Editing Lake Washington (section)

==Geography==
Lake Washington's basin was formed by glacial processes associated with the Puget lobe of the [[Cordilleran Ice Sheet]] during the [[Vashon Glaciation]], likely through a combination of preferential erosion of weak rock and sediments by the glacier itself and by [[Subglacial channel|subglacial meltwater]] during the glacier's retreat. At the end of the [[Pleistocene]], the basin that is now Lake Washington connected directly to the channels of [[Puget Sound]] through the north end of the Duwamish Valley.<ref name="DuwamishConnection">{{cite web | title=Holocene Geologic History and Sedimentology of the Duwamish and Puyallup Valleys, Washington|url=https://www.dnr.wa.gov/Publications/ger_misc_holocene_duwamish_puyallup.pdf| access-date=2025-01-23 }}</ref> The basin may or may not have been a waterway at this point, as [[eustatic sea level]]s were approximately {{convert|150|m|ft|abbr=off|sp=us}} lower than at present<ref name="SeaLevels">{{cite web | title=Sea level and global ice volumes from the Last Glacial Maximum to the Holocene|url=https://www.pnas.org/doi/10.1073/pnas.1411762111| access-date=2025-01-23 }}</ref> and the land around Seattle was about {{convert|75|-|85|m|ft|sp=us}} lower due to [[isostatic depression]] from the weight of the glacier.<ref name="IsostaticEffects">{{cite web | title=Isostatic Effects of the Last Glaciation in the Puget Lowland|url=https://pubs.usgs.gov/of/1981/0370/report.pdf| access-date=2025-01-23 }}</ref> However, the rapid sea level rise from the end of the [[Pleistocene]] through the early [[Holocene]] had flooded the Duwamish Valley and Lake Washington within a couple thousand years. Lake Washington did not become a freshwater lake, isolated from Puget Sound, until some time after 5,700 years [[Before Present]], when sedimentation in the Duwamish Valley closed off its southern end.<ref name="DuwamishConnection">{{cite web | title=Holocene Geologic History and Sedimentology of the Duwamish and Puyallup Valleys, Washington|url=https://www.dnr.wa.gov/Publications/ger_misc_holocene_duwamish_puyallup.pdf| access-date=2025-01-23 }}</ref> The new lake, lacking any other outlets, drained south through the [[Black River (Duwamish River tributary)|Black River]] into the Duwamish Valley and, ultimately, Puget Sound until the construction of the [[Lake Washington Ship Canal]] in 1916.<ref name="blackriver">{{cite web | title=Black River disappears in July 1916|url=http://www.historylink.org/File/686| access-date=2018-02-09 }}</ref>