Venice may still be in peril. However, the city known as La Serenissima is no longer sinking, but rising. A new study from e

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    Venice may still be in peril. However, the city known as La Serenissima is no longer sinking, but rising.
    A new study from experts appointed by the Italian environment ministry has discovered that the level of the ground surrounding St Mark’s Square--among the lowest-lying in Venice--has been raised by half a centimetre since 1973. Several other parts of the city’s historic centre are as much as one centimetre higher.
    Scientists say the city has been rising since a halt was called to the pumping of large amounts of ground water from artesian wells running under the city. The water supplied an industrial complex at Marghera on the mainland nearby.
    This had dried out the rock below and allowed Venice to sink by up to 12 cm. Since the water has begun flowing back in, the rock has swollen like a sponge, pushing up the level of the alleyways and buildings.
    The Venetians will not be putting their waterproof boots away yet, though. Although the number of high water floods has remained fairly constant over the past 30 years, smaller floods have become more common.
    In 1996 Venice was hit by flooding of 80 cm. or more. Changing weather patterns are to blame, as well as damage to the lagoon from erosion and a deep channel dug to allow tankers through.
    "The new study shows that Venice is not sinking the way most people believe, but of course it is still in danger," said Giorgio Sarto, senator for Venice and an urban planner.
    "The city could start subsiding again in future, and we still have to act against the flood. But we’ve lost precious time. Given the new data, we should have started trying to raise the city 10 years ago. "
    Under a new scheme, the edge of St Mark’s running along the Grand Canal--which is as little as 85 cm. above sea level--would be elevated by 15 cm. to one metre above.
    A section beyond would be rebuilt to slope gently upwards to a maximum height of 1.15 metres above sea level before rolling back down towards the Doge’s palace.

    "Apart from restoring the environmental balance of the lagoon," said Mafia Rosa Vittadini, who chaired the commission, "we must concentrate on raising the ground levels of the canal embankments, and of any other areas where this can be done. "
    The backers of the project had originally suggested raising the whole of St Mark’s, but this was vetoed by local authorities as an unacceptable threat to the basilica, palaces and landmark bell tower around it, the level of which cannot be changed.
    The last attempt to resolve Venice’s woes--the £ 1.5 billion Project Moses, which involved placing a 30 metre high flood barrier at three openings from the lagoon into the Adriatic--was dropped by the Italian government. There were fears that it could jeopardize the lagoon’s sensitive ecology.
    "It’s an awful thing to say, but what Venice really needs is another catastrophe like the flooding of 1966," said Lord Norwich, chairman of Britain’s Venice In Peril fund. "That would shake people into doing something.  If we go on doing nothing, Venice might well not be there for our great-grandchildren. "
What two materials will be laid under St Mark’s Square when it is raised?

选项

答案Clay and sand.

解析 (从第二幅图中可以知道如果要提高圣马可广场的水平高度,应该填黏土和沙子Clay and sand。)
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