subjects? 4. 这篇文章最有可能在教科书中找到下列哪一个主题？
A. Astronomy. A. 天文学。
B. Botany. B. 植物学。
C. Geology. C. 地理学。
D. Chemistry. D. 化学。
【考查点】推理判断题。
【解题思路】通读全文可知，这篇文章主要描述的是大峡谷形成的成因，而这是地质学研究的范畴，所以这篇文章可能见于一本地质学教材，因此C项“地理学”正确。
【干扰项排除】A项“天文学”、B项“植物学”和D项“化学”都与本文无关，属于张冠李戴。
