The Ice Age
Twenty thousand years ago, the earth was held in control by relentlessly (不宽容地) probing fingers of ice that drew power from frigid strongholds in the north and crept southwestward to bury forests, fields, and mountains. Landscapes that were violated by the slowly moving glaciers(冰川)would carry the scars of this advance far into the future. Temperatures dropped deeply, and land surfaces in many parts of the world were depressed by the unrelenting weight of the thrusting ice. At the same time, so much was drawn from the oceans to form these huge glaciers that sea levels around the world fell by three hundred and fifty feet, and large areas of the continental shelf became dry land.
This period of the Earth’s history had come to be called the Ice Age. In all, about eleven million square miles of land were covered with ice. The Ice Age terminated about fourteen thousand years ago when the ice sheets began to retreat. It took about seven thousan
A. Right
B. Wrong
C. Not mentioned
The Ice Age
Twenty thousand years ago, the earth was held in control by relentlessly (不宽容地) probing fingers of ice that drew power from frigid strongholds in the north and crept southwestward to bury forests, fields, and mountains. Landscapes that were violated by the slowly moving glaciers(冰川)would carry the scars of this advance far into the future. Temperatures dropped deeply, and land surfaces in many parts of the world were depressed by the unrelenting weight of the thrusting ice. At the same time, so much was drawn from the oceans to form these huge glaciers that sea levels around the world fell by three hundred and fifty feet, and large areas of the continental shelf became dry land.
This period of the Earth’s history had come to be called the Ice Age. In all, about eleven million square miles of land were covered with ice. The Ice Age terminated about fourteen thousand years ago when the ice sheets began to retreat. It took about seven thousan
A. Right
B. Wrong
C. Not mentioned
About one million years ago, the Ice Age began. The Ice Age was a long period of time in which four great glaciers pushed southward to cover almost all the upper half of North America, and then melted away. Each glacier was a thick sheet of ice and snow that spread out from a centre near what is now Hudson Bay in Canada. The winters were long, and the cool summers were too short to melt much of the ice and snow. The ever-growing sheet built up to a thickness of two miles at its centre.
As all glaciers do, these great glaciers slid. They pushed down giant trees in their paths and scraped the earth bare of soil. Many animals moved farther south to escape. Others stayed and were destroyed.
When winters of little snow came, the summer sun cut into the edges of the ice sheets. As the glaciers melted, rocks, soil and other things that had mixed with the ice and snow were left. New hills, lakes and rivers were formed.
The last of the great glaci
A. the Ice Age was a long period of time
B. great glaciers covered North America many years ago
C. changes in climate helped to melt the glaciers
D. how glaciers changed North America
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