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How
Did the Three Gorges Come into Existence
by Daniel Xia
Changjiang Overseas Travel |
| Travelling
through the Three Gorges and looking at the torrential waters, cloud-piercing
peaks and sheer precipices, people often wonder how the Three Gorges
came into existence. |
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| Before
mankind had any knowledge of science, people relied on legends to
explain the natural phenomena. It was said that the Three Gorges were
blazed by Da Yu, the legendary king, or by the fairy Yao Ji. These,
however, are only fairy tales. |
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Dragon
Back Rock in Golden Helmet and Silver Amour Gorge |
| Geologically,
the Three Gorges were formed by powerful organic movement, which turned
sea into land and land into sea and created new rivers. |
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| As
early as 200 million years ago, during the Triassic period, China
was topographically higher in the east and lower in the west. The
area to the west of today?s Yangtze River valley was an extensive
sea linked with the ancient Mediterranean Sea. The vast sea extended
from the Three Gorges area to Tibet, Qinghai, Yunnan, Guizhou and
Sichuan. Today's Zigui was on the sea shore. Coal-containing sediments
of alternating land-sea faces have been discovered in the area. |
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At
the end of the Triassic period nearly 200 million years ago, a powerful
organic movement ( the Indochina movement) took place on earth, The
Three Gorges area of today was of course also affected. The movement
did not form any tall mountains in this area. But as a result of the
rise of the earth?s crust, the ancient Mediterranean Sea fell back
a long distance to the west and the Three Gorges area became dry land.
At the same time, the Qinling Mountains in China began to rise.
As a result, the land rose in the east and fell in the west. Also
in this period the now famous Huangling anticline began to take shape
and emerged above the sea level. Several large bodies of water, including
the lakes Zigui, Bashu, Xichang and Dianchi, remained in its west.
Three lakes, with the exception of Zigui, were linked by a water system
flowing the east to the west through the Nanjian Straits into the
Mediterranean Sea. This water system was the embryo of the western
section of the Yangtze River. To the east of the Huangling anticline
were the lakes Dangyang, Exiang, Poyang and many others which were
also linked by a large river, the embryo of the eastern section of
the Yangtze. |
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Nine
Dragons Sailing on the River |
About
70 million years ago, another mountain forming movement, the Yanshan
movement, took place. The Sichuan Basin and the Three Gorges area
rose and Lake Zigui disappeared, and the Dongting and Yunmeng basins
began to fall. Large quantities of pebbles and fossils which remained
at lake bottom of the past geological periods can be found on top
of the mountains as high as 1,000 meters above sea level in the Three
Gorges area.
In the immensely powerful mountain-making movements, the think crust
of rock was crushed and bent like waves in the sea. These wave-like
rock strata are geologically known as "folds". The top of
a wave is called "anticline" and the wave bottom, "syncline".
The three anticlines of Qiyao, Wushan and Huangling in the Three Gorges
area were formed in the Yanshan movement. After the rise of the three
anticlines, the rivers on either side flow in different directions.
The Yangtze River water system had not yet come into existence. |
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An
isle in the river, with a Daoist Temple |
During
the organic Himalayan movement of 30-40 million years ago, the earth
surface of the Yangtze River valley rose intermittently, most drastically
in the upper reaches, giving rise to many tall mountains, high plateau
and deep valleys. The middle and lower reaches rose less drastically
and some places even continued to fall, forming many hilly areas,
plains, lowlands and lakes.
As a result, the topography became higher in the west and lower
in the east. Even today, the earth crust in the Three Gorges area
is still slowly on the rise. It has been measured that the Huangling
anticline rises 2-4 millimeters every year. After the rise of the
anticline of the Three Gorges area, the rivers on either side of
them, i.e., the west "Yangtze" and east "Yangtze"
came gradually closer as a result of the downward flow of one and
the erosion on the upper reaches of the other in tens of thousands
of years. Because the terrain was higher in the west and lower in
the east and the east river flew down a steeper gradient, it was
more powerful in its erosion than the west river. The three anticlines
of the Three Gorges were eventually pierced and the two rivers became
one and flows now to the east.
After the Three Gorges came into existence, the turbulent river
began to wash the river bed and the banks continually day and night.
The river bed deepened and valley widened. Stubbornly and irresistibly
the great Yangtze thus broke through the valley and the mountains
and flows forever onwards. |
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Silver
armor |
| Rock
structure in some places in the Three Gorges area. Shale and thin
limestone that used to lie at the bottom of an ancient ocean have
been folded to become a mountain. The lower part of the picture shows
the water line of the present-day Yangtze River. |
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