Puget Sound Plate Tectonics

Plate tectonics and the geology of the Puget Sound:

The Juan de Fuca slab suction vs the cessation of the Farallon Plate:

Predicting the future of bridges.

Summary: I believe the fundamental future geology from the Olympic Mountains, Puget Sound, and east to the Cascades, will depend on a plate tectonic process known as slab suction.

Background: Most current explanations of the major forces behind the movement of the continents ascribe those processes to the hot rock (less dense) thermal upwelling occurring along the mid oceanic ridges. This upwelling then pushes the plates outward, causing them to ride up and over other plates.

Contrarywise, the slab suction force modeling is a ‘mirror image’ of the upwelling model, in that the newly formed basaltic basement rocks at the ridges will slowly cool due to their contact to the sea. This colder rock will become heavier over hundreds of million years, to an unstable density that will at some point begin to slide back into the lower mantle. As it slides downward, (little horizontal movement, mostly vertical dropping) the leading edge of the tectonic plate moves backwards away from the lighter crust, pulling it along.

A number of elements point to slab suction as being a greater player than upwelling:

The depth of the mid-ocean ridges slowly increases as you go away from the ridge axis indicating reduced rock volume due to increased density due to cooling. One can accurately model exponentially ocean depth based upon the age of the submerged rocks.
The most energetic orogenesis (mountain building) occurs at the subduction boundaries, not at the ridges. One might infer that plate boundaries are highly unstable and thunderous forces are pushing rocks together to make mighty mountains, while ridges are slowly oozing apart.
Note: teasing apart cause and effect is frightfully difficult on a rotating geoidal shape with non-linear historical mashups scattering the evidence all-about (I know, way too poetic for a scientific post), with most of data buried or worn away.

Proposition: The Juan de Fuca oceanic subduction will lurch Puget Sound and the Olympics westward towards the Pacific Ocean

Background:

The Farallon plate has been significantly consumed and does not seem to be pulling the North American plate westward, and neither does the Pacific Plate seem to contribute.
GPS data indicates that Washington State is being tugged in multiple directions at once, and directive data depends upon location, indicating Washington State is slowly rotating, not translating..
However, we do not have GPS data after a significant plate boundary earthquake. The boundary Fukushima earthquake data indicated some land movements as much as 20 feet seaward, decreasing as the observations go away from the sea towards the land.
Therefore, we should not conclude that the existing land movement data is all there is, and perhaps over geological times Western Washington will be tugged further west.
Observations of river siltation of lakes causes one to inquire how long it would take landbound lakes Washington and Sammamish take to fill up from the local erosion of the loose glacial till left behind by the last ice age? Satellite images of those two similar lakes makes one wonder if they are the result of the same formation processes, basement rock spreading?
Puget Sound is lined by significant bluffs which are continuously eroding into the Sound. Is the Sound basement rock spreading, or is the detritus being washed out to the Pacific by other processes?
Observation of the Hood Canal from above teases one to boldly proclaim a Wegener style of ‘ah-ha’. Look! One can map the shores back into a cohesive whole!

Conclusion:

If the hypothesis is correct, then Puget Sound may not receive an ocean style tsunami from the Pacific, but the landforms are likely to separate, dropping the many bridges in the region into the water. In addition, the motion of the landforms can possibly create seiche or tsunami style waves racing throughout the basin as large as those seen in Alaska.