Home Random Page





In 1990 the US Geological Survey claimed that there were 540 active volcanoes in the world. Three-quarters of those were in the Pacific Ring of Fire. The list did not include a little known volcano in the Philippines which had not erupted since 1380. On 9June 1991, Mount Pinatubo hit the headlines. It became one of the three largest eruptions in the world in the 20th century.

The Philippines lie on a destructive plate margin. The Philippines Plate, composed of oceanic crust, moves north-westwards towards the Eurasian Plate, which is continental crust. Where they meet, the Philippines Plate is forced to dip steeply down under the Eurasian Plate. The oceanic crust is turned into magma, rises, and erupts on the surface. The Philippines owe their existence to the almost constant ejection of lava over a period of several million years. Even before Pinatubo erupted, there were over 30 active volcanoes spread across the country’s many islands.

Fortunately there were several advance warnings of a possible eruption. On 7 June the Americans evacuated all 15,000 personnel from their nearby airbase, From 9 June there were many eruptions, but none matched that of 12 June. An explosion sent a cloud of steam and ash 30km into the sky. As the ash fell back to earth, it turned day into night. Up to 50cm of ash fell on nearby farmland, villages and towns. Over 10cm fell within a 600km radius, and some even reached as far away as Australia. The eruptions continued for several days. They were accompanied by earthquakes and torrential rain – except that the rain fell as thick mud. The weight of the ash caused buildings to collapse, including 200,000 homes, a local hospital, most of the schools and many factories. Power supplies were cut off for three weeks and water supplies were contaminated. Roads became unusable and bridges were destroyed making relief operations even more difficult.

The area surrounding Mount Pinatubo was excellent for rice growing. The thick fall of ash, however, ruined the harvest in 1991, and made planting for 1992 impossible. Over one million farm animals died, either through starvation (no grass to eat) or from drinking contaminated water. Hundreds of farmers and their families were forced to move to cities to seek shelter and food. Huge shanty-type refugee camps were set up. Disease spread rapidly, especially malaria, chicken-pox and diarrhoea. Within a few days the monsoon rains started. Normally these rains are welcomed as they bring water for the rice crop. In 1991, and again in 1993, they were so heavy that they caused flooding and lahars (mud flows). Lahars form when heavy rain flows over, and picks up, large amounts of volcanic ash. Lahars and landslides covered many low-lying areas in thick mud. Finally, ash ejected into the atmosphere encircled the earth within a few days. It blocked out some of the sun’s heat for several months, and lowered world temperatures. Scientists believe the eruption may delay global warming by several years. The eruption and after effects caused the deaths of about 700 people. Only six died as a direct result of the initial eruption. Over 600 died later through disease, and another 70 were suffocated by lahars.

► Answer the questions.

1. Why did so many people live on the slopes of Mount Pinatubo in June 1991?

2. Do you believe that eruptions can be a considerable hazard to human activity and, sometimes, to human life?

3. What caused the eruption of Mount Pinatubo?

4. Is it true that the most violent volcanic eruptions occur at destructive plate margins?

5. List the: a) immediate effects

b) long-term effects of the eruption of Mount Pinatubo.


10. Read the text The Great Forests and say whether the statements after it true (T)or false (F).


On the western slopes of the United States, south of Puget Sound, warm, gentle rain falls almost constantly. On these mountain slopes, giant Douglas firs grow as they grow nowhere else in the world. For kilometres, pine and fir and other evergreen trees cover the western side of the Cascade Mountains. Farther south, in California, there are the great redwoods, the largest and oldest living things.

When America was first discovered, forests covered more than half the area that is now the United States. Trees had to be cut down to prepare the land for farming and to provide shelter and fuel. In addition, the pioneers travelled in wooden boats and wooden wagons, drawn over wooden roads and bridges. They used wood for their houses, furniture and tools.

As America grew, the need for timber increased, and by the time settlers had reached the Midwest, industry needed wood in vast quantities. Railroads stretched father and father westward, and lumbermen harvested what then seemed like limitless reserves of trees.

What was not at first realized was that a forest is more than a collection of trees. It is a complex community of plant and animal life. Each tree must have sunlight, moist rich soil, and enough space for its roots. At the same time, it is a source of food for birds and animals, and protects the soil from erosion. By absorbing rainwater and slowing the melting snow in the spring, it lessens the danger of floods and regulates the flow of streams.

In a living forest, two opposing forces are constantly at work: growth and decay. The growth of new seedlings balances destruction by insects, plant diseases and occasional storms. But the unrestricted cutting of timber disturbs this natural balance and in America in earlier years, many forests were depleted more rapidly than they could grow. On such cutover land, fires burned out of control, wildlife disappeared, and worst of all, the rich soil of the forest floor was washed away by unchecked rain water.

About the beginning of the 20th century, the national government became concerned about the disappearing forest and in 1905, created the Forest service in the Department of Agriculture, giving it three major responsibilities: to manage the national forest for the public welfare; to cooperate with the states and with the owners of private forest land to prevent and control fires, plant trees, improve watersheds, and fight insects and diseases; and to undertake research in forest management, use and protection.

More than 75 million hectares of timber and range lands are now managed as national forests and national grasslands to serve many purposes including recreation and the continuing yield of such resources as wood, water, wildlife, forage and special products like honey, nuts and Christmas trees.

About 75% of US forest land is on farms and other small, privately owned tracts. In cooperation with the states, the national government is encouraging better management of these lands by providing information and technical assistance, cost-sharing, and low-cost loans. Under this cooperative programme, the Forest service has given technical help to more than 2,124,000 owners of forest land. Since 1940 some 50 million hectares have been involved. These owners have planted more than 1.2 million hectares and have improved timber stands on another 1,000,000 hectares.

Forest industry organizations also encourage better management. Perhaps the least known programmes are those called “Keep America Green”, a fire-prevention project, and the American Forest Institute’s tree-farm-system under which 41,600 privately owned tracts covering about 33 million hectares have been set aside as tree-farms, where modern methods are used for growing high-quality plants. The ‘farms’ range in size from about four to 897,596 hectares.

Each year, owners of private forest land and national, state and local agencies plant or seed more than 520,000 hectares. Practices like these, combined with better protection from fire, disease, insects and other destructive agents, have brought enormous improvement to the forests of America. Timber growth in its woodlands now exceeds the loss that comes from destruction and cutting, and a good reserve is being built to meet future needs.

► 1. Forests cover more than half the area of the United States.

2. A forest is a collection of trees.

3. Trees protect the soil from erosion.

4. Wildlife mostly disappeared because of unrestricted cutting of timber.

5. There are private forests in America.

6. National forests are a source of wood for building houses, furniture manufacturing.

7. Forest land owners have to pay much to the government to be provided with technical assistance.

8. Forest land owners cut trees in harmony with nature.

9. Private forest land and national, state and local agencies work side by side.

10. Timber growth in its woodlands now prevails the loss that comes from destruction and cutting.

(Bryant, Richard H. Geography Made Simple, Oxford, 1993)


11. You are going to read the text Deforestation and some quotations from a number of writers around the world. Read and decide how important forests can be in people’s lives. Give reasons.


It has been estimated that an area of tropical rain forest the size of 100 football pitches is destroyed every minute. If this continues the tropical rain forest will have disappeared in about forty years. Forests in more temperate climates are also under threat and you may have read in newspapers about the threat to trees from acid rain. There are many important reasons why we should conserve the forests.

Trees slow down heavy rain before it reaches the soil and their roots help anchor the soil to hillsides. They help to control the amount of moisture in the soil and to maintain its fertility through the rotting of fallen leaves and other fallen vegetation. This natural system of protection fails if the trees are removed.

In every continent of the world soils are being devastated because trees are being cut down, without any regard for the environment, by large timber companies who make huge profits by selling the valuable timber to the richer nations. Some governments encourage the clearing of forests to make more farmland. In many parts of the world local people depend on firewood for fuel for cooking and warmth. They use up trees at an alarming rate and could not afford alternative fuels even if they were available.

You may have seen on television the barren landscape in parts of Africa. Ethiopia is often in the news and when we see that dried-up landscape it is difficult to imagine that only 55 years ago half of Ethiopia was forested. Even fifteen years ago many of the hillsides were covered in trees. Today Ethiopia loses one billion tonnes of soil each year because of wind and water erosion. In Nepal about half the forests have been lost since 1950s and about 20 tonnes of soil are lost from every hectare of treeless mountainside. Soil is thus washed down towards the sea causing rivers to rise and floods to become more and more serious among the villages on the river plains.

In South and Central America farmers have been encouraged to clear the forest to make room for growing crops. This has not been particularly successful as the intensive cropping. After two or three crops have been harvested the soil is no longer fertile and becomes suitable only for rough grazing. From 1966 some 50,000 square kilometres of Brazil’s Amazon jungle were cleared to make way for 336 cattle ranches. The intention was to produce a surplus of beef to export to the USA and Europe. Soon it was realized that the amount of beef produced on this cleared land was a lot less than had been expected, as the forest soils were not as fertile as they had hoped. Only 22 kilogrammes of beef were produced per hectare of land which compares very poorly with 270 kilogrammes per hectare on European farms. Similarly in Nepal, where large areas of trees have been destroyed, yields of rice have gone down by 20 per cent and of maize by 30 per cent.

When we think of forests we often think of them as being useful only for timber and producing very little in the way of food for people. Yet the tropical forests provide food, shelter and medicines for millions of people. They can be for growing crops. In Brazil it has been calculated that an area of untouched forest could produce ten times more food than the beef cattle that graze there. Fruits, nuts, game and fish are the main foods found in the tropical forest. Many of the remote and almost forgotten peoples of the world, like the Baka people of Cameroon, get all they need to survive from the forest, as do the peoples and tribes of the South American rain forest, such as the Yanomami who are completely in tune with their natural surroundings. In Britain we have now forgotten what our ancestors knew about the productivity of our forests: providing timber for houses and ships; fodder for farm animals and game and berries to eat. In medieval times the forests were regulated and farmed so they would remain productive and be conserved for future generations. Perhaps we should be encouraging this kind of ‘forest farming’ in other parts of the world so that the fragile soils will be protected and people fed.


Deforestation is usually followed by massive soil erosion with valuable topsoil washed away into rivers. This is a loss of a most vital resource required for agriculture and at the same time a siltation of the river systems causes widespread floods.

(Khor Kok Peng, 1989)


Kenya fells up to 20,000 hectares of trees a year but … thanks to efforts at grassroots level, encouraged by government, the country now has a record unparalleled in the developing world of efforts to eventually planting more trees than it fells.

(UNEP News, 1987)

South America

In other regions pristine tropical forest has been converted on a massive scale to cattle pasture. Ironically even small farmed plots in cleared tropical forest areas are often converted to pasture after two or three years because of declining yields on poor soils. Perhaps 90% of tropical moist forest soils are completely unsuitable for any kind of annual agriculture. The only people that have evolved sustainable agroecosystems in these areas are the indigenous and tribal peoples who inhabit many of the still intact rainforests. (Ecoforum, 1988)


The variety of forest resources available and used by the rural people are neither recorded nor appreciated by the government foresters. Arttabandhu Mishra, a researcher … in the eastern coast of Orissa, has recorded that rural people in Orissa get almost all their needs in the forest without destroying it. “There are at least 30 to 40 varieties of roots and rhizomes collected by the villagers from the hill slopes and by asking the old ladies in the villages I learned of 40 types of spinaches and edible flowers …”, Mr Mishra reported. So abundant is the resource that in certain seasons people taking cattle for grazing in the forest rarely take lunch with them because fruits, berries, mushrooms etc. Are so readily available.

(Ravi Sharma, Ecoforum, Dec. 1989)


12. Read the text The Greenhouse Effect and think what consequences of this phenomenon can be. Name them.

Date: 2016-04-22; view: 399

<== previous page | next page ==>
doclecture.net - lectures - 2014-2020 year. Copyright infringement or personal data (0.004 sec.)