View source for Geologic timeline of Western North America

{{no footnotes|date=June 2019}}
The '''geological timeline of Western North America''' includes significant [[geological event]]s over millions of years in the evolution of [[Western North America]], including several [[list of tectonic plate interactions|tectonic plate interactions]] involving the [[North American Plate]] and leading to the formation of various [[mountain ranges]] and [[seaways]]. Most of these events occurred during the [[Mesozoic Era]] (252 to 66 million years ago) and the [[Cenozoic Era]] (from 66 million years ago).
==Timeline==
Dates in the table are approximate ("Ma" = millions of years ago).
{| class="wikitable"
|-
! Date
! Period/Epoch
! Event
|-
| 350&nbsp;Ma
| [[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&nbsp;Ma
| [[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&nbsp;Ma
| [[Triassic]]
| [[Sierra Nevada batholith]] first develops.
|-
| 180&nbsp;Ma
| [[Jurassic]]
| The [[Intermontane Plate]] collides with the Pacific Northwest, the remnants of which form the [[Intermontane Belt]] today.
|-
| 165&nbsp;Ma
| 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&nbsp;Ma
| Jurassic
| Second wave of [[pluton]]s added to Sierra batholith.
|-
| 115&nbsp;Ma
| [[Cretaceous]]
| The [[Insular Plate]] collides with the Pacific Northwest.   The remnants of that terrane comprise the [[Insular Belt]] today, of which [[Vancouver Island]] is a part.
|-
| 90&nbsp;Ma
| Cretaceous
| Third and last wave of plutons added to Sierra batholith.
|-
| 51&nbsp;Ma
| [[Eocene]]
| The [[Siletzia]] Plate collides with the Pacific Northwest, forming the coast of much of Washington and Oregon
|-
| 43&nbsp;Ma
| [[Eocene]]
| The Pacific Plate changes its direction of motion from north to northwest.
|-
| 35&nbsp;Ma
| Eocene
| [[Rio Grande Rift]] begins to form.
|-
| 20&nbsp;Ma
| [[Miocene]]
| [[San Andreas Fault]] comes into being as the North American Plate begins splitting the [[Farallon Plate]] in two.
|-
| 17&nbsp;Ma - 14&nbsp;Ma
| [[Miocene]]
| [[Columbia River Basalt Group]] Forms.
|-
| 8&nbsp;Ma
| Miocene
| Onset of faulting creating the [[Basin and Range Province|Basin and Range]] geologic province.
|-
| 5&nbsp;Ma
| Miocene&nbsp;-&nbsp;[[Pliocene]]
| Northward propagation of the [[East Pacific Rise]] into the North American Plate initiates rifting off of the [[Baja California peninsula]].
|-
| 4&nbsp;Ma
| Pliocene
| [[Sierra Nevada]] begins to rise.
|-
| 3.5&nbsp;Ma
| Pliocene
| The [[Pacific Plate]] changes its direction of motion about 11 degrees east of its previous heading, from northwest to the present northwest by north.
|}
==External links==
* [https://web.archive.org/web/20080808112624/http://www.geog.ucsb.edu/~joel/g148_f06/readings/geol_history/geol_history.html Geologic History of California: A Brief Overview by Joel Michaelsen]
* [https://web.archive.org/web/20150923210251/http://www.colorado.edu/GeolSci/Resources/WUSTectonics/SierraBatholith/mesozoic.htm#pt4 Dating of the Ages of Three Plutonic Episodes in the Sierra]
{{DEFAULTSORT:Geologic Timeline Of Western North America}}
[[Category:Geology timelines]]
[[Category:North America geology-related lists]]
[[Category:Timelines of North American history]]
[[Category:Natural history of North America]]
[[Category:Geology of California]]
[[Category:Western United States]]