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THE PEOPLE AND THE EARTH

THE PEOPLE AND THE EARTH. WE ONLY HAVE ONE EARTH. 制作人 : 王忠民. THE EROSION.

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THE PEOPLE AND THE EARTH

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  1. THE PEOPLE AND THE EARTH WE ONLY HAVE ONEEARTH 制作人:王忠民

  2. THE EROSION The ordinary raindrop is a strong earth mover with enough strength to cut rock . When rainwater collects on the surface of the ground , some of it evaporates and some of it sinks into the earth. The remainder starts to flow downhill, beginning its long journey from the brook to the stream, to the lake , or to the river that will carry it to the sea. As water flows along the ground , it picks up sand ,small stones and even large pieces of loose rocks . It uses them to gnaw at the sand bottom of its channel , gradually loosing more earth .

  3. By this process large amounts of mud and rock are moved from the land to the sea . Each year the Mississippi River carries 730 million tons of solid matter into the Gulf of Mexico. This constant pulling of land into the sea is lowering the United States 'average height above sea level at a rate of about one foot every 9000 years. If erosion continues at the same rate,the United State will be worn completely down to sea level in about 23 million years.

  4. THE DIRTY RIVER All our food comes directly or indirectly from soil. The soil which is dark in colour is humus. Humus contains plenty of useful materials taken from dead plants and waste matter from animals. Soil needs its food. If we do not supply it with any, plants will not grow well on it. Animal waste is the best food for soil, and chemical fertilizers are good too. A change of crop every year in the same soil will also do good.

  5. When soil is too dry, winds blow it away, and the land will soon look like a desert. Farmers can stop this by growing trees near their fields. This will weaken the force of the wind. After a heavy rain, the water carries the humus down to the river. this often happens where the fields are on the hillsides.Farmer can lever their fields and make them stair-like. At the end of the century there will be about 7,000 million people on the earth. We now ought to save every bit of the soil. Otherwise where will such a large population grow their food?

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