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Scientists have searched for many years for a method to tell whether a volcano（火山）explosion will be small or large. Now, four scientists say they have discovered something in lava（熔岩）that will help do this. They did the research on Mount Unzen on the southern Japanese island of Kyushu.
Mount Unzen exploded in November, 1990. Since then, more explosions have killed 43 people and destroyed the homes of more than 2,000 others. The volcano is still active today.
The scientists say the lava of the volcano contains high level of an element（成份），which is a sign of the presence of the lava from deep in the earth, not from the surface. They say it shows that the lava coming directly from inside the earth is connected with huge explosions instead of smaller ones.
The scientists examined the lava from 18 explosions of Mount Unzen that took place during many thousands of years. They also studied the lava from other volcanoes in the area that are older than Mount Unzen. The lava studied came from both large and small explosions. The scientists found that large explosions contained more of the element than small ones. The scientists say if they had known this two years earlier, they could have warned the people living in the area near Mount Unzen and saved many lives.
56. Scientists have searched for a long time in order to ______.
A. tell whether a volcano explosion will be small or large
B. tell whether a volcano explosion will be worthy or not
C. tell the number of active volcanoes in the world
D. find if there is any volcano in Japan
57. From the passage we learn that Mount Unzen is the name of ______.
A. an active volcano
B. a Japanese island
C. a huge volcano explosion
D. a kind of lava
58. Where does lava come from?
A. It comes from the deepest part of the ocean.
B. It comes from the earth surface.
C. Not mentioned in the passage.
D. It is from deep part in the earth.
59. The four scientists discovered that the level of the element contained in the lava could tell ______.
A. the place of a possible explosion
B. the degree of a volcano explosion
C. the number of volcano explosions
D. the time of a possible explosion
60. The research of the four scientists was based on ______.
A. the lava from different explosions in the area
B. the presence of the lava from the surface
C. the damages caused by the 1990 explosion
D. the lava that caused explosions
查看习题详情和答案>>in the past. They are still changing it today.
The Colorado River slowly cut through stone to make the Grand Canyon.
Long ago, ice sheets cut Yosemite Valley and glaciers (冰川) were moving in Alaska.
Rains and storms hit the land from time to time. Fires sometimes burn down forests and destroy the homes
of wide animals. This happened in Yellowstone Park in 1998.
Dead volcanic (火山的) mountains such as Haleakala on Moui and Crater Lake in Oregon are beautiful to
look at. There are also several active volcanoes in the US, especially along the Pacific Coast. There are also
many earthquakes in this area. Scientists can do nothing to control earthquakes or volcanoes. This was shown
clearly on May 18, 1980. At 8: 32 that morning, Mount St. Helens in Washington State erupted (爆发). The top
of the mountain was blown off.
Over 60 people-campers, scientists, journalists, and forest workers were killed. Hundreds of square miles
of forests were knocked down. In towns over 100 miles away, day suddenly became night. An ash cloud hid
the sun for many hours. Town and fields in Washington, Oregon, and Idaho were covered with dirty grey ash.
Scientists knew that Mount St. Helens could erupt soon but no one could say when. And no one expected
the terrible strength of the eruption. Many people were surprised and weren't ready. Harry R. Truman, 84,
owned a small hotel in Mount St. Helens. Scientists had asked him to leave because the volcano was becoming
dangerous.
Harry Truman would not leave his home. Now it is covered with many feet of dirty ash. A small cross
stands above the place where Harry probably died. Perhaps it is better that he did not see what happened to
Mount St Helens, the once beautiful lake, and the forests.
But slowly, life is returning to the dead area around the mountain. Grass and small plant are beginning to
grow again. Deer and birds have been seen in the area. The land will never be the same as it once was. Perhaps
Mount St. Helens will erupt again but this is all part of nature's pattern of change, and man has little power to
control it.
( )1. The Colorado River slowly cut through stone to make the Grand Canyon.
( )2. Long ago, ice sheets made Yosemite Valley and the Great Lakes, and glaciers are not moving in Alaska.
( )3. Scientists knew exactly when Mount St. Helens would erupt.
( )4. Harry was finally persuaded to leave his home.
( )5. Now the land is not the same as it once was.