German scientist detected a severe earthquake in Japan
Scientists have long struggled to understand what lies at the planets center. Direct observation of its center is impossible, so researchers must (1) to other evidence.
In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves (2) jolts (晃动) from one side of Earth through the center to the other side. Then in 1936, Danish geophysicist Inge Lehmann studied the waves (3) to determine that within Earths core of molten (熔化了的) iron lies a solid inner core - but (4) that core was made of eluded (难倒) her. Other geophysicists quickly determined that Lehmanns inner core was composed mostly (5) iron. Since then, Lehmanns discovery has (6) conventional Earth science.
But now scientists are challenging traditional theory with new and radical (7). For example, Earths center could actually contain an inner core within the inner core, claim Ishii and colleague Adam Dziewonski.
Analyzing hundreds of thousands of earthquake wave (8), they maintain that the inner core has at its heart a tiny, even more solid sphere (球体). This sphere may be the oldest fossil (9) from the formation of Earth, says Dziewonski.
Dziewonski and Ishii speculate that shortly (10) Earth formed around 4.8 billion years ago, a giant asteroid (小行星) smashed into the young planet and nearly melted it. But Earths center didnt quite melt; it (11) mass as the planet cooled. The core within a core may be the kernel (核心) that endured. Its presence could change our basic ideas about the (12) of the planet, Dziewonski says.
Dziewonskis idea is tame (温和的) compared to the (13) theories of independent geophysicist J. Marvin Herndon. Earths inner core is made not of iron, he claims, but a (14) of nickel and silicon. Herndon has a truly revolutionary notion: Within the nickel silicide (硅化物) inner core is also an inner inner core - an 8 km-wide ball of the element uranium. Uranium is radioactive. Herndon thinks the uranium releases heat energy as its atoms (15) fission-split and crash into one another in a chain reaction. In other words, we may live on top of a gigantic, natural nuclear power plant.
1 A try B leave C turn D point
2 A create B receive C feel D overcome
3 A work B solution C job D patterns
4 A whether B what C why D how
5 A from B within C of D to
6 A followed B dominated C restored D opposed
7 A ideas B demands C phenomena D movements
8 A things B acts C methods D records
9 A taken B benefited C left D kept
10 A after B before C since D when
11 A expanded B modified C gained D melted
12 A size B origin C structure D shape
13 A radical B traditional C classical D conventional
14 A system B copy C model D compound
15 A charge B last C experience D show
参考答案:
1. C 2. A 3. D 4. B 5. C
6. B 7. A 8. D 9. C 10. A
11. C 12. B 13. A 14. D 15. C
北京高考英语“减分”
习近平现身“包子铺”
苏州“旅游地图”发布
湖南严查“破坏选举”案
新土改或促进“农地流转”
户籍“城镇化率”偏低
“高铁抽烟”将严惩
上海“自由贸易试验区”将挂牌
百度“在线理财产品”
薄熙来案“宣判”
全面深化改革 Comprehensively deepening reform
第三方支付机构获“跨境支付”牌照
阿里巴巴将进军中国“大后方”
债务展期 debt extension
台风“天兔”
什么是“负面清单管理”?
雾霾导致“停课”
未来五年中央将保持反腐“高压态势”
“阳澄湖大闸蟹”订单减少
中印“边防合作协议”
“华盛顿海军工厂”枪击案
首条“跨省地铁”开通
“习总套餐”走红
星巴克“遭抨击”
“失独家庭”补助提高
澳门官员“申报个人财产”
离婚相关词汇
王金平“关说”案
“地方政府债务”逾10万亿
用好“批评和自我批评”的武器
不限 |