Passage 62
学霸导读 地球上最大的荒漠是什么？撒哈拉沙漠？恭喜你答错了！
Across a stretch of thirsty land， silence is met with the occasional caw （ 聒叫 ） of a passing vulture （ 秃鹰 ） or the howl （ 呼啸 ） of the wind.
We often i 1 this typical scene when we think of our planet’s deserts. But deserts are not def ined by the amount of sand they hold or how sun-baked （ 太阳暴晒的 ） their landscapes are. A desert is a region that receives l 2 to no precipitation （ 降 水 ）—typically less than 25 centimeters annually （ 每年 ）. Some of the world’s largest deserts are indeed hot stretches of sand， such as the Sahara Desert， but in fact the largest of them all is quite the opposite.
Spanning over 14 million square kilometers and the coldest place on Earth, the Antarctic wins the title of the world’s largest desert. Due to cold air’s poor a 3 to hold water vapor, the icy expanse doesn’t receive much precipitation. With a large surface area, the Antarctic, as well as its Northern cousin, the Arctic ( the world’s second-largest desert ), has a 4 being melted by the Sun’s heat.
It is not the s 5 for Sahara Desert. Located around 30 degrees from the Earth’s equator （ 赤道 ）， the subtropical deserts were deprived of regular rainfall and dehydrated （ 脱水的 ） by the Sun over thousands or even millions of years.
One theory suggests that during the breakup of the world’s supercontinents （ 超大陆 ）， which started around 250 million years ago， the African and Eurasian plates （ 板块 ） collided. As a result， the Alps were slowly formed， while a sea known as Tethys （ 特提斯，古地中海 ） was l 6 . As sea shrunk， the precipitation gradually diminished and the Sahara’s dry spell （ 干旱期 ） began， lasting to the modern-day. High winds and little rainfall r 7 in the vast expanse of desert we see today.
Deserts may appear to be lifeless expanses but are actually h 8 to highly adapted survivalist species. Mammals such as the fennec fox （ 耳廓狐 ）， found in the Sahara， have evolved to be nocturnal （ 夜间活动的 ） hunter. They take a 9 of the desert’s cold nights to avoid the Sun’s daytime heat.
Water is a hot commodity among the scorching （ 酷热的 ） sands， and some species have developed c 10 ways to f ind water. Some beetles in the Namib Desert utilize hydrophilic （ 亲水的 ） points on their back to collect water vapor from fog. As droplets （ 水滴 ） form on the beetle， hydrophobic （ 疏水的 ） wax directs the water towards the beetle’s mouth.
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6.__________7.__________8.__________9.__________10.__________
高频词汇
desert /'dezət/ n. 荒漠；沙漠
occasional /ə'keɪʒənl/ adj. 偶尔的；偶然的
typical /'tɪpɪkl/ adj. 典 型 的；有 代 表 性的；一贯的
span /spæn/ v. 持续；贯穿
deprive /dɪ'praɪv/ v. 剥夺；使丧失
collide /kə'laɪd/ v. 碰撞，相撞
expanse /ɪk'spæns/ n. （陆地、水面或天空的） 广阔区域