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1996年10月托福阅读全真试题

时间:2021-09-06 17:00:32 托福英语 我要投稿

1996年10月托福阅读全真试题

Question 1-8

1996年10月托福阅读全真试题

When Jules Verne wrote Journey to the Center of the

Earth in 1864, there were many conflicting theories about the

nature of the Earth's interior. Some geologists thought that it

contained a highly compressed ball of incandescent gas, while

others suspected that it consisted of separate shells, each made

of a different material. Today, well over a century later, there

is still little direct evidence of what lies beneath our feet. Most

of our knowledge of the Earth's interior comes not from mines

or boreholes, but from the study of seismic waves - powerful

pulses of energy released by earthquakes.

The way that seismic waves travel shows that the Earth's

interior is far from uniform. The continents and the seabed

are formed by the crust - a thin sphere of relatively light, solid

rock. Beneath the crust lies the mantle, a very different layer

that extends approximately halfway to the Earth's center.

There the rock is the subject of a battle between increasing

heat and growing pressure.

In its high levels, the mantle is relatively cool; At greater

depths, high temperatures make the rock behave more like a

liquid than a solid. Deeper still, the pressure is even more

intense, preventing the rock from melting in spite of a

higher temperature.

Beyond a depth of around 2,900 kilometers, a great

change takes place and the mantle gives way to the core. Some

seismic waves cannot pass through the core and others are bent

by it. From this and other evidence, geologists conclude that

the outer core is probably liquid, with a solid center. It is

almost certainly made of iron, mixed with smaller amounts

of other elements such as nickel.

The conditions in the Earth's core make it a far more

alien world than space. Its solid iron heart is subjected to

unimaginable pressure and has a temperature of about 9,000oF.

Although scientists ca