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  3. Shooting molten rock more than 500 meters into the air, Etna sent streams of lava rushing down its northeastern and southern fla

Shooting molten rock more than 500 meters into the air, Etna sent streams of lava rushing down its northeastern and southern fla

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问题     Shooting molten rock more than 500 meters into the air, Etna sent streams of lava rushing down its northeastern and southern flanks. The eruption was accompanied by hundreds of earthquakes measuring up to 4.3 on the Richter scale. As a huge plume of smoke and ash drifted across the Mediterranean Sea, residents of Linguaglossa(the name means "tongues" of lava)tried to ward off the lava flows by parading a statue of their patron saint through the town’s streets.【R1】______. But the episode was unnerving because it was so similar to an erratic eruption on the volcano’s southern flank in the summer of 2001 that destroyed parts of a tourist complex and threatened the town of Nicolosi. Some of the lavas discharged in both events were of an unusual type last produced in large amounts at the site about 15,000 years ago.【R2】______.
    The Sicilians living near Mount Etna have long regarded the volcano as a restless but relatively friendly neighbor.【R3】______. But now some researchers believe they have found evidence that Etna is very gradually becoming more dangerous. It is unlikely that Etna will explode like Mount Saint Helens in the near future, but fierce eruptions may become more common.
   【R4】______. Extensive reports and legends record about 3,000 years of the volcano’s activity, but a reliable chronicle has been available only since the 17th century. Most of the earlier accounts are limited to particularly violent eruptions, such as those occurring in 122 B.C. and A.D. 1169, 1329, 1536 and 1669. During the eruption in 1669, an enormous lava flow buried part of the city of Catania before pouring into the sea.
    With a surface area of approximately 1,200 square kilometers, Etna is Europe’s largest volcano. Its 3,340-meter-high peak is often covered with snow.【R5】______. Blocks of this material are occasionally caught in the magma — the molten rock moving upward—and ejected at the surface. Numerous blocks of white sandstone were blown out during the 2001 and 2002 eruptions. This phenomenon occurs whenever magma must open new paths for its ascent, as is usually the case with lateral eruptions(those that occur on the volcano’s flanks).
    The volcano is more than 500,000 years old. Remnants of its earliest eruptions are still preserved in nearby coastal regions in the form of pillow lavas, which emerge underwater and do in fact look like giant pillows.【R6】______. Today a much steeper cone rests on the ancient shield volcano. It consists of at least five generations of volcanic edifices that have piled up during the past 100,000 to 200,000 years, each atop the remnants of its eroded or partly collapsed predecessor.【R7】______. Among Etna’s special features are the hundreds of small cinder cones scattered about its flanks. Each marks a lateral outbreak of magma.【R8】______.
    A. Only the upper 2,000 meters consists of volcanic material; the mountain rests on a base of sedimentary rock beds.
    B. Perhaps because of divine intervention, nobody was hurt and damage was not widespread.
    C. The name of "Etna" is derived from an old Indo-Germanic root meaning "burned" or "burning".
    D. At first, a shield volcano — so called because it resembles a shield placed face-up on the ground — grew in a depression in the area where Etna now stands.
    E. One of the world’s most productive volcanoes, Etna has spewed about 30 million cubic meters of igneous material each year since 1970, with a peak eruption rate of 300 cubic meters a second.
    F. At that time, a series of catastrophic eruptions led to the collapse of one of Etna’s predecessor volcanoes.
    G. Though persistently active, Etna has not had a major explosive eruption — such as the devastating 1980 event at Mount Saint Helens in Washington State — for hundreds of years.
    H. The present-day cone has been built in the past 5,000 to 8,000 years.
【R5】
选项
答案A
解析 这段讲到了火山的组成，A句说：“只有上面的2000米是火山质物质，其余都是由沉淀的岩石层构成的。”正好讲述了火山的组成。故A正确。
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