Isolated From the Rest of the World by Circumpolar Currents and Ice Fields, the Dry Valleys of Antarctica Never See Snowfall. GMAT Reading Comprehension

Reading Passage Question

Isolated from the rest of the world by circumpolar currents and ice fields, the Dry Valleys of Antarctica never see snowfall. They are the coldest, driest places on earth, yet this arid, frigid climate supports several delicate ecosystems. Life in these ecosystems consists of relatively few groups of algae, microorganisms, and invertebrates, as well as plants such as lichen and fungi that live beneath the surface of rocks, where just enough light penetrates for photosynthesis to occur during the short period each year when meltwater is available. This region has proven interesting specifically to scientists researching the possibility of life on Mars because the features of the Dry Valleys are strikingly similar to the Martian landscape.

The Dry Valleys' system of lakes provides a particularly interesting area of research. Lake Hoare boasts a clear ice sun-cover fifteen meters thick that intensifies solar radiation in a way similar to solar panels; summer temperatures in bottom waters can become as high as 25° C, solely from solar heating, and not geothermal heating. This temperature permits huge mats of cyanobacteria to survive and even thrive on the lake floor. Pieces of this mat occasionally break free, floating up to the underside of the icy lake cover to melt through the ice toward the surface. The intense Antarctic winds, sweeping across the lake's surface, cause the ice to sublimate—turn directly from ice into vapor—rapidly. Such continuous sublimation should eventually cause the lake to vanish, but a continuous trickle of water from a nearby glacier—melted by the sun—refreshes the water. With a constant source of water, however small, and the heat generated by the solar radiation and retained by insulation from the thick ice cover, this lake offers an odd paradox: thick ice is responsible for maintaining this lake's liquid state.

The ancient river deltas around the slopes of Lake Fryxell present one feature typical of all river deltas: sediment thick enough to bury fossil life forms. This very thickness, however, makes a formal scientific search for signs of - life impracticable. The floor of Lake Vida, on the other hand, is covered with discrete piles of sediment up to a meter high that have preserved clear signs of life because rocks lying on the lake's surface, heated by sunlight, melt their way through the thick ice cover. Since smaller rocks, with a larger surface-area-tovolume ratio, get warmer and sink lower than larger rocks, pieces of gravel penetrate by as much as a meter, forming cracks in the ice that cause the finest sediment to sink even deeper. When the lake dries seasonally, the refined sediment within the ice drops to the lake floor, leaving a protective layer of gravel on top of the finer sediment. Dried bacteria in Lake Vida sediment have been dated back tens of thousands of years. Some researchers are hoping that exploration of similar terrain on Mars may yield similar results.

“Isolated from the rest of the world by circumpolar currents and ice fields, the Dry Valleys of Antarctica never see snowfall.”- is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 4 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

Question1
According to the passage, thick sediment found in the ancient river deltas of Lake Fryxell

1. forms layers of deposits laden with dried bacteria that are tens of thousands of years old
2. masks life forms by continuously depositing new layers on top of older ones
3. makes it unlikely that scientists will search there for traces of life
4. collects liquid water from nearby glaciers warmed by sunlight during the Antarctic summer
5. is devoid of life due to the impenetrable barrier formed by the sediment

Question 2
The passage is primarily concerned with

1. the adaptations of microorganisms that allow them to live in the Dry Valleys' hostile environment
2. the relationship between frozen lakes and glaciers which contributes to the availability of fresh water in the Dry Valleys
3. evidence of past and present life forms in the extreme conditions of Antarctica's Dry Valleys
4. the evolutionary histories of ancient lakes and the clues they hold about life in cold, dry ecosystems
5. the differences and similarities between ancient river deltas and ancient lakes

Question 3
Based on the information in the passage, scientists looking for life on Mars in conditions similar to those in the Dry Valleys would be most likely to find it in which of the following areas?

1. former river deltas
2. circumpolar ice fields
3. larger rocks
4. former glaciers
5. former lakebeds

Question 4
Based on the information in the passage, mounds of sediment found at the bottom of Lake Vida are refined by

1. Continual sublimation and ice cover
2. Large pieces of rock decomposing on the lake floor
3. Cracks formed in the ice by sinking rocks and gravel

1. I only
2. I and II
3. III only
4. II and III
5. I, II, and III

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