2015考研英语作文素材精选 (十)
考研英语作文是一个考察综合运用语言的部分，需要同学们运用逻辑思维下笔成文，因此，考前看一些意义深远、质量好的文章很有必要。以下是2015考研英语作文备考素材精选，请作参考。2015考研英语作文素材精选 (十)
35.Oil Refining
An important new industry, oil refining, grew after the Civil war. Crude
oil, or petroleum - a dark, thick ooze from the earth - had been known for
hundreds of years, but little use had ever been made of it. In the 1850's Samuel
M. Kier, a manufacturer in western Pennsylvania, began collecting the oil from
local seepages and refining it into kerosene. Refining, like smelting, is a
process of removing impurities from a raw material.
Kerosene was used to light lamps. It was a cheap substitute for whale oil,
which was becoming harder to get. Soon there was a large demand for kerosene.
People began to search for new supplies of petroleum.
The first oil well was drilled by E.L. Drake, a retired railroad conductor.
In 1859 he began drilling in Titusville, Pennsylvania. The whole venture seemed
so impractical and foolish that onlookers called it " Drake's Folly". But when
he had drilled down about 70 feet(21 meters), Drake struck oil. His well began
to yield 20 barrels of crude oil a day.
News of Drake's success brought oil prospectors to the scene. By the early
1860's these wildcatters were drilling for " black gold" all over western
Pennsylvania. The boom rivaled the California gold rush of 1848 in its
excitement and Wild West atmosphere. And it brought far more wealth to the
prospectors than any gold rush.
Crude oil could be refined into many products. For some years kerosene
continued to be the principal one. It was sold in grocery stores and
door-to-door. In the 1880's refiners learned how to make other petroleum
products such as waxes and lubricating oils. Petroleum was not then used to make
gasoline or heating oil.
36.Plate Tectonics and Sea-floor Spreading
The theory of plate tectonics describes the motions of the lithosphere, the
comparatively rigid outer layer of the Earth that includes all the crust and
part of the underlying mantle. The lithosphere(n.[地]岩石圈)is divided into a few
dozen plates of various sizes and shapes, in general the plates are in motion
with respect to one another. A mid-ocean ridge is a boundary between plates
where new lithospheric material is injected from below. As the plates diverge
from a mid-ocean ridge they slide on a more yielding layer at the base of the
lithosphere.
Since the size of the Earth is essentially constant, new lithosphere can be
created at the mid-ocean ridges only if an equal amount of lithospheric material
is consumed elsewhere. The site of this destruction is another kind of plate
boundary: a subduction zone. There one plate dives under the edge of another and
is reincorporated into the mantle. Both kinds of plate boundary are associated
with fault systems, earthquakes and volcanism, but the kinds of geologic
activity observed at the two boundaries are quite different.
The idea of sea-floor spreading actually preceded the theory of plate
tectonics. In its original version, in the early 1960's, it described the
creation and destruction of the ocean floor, but it did not specify rigid
lithospheric plates. The hypothesis was substantiated soon afterward by the
discovery that periodic reversals of the Earth's magnetic field are recorded in
the oceanic crust. As magma rises under the mid-ocean ridge, ferromagnetic
minerals in the magma become magnetized in the direction of the magma become
magnetized in the direction of the geomagnetic field. When the magma cools and
solidifies, the direction and the polarity of the field are preserved in the
magnetized volcanic rock. Reversals of the field give rise to a series of
magnetic stripes running parallel to the axis of the rift. The oceanic crust
thus serves as a magnetic tape recording of the history of the geomagnetic field
that can be dated independently; the width of the stripes indicates the rate of
the sea-floor spreading.
37 Icebergs
Icebergs are among nature's most spectacular creations, and yet most people
have never seen one. A vague air of mystery envelops them. They come into being
----- somewhere ------in faraway, frigid waters, amid thunderous noise and
splashing turbulence, which in most cases no one hears or sees. They exist only
a short time and then slowly waste away just as unnoticed.
Objects of sheerest beauty they have been called. Appearing in an endless
variety of shapes, they may be dazzlingly white, or they may be glassy blue,
green or purple, tinted faintly of in darker hues. They are graceful, stately,
inspiring ----- in calm, sunlight seas.
But they are also called frightening and dangerous, and that they are ----
in the night, in the fog, and in storms. Even in clear weather one is wise to
stay a safe distance away from them. Most of their bulk is hidden below the
water, so their underwater parts may extend out far beyond the visible top.
Also, they may roll over unexpectedly, churning the waters around them.
Icebergs are parts of glaciers that break off, drift into the water, float
about awhile, and finally melt. Icebergs afloat today are made of snowflakes
that have fallen over long ages of time. They embody snows that drifted down
hundreds, or many thousands, or in some cases maybe a million years ago. The
snows fell in polar regions and on cold mountains, where they melted only a
little or not at all, and so collected to great depths over the years and
centuries.
As each year's snow accumulation lay on the surface, evaporation and
melting caused the snowflakes slowly to lose their feathery points and become
tiny grains of ice. When new snow fell on top of the old, it too turned to icy
grains. So blankets of snow and ice grains mounted layer upon layer and were of
such great thickness that the weight of the upper layers compressed the lower
ones. With time and pressure from above, the many small ice grains joined and
changed to larger crystals, and eventually the deeper crystals merged into a
solid mass of ice.
38 Topaz
Topaz is a hard, transparent mineral. It is a compound of aluminum, silica,
and fluorine. Gem topaz is valuable. Jewelers call this variety of the stone
"precious topaz". The best-known precious topaz gems range in color from rich
yellow to light brown or pinkish red. Topaz is one of the hardest gem minerals.
In the mineral table of hardness, it has a rating of 8, which means that a knife
cannot cut it, and that topaz will scratch quartz.
The golden variety of precious topaz is quite uncommon. Most of the world's
topaz is white or blue. The white and blue crystals of topaz are large, often
weighing thousands of carats. For this reason, the value of topaz does not
depend so much on its size as it does with diamonds and many other precious
stones, where the value increases about four times with each doubling of weight.
The value of a topaz is largely determined by its quality. But color is also
important: blue topaz, for instance, is often irradiated to deepen and improve
its color.
Blue topaz is often sold as aquamarine and a variety of brown quartz is
widely sold as topaz. The quartz is much less brilliant and more plentiful than
true topaz. Most of it is variety of amethyst: that heat has turned brown.
NOTE:
topaz / 'tэupжz; `topжz/ n (a) transparent yellow mineral 黄玉(矿物).
(b) semi-precious gem cut from this 黄玉; 黄宝石.
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