Listening Device Provides Landslide Early WarningA device that provides earlywarning of a landslide by monitoring vibrations in soil is being tested by UKresearchers. The device could save thousands of lives each year by warning whenan area should be evacuated, the scientists say. Such natural disasters arccommon in countries that experience sudden, heavy rainfall, and can also betriggered by earthquakes and even water erosion.
Landslides start when afew particles of soil or rock within a slope start to move, but the early stagescan be hard to spot. Following this initial movement, "slopes can becomeunstable in a matter of hours or minutes," says Nell Dixon at SouthboroughUniversity1, UK. He says a warning system that monitors this movement "might beenough to evacuate a block of flats or clear a road, and save lives. "
Themost common way to monitor a slope for signs of an imminent landslide is towatch for changes in its shape. Surveyors can do this by measuring asidedirectly, or sensors sunk into boreholes or fixed above ground can be used tomonitor the shape of a slope. Slopes can. however, change shape withouttriggering a landslide, so either method is prone to causing false alarms. NowDixon's team has developed a device that listens for the vibrations' caused whenparticles begin moving within a slope.
The device takes the form of a steelpipe dropped into a borehole in a slope. The borehole is filled in with gravelaround the pipe to help transmit high-frequency vibrations generated byparticles within the slope. These vibrations pass up the tube and are picked upby a sensor on the surface. Software analyses the vibration signal to determinewhether a landslide may be imminent.
The device is currently being testedin a 6-metre-tall artificial clay embankment in Newcastle2, UK. Early resultssuggest it should provide fewer false positives than existing systems. Once ithas been carefully and thoroughly tested, the device could be used to create acomplete early-warning system for dangerous Slopes.
" Locations with asignificant risk of landslides could definitely benefit from a machine likethis," says Adam Poulter, an expert at the British Red Cross. "As long as itdoesn't cost too much, " But, Poulter adds that an early-warning system may notbe enough on its own. "You need to have the human communication," he says."Making systems that get warnings to those who need them can be difficult."
41. What does "Such natural disasters" in the first paragraph referto?
A Sudden, heavy rainfall.
B Earthquakes.
C Watererosion.
D Landslides.
42. Which of the following statements is trueof landslides?
A The initial movement is hard to spot.
B They startwith a movement of a few particles of soil or rock.
C They can bedestructive in a matter of hours or minutes.
D All of the above.
43.Why do researchers develop a new device to monitor signs of landsides?
ABecause the new device can measure the site directly.
B Because the newdevice can be sunk into boreholes or fixed above ground.
C Because thecommon methods .can cause false alarms.
D Because the common methods areuseless.
44. Which of the following statements is NOT true of the device,according to Paragraph 4?
A It is filled in with gravel.
B It consistsof a steel pipe.
C It is dropped into a borehole filled in withgravel.
D It is connected to a sensor on the surface.
45. According tothe context, what does the word "positives" in the fifth paragraph mean?
APositive electric charges.
B Evidences.
C Warnings.
DPredictions.
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