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Earthquakes
 
@ Copyright TamilNet January 10, 2005 03:30 GMT
 
Earth as a Living Planet: Plate Tectonics Theory is Challenged by a New Theory

According to the US Geological Survey more than three million earthquakes occur every year. That is, 8.000 quakes a day or one every 11 seconds. But researchers still debate on what causes earthquakes. For the last 30 years the plate tectonics theory was predominant but recently it has been challenged by a new Global Wrench Tectonics theory created by the Norwegian professor Karsten M. Storetvedt. According to his theory earthquakes are caused by gas explosions and can happen anywhere, not only along the plate borders, as suggested by earlier theories.

Earthquakes, tsunamis and other natural disasters came to our attention when on December 26, 2004, a massive underwater earthquake off the Sumatra coast shook the Earth in its orbit. The quake was the largest since 1964 and measured 9.0 on the Richter scale. 5.0 or higher aftershocks have occurred in the following days. But the most powerful and destructive aftermath of this earthquake was the tsunami it triggered.

The word “tsunami” comes from Japanese words “tsu,” meaning harbour and “nami,” meaning waves. A tsunami is a wave or series of waves which can be hundreds of kilometres long and over ten meters high. They can travel as fast as or faster than a jet plane and on Dec. 26 tsunami they covered 600 km in 75mins, what makes its speed an astonishing 480kph. Strictly speaking, the water itself does not move till it reaches shallow grounds near the shores. What we are speaking of is a transport of energy that is freed by underwater earthquake, volcanic eruption or mudslide. The wave energy moves in the form of a tube and when the friction at the bottom of the sea exceeds the friction of the water with the air, this makes the water turn and thus the tsunami wave is formed.

Up to recently it was the plate tectonics theory that was predominant in explaining earthquakes, volcanism and Earth development as a planet in general. It is a combination of two earlier ideas, Continental drift, i.e. movement of continents over the earth’s surface, and sea-floor spreading, i.e. creation of new oceanic crust at mid-ocean ridges and movement of the crust away from them. It suggests that lithosphere, that is the top layer of Earth, is made of 7 major and 20 smaller plates that are from 40 to 800 km thick. They rest on the underlying layer called asthenosphere.

As the underlying layer is “liquid,” the plates are in constant motion, moving at a speed of 2,5 - 5 cm per year. Where the plates border these motions produce earthquakes and volcanism.

Sometimes a heavier plate can slip under a lighter one in the boundary region. In some cases part of a seafloor connected to the lighter plate can suddenly break causing an earthquake. If it happens underwater the energy of land masses that “snap up” is transferred to water masses and it is pushed above normal sea level. This is how tsunami is born. The earthquake that generated the tsunami of 2004 is estimated to have released the energy of 23,000 Hiroshima-type atomic bombs, according to the U.S. Geological Survey (USGS).

Plate tectonics is a relatively new theory that has revolutionized the way geologists think about the Earth. The word tectonics comes from the Greek root "to build." So the term plate tectonics describes how the Earth’s surface is built of plates. Still, there are many blank spots that this theory has not found the answer yet.

Exactly what drives plate tectonics is not known. One theory is that convection within the Earth's mantle pushes the plates, in much the same way that air heated by your body rises upward and is deflected sideways when it reaches the ceiling. Another theory is that gravity is pulling the older, colder, and thus heavier ocean floor with more force than the newer, lighter seafloor.


Professor Karsten M. Storetvedt, Geophysics Institute, University of Bergen
It was the gradual realization that plate tectonics theory is full of paradoxes that encouraged Professor Karsten M. Storetvedt, the chair in geomagnetism at the University of Bergen, Norway since 1973, into re-thinking on the global dynamic system. Professor Storetvedt criticizes the theory of plate tectonics, and proposes a new model of Earth evolution, where Earth is regarded as a system of interlinking processes.

The basic idea is that the Earth’s development is influenced by internal degassing together with vertical mass transfer caused by planet’s rotation. As an underlying postulate, Global Wrench Tectonics (GWT) takes that the Earth had a relatively thick pan-global outer layer which has undergone substantial reduction, having eventually, in modern times, been replaced by a thin basaltic crust in places. Hydrous fluids have caused overpressure in Earth’s outer layering, which in turn has given rise to gravitational instability of the transformed rocks. Thin basaltic crust of the deep oceanic basins is regarded the stable cover layer of the modern Earth. Deep continental roots, extending at least a few hundred kilometres into the upper mantle, represent leftovers of the early crust. All continents are in constant movement under the influence of various factors, both tectonic and gravitational.

Full version of the theory can be found in the book “Global Wrench Tectonics” written by Karsten Storetvedt. “What happened (in Southeast Asia) is not unusual but happens rarely. Unfortunately, one day it will happen again. Earth is a living planet that is still not ready with its chemical processes,” says professor Storetvedt.

According to his theory earthquakes are caused by gas explosions and can happen anywhere, not only along the plate borders, as suggested by earlier theories.

Equators are more prone to catastrophes – earth rotation and difference in speed of rotation cause strain and the mantel cracks. As the region of Southeast Asia has lots of such cracks, gasses from underneath break out there more often than anywhere else. This make this region special and even abnormal.

If the earthquake epicentre is above the water, gas leaking through the cracks in earth will make it difficult to breath for animals living underground and they will flee. This was used as a sign of an impending earthquake in China and Greece since ancient times.

It is not possible to predict where and when the gas will erupt but at least it is possible to establish a tsunami warning system when the earthquakes happen underwater.

It seems that we will have to live with earthquakes and hope that most of them are minor. Remember, there is one every 11 seconds!


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