Geologic timeline of Western North America
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A timeline of significant geological events in the evolution of western North America. Dates are approximate.
- 350 million years B.P. (Devonian) - An unnamed terrane collides and accretes to the North American Plate, along a line roughly coinciding with the Nevada-Utah border and called the Carlin Unconformity.
- 250 million years B.P. (Permian) - The Sonomia Terrane collides and accretes to the North American Plate, along a line called the Golconda Thrust (also the name of the event) which runs through central Nevada.
- 200 million years B.P. (Triassic) - Sierra Nevada batholith first develops.
- 165 million years B.P. (Jurassic) - The Smartville Block, an island arc terrane collides and accretes to the North American Plate, along a line which coincides with the Mother Lode country of California.
- 140 million years B.P. (Jurassic) - Second wave of plutons added to Sierra batholith.
- 90 million years B.P. (Cretaceous) - Third and last wave of plutons added to Sierra batholith.
- 43 million years B.P. (Eocene) - The Pacific Plate changes its direction of motion from north to northwest.
- 35 million years B.P. (Eocene) - Rio Grande Rift begins to form.
- 20 million years B.P. (Miocene) - San Andreas Fault comes into being as the North American Plate begins splitting the Farallon Plate in two.
- 8 million years B.P. (Miocene) - Onset of faulting creating the Basin and Range geologic province.
- 5 million years B.P. (Miocene-Pliocene)- Northward propagation of the East Pacific Rise into the North American Plate initiates rifting off of the Baja California peninsula.
- 4 million years B.P. (Pliocene) - Sierra Nevada begins to rise.
- 3.5 million years before present (Pliocene) - The Pacific Plate changes its direction of motion about 11 degrees east of its previous heading, from northwest to the present north by northwest.
