Devastating 7.9-magnitude quake strikes Nepal, India: India is like Australia. It is a very fast moving piece of tectonic plate that moved fairly rapidly from Antarctica to smash into Asia causing the fastest growing and tallest mountains on earth as Asia buckles and folds as the relentless grind of India is shoved under Asia. Africa is moving at a much slower rate into Europe and will eventually crush the Mediterranean Sea and the Alps will eventually be as high as Mount Everest but this is in the far, far future.
Most earthquake deaths are due entirely to human construction techniques except along subduction zones where tsunamis are frequent especially along the Ring of Fire in the Pacific. The Atlantic Ocean is widening but the Pacific Ocean is getting smaller which is why it is much more volcanic/subduction prone.
We still don’t understand why some tectonic plates move very fast while others poke along at a much more leisurely rate. This dynamic does cause a lot of speculation. Just this last month there was a new theory put forth: A stiff new layer in Earth’s mantle | University of Utah News
March 23, 2015 – By crushing minerals between diamonds, a University of Utah study suggests the existence of an unknown layer inside Earth: part of the lower mantle where the rock gets three times stiffer. The discovery may explain a mystery: why slabs of Earth’s sinking tectonic plates sometimes stall and thicken 930 miles underground.
The findings – published today in the journal Nature Geoscience – also may explain some deep earthquakes, hint that Earth’s interior is hotter than believed, and suggest why partly molten rock or magmas feeding midocean-ridge volcanoes such as Iceland’s differ chemically from magmas supplying island volcanoes like Hawaii’s.
“The Earth has many layers, like an onion,” says Lowell Miyagi, an assistant professor of geology and geophysics at the University of Utah. “Most layers are defined by the minerals that are present. Essentially, we have discovered a new layer in the Earth. This layer isn’t defined by the minerals present, but by the strength of these minerals.”
Earth’s main layers are the thin crust 4 to 50 miles deep (thinner under oceans, thicker under continents), a mantle extending 1,800 miles deep and the iron core. But there are subdivisions. The crust and some of the upper mantle form 60- to 90-mile-thick tectonic or lithospheric plates that are like the top side of conveyor belts carrying continents and seafloors…
The researchers found that ferropericlase’s strength starts to increase at pressures equivalent to those 410 miles deep – the upper-lower mantle boundary – and the strength increases threefold by the time it peaks at pressure equal to a 930-mile depth.
And when they simulated how ferropericlase behaves mixed with bridgmanite deep underground in the upper part of the lower mantle, they calculated that the viscosity or stiffness of the mantle rock at a depth of 930 miles is some 300 times greater than at the 410-mile-deep upper-lower mantle boundary.
“The result was exciting,” Miyagi says. “This viscosity increase is likely to cause subducting slabs to get stuck – at least temporarily – at about 930 miles underground. In fact, previous seismic images show that many slabs appear to ‘pool’ around 930 miles, including under Indonesia and South America’s Pacific coast. This observation has puzzled seismologists for quite some time, but in the last year, there is new consensus from seismologists that most slabs pool.”
Here is an amusing video explaining one present theory about why some parts of the planet surface is moving faster than other parts: Plate Tectonics Explained – YouTube
But that doesn’t explain the HUGE plate upon which India and Australia sit. This one has been moving northwards for much of the Mammalian Age. Why Antarctica sits firmly afixed at the South Pole while this plate has swift continental movement northwards is no well understood. Why the earth goes through cycles of breaking up and shoving together has theories to explain this but questions abound as we discover more and more information.
The other thing humans have to realize is, we have to go with the flow and this means, our attempts at building firm structures is constantly under stress from dynamic planetary forces which we can’t control anymore than we can control wether or not we are going into another Ice Age. We have to adapt to Nature’s efforts.
The death toll in Nepal which is big, is smaller by 10 times over compared to the death toll in tsunami/earthquake events. And it would have been smaller, too, if people lived in safer buildings. In general, people prefer ‘typical’ buildings to safe buildings. Just like houses in tornado-prone areas are not built to reduce tornado damage, hurricane prone areas have buildings that are ridiculous in hurricanes, we have big, tall, weak mud/cement houses that fall with a resounding crash in earthquakes being built and rebuilt in earthquake prone areas.
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