[单项选择]

Earthquakes Influence on the Planet

They approach the topic carefully, wary of sounding merciless, aware that the geology they admire has just caused a staggering loss of life. Even so, scientists argue that in the very long view, the global process behind great earthquakes is quite advantageous for life on earth — especially human life.
Powerful tremors (震动) like the one that sent killer waves racing across the Indian Ocean on Dec. 26 (2004) are inevitable side effects of the constant recycling of planetary crust, which produces a cozy, habitable planet. Some experts refer to the regular blows — hundreds a day — as the planet’s heartbeat.
The advantages began billions of years ago, when this crustal recycling made the oceans and atmosphere and formed the continents. Today, it builds mountains, enriches soils, regulates the p Janet’s temperature, concentrates gold and other rare metals and maintains the sea’s chemical balance.A. By historical studies.
B. By prediction.
C. By studying legendaries.
D. By studying the invisible benefits.

[单项选择]
They approach the topic carefully, wary of sounding merciless, aware that the geology they admire has just caused a staggering loss of life. Even so, scientists argue that in the very long view, the global process behind great earthquakes is quite advantageous for life on earth — especially human life.
Powerful tremors (震动) like the one that sent killer waves racing across the Indian Ocean on Dec. 26 (2004) are inevitable side effects of the constant recycling of planetary crust, which produces a cozy, habitable planet. Some experts refer to the regular blows — hundreds a day — as the planet’s heartbeat.
The advantages began billions of years ago, when this crustal recycling made the oceans and atmosphere and formed the continents. Today, it builds mountains, enriches soils, regulates the p Janet’s temperature, concentrates gold and other rare metals and maintains the sea’s chemical balance.A. Big crustal slabs.
B. Volcanoes.
C. The sea of melted rock.
D. Earthquakes.

[单项选择]
They approach the topic carefully, wary of sounding merciless, aware that the geology they admire has just caused a staggering loss of life. Even so, scientists argue that in the very long view, the global process behind great earthquakes is quite advantageous for life on earth — especially human life.
Powerful tremors (震动) like the one that sent killer waves racing across the Indian Ocean on Dec. 26 (2004) are inevitable side effects of the constant recycling of planetary crust, which produces a cozy, habitable planet. Some experts refer to the regular blows — hundreds a day — as the planet’s heartbeat.
The advantages began billions of years ago, when this crustal recycling made the oceans and atmosphere and formed the continents. Today, it builds mountains, enriches soils, regulates the p Janet’s temperature, concentrates gold and other rare metals and maintains the sea’s chemical bala
A. produces more advantages than disadvantages
B. may finally kill all human life on earth
C. annoyingly destroys the cozy, habitable earth
D. works just as the blood recycling in human body

[填空题]Scientists find that on our planet earthquakes are much more frequent where the plates ______.

[简答题] Earthquakes What causes earthquakes The earth is formed of layers. The surface of the earth, about 100 kilometers thick, is made of large pieces. When they move against each other, an earth quake happens, A large movement causes a violent earthquake, but a small movement causes a mild one. Earthquakes last only a few seconds. The rolling movements are called seismic (地震的) waves. The seismic waves start in one place, called the epicenter (震中) , and roll outward. A seismic wave travels around the earth in about twenty minutes. Usually, an earthquake is strong enough to cause damage only near its epicenter. However, epicenters at the bottom of the ocean create huge sea waves as tall as 15 meters. These waves cross the ocean in several hours. Rushing toward land, they destroy small islands and ships in their path. When they hit land, they flood coastal areas far from the epicenter of the earthquake. In 1868, a wave reached 4. 5 kilometers inland in P