Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.


География Climate and Man
просмотров - 778

Getting into Deep Water

Gold mines under the sea

Man is only just beginning to realize how much he must look to the sea. When we got to the bottom of the sea, we find things that no one dreamed existed until recently. Lands which were covered with water when the ice melted at the end of the Ice Age are rich in minerals. Off the South African coast, for example, is a place where there are five times the number of diamonds as in the mines on the land. One of these diamond mines on the sea of the bottom is near the mouth of the Orange River. Oil is brought from the bottom of the Caspian Sea near Baku. Sand with gold in it has been found off the Alaskan coast near Nome, and tin is mined off Thailand and Indonesia. But if man wants to continue gathering riches from the sea he is going to have to look after it. The effects of radio-activity, and even of household detergents are harmful to the creatures that live in the sea and can be harmful to the people who eat them. One recent discovery shows that there is now ten times more lead in the upper levels of the sea than there was forty years ago because lead from the high-octane petrol used in motor-cars goes into the atmosphere.

The dark depths of the Gulf of Mexico, once frequented by only the sea creatures, are now alive with human activity. Miniature submarines and robot-like vehicles move around the ocean bottom while divers make their way around incredible underwater structures-taller than New York City skyscrapers but almost totally beneath the surface of the waves. Modern-day explorers are using technology worth of Jules Verne and Jakques Cousteau to find fresh supplies of oil and natural gas.Until recently, drilling in the Gulf was concentrated close to shore in water as deep as 9 km. But now the scientists are looking to hundreds of meters deep and 160 kilometres and more from land. The deep water research began in 1984. Since many American companies have built the world’s deepest production platforms of more than 100 stories high.

It’s easy to think of the earth’s climate as unchanging, and for many purposes this would be an adequate assumption. However, the climate does change, slowly but continually. Paleoclimatologists have found convincing evidence of major climatic variations. Recorded history going back some 2,000 years clearly shows changes in climate and their effects on man, animals, plants and the landscape. Great migrations of people and animals accompanied periods of unusual cold and prolonged droughts. The movement of plant communities toward different latitudes and different elevations indicate important alterations in climate. The rise and fall of lake levels, particularly those more or less closed from the sea, show period of wet or dry climate. The extent of sea ice and its effect on shipping to the ports of northern Europe point to the warming or cooling of the earth’s atmosphere.

There is no doubt that climate changes continually, and that it did so long before man and his technology came on the scene.

Until fairly recent times, man’s effect on climate must have been insignificant. The discovery and the Industrial Revolution signalled the start of man’s competition with nature on a major scale. Internal combustion engines using such fossil-fuel-powered furnaces and so forth, began to introduce into the atmosphere huge masses of gases, particles, and grey amounts of heat.

As the population of the earth has been increasing at an alarming rate, the quantity of pollutants put into the air has done likewise. There is growing conviction that the increasing concentrations of carbon dioxide and particles put into the atmosphere by human activities are playing an important role in causing changes in climate. Theoretical analysis have shown that small changes in the cloud cover of the earth can have important effects on the air temperature near the ground. Atmosphere pollution might be affecting climate by causing changes in the cloud cover.