The Americans proposed that the floor of the Atlantic Ocean is moving away from each side of the split and expanding. The movement is very slow -- a few centimeters a year. In time, they said, the moving ocean floor is blocked when it comes up against the edge of a continent. Then it is forced down under the continent, deep into the Earth, where it is melted again. Harry Hess said the Pacific Ocean was getting smaller.
He 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 Alfred 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.
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.
New research also supports Mr. Wegener ideas. Scientists in Britain recently reported that large amounts of water may be trapped under the ocean plates near northern Japan. Their findings were published in the journal Geology.
A strong earthquake hit Japan in March of 2011. The quake and resulting tsunami waves killed almost 16,000 people. A team of researchers from the University of Liverpool studied the tectonic plates in the area where the earthquake took place. Their report says that when two plates meet, one may bend and end up underneath the other. During this process, it says, ocean water gets trapped below the plates and goes down past the Earth crust to its mantle.
The researchers said a large hole lies near the fault lines in Japan. They said the hole could be as much as 150 kilometers deep. Water gets carried down the hole. The report says there could be 3?times more water in the Earth mantle than there is in all the oceans.
The idea of plate tectonics explains both volcanoes and earthquakes. Many of the world volcanoes are found at the edges of plates. The large number of volcanoes around the Pacific plate has earned this area the name ing 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.
Similar to earthquakes, volcanos can cause destruction and displace populations. Because of this, scientists are also hoping to learn more about volcanic activity.
Recently, the United States National Science Foundation provided financial support for research on volcanos. Geoscientists from the University of Oregon and the University of California Davis studied Mt. Hood in Oregon.
The scientists say that volcanos become active when the rock or magma inside becomes as hot as 750 degrees Celsius. The volcano becomes active when the hot magma from the Earth crust rises and meets cooler solid magma. This can happen in as little as a few months?time.
The American scientists believe the magma at Mt. Hood had been stored in the volcano for at least 20,000 years, or even as long as 100,000 years. They say that modern technology should be able to sense when the magma is getting warmer, and could possibly explode. This could prevent disasters when volcanos erupt around the world.
This Science in the News was written by Kim Varzi and Christopher Cruise.
I'm Anna Matteo.
And I'm Christopher Cruise.
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