2024年4月27日发(作者：)

Passage 1

Everyone has heard of the San Andreas fault （断层）, which constantly

threatens California and the West Coast with earthquakes. But how many people

know about the equally serious New Madrid fault in Missouri?

Between December of 1811 and February of 1812, three major earthquakes

occurred, all centered around the town of New Madrid, Missouri, on the

Mississippi River. Property damage was severe. Buildings in the area were almost

destroyed. Whole forests fell at once, and huge cracks opened in the ground,

allowing smell of sulfur（硫磺）to filter upward.

The Mississippi River itself completely changed character, developing sudden

rapids and whirlpools. Several times it changed its course, and once, according to

some observers, it actually appeared to run people were killed in

the New Marid earthquakes, probably simply because few people lived in the area

in 1811; but the severity of the earthquakes are shown by the fact that the shock

waves rang bells in church towers in Charleston, South Carolina, on the coast.

Buildings shook in New York City, and clocks wer stopped in Washington, D.C.

Scientists now know that America's two major faults are essentially different. The

San Andreas is a horizontal boundary between two major land masses that are

slowly moving in opposite directions. California earthquakes result when the

movement of these two masses suddenly lurches （倾斜） forward.

The New Madrid fault, on the other hand, is a vertical fault; at some points,

possibly hundreds of millions of years ago, rock was pushed up toward the surface,

probably by volcanoes under the surface. Suddenly, the volcanoes cooled and the

rock collapsed, leaving huge cracks. Even now, the rock continues to settle

downwards, and sudden sinking motions trigger （触发） earthquakes in the region.

The fault itself, a large crack in this layer of rock, with dozens of other cracks that

split off from it, extends from northeastArkansas through Missouri and into

southern lllinois.

Scientists who have studied the New Madrid fault say there have been

numerous smaller quakes in the area since 1811; these smaller quakes indicate that

larger ones are probably coming, but the scientists say have no method of

predictingwhen a large earthquake will occur.

1. This passage is mainly about .

New Madrid fault in Missouri

causes of faults

San Andreas and the New Madrid faults

t scientific knowledge about fault

2. The New Madrid fault is .

A.a vertical fault