The geological timeline of Western North America includes significant geological events over millions of years in the evolution of Western North America, including several 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).
External links Geologic History of California: A Brief Overview by Joel Michaelsen Dating of the Ages of Three Plutonic Episodes in the Sierra