Chapter nine of this book outlines
some of the basic facts and ideas that undergird the linking of the creation of
the Siberian continent with the Permian extinction that occurred approximately
250 MYA.
These basics include a 300
mile-in-diameter crater in Eastern Antarctica, the existence of the Siberian
traps, the blob with a tail shape of the Siberian continent and the flood
basalt lava in southern Alaska 235 MYA leading out to the Aleutian island chain
(the follow-on hotspot).
The purpose of Appendix I is to
provide more detail about the formation and movement of the Siberian continent.
The impact crater location in Eastern
Antarctica and the Wrangellia flood basalts (231 - 225 MYA, which would have
been the first separate activity of the Siberian hotspot after falling behind
the moving Siberian continent) in Alaska and Canada give us a reasonably good
picture of where the Siberian continent started out. We can see from the final
position of Siberia that the Siberian traps were on the east side of the
continent when it was first formed.
The blob part of the continent had a
significant south and western momentum that caused it to turn to the west and
then to the south.
This movement is corroborated in an
unusual way by an article in the Journal of the Geological Society in 2007.
Entitled "Siberian trap magmatism on the New Siberian islands" by Alexander B.
Kuzmichev and Victoria L. Pease, this article presents evidence that islands
near the Siberian traps are not geologically different from Siberia, itself.
In the course of the investigation, the
authors found that the arctic basin in the Alaska/Siberia area showed a rotated
terrane. Furthermore, the terrane rotated around a pivot point in extreme
northeast Alaska. The rotation in the Siberian area was to the south. 81
pg 960
The authors were not looking to
corroborate a model such as the one that I present. Nevertheless, their terrane
conclusions do actually match the scenario that my model proposes. With the
flood basalt lava located on the east side of the newly uplifted continent, we
would expect movement to the west (see Appendix VII, Sidespin). Later, due to
the Coriolis effect, we would expect movement to the south. A pivot point near
northeast Alaska is right about where we would expect to find it.
THE ROCKY MOUNTAINS
The creation and movement of the
Siberian continent had a significant impact on the western side of the North
American continent.
Not only did it create the Rocky
Mountains (as well as most of the western mountains in Canada and Alaska), but
it also left behind a ridge on the Pacific tectonic plate. This ridge was
formed by the westward turn of the Siberian tail of the new continent (just as
the Indian Continent pushed up part of Java and Sumatra and the Thailand and
Malay peninsulas).
This westward turn of the tail pushed
up enough material that the Pacific plate could not subduct beneath the North
American plate, once the tail of the Siberian plate had moved to the north.
Therefore, at this juncture of the Pacific plate and the North American plate,
we see the San Andreas fault and a strike slip system, rather than a subduction
system.
The creation of the Rocky Mountains, as
well as the western Canadian mountains and the mountains in Alaska happened
over a period of millions of years and involved several different aspects of
the movement and breakup of the Siberian continent.
The Siberian continent was originally a
very large continent. It was so big that it ended up breaking into several
distinct pieces as it pivoted, turned and moved to the west and then to the
south. The resulting plates from the creation of the Siberian continent are:
1. The western part of the
North American plate (which includes Alaska and the eastern part of Siberia).
2. The eastern part of the Eurasian plate (which includes the rest of
Siberia).
3. The middle tail piece pulled north and west along the
Canadian Rockies.
4. The end of the Siberian tail broke off and was
trapped between the San Andreas Fault and the high plains of the
U.S.
TOO BIG TO BE
STABLE
The original Siberian continent that
was uplifted was so large that it was intrinsically unstable as it tried to
move in one piece. If this huge continent had been moving on a truly flat
surface, then it might have held together. However, it was moving on a curved
surface, where the Coriolis effect gives a different direction of movement to
each segment of this large object. Besides that, the underlying magma had
different directional pressure along the length of the continent.
The magma that was located under each
part of this huge, upraised continent was being pushed in different directions,
due to the rotational nature of the energy at that point under the earth. In
the case of a smaller, stubby continent (i.e. India), the rotational energy of
the blob would take over and move the entire continent in that direction. In
the case of a much larger continent, the different energies will cause the
continent to split apart into multiple tectonic plates.
The far northern part of the Siberian
blob contained an underlayment of magma with energy pushing in a southwestern
direction. The southern part of the blob was underlain by magma pushing in a
western direction.
It is also possible that the leading
edge of the blob was initially located beyond the North Pole, accounting for
its slight southward movement. This would mean that Old Australia was farther
south, but that is certainly possible.
The result of these competing
directional pressures was the eventual breakup of Siberia into either three or
four plates:
1. UPPER BLOB - This part
moved west and eventually south and became permanently affixed to Eurasia, as
it crashed into the Ural Mountains and China.
2. LOWER BLOB - This part moved west but was also pushed north by
the tail. The western edge of the Eastern North American Continent eventually
ran into this section and raised up the Canadian Rockies as it was subducted.
This combined mass continued moving west. Eventually, the western pull of the
Upper Blob caused the far northern part of the North American to stretch apart
(a quick glance at a map of northern Canada and Greenland will show how this
area is stretched out like a fan). Finally, the southern movement of the Upper
Blob was too much for the structural integrity of this part of the Siberian
continent
the Upper Blob ended up permanently affixed to Asia, while the
Lower Blob remained part of the stretched-out North American plate.
3. MAIN TAIL - Meanwhile, the main part
of the tail of the blob was moving in a northern direction with at least a bit
of a western twist. This piece experienced subducted the Eastern North American
Plate in the Southern Canadian Rockies.
4.
TAIL END - The tail end of the Siberian Continent followed the blob north and
west. The tail subducted the western side of the Eastern North American
Continent later on in Canada, forming the Canadian Rockies. Part of the blob
and the tail pushed up earth on the Pacific Plate as the Siberian Continent
made its arcing movement to the north and west. This pushed up earth prevented
the Pacific Plate from subducting and consists of the land to the west of the
San Andreas Fault, as well as Baja California. The lower part of the tail broke
off as it was trapped between the San Andreas pushed up land and the western
edge of Eastern North America, becoming the high plains and the American
Rockies.
THE ROCKIES - A COMPLEX
SYSTEM
One point in favor of examining the
Rocky Mountains in North America is the fact that they have been studied a lot.
And yet, the formation of the mountains in the western U.S. is so complex that
not all answers are known. Answers to these questions are explored in detail in
Appendix IV.
THE FOLLOW-ON HOTSPOT
The follow-on hotspot for the Siberian
continent moved almost directly west from its original position at Wrangellia
in Alaska, forming the Aleutian Islands.
However, because the North American
plate did not move in a consistent manner during the 230 million years since
the hotspot separated from the Siberian basalt flows, the Aleutians formed an
arc, rather than a straight line. The reasons for this changing movement and
the shape of the arc are detailed in the next three paragraphs.
The initial result of the collision of
the Siberian continent and the western side of the North American continent was
a gradual movement of the Siberian part of the North American continent
(Alaska) to the north, as the blob rotated, pulling up the lower part of the
blob and bringing the tail along, until the tail broke off.
Because the Alaska area was moving
north, the west-moving hotspot appeared to be moving south.
This all changed 65 MYA, when the
Chicxulub impact pulled the North American continent to the south, causing the
west-moving hotspot to appear to move north. 41 pg 960, 42, 43 pg 14
|