英國學(xué)生科學(xué)讀本 Lesson 80 我們腳下的土地(2)

The rock called sandstone is made up of a great many grains of sand. The beating of the rain on this rock washes the grains apart, and so the hard sandstone slowly changes into loose sand.

砂巖主要由大量沙粒組成。當(dāng)雨水打下來的時候, 這種巖石中的沙粒便被沖刷下來。久而久之, 堅硬的砂巖逐漸變成了松散的沙子。

All rocks are full of tiny cracks and pores. After rain these are filled with water. In winter it often happens that the rain is followed by frost, which changes this water into ice. Now the ice takes up more room than the water, and as it freezes it widens the cracks and pores of the rocks, and thus breaks off some pieces.

任何巖石中都存在許多細(xì)微的裂縫與孔洞。雨天, 這些地方便充滿了雨水。如果是冬天, 雨水之后便會降霜, 而縫隙中的雨水也就變成了冰。冰比水占據(jù)的空間要大, 當(dāng)它凝結(jié)時就會使得巖石中的裂縫與孔洞變得更寬。于是, 一些巖石碎塊便會掉落下來。

The waves of the sea beat on the cliffs all round the coast, break off large pieces of the rocks, and dash them about on the shore, until at last they are broken into the tiny particles which we call "sand" and "mud. " The rivers, too, which run over the land wear away their rocky banks in the same way.

海浪反復(fù)拍打著海岸周圍的崖壁, 巨大的巖石碎塊隨著海浪來到了海灘上。經(jīng)過歲月的沉淀, 它們變成了細(xì)小的微粒, 這就是我們所說的“沙子”與“泥土”。河流也是這樣, 當(dāng)它們流過時都會將周圍的河畔沖刷成這樣的微粒。

Do you know why the soil is so much darker in colour than the subsoil and the rock beneath it? It is because a good deal of matter from decayed plants is mixed with the soil. The roots of plants, the leaves which fall off the trees, and the greater part of the manure which we add to the soil, are all made of vegetable matter; and there is sometimes so much of this in the ground that the soil is nearly black.

你知道嗎, 土壤的顏色為什么比底土及其下方的巖石深那么多? 這是因為很多腐爛的植物與土壤混合在了一起。植物的根部、樹上飄落的葉子以及我們在土壤中添加的肥料, 這些都是土壤中的植物成分。有時候, 土壤中的這一類物質(zhì)過多, 土壤也就幾乎變成了黑色。

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