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  3. Look at an atlas.How are mountains shown? Where are the highest mountains? A few mountains stand alone, such as Mount Egmont in

Look at an atlas.How are mountains shown? Where are the highest mountains? A few mountains stand alone, such as Mount Egmont in

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问题          Look at an atlas.How are mountains shown? Where are the highest mountains? A few mountains stand alone, such as Mount Egmont in New Zealand, and Mount Kenya in Africa.Most mountains are found in long chains called mountain ranges.The Pennines, the Cambrian Mountains, the Alps, the Andes and Rockies are examples of mountain ranges.The highest mountain range on the Earth is the Himalayas in Asia.
         In order to understand how mountains are formed, we need to know what the inside of the Earth is like.The Earth is made up of layers of rock.The outside layer of rock, the one we live on, is called the Earth’ s crust.Beneath the crust is a layer called the mantle.Near the top of the mantle, some of the rocks have melted and are a liquid, like sticky tar.Because all the rocks around it press on the mantle, the molten rock tries to force its way out.If the molten rock does find a weak spot, it bursts through the Earth’s crust, forming a volcano.Some mountains were made by volcanoes.
         The Earth’ s crust is made up of large pieces, called plates, which fit together like the pieces of a jigsaw puzzle.Some of the plates carry continents, others carry oceans.The plates move slowly, floating on the molten rocks of the mantle below.As the plates move, they push against each other, slowly pushing up the rocks in folds to form mountains.
         India used to be a long way from Asia, but gradually the plate with India on it moved closer to the plate bearing Asia.The rooks in the sea between India and Asia were pushed up in folds that now form the Himalayan mountain range.That is why it is sometimes possible to find seashells near the tops of the Himalayas.Many other mountain ranges, including the Alps, Rockies and Pennines, are similar great folds of rock.
         While some plates are pushing together, others are moving further apart.Europe and North America are slowly moving further apart.Each year the Atlantic Ocean is a few centimetres wider.As the rocks move, they often crack or break.These breaks are called faults.Sometimes, great blocks of rocks are pushed up between two faults.These blocks may be so large and high that they form mountains.Some of the highland areas of East Africa are block mountains, so are the Vosges mountains in France and the Sierra Nevada mountains in the western United States.Block mountains often have flat tops.A flat-topped highland is called a plateau.
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答案the mantle
解析 由空缺处前信息“The layer under the crust”可以定位到文章第二段第四句Beneath the crust is a layer called the mantle.”因此本空填the mantle。
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本试题收录于： C类竞赛（非英语专业本科）题库大学生英语竞赛（NECCS）分类
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C类竞赛（非英语专业本科）

大学生英语竞赛（NECCS）

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