Scientists have long struggled to understand what lies at the planets center, Direct
observation of its center is impossible,so researchers must_____to other evidence.
In 1889,a German scientist detected a severe earthquake in Japan.Geophysicists concluded
that shock waves_____joltsfrom one side of Earth through the center to the
other side.Then in 1936,Danish geophysicist Inge Lehmann studied the waves______
to determine that within Earths core of molteniron lies a solid inner core-but_____
that core was made of eludedher.Other geophysicists quickly
determined that Lehmanns inner core was composed mostly_____iron. Since then,
Lehmanns discovery has_____conventional Earth science.
But now scientists are challenging traditional theory with new and radical _____
For example,Earths center could actually contain aninner core within the inner core,claim Ishii and colleague Adam Dziewonski.
Analyzing hundreds of thousands of earthquake wave _____,they maintain that the inner core has at its heart a tiny, even more solid sphere . This spheremay be the oldest fossil____from the formation of Earth,says Dziewonski.
Dziewonski and Ishii speculate that shortly_____ Earth formed around 4.8billion years ago,a giant asteroidsmashed into the young planet and nearly melted it. But Earths center didnt quite melt;it______mass as the planet cooled. The core within a core may be the kernelthat endured.Its presence could change our basic ideas about the_____ of the planet,Dziewonski says idea is tamecompared to the_____theories of independent geophysicist J.Marvin Herndon.Earths inner core is made not of iron,he claims
【2014年职称英语考试理工类A级完形填空试题1】相关文章:
★ 2014年职称英语理工类B级完形填空模拟练习题及答案(5)
★ 2014年职称英语考试卫生类A级完型填空模拟练习题(19)
★ 2014年职称英语考试综合类完形填空精编练习题及答案(1)
最新
2016-03-01
2016-03-01
2016-03-01
2016-03-01
2016-03-01
2016-03-01