Harry Hess and Robert Dietz said this spreading does not make the Earth bigger. As new ocean floor is created, an equal amount is destroyed.
The two scientists said Wegener was correct. The continents do move as new material from the center of the Earth rises, hardens and pushes older pieces of the Earth away from each other. The continents are moving all the time, although we cannot feel it. They called their theory “sea floor spreading.” The theory explains that as the sea floor spreads, the tectonic plates are pushed and pulled in different directions.
The idea of plate tectonics explains both volcanoes and earthquakes. Many of the world’s volcanoes are found at the edges of plates, where geologic activity is intense. The large number of volcanoes around the Pacific plate has earned this area the name “Ring of Fire.” Volcanoes are also found in the middle of plates, where there is a well of melted rock. Scientists call these wells “hot spots.” A hot spot does not move. However, as the plate moves over it, a line of volcanoes is formed. The Hawaiian Islands were created in the Pacific Ocean as the plate moved slowly over a hot spot. This process is continuing, as the plate continues to move.
Moving Plates Cause Violence
Volcanoes and earthquakes are among the most frightening events that nature can produce. They cause us to remember that the Earth is not as solid and unchanging as we might like to think. An American scientist says because of expected population increases, more people will die in earthquakes. And he thinks there will be more of what he calls “catastrophic earthquakes,” where large numbers of people die.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25