A Zone of Continental Rifting ?

Quite a while back, as the North American continental landmass moved westward across the face of the earth, it overrode a section of the oceanic rift system. This section of the oceanic rift system then ended up beneath the western part of the landmass. After this happened, it appears that Baja California was "captured" by the Pacific Plate which resides on the western side of this rift system. This "sliver" of land was then ripped loose from the mainland of Mexico (link). Baja was then shifted approximately 300 miles north, forcing strongly against other sections of the North American landmass, during its northward travel.

At this point, it appears that Baja California and those portions of of the state of California which reside to the west of the San Andreas fault are more firmly "captured" by the northwesterly moving Pacific Plate. And, to the east of the San Andreas fault, it appears that California is similar to a "train wreck" of "loose" microplates which are not so firmly captured by the northwesterly moving Pacific Plate. One of the California microplates caught in this geologic "train wreck" is the Sierra Nevada-Great Valley microplate (link).

A 2013 page linked here states that "the heart of California -- the Central Valley and the mountains that ring it -- is a separate tectonic plate, bounded by fault zones all the way around. The Sierra Nevada microplate rotates slightly and moves northwest at a few millimeters per year relative to the rest of the North America plate." The page speaks of "the other side of the Sierra Nevada microplate [to the east of the Sierra Nevada], where the Earth's outer shell is secretly splitting apart." But, what is actually happening in that area to the east of the Sierra Nevada?

To understand what is happening to the east of the Sierra Nevada, we must once again look to that section of the oceanic rift which ended up beneath the landmass of western North America, in earlier times. To decipher where this section of oceanic rift lies deep beneath the continental landmass, we must look for a string of sites where there is thermal and volcanic activity which is of a nature that is similar to that which commonly occurs along the worldwide, mid-oceanic ridge and rift system (1)(2)(3)(4).

To the east of the Sierra Nevada is the northwesterly-trending Walker Lane. A document linked here is titled Siting of Large Volcanic Centers at Releasing Fault Stepovers, Walker Lane Rift. On PDF page 5 of 54, the document declares that the Walker Lane Belt "has the structure that is the most similar to Gulf of California transtensional rift basins..." Why is this? Possibly it is this way because the Walker Lane is actually where the northern extension of the oceanic rift from the bottom of the Gulf of California truly lies beneath the continental landmass.

At this point, there is something to clearly note. The San Andreas fault does not appear to mark the true path of the oceanic rift which resides deep beneath the continental landmass in California. In the geologic "trainwreck" of California, the San Andreas fault is related to the rifting, but it is something else altogether. The true rift appears to be further to the east.

To help identify the different nature of the San Andreas fault, along its path it should be observed that it is missing that large amount of volcanic activity with is common to the worldwide oceanic rift system. But, to the east of the Sierra Nevada, there is "the structure that is the most similar to Gulf of California transtensional rift basins," with volcanic activity and all.

As noted in the title of that document linked a couple of paragraphs above, the Walker Lane is a rift. It is the area in California where the continental landmass is pulling apart or breaking up (1)(2). Because the continental landmass is pulling apart in this area, there are found here those geologic features known as "grabens" or central rift valleys (1)(2)(3)(4)(5). And, because of the continental rifting in this area, the Walker Lane is a geologic trough (1)(2)(3)(4)(5)(6). A geologic trough is an area where the structure of the landmass has sunk down for some distance in a linear feature. But, there is more to this story.

At its northern end, the Walker Lane joins into the southern end of the Cascade Mountains, which is that line of mighty volcanoes. And, there is something important to note about this line of volcanoes. At the southern, California end of the Cascade Range, there is the volcano known as Lassen Peak (link). But Lassen Peak is not in line with the other volcanoes of the Cascade Range. Lassen Peak is on a "dogleg," where the Cascade Range sharply bends to the southeast. Why is this? Possibly it is because the Cascade Range is associated with that rift system buried deep beneath the Walker Lane, where things are pulling apart (1). It appears that the Cascades are part of the volcanic features related to that section of oceanic rift which is buried deep beneath the continental landmass in the western part of North America.

It appears that the Walker Lane shows the surface effects of the deeply buried section of the oceanic rift system, especially with its volcanoes and other thermal features. There is something else to now consider. A page linked here indicates that "rifts in the interior of continents" last for a while "before complete rupture of the continent and onset of sea-floor spreading." Once the massive earthquakes begin, as the rift affecting the area to the east of the Sierra Nevada starts spreading in earnest, it appears that the Gulf of California will begin to extend further and further north. As this major geologic activity continues, California will be separated further and further from the United States. But, again, there is more to this story.

There is that dogleg in the southern Cascade Range, which was noted above, where the Cascades join into the Walker Lane and its associated rift system and volcanic features (1)(2)(3). It appears that the Cascade Range, with its volcanoes and hot springs, is also the surface effect of that section of oceanic rift system which is buried deep beneath the continental landmass. At this point, there is something to once again note.

Because of the spreading on the rift system buried far below, the landmass in the Walker Lane has sunk down and formed into a geologic trough (link). Within this trough are a number of geologic features known as grabens. And now, let us continue onward. To the north, in the Cascade Range, there is also a graben. This graben in the Cascade Range indicates that this volcanic mountain range may actually mark the location of that spreading oceanic rift, which is buried deep beneath the continental landmass.

There are some things to note about the zone of spreading in the Cascade Mountains. A link here accesses a portion of a document titled Oregon Geology. On PDF page 3 of 32, the document speaks of the "High Cascade trough or graben, which extends most of the length of the state [of Oregon]." It indicates that this graben and its associated faults represents "crustal failure on a grand scale." It appears that it is crustal failure on a grand scale because the landmass above is being strongly affected by that active section of oceanic rift which is buried deep beneath the continental landmass.

There is now something even more revealing to note about this trough or graben in the High Cascades. In the lower-right portion of PDF page 13 of 32, in the document linked in the paragraph above, it notes that the High Cascades graben is "associated with extensional tectonics." On PDF page 14 of 32, the document speaks about this High Cascades graben "opening like a zipper from the south." In the south, the graben has subsided "as deep as two miles," while further north in the central portion of this graben, the landmass has subsided "less than a mile."

In the paragraph above, when is speaks about the High Cascades graben being "associated with extensional tectonics" and also "opening like a zipper from the south," there is something to think about. It appears that there may be some association with that separation of the landmass which initially formed the Gulf of California. Possibly in the future, as things progress, the Gulf of California could extend much further north. And now, there is something else to note.

On PDF page 14 of 32 in the document linked above, when it comes to the High Cascades graben, it declares: "Lavas, emerging with the rifting, closely resemble mid-ocean ridge basalts (MORB)." Now, why would this be? Well, once again, it possibly has something to do with that section of the oceanic rift system which is now buried deep beneath the continental landmass. And, that buried section of oceanic rift system would naturally be discharging lavas which "closely resemble mid-ocean ridge basalts (MORB)."

At this point, there are some who are wondering if the typical Cascadia Subduction Zone models (1)(2)(3) may not be completely accurate. Possibly they are not properly portraying what is actually happening in the Cascadia region of North America. In reality, it appears that the Cascadia region may be dealing with something just a bit different than simply a subduction zone, especially when things appear to be "unzipping" from the south to the north along a line which includes the Gulf of California, the Walker Lane to the east of the Sierra Nevada, and the graben in the High Cascades of Oregon.

Possibly there could be some unexpected things happening in the Cascadia region in the times ahead, especially if that geologic "zipper" decides to unzip even further. So, there are now some things to think about. A few things which could possibly stand between those who reside in the western coastal regions of North America and a very wild geologic ride could potentially be the resistance caused by the embedded Klamath Mountains and, looking further to the north, the embedded Olympic Mountains. But, once the "resistance" now holding things in place is overcome, as the Pacific Plate continues in its northerly travel, it may than be time to really "hang on to your hat."

In closing, there are some words of wisdom for the scientists, with their high-tech computerized earthquake models and all. In more recent times, they have been getting horrendously blindsided by the nature and magnitude of large earthquake events. So, let us look back to Ralph Waldo Emerson, of earlier times. In his wisdom, Emerson declared: "We learn geology the morning after the earthquake, on ghastly diagrams of cloven mountains, upheaved plains, and the dry bed of the sea."(1)(2)(3) What is potentially coming to the West Coast region of North America may have to be seen, in order to be believed.






For further reading:

Current Expectations for a Cascadia Mega-Quake
https://cascadian.neocities.org/cascadiaquake.htm

The Greatest Earthquake Ever Felt
http://ourworld.freevar.com/greatestearthquake.htm