Obtaining Fresh Water from Icebergs
The concept of obtaining fresh water from icebergs that are towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations, especially since scientists have warned that the human race will outgrow its fresh water supply faster than it runs out of food. Glaciers are a possible source of fresh water that has been overlooked until recently. Three-quarters of the Earths fresh water supply is still tied up in glacial ice, a reservoir of untapped fresh water so immense that it could sustain all the rivers of the world for 1,000 years. Floating on the oceans every year are 7,659 trillion metric tons of ice encased in 10,000 icebergs that break away from the polar ice caps, more than ninety percent of them from Antarctica. Huge glaciers that stretch over the shallow continental shelf give birth to icebergs throughout the year. Icebergs are not like sea ice, which is formed when the sea itself freezes, rather, they are formed entirely on land, breaking off when glaciers spread over the sea. As they drift away from the polar region, icebergs sometimes move mysteriously in a direction opposite to the wind, pulled by subsurface currents. Because they melt more slowly than smaller pieces of ice, icebergs have been known to drift as far north as 35 degrees south of the equator in the Atlantic Ocean. To corral them and steer them to parts of the world where they are needed would not be too difficult. The difficulty arises in other technical matters, such as the prevention of rapid melting in warmer climates and the funneling of fresh water to shore in great volume. But even if the icebergs lost half of their volume in towing, the water they could provide would be far cheaper than that produced by desalinization, or removing salt from water.
SAT作文有字数的要求吗?
SAT作文主题表达是评分关键
SAT写作:满分作文欣赏
SAT写作素材——名人生平(1)
如何解决SAT作文词汇和举例过于简单
SAT写作素材——生物和医学领域的重大事件
SAT作文素材 历史与战争
SAT写作练习十大话题
一篇SAT作文批改实例讲解
SAT写作素材——名人生平(4)
6类SAT写作常见问题之六 用词与文章风格不符
不要过分依赖SAT写作模板
SAT作文推荐背诵范文
SAT写作素材——发明创造
6类SAT写作常见问题之五 名词的单复数、冠词
SAT写作素材——科学发明领域的重大事件
SAT作文题目解析 利用一个人故事的不同部分来论证
SAT写作优秀范文借鉴
SAT作文素材 社会事件
6类SAT写作常见问题之四 动词形式
6类SAT写作常见问题之一 容易混淆的词汇
SAT作文题型介绍及写作技巧
SAT写作学生原作与老师修改文章示例
6类SAT写作常见问题之三 表达受中文影响
SAT写作句型汇总
SAT写作要以静制动
SAT写作素材——名人生平
一篇优秀SAT作文范例
SAT写作的五大基本要求
SAT写作32个最易拼写错误的单词
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |