TPO 15 Glacier Formation - 英檢

請教第2個選項為何是對的?

When there are glaciers on Earth, water is cycled through the glacier
: system, but the cycle period may be hundreds of thousands of years during
: periods of ice ages.

因為Paragrah 4只有1句是提到water

(Here water may be stored in ice form for hundreds
: or even hundreds of thousands of years before being released again into the
: liquid water system as meltwater)

其他都在說glacier的development

所以有點不解

謝謝!




※ 引述《houng (Azure Song)》之銘言：
: Glaciers are slowly moving masses of ice that have accumulated on land in
: areas where more snowfalls during a year than melts. Snowfalls as hexagonal
: crystals, but once on the ground, snow is soon transformed into a compacted
: mass of smaller, rounded grains. As the air space around them is lessened by
: compaction and melting, the grains become denser. With further melting,
: refreezing, and increased weight from newer snowfall above, the snow reaches
: a granular recrystallized stage intermediate between flakes and ice known as
: firn. With additional time, pressure, and refrozen meltwater from above, the
: small firn granules become larger, interlocked crystals of blue glacial ice.
: When the ice is thick enough, usually over 30 meters, the weight of the snow
: and firn will cause the ice crystals toward the bottom to become plastic and
: to flow outward or downward from the area of snow accumulation.
: Glaciers are open systems, with snow as the system’s input and meltwater as
: the system' s main output. The glacial system is governed by two basic
: climatic variables: precipitation and temperature. For a glacier to grow or
: maintain its mass, there must be sufficient snowfall to match or exceed the
: annual loss through melting, evaporation, and calving, which occurs when the
: glacier loses solid chunks as icebergs to the sea or to large lakes. If
: summer temperatures are high for too long, then all the snowfall from the
: previous winter will melt. Surplus snowfall is essential for a glacier to
: develop. A surplus allows snow to accumulate and for the pressure of snow
: accumulated over the years to transform buried snow into glacial ice with a
: depth great enough for the ice to flow. Glaciers are sometimes classified by
: temperature as faster-flowing temperate glaciers or as slower-flowing polar
: glaciers.
: Glaciers are part of Earth’s hydrologic cycle and are second only to the
: oceans in the total amount of water contained. About 2 percent of Earth’s
: water is currently frozen as ice. Two percent may be a deceiving figure,
: however, since over 80 percent of the world’s freshwater is locked up as ice
: in glaciers, with the majority of it in Antarctica. The total amount of ice
: is even more awesome if we estimate the water released upon the hypothetical
: melting of the world’s glaciers. Sea level would rise about 60 meters. This
: would change the geography of the planet considerably. In contrast, should
: another ice age occur, sea level would drop drastically. During the last ice
: age, sea level dropped about 120 meters.
: When snowfalls on high mountains or in polar regions, it may become part of
: the glacial system. Unlike rain, which returns rapidly to the sea or
: atmosphere, the snow that becomes part of a glacier is involved in a much
: more slowly cycling system. Here water may be stored in ice form for hundreds
: or even hundreds of thousands of years before being released again into the
: liquid water system as meltwater. In the meantime, however, this ice is not
: static. Glaciers move slowly across the land with tremendous energy, carving
: into even the hardest rock formations and thereby reshaping the landscape as
: they engulf, push, drag, and finally deposit rock debris in places far from
: its original location. As a result, glaciers create a great variety of
: landforms that remain long after the surface is released from its icy
: covering.
: Throughout most of Earth’s history, glaciers did not exist, but at the
: present time about 10 percent of Earth’s land surface is covered by
: glaciers. Present-day glaciers are found in Antarctica, in Greenland, and at
: high elevations on all the continents except Australia. In the recent past,
: from about 2.4 million to about 10,000 years ago, nearly a third of Earth’s
: land area was periodically covered by ice thousands of meters thick. In the
: much more distant past, other ice ages have occurred.
: 14. Glaciers are part of Earth's hydrologic cycle.
: ●
: ●
: ●
: Answer Choices
: ○Glaciers, which at present contain 80 percent of Earth's freshwater, form
: when accumulated snow is compressed and recrystallized into ice over a period
: of years.
: ○When there are glaciers on Earth, water is cycled through the glacier
: system, but the cycle period may be hundreds of thousands of years during
: periods of ice ages.
: ○The glacial system is governed by precipitation and temperature in such a
: way that glaciers cannot form in temperate latitudes.
: ○When glacial ice reaches a depth of 30 meters, the weight of the ice causes
: ice crystals at the bottom to flow, and the resulting movement of the glacier
: carves the landscape.
: ○If global warming melted the world's glaciers, sea level would rise about
: 60 meters worldwide.
: ○Glaciers have had little effect on Earth's surface because only 2 percent
: of Earth's water is currently contained in glaciers, and there are fewer
: glaciers now than at most times in the past.
: 各位好，以上這題我百思不得其解。
: 答案給的是1,2,4 但是我對4很有意見。
: 因為主題是指glacier也是hydrologic cycle的一部份。但是4指的是glacier會對地
: 貌造成影響，並不符summary的條件才對。
: 相較起來5. glacier融化造成海面上升比較符合「glacier為hydrological circle」
: 這個主題。
: 請大家不吝賜教！

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