In which one of the following regions of the Earth is the ozone hole prominently observed in the stratosphere?
- A.Equatorial region
- B.Arctic region
- C.Antarctic region
- D.Tropical region
Correct answer
Explanation
The correct answer is C, Antarctic region. The ozone hole, a sharp seasonal thinning of stratospheric ozone, forms every southern spring over Antarctica.
During the long polar winter a strong circular wind, the polar vortex, isolates the air over Antarctica, and temperatures fall low enough to form polar stratospheric clouds. On the surfaces of these clouds, chlorine and bromine compounds released by CFCs, halons and similar chemicals turn into active forms. When sunlight returns in September and October, this chlorine destroys ozone very quickly, creating the hole. It was reported by British Antarctic Survey scientists in 1985, and the Montreal Protocol of 1987 was agreed to phase out the chemicals responsible.
A and D are wrong because the tropics have no polar vortex or stratospheric clouds, so no hole forms there. B is wrong because the Arctic vortex is weaker and warmer, so Arctic ozone loss is smaller and occasional, not a regular hole.
Exam tip: ozone hole over Antarctica in September–October; ozone measured in Dobson units; treaty is the Montreal Protocol, 1987.
Practice Questions
View allFor acid rain, the pH of rain water should be less than
- A.7.0
- B.6.6
- C.5.6
- D.8.0
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Rain is called acid rain when its pH falls below 5.6. Even clean rain is slightly acidic, because carbon dioxide in the air dissolves in it and forms weak carbonic acid, which brings its pH down to about 5.6.
Read the full explanation →Which one of the following statements with regard to ozone is not correct?
- A.Ozone is found mostly at 15-55 km in the atmosphere.
- B.Ozone is produced by gaseous chemical reactions.
- C.16th November is celebrated as the International Day for the Preservation of the Ozone Layer.
- D.Ozone is a form of oxygen in which three oxygen atoms are bounded together.
Show answer
The International Day for the Preservation of the Ozone Layer is observed on 16 September, not 16 November. The date marks the signing of the Montreal Protocol on 16 September 1987, the treaty that phased out chlorofluorocarbons and other ozone-depleting substances.
Read the full explanation →Energy and nutrients flow from one trophic level to another in an ecosystem. Which one of the following statements correctly describes the direction of flow of energy and nutrients in an ecosystem ?
- A.Energy flow is cyclic and nutrient flow is unidirectional.
- B.Energy flow is unidirectional and nutrient flow is cyclic.
- C.Both energy and nutrient flow are unidirectional.
- D.Both energy and nutrient flow are cyclic.
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Energy passes one way from the Sun through the food chain and is lost as heat, while nutrients are used again and again.
Read the full explanation →UNESCO World Heritage site Nanda Devi National Park is located in which one of the following States ?
- A.Arunachal Pradesh
- B.Uttarakhand
- C.Himachal Pradesh
- D.Sikkim
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Nanda Devi National Park lies in the Chamoli district of Uttarakhand, around India's second-highest peak, Nanda Devi. The park is a vast glacial basin ringed by high peaks and was inscribed on the UNESCO World Heritage list in 1988 for its wild, untouched landscape.
Read the full explanation →Which one of the following is related to global dimming?
- A.Fall of atmospheric pressure due to increased particulates
- B.Rise of atmospheric pressure due to increased particulates
- C.Rise of temperature due to increased particulates
- D.Fall of temperature due to increased particulates
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Global dimming is the drop in sunlight reaching the ground, and the cooling that follows, caused by particles in the air.
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