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patanjali.purpose
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Antarctica has not always been the ice covered desert it is today. More than 170 million years ago, Antarctica was part of the supercontinent Gondwana, which had a mild climate. Over time, Gondwana gradually broke apart, and Antarctica as we know it today was formed around 25 million years ago. Initially, West Antarctica was partially in the Northern Hemisphere whereas East Antarctica was at the equator, where sea floor invertebrates and trilobites flourished in the tropical seas. At the end of the Devonian period, 360 million years ago, Gondwana became centered around the South Pole and its climate cooled, though flora remained. Towards the end of the Permian period, continued warming led to a dry, hot climate over much of Gondwana. As a result of continued warming, the polar ice caps melted and much of Gondwana became a desert.
The breakup of Gondwana was a very slow and gradual process, lasting millions of years and correlating with climatic changes. Africa was the first continent that separated from Antarctica around 160 million years ago, followed by the Indian subcontinent, in the early Cretaceous period, about 125 million years ago. About 65 million years ago, Antarctica, then still connected to Australia, still had a tropical to subtropical climate. About 40 million years ago Australia-New Guinea separated from Antarctica, and the first ice began to appear. Around 23 million years ago, the Drake Passage opened between Antarctica and South America, which resulted in the Antarctic Circumpolar. The ice spread, replacing the forests that then covered the continent. Since about 15 million years ago, the continent has been mostly covered with ice, with the Antarctic ice cap reaching its present extension around 6 million years ago.
The primary purpose of the passage is to
A) review the desertification and icing of Antarctica in light of the continental spread
B) depict the gradual disintegration of the Gondwana supercontinent
C) show how Antarctica reached its current location
D) explain the geological changes that occured in Earth's continents over history
E) elaborate on the climactic changes that affected trees in Antarctica
OA - A
The breakup of Gondwana was a very slow and gradual process, lasting millions of years and correlating with climatic changes. Africa was the first continent that separated from Antarctica around 160 million years ago, followed by the Indian subcontinent, in the early Cretaceous period, about 125 million years ago. About 65 million years ago, Antarctica, then still connected to Australia, still had a tropical to subtropical climate. About 40 million years ago Australia-New Guinea separated from Antarctica, and the first ice began to appear. Around 23 million years ago, the Drake Passage opened between Antarctica and South America, which resulted in the Antarctic Circumpolar. The ice spread, replacing the forests that then covered the continent. Since about 15 million years ago, the continent has been mostly covered with ice, with the Antarctic ice cap reaching its present extension around 6 million years ago.
The primary purpose of the passage is to
A) review the desertification and icing of Antarctica in light of the continental spread
B) depict the gradual disintegration of the Gondwana supercontinent
C) show how Antarctica reached its current location
D) explain the geological changes that occured in Earth's continents over history
E) elaborate on the climactic changes that affected trees in Antarctica
OA - A
Last edited by patanjali.purpose on Thu Feb 09, 2012 12:05 pm, edited 1 time in total.
