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
中考英语专题复习资料:阅读理解专项练习(四)
中考英语重要短语的用法及区别:sometime some time
九年级英语上册单元检测考试试卷Unit12(附答案)
2016年中考英语词组辨析:leave/ forget
中考英语重要短语用法及区别:join take part in join in
中考英语重要短语的用法及区别:alone lonely
中考英语重要短语的用法及区别:either neither both
中考英语重要短语的用法及区别:not … until until
中考英语重要短语的用法及区别:besides except but
中考英语专题复习资料:阅读理解专项练习(三)
中考英语专题复习资料:阅读理解专项练习(五)
中考英语重要短语的用法及区别:across cross through
中考英语重要短语的用法及区别:agree with agree to
中考英语重要短语的用法及区别:at on in
中考英语重要短语的用法及区别:because because of
中考英语重要短语的用法及区别:among between
中考英语重要短语的用法及区别:after in
中考英语重要短语的用法及区别:ago before
中考英语重要短语的用法及区别:take care of look after
中考英语重要短语的用法及区别:borrow lend
中考英语重要短语的用法及区别:also either too as well
中考英语重要短语用法及区别:date day
2016年中考英语语法知识考点总结:There be句型与中考试题
中考英语重要短语的用法及区别:hear hear of hear from
中考英语重要短语的用法及区别:few little
中考英语重要短语用法及区别:say tell speak talk
中考英语重要短语的用法及区别:look see watch
中考英语重要短语的用法及区别:finally at last in the end
In my friends’ eyes I am a lucky dog. Beijing Foreign Studies完形填空答案
中考英语重要短语的用法及区别:begin start
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