Lake Superior's Rift Is Over a Billion Years Old. The Lake Isn't.

Lake Superior's rift is over a billion years old. The lake isn't. In 2013, Shi Yong Yu, Steven Colman and Glenn Milne dated basal peat at Bark Bay Slough, Wisconsin, and placed Sault Ste. Marie's emergence as Superior's controlling outlet at about 1,250 calibrated years before 1950: around the year 700. A 2012 beach-ridge study led by John Johnston put the final separation from Lakes Michigan and Huron at 1,060 years, give or take 100. The shore's rock formed about 1.1 billion years ago. The lake's own level is medieval. This is the documented story of three ages in one place: a rift that stopped before an ocean could form, the glaciers that sculpted the basin about 10,000 years ago, and an outlet at the Soo that took control of Superior's level only in the Middle Ages, on ground that is still rising. In this video: About 1.1 billion years ago: the Midcontinent Rift stretches the crust and floods it with lava; it stops before an ocean forms; why is still unknown 1990: Davis and Paces date the Keweenaw's Greenstone Flow at 1,094 million years, give or take 1.5 million Sleeping Giant's diabase against Isle Royale and Keweenaw basalt: an intrusion and a lava flow from one rifting 1986 to 2020: GLIMPCE's seismic lines; Cannon's deep central graben (1989); Tréhu's fill at least 30 km thick, crust 55 to 60 km under the axis, about 40 under the south shore (1991); Grauch's alternate reading (2020) November 1913: flags for Superior around 10 am on Friday the 7th; no radio aboard; 235 or more than 250 lives by the NWS's two accounts; the Henry B. Smith, crew of 25, found May 24th, 2013, about 30 miles north of Marquette, more than 500 feet down Isle Royale's wolves: an ice bridge in the winter of 1948; a relocated wolf walks back to the mainland on January 31st, 2019 Ice: 94.9 percent cover on March 9th, 2019; 22.6 percent the next winter Glacial grooves in Keweenaw basalt; float copper; Glacial Lake Duluth over the Apostle Islands; Isle Royale's beach ridges and terraces 191 years: the EPA's retention time, a turnover measure, not a residence time November 10th, 1975: the Edmund Fitzgerald sinks about 17 miles from Whitefish Bay; 29 lost (NTSB) The Saint Marys Rapids drop more than 6 metres in a little over a kilometre; locks since 1797; the Board of Control since 1914 2007 and 2012: Johnston's beach ridges; four strandplains, 321 foreshore elevations, 56 luminescence ages; separation at 1,060 years, give or take 100 The International Great Lakes Datum, updated about every 25 to 30 years for crustal movement: uplift north, subsidence south Key figures: about 1.1 billion years; 1,094 million years; at least 30 km of rift fill; 94.9 and 22.6 percent; 191 years; about 1,250 calibrated years before 1950; 1,060 years, give or take 100. Timeline: 1797, 1913, 1914, 1948, 1975, 1986, 1989, 1990, 1991, 2007, 2012, 2013, 2019, 2020. Watch next:    • The Lake Count Crowns Canada. It Can't Spl...   The Lake Count Crowns Canada: the lake count that crowns Canada and still hands all four shared Great Lakes to the United States    • Hudson Bay's Ice Retreated 8,000 Years Ago...   Hudson Bay's Ice Retreated 8,000 Years Ago: the ice that retreated 8,000 years ago and the gravity that kept the evidence Chapters: 0:00 The drop at the Soo 2:04 Deepest and coldest 2:54 Sleeping Giant 5:05 The Midcontinent Rift 5:49 Dating the flows 7:23 November 1913 8:55 GLIMPCE, 1986 11:35 A wolf crosses the ice 12:59 Two shores, one fold 14:03 Ice, grooves and copper 16:21 Moraines and terraces 17:04 The Apostle Islands 18:53 191 years 19:31 The land still rising 20:41 The Edmund Fitzgerald 21:42 The Saint Marys Rapids 22:08 One level, then two 23:30 Beach ridges 25:25 Peat at Bark Bay 27:31 Regulating the exit 29:46 The datum 31:36 Back to the Giant 32:31 The ledger Every claim in this video is drawn from the documented record: the US Geological Survey and the National Park Service; Stein and colleagues, Park Science, 2015; Davis and Paces, 1990 (USGS Geolex); Cannon and others, 1989; Tréhu and others, 1991; Grauch and others, 2020; Johnston and others, 2007 and 2012; Yu, Colman and Milne, 2013; the US EPA; NOAA GLERL; NOAA's International Great Lakes Datum pages; the National Weather Service's two 1913 accounts; the Duluth News Tribune, 2013; the NTSB; the International Joint Commission; Ontario Parks; Parks Canada. The two separation dates are separate study estimates, not one anniversary; the 2012 figure is a luminescence age, spoken with its uncertainty. Over a billion is a floor; the sources say about 1.1 billion. Living persons are described by their published work only. Subscribe and turn on notifications. Tell us in the comments: is there a shoreline photograph, local record or published study that adds to this history of Superior? Give us the place, the date and a source we can check. #Canada #Geography #LakeSuperior #GreatLakes #Ontario #SaultSteMarie #IsleRoyale #Keweenaw #MidcontinentRift #SleepingGiant