Editing Paleogene (section)

=== Pacific Ocean ===
At the beginning of the Paleogene, the Pacific Ocean consisted of the Pacific, Farallon, [[Kula plate|Kula]] and [[Izanagi plate|Izanagi]] plates. The central Pacific plate grew by seafloor spreading as the other three plates were subducted and broken up. In the southern Pacific, seafloor spreading continued from the Late Cretaceous across the Pacific–Antarctic, Pacific-Farallon and Farallon–Antarctic mid ocean ridges.<ref name=":1" />

The Izanagi-Pacific spreading ridge lay nearly parallel to the East Asian subduction zone and between 60–50 Ma the spreading ridge began to be subducted. By c. 50 Ma, the Pacific plate was no longer surrounded by spreading ridges, but had a subduction zone along its western edge. This changed the forces acting on the Pacific plate and led to a major reorganisation of plate motions across the entire Pacific region.<ref name=":18">{{Cite journal |last1=Seton |first1=Maria |last2=Flament |first2=Nicolas |last3=Whittaker |first3=Joanne |last4=Müller |first4=R. Dietmar |last5=Gurnis |first5=Michael |last6=Bower |first6=Dan J. |date=2015-03-28 |title=Ridge subduction sparked reorganization of the Pacific plate-mantle system 60–50 million years ago |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015GL063057 |journal=Geophysical Research Letters |language=en |volume=42 |issue=6 |pages=1732–1740 |doi=10.1002/2015GL063057 |bibcode=2015GeoRL..42.1732S |issn=0094-8276}}</ref> The resulting changes in stress between the Pacific and [[Philippine Sea plate|Philippine Sea]] plates initiated subduction along the [[Izu–Bonin–Mariana Arc|Izu-Bonin-Mariana]] and [[Kermadec-Tonga subduction zone|Tonga-Kermadec]] arcs.<ref name=":18" /><ref name=":16" />

Subduction of the Farallon plate beneath the American plates continued from the Late Cretaceous.<ref name=":1" /> The Kula-Farallon spreading ridge lay to its north until the Eocene (c. 55 Ma), when the northern section of the plate split forming the [[Juan de Fuca plate|Vancouver/Juan de Fuca plate]].<ref name=":16" /> In the Oligocene (c. 28 Ma), the first segment of the Pacific–Farallon spreading ridge entered the North American subduction zone near [[Baja California]]<ref name=":19">{{Cite journal |last1=Wright |first1=Nicky M. |last2=Seton |first2=Maria |last3=Williams |first3=Simon E. |last4=Müller |first4=R. Dietmar |date=2016-03-01 |title=The Late Cretaceous to recent tectonic history of the Pacific Ocean basin |url=https://www.sciencedirect.com/science/article/abs/pii/S001282521530074X |journal=Earth-Science Reviews |volume=154 |pages=138–173 |doi=10.1016/j.earscirev.2015.11.015 |bibcode=2016ESRv..154..138W |issn=0012-8252}}</ref> leading to major strike-slip movements and the formation of the [[San Andreas Fault]].<ref name=":1" /> At the Paleogene-Neogene boundary, spreading ceased between the Pacific and Farallon plates and the Farallon plate split again forming the present date [[Nazca plate|Nazca]] and [[Cocos plate|Cocos]] plates.<ref name=":16" /><ref name=":19" />

The Kula plate lay between Pacific plate and North America. To the north and northwest it was being subducted beneath the [[Aleutian Trench|Aleutian trench]].<ref name=":1" /><ref name=":16" /> Spreading between the Kula and Pacific and Farallon plates ceased c. 40 Ma and the Kula plate became part of the Pacific Plate.<ref name=":1" /><ref name=":16" />

==== Hawaii hotspot ====
The [[Hawaiian–Emperor seamount chain|Hawaiian-Emperor seamount chain]] formed above the [[Hawaii hotspot|Hawaiian hotspot]]. Originally thought to be stationary within the mantle, the hotspot is now considered to have drifted south during the Paleocene to early Eocene, as the Pacific plate moved north. At c. 47 Ma, movement of the hotspot ceased and the Pacific plate motion changed from northward to northwestward in response to the onset of subduction along its western margin. This resulted in a 60 degree bend in the seamount chain. Other seamount chains related to hotspots in the South Pacific show a similar change in orientation at this time.<ref>{{Cite journal |last1=Jiang |first1=Zhaoxia |last2=Li |first2=Sanzhong |last3=Liu |first3=Qingsong |last4=Zhang |first4=Jianli |last5=Zhou |first5=Zaizheng |last6=Zhang |first6=Yuzhen |date=2021-04-01 |title=The trials and tribulations of the Hawaii hot spot model |url=https://www.sciencedirect.com/science/article/abs/pii/S001282522100043X |journal=Earth-Science Reviews |volume=215 |pages=103544 |doi=10.1016/j.earscirev.2021.103544 |bibcode=2021ESRv..21503544J |issn=0012-8252 |access-date=2024-08-19 |archive-date=2023-11-08 |archive-url=https://web.archive.org/web/20231108111121/https://www.sciencedirect.com/science/article/abs/pii/S001282522100043X |url-status=live }}</ref>