Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly productive land. Since the first great urban-agricultural centers in Mesopotamia nearly 6,000 years ago, human activity has had a destructive impact on soil quality, leading to gradual desertification in virtually every area of the world. It is ...
Phạm Văn Phú | Chat Online | |
02/09 10:48:57 (Tiếng Anh - Lớp 12) |
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42.
Desertification is the degradation of once-productive land into unproductive or poorly productive land. Since the first great urban-agricultural centers in Mesopotamia nearly 6,000 years ago, human activity has had a destructive impact on soil quality, leading to gradual desertification in virtually every area of the world.
It is a common misconception that desertification is caused by droughts. Although drought does make land more vulnerable, well-managed land can survive droughts and recover, even in arid regions. Another mistaken belief is that the process occurs only along the edges of deserts. In fact, it may take place in any arid or semiarid region, especially where poor land management is practised. Most vulnerable, however, are the transitional zones between deserts and arable land; wherever human activity leads to land abuse in these fragile marginal areas, soil destruction is inevitable.
Agriculture and overgrazing are the two major sources of desertification. Large-scale farming requires extensive irrigation, which ultimately destroys lands by depleting its nutrients and leaching minerals into the topsoil. Grazing is especially destructive to land because, in addition to depleting cover vegetation, herds of grazing mammals also trample the fine organic particles of the topsoil, leading to soil compaction and erosion. It takes about 500 years for the earth to build up 3 centimeters of topsoil. However, cattle ranching and agriculture can deplete as much as 2 to 3 centimeters of topsoil every 25 years- 60 to 80 times faster than it can be replaced by nature.
Salinization is a type of land degradation that involves an increase in the salt content of the soil. This usually occurs as a result of improper irrigation practices. The greatest Mesopotamian empires- Sumer, Akkad and Babylon- were built on the surplus of the enormously productive soil of the ancient Tigris-Euphrates alluvial plain. After nearly a thousand years of intensive cultivation, land quality was in evident decline. In response, around 2800 BC the Sumerians began digging the huge Tigris-Euphrates canal system to irrigate the exhausted soil. A temporary gain in crop yield was achieved in this way, but over-irrigation was to have serious and unforeseen consequences. From as early as 2400 BC we find Sumerian documents referring to salinization as a soil problem. It is believed that the fall of the Akkadian Empire around 2150 BC may have been due to a catastrophic failure in land productivity; the soil was literally turned into salt. Even today, four thousand years later, vast tracks of salinized land between the Tigris and Euphrates rivers still resemble rock-hard fields of snow.
Soil erosion is another form of desertification. It is a self-reinforcing process; once the cycle of degradation begins, conditions are set for continual deterioration. As the vegetative cover begins to disappear, soil becomes more vulnerable to raindrop impact. Water runs off instead of soaking in to provide moisture for plans. This further diminishes plan cover by leaching away nutrients from the soil. As soil quality declines and runoff is increased, floods become more frequent and more severe. Flooding washes away topsoil, the thin, rich, uppermost layer of the earth’s soil, and leaves finer underlying particles more vulnerable to wind erosion. Topsoil contains the earth’s greatest concentration of organic matter and microorganisms, and is where most of the earth’s land-based biological activity occurs. Without this fragile coat of nutrient-laden material, plan life cannot exist. An extreme case of its erosion is found in the Sahel, a transitional zone between the Sahara Desert and the tropical African rain forests; home to some 56 million people. Overpopulation and overgrazing have opened the hyperarid land to wind erosion, which is stripping away the protective margin of the Sahel, and causing the desert to grow at an alarming rate. Between 1950 and 1975, the Sahara Desert spread 100 kilometers southward through the Sahel.
The word “leaching” in paragraph 5 is closest in meaning to _________.
Lựa chọn một trả lời để xem Đáp án chính xác Báo sai đáp án hoặc câu hỏi |
A. washing 0 % | 0 phiếu |
B. depositing 0 % | 0 phiếu |
C. dispersing 0 % | 0 phiếu |
D. concentrating 0 % | 0 phiếu |
Tổng cộng: | 0 trả lời |
Trắc nghiệm liên quan
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 35 to 42. Desertification is the degradation of once-productive land into unproductive or poorly ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34. Though Edmund Halley was very famous because of his achievements as an astronomer, he was ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34. Though Edmund Halley was very famous because of his achievements as an astronomer, he was ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 28 to 34. Though Edmund Halley was very famous because of his achievements as an astronomer, he was ... (Tiếng Anh - Lớp 12)
Trắc nghiệm mới nhất
- Dialogue completion: Choose A, B, C, or D to complete each dialogue. Mike: You’ve been working out regularly, haven’t you? Nhung: _____________ (Tổng hợp - Lớp 12)
- You can’t just bury your head in the sand and hope that this problem goes away, you know. (Tổng hợp - Lớp 12)
- Antonyms: Choose A, B, C, or D that has the OPPOSITE meaning to the underlined word/ phrase in each question. Why do you always contradict me and say that what I’m saying isn’t true? (Tổng hợp - Lớp 12)
- ‘I want each and every one of you here to put forward as many suggestions as possible’, said the boss bossily. (Tổng hợp - Lớp 12)
- Synonyms: Choose A, B, C, or D that has the CLOSEST meaning to the underlined word/ phrase in each question. The outer structure of the building has been completely renovated and the interior decorators will be starting inside next week. (Tổng hợp - Lớp 12)
- At the end of the performance, the audience _______ the cast of Mamma Mia! by giving them a standing ovation. (Tổng hợp - Lớp 12)
- You should _______ a professional to check your house for earthquake damage, just to be sure there’re no hidden cracks that could cause problems later. (Tổng hợp - Lớp 12)
- If the school _______ aren’t written down anywhere, how are students supposed to know what they are to follow? (Tổng hợp - Lớp 12)
- Tom Cruise wouldn’t be the star he is today _______ made a good impression in his early films. (Tổng hợp - Lớp 12)
- Pia has always wanted to be a travel _______ and take pictures of exotic places. (Tổng hợp - Lớp 12)