My Blogs (olelog) are mainly based on my daily reading of earth science news.
Here on whatonearth.olehnielsen.dk I try to weave some of the pieces together to a greater whole with added background info.
The Farallon plate was an enormous oceanic plate located west of the Americas during the Cenozoic and Mesozoic eras. The Farallon Plate plate has now been almost completely subducted beneath the American plates. The Farallon Plate began subducting under the west coast of the North American Plate— then located in modern Utah— as Pangaea broke apart during the Jurassic period. Over time the central part of the Farallon Plate completely subducted under the southwestern part of the North American Plate. Around 23 million years ago, the remnant of the Farallon Plate split into the Juan de Fuca Plate subducting under the northern part of the North American Plate, the Cocos Plate subducting under Central America and the Nazca Plate subducting under the South American Plate.
It is thought that much of the plate initially went under North America (particularly the western United States and southwest Canada) at a very shallow angle, creating much of the mountainous terrain in the area (particularly the American Rocky Mountains). A large fragment of the subducted plate is believed to presently be in the mantle under eastern North America.
In early Cretacious the ridge system in the Pacific Ocean was nearly symmetrically arranged with two triple junctions seperating four oceanic plates: the Kula Plate in the north, the Farallon Plate in the northeast, the Pacific Plate in the southwest and the Phoenix Plate in the southeast. Subduction zones formed an almost continuous rim around the Pacific Ocean of that time.
Mid-Cretaceous sea-level rise was mainly the result of mid-plate volcanism
that produced swells in the Pacific and Farallon plates.
"Descent of the ancient Farallon slab drives localized mantle flow below the New Madrid seismic zone" is the title of an article in the Geophysical Research Letters, VOL. 34, L04308, doi:10.1029/2006GL027895, 2007
Scientists studying extraordinary earthquakes along the New Madrid seismic zone nearly 100 years ago find that remnants of the ancient Farallon plate, a slab of crust swallowed beneath the western North American continental margin several million years ago, continue to descend into the deep mantle under central North America. The descent induces mantle flow towards the Earth’s deep interior directly below the New Madrid seismic zone, which may lead to earthquakes in the overlying crust.
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