Hi
As mentioned earlier ,this month will witness few major 7+quakes.
Keep counting
Today ,ie 12th November 22 a 7.1 quake at Fiji.
The problem is the quake occured at 587.2km depth.(ref USGS)
Woh!
How do we explain this with plate tectonics.
The maximum depth of earth crust is around 50 -60 kms.
How the quake occured at a depth where there is no plate to collide at a whooping depth of 587.2 km
ANY ANSWERS OR EXPLANATION BY PLATE TECTONICS?
Now I will discuss the arguments given by plate tectonics for quakes at this depth.
Explaination given...
Quakes at such greater depth ( say this one at 587 kms) occurs at subduction zone. One plate slides below the another plate and keep sliding downward. At great depth this plate (which is going down ) deforms and create quakes at such great depth.
Now some points
1) At such depth of 587 kms the temp could be around 2500 to 3000 degree Celsius.
2) The melting point temp of rocks is around
2000 to 2400 degree Celsius
3) Why then this crust whichbis going down should not get melted ,before reaching this great depth?
4) At a rate of say 5 mm per year ,if the plate is going down ,it will take 117 million years to reach this depth. How can the solid rock remain solid at 3000 degree temp and for 117 million years?
Any Explation?
AMIT DAVE
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