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By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago.
答案
通过研究岩石，陶器等一系列材料中含有的矿物颗粒，先前的研究人员已能够确认早在1.7亿年发生的磁场两极转化现象，以及发生在73万年以前的最新一次两极转化现象。
更多“By studying mineral grains found in material ranging from rocks to clay articles, prev”相关的问题
第1题
听力原文： Diamonds are the hardest substance known on Earth and they make sparkling jewelry as well as sawblades that can cut through pretty much anything. They form. deep within the Earth's mantle layer (about 200 km deep ) when atoms of the element carbon arrange themselves into a lattice under huge amounts of pressure from the load of rocks above.
Recently, geologists studying diamonds have identified the ages of thousands of diamonds from Southern Africa, where the mineral is most abundant. Their research found that there were only three times in Earth's history when diamonds were made and that the Earth no longer makes diamonds like it used to. Something was different then. Perhaps the planet was hotter on the inside, or the composition of the rocks was subtly different. "Whatever it was it has changed now," stated Steve Shirey of the Carnegie Institution in Washington, D.C., one of the project researchers.
The oldest diamonds were made 3.3 billion years ago when Earth was relatively young. The second time diamonds formed was 2.9 billion years ago. The youngest diamonds on Earth are 1.2 billion years old although a few smaller diamonds are about 100 million years old. Small bits of rock within those diamonds, called impurities, indicate that they probably formed from rocks laid down in a shallow sea suggesting that the carbon that made the diamonds probably came from the remains of ancient sea life.
Some people like diamonds because they are pretty, rare, or expensive but Dr. Steve Shiley has a different perspective. "I think of diamonds," he said, "as being tiny time capsules that encase a little piece of rock protecting it for billions of years and providing us with a unique window on ancient times."
(33)
A．Always.
B．Once.
C．Twice.
D．Three times.
第2题
Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 meters of deep sea sediment (沉淀物) core, they have obtained measurements of magnetic-field intensity that span 11 polarity reversals and four million years. The analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred thousand years—the magnetic field rapidly regains its strength and the cycle is repeated.
The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten (熔化的) iron in the outer core, 3,000 kilometers beneath the earth's surface. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730, 000 years ago. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor (陨星) impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is un. likely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. If the results prove to be valid, geophysicists will have a new theory to guide them in their quest to understand the earth's inner physics. It certainly points the direction for future research.
Which of the following titles is most appropriate to the passage？
A．Polarity Reversal: A Fantastic Phenomenon of Nature.
B．Measurement of the Earth's Magnetic-Field Intensity.
C．Formation of the Two Poles of the Earth.
D．A New Approach to the Study or Geophysics.
第3题
Groundbreaking research by two French geophysicists promises to shed some light on the mystery. Using 80 metres of deep sea sediment (沉淀物) core, they have obtained measurements lots of magnetic-field intensity that span 11 polarity reversals and four million years. The analysis reveals that intensity appears to fluctuate with a clear, well-defined rhythm. Although the strength of the magnetic field varies irregularly during the short term, there seems to be an inevitable long-term decline preceding each polarity reversal. When the poles flip—a process that takes several hundred thousand years-the magnetic field rapidly regains its strength and the cycle is repeated.
The results have caused a stir among geophysicists. The magnetic field is thought to originate from molten (熔化的) iron in the outer core, 3,000 kilometers beneath the earth’s surface. By studying mineral grains found in material ranging from rocks to clay articles, previous researchers have already been able to identify reversals dating back 170 million years, including the most recent switch 730,000 years ago. How and why they occur, however, has been widely debated. Several theories link polarity flips to external disasters such as meteor (陨星) impacts. But Peter Olson, a geophysicist at the Johns Hopkins University in Baltimore, says this is unlikely if the French researchers are right. In fact, Olson says intensity that predictably declines from one reversal to the next contradicts 90 percent of the models currently under study. If the results prove to be valid geophysicists will have a new theory to guide them in their quest to understand the earth’s inner physics. It certainly points the direction for future research.
第26题：Which of the following titles is most appropriate to the passage？
A) Polarity Reversal: A Fantastic Phenomenon of Nature.
B) Measurement of the Earth’s Magnetic-Field Intensity.
C) Formation of the Two Poles of the Earth.
D) A New Approach to the Study or Geophysics.
第4题
New mineral resources may be discovered during the forthcoming Antarctic_________.
A．expedition
B．excursion
C．execution
D．exposition
第5题
New mineral resources may be discovered during the present Antarctic _________.
A．excursion
B．expedition
C．voyage
D．journey
第6题
According to the passage, which of the following statements is TRUE？
A．The mineral elements will not be absorbed by the plant unless they are dissolved in its root.
B．The stems contain more water than the leaves.
C．Air around the leaf is found to be saturated.
D．Part of the carbon dioxide in the plants is synthesized.
第7题
听力原文：M: Want to go out and get something to eat？
W: I can't. I have a chemistry midterm on Monday and a German exam on Tuesday.
M: I have a geology exam Monday myself, but I think I'm ready for it.
W: What kind of exam is it going to be—multiple choice or essay？
M: Neither. The professor is going to give us a mineral sample and we have to identify it.
W: How do you do that？ I mean, a rock's a rock, isn't it？
M: Actually, there are a lot of tests you can perform. on minerals to help you figure out what they are. Probably the first tests I'll do are scratch tests. When you do a scratch test, you rub the sample on a known mineral to see if the unknown mineral scratches the known mineral or vice versa. That tells you the relative hardness of the sample.
W: What other tests will you do？
M: I'll probably do a streak test next. In that test, you rub an unknown mineral against a piece of china to see what color the streak is.
W: Why can't you just look at the mineral to see what color it is？
M: Well, you can, but sometimes a mineral has some other substance in it, and the substance can change its color. But a streak test shows the mineral's true color. Then there's always the specific gravity test, the blowpipe test...oh, and...
W: And after you've done all these tests, you can positively identify any mineral？
M: Well, usually...but not always. I just hope I can on Monday!
(20)
A．A multiple-choice exam.
B．A chemistry exam.
C．A German exam.
D．A geology exam.
第8题
New mineral resources may be discovered during the forthcoming Antarctic ______.
A．expedition
B．execution
C．excursion
D．extraction
第10题
A) respectively
B) extraordinarily
C) incredibly
D) exclusively
第11题
A．respectively
B．incredibly
C．extraordinarily
D．exclusively
