Roger,

I've been looking closely today at modern theories of plate tectonic driving forces. To begin with, seismologists with degrees admit they don't know what drives the tectonic plates. Not even seismologists believe convection can satisfactorily explain tectonic movement.

According to a USGS web site (link is below) it is only a theory, not a proven fact, that convection drives plate tectonics.

So I went to a globe of the earth, looked at that portion of the planet that the Pacific Plate covers and found it unlikely that it is physically impossible to have the size of convection cells necessary to drive half of the planet in one movement. Siesmologists are divided over this very issue. If the Pacific Plate is driven by convection, then there must be several cells beneath it. But due to the topography of the Pacific Plate, there is no indication that any cells exist at all. Certainly if the convection was strong enough to suck a continent under another then it would also show other indications such as ripples, tears, bulges, and other fluid pressure induced anomolies. But such anomolies do not exist.

The convection theory doesn't make sense particularly along the Atlantic Ridge and Southeastern Pacific Ridge. If magma were being forced up from convection, then the surface feature would look more like the Emperor Seamount Chain that created Hawaii. Instead, the Atlantic Ridge and Southeastern Pacific Ridge must be caused from stretching of the crust in these areas and not from an upward draft of magma below. The topographies of these features do not support an upward flowing magma theory.

If fact, if you look all the way up and down the Eastern Pacific and Atlantic seafloor, you see countless isolated volcanoes that appear to be caused from crustal stretching as opposed to an upward magma convection.

Also, the convection theory does not explain Pacific Rim subduction zones, at least not the way they are formed on earth. If the Pacific Plate were truly moved only by convection, then the collision of the Pacific Plate with surrounding plates would result in high mountains, not shear cliffs as every subduction zone around the Pacific Rim does.

Any bathymetric map of the Pacific Rim clearly shows very steep and shear cliffs at the subduction zone. The only reasonable explanation for this type of feature is that the subducting force is a pressure on top of the plate (and spread evenly over the surface) and not from the bottom of the crust.

There is absolutely no scientific basis for a convection theory as primary plate mover that can cause the geological shear cliffs in the Pacific subduction zones. And yet a tidal explanation as the primary mover of the Pacific Plate does predict the exact geological features we see today along the Pacific Rim as well as the rotational movement.

It is more likely that the tidal caused tectonic movements are the prime cause of convection within the mantle.

Now before you spout off with your all knowing, outdated seismological understanding, go look at a bathymetric globe and ask yourself if the features and plate movements you see can be generated by convection alone. No reasonable person, regardless of how many papers hang on their walls, can say that the shear cliffs in the Pacific subduction zones can be caused from convection as the primary tectonic mover.

If convection were the primary tectonic mover then the Pacific Rim would look more like the Eastern Himalayas.

Dave

• Unanswered Tectonic Questions by USGS