Monday Map: The Farallon Plate

I like maps.  I like the visual display of information, and the Zen-like moments of consideration as I absorb the information on a visceral level.

This is one of those that stuns me.  It shows the remnants of the Farallon Plate underneath North America.  If you aren't a geology nerd, this may bring a ho-hum moment.  And that's okay.  How boring the world would be if we all shared the same few interests. But this picture excites me in the same way an actual photograph of the surface of Pluto excites me.  It gives substance to scientific theories and helps me visualize a complex process.

Also, I have lived most of my life around the scraping of this plate, and feel a strange sense of kinship and longing for that ancient, lost land.

A software model by NASA of the remnants of the Farallon Plate, deep in Earth's mantle.

From Wikipedia

The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.

Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, 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.

The Farallon Plate is also responsible for transporting old island arcs and various fragments of continental crustal material rifted off from other distant plates and accreting them to the North American Plate. These fragments from elsewhere are called terranes (sometimes, "exotic" terranes). Much of western North America is composed of these accreted terranes.

The Farallon Plate had a lasting effect on the landscape of the western America, as this geology blog remarks:

The Farallon plate went under at a shallow angle, and hence the subduction process was long and complicated. The plate scraped along the underside of the continent for awhile, and the resulting volcanoes formed the Sierra Nevada in California. Due to motions in the mantle, underneath the crust, the continental plate moved westward over the subducted plate; the progress of the Farallon plate under the continent was instrumental in forming the Rocky Mountains. And all these millions of years later, the plate is evidently still descending, and as it moves it affects the flow of molten rock in the mantle beneath parts of the eastern US.

The new paper describes how the resulting stresses in the crust could have triggered the New Madrid earthquake, and perhaps could contribute to further seismic activity in the area in the future.

 The Sierra Nevada, the Basin and Range, the tilted strata of the Southwest--all the landscapes I will dwell on are the direct consequence of this ancient collision and the islands that came in with it   I wonder what populations of life originated on the Farallon Plate and rode the terranes in until they merged with the North American Plate.  Geologic times are long.