WHAT CAUSES TECTONIC PLATE STRESS

Over the years, I have often wondered what the underlying cause of earthquakes is. I fully understand that an earthquake is the result of a release of stress between tectonic plates. Two or more plates pressing others in any manner of ways and hung-up or caught on a type of blockage, then breaking free and releasing the stress. A ridge or rock formation acts as a block similar to the hammer on a gun’s trigger mechanism. Once the blockage is removed or fails, the hammer falls setting the process into motion. If a rock formation breaks, the stored energy is released. The result is an earthquake. This process is simple. However, what causes the stress in the plates in the first place?

How was the metaphorical hammer locked back in the first place to create a system to store up all of the energy?

In writing “Are We Worth Our Salt?” I came up with three closely related factors that work to build up the energy. All of these contribute to the process that enables the movement of tectonic plates described in the chapter “Continental Drift – Pangaea in Reverse”, a subject that should keep Geologists busy for years. These factors are all primarily caused by the friction and resistance created by the Earth’s rotation on its axis.

Granted all three of these factors were not discussed in the book. This was due to a lack of need to address them to lead the reader to main point of tectonic plate movement as it related to a pole shift. The main topic was that certain parameters were needed to enable continental drift. Parameters that only permitted slow gradual movement that would not answer anomalies identified in the fossil record. This discussion was to show that the Earth’s crust is not hard-bound attachment to its core and was merely floating on the magma similar to boats tied together on a lake. Like the boats, the plates will shift back and forth to the limits of their ropes and will bob up and down next to each other, yet they will not drift away from each other.

Enough on continental drift, let’s get back to the stress builders. Like I said above there are three factors that are closely related and are all the result of the Earth’s rotation. Here they are, in no particular order because they are all appear to be equal in their resulting stress creation.

First, the Earth is really a ball rotating within a ball with a substance that is basically liquid (magma) in between. This ball within a ball example is important with regard to the amount of friction producing surface area ratios. Imagine the area differences when comparing the equatorial regions with the polar regions. There is a considerably larger amount of contact area at the equator. This will create vastly more friction than that which would be made at the poles. Scientists look at the odd flow patterns of the sun during its rotation and see that its equator seems to rotate approximately three times faster than its polar regions. Another way to look at it, is the poles lag behind. The core’s influence at the equator is greater than that of the poles due to the difference in contact area with the gaseous/liquid matter at the surface. This same principle will also be present on Earth and is just less noticeable due to the solid nature of the planet’s surface at the poles. The hammer begins to lock back or the rubber band is tightening - Stress builds.

Second is the simple influence of centrifugal force. A physical law that comes into play when the ball in the ball scenario is again looked at. Imagine now that the center ball representing the Earth’s core is rotating faster than the outer ball that simulates the crust. Scientists have determined that the Earth’s core is rotating approximately 1100 mph faster than the crust/surface. This is the reason for our weather moving generally from west to east – but that is a subject for another day. With the influences of friction building from contact area outlined above being applied to centrifugal force causing the heavier areas to be influenced to move towards the equator, you find that the plates are trying to move both east and towards the equator. Which is evidence that equatorial regions/plates will not and can not move into polar regions by themselves. This easterly/ equatorial movement is the cause for the equatorial bulge that the Earth has. A bulge that is around 13 miles greater than if the planet is measured from pole to pole. More stress applied!

Third is the relatively uneven surface of the Earth’s crust that comes in contact with the magma. The magma is the result of melting metals and rock when immense pressure is applied. The melting point varies based on the material that is liquefying, therefore the amount of material over the top needed to create the needed pressure changes. In essence, if you turned the crust upside down, there would be mountain ranges there also. Let’s say that 20 miles (example only) of weight producing material is needed to achieve magma, that would mean that (in theory) where we see a mountain range, there would be a valley beneath in contact with the liquid. This would create a pocket of resistance that would trap the east flowing magma current resulting in a push on the crust. Yet again, a stress builder!!

With all of this pushing in a eastward direction and the physical law of centrifugal force in play there can be little doubt that the tectonic plates are under tremendous stress. The hammer locks back and the rubber band is stretched. That is until the block falls and the band breaks. Earthquakes are a reality we have come to expect and live with. Now you know why they happen. Cause and Effect.

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