Glacial erratic boulders of King County, Washington

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File:King County Erratics.png
Locations of glacial erratics in King County, Washington

Glacial erratic boulders of King County are large glacial erratic boulders of rock which were moved into King County, Washington by glacial action during previous ice ages.

The Pleistocene ice age glaciation of Puget Sound created many of the geographical features of the region, including Puget Sound itself,[1] and the erratics are one of the remnants of that age.[2] According to Nick Zentner of Central Washington University Department of Geological Sciences, "Canadian rocks [are] strewn all over the Puget lowland, stretching from the Olympic Peninsula clear over to the Cascade Range."[3] Erratics can be found at altitudes up to about 1,300–1,600 feet (400–490 m) in the Enumclaw area,[4] along with kames, drumlins,[5] and perhaps also the unique Mima mounds.[6] The soil of Seattle, the county's (and state's) largest city, is approximately 80% glacial drift, most of which is Vashon glacial deposits (till),[7] and nearly all of the city's major named hills are characterized as drumlins (Beacon Hill, First Hill, Capitol Hill, Queen Anne Hill) or drift uplands (Magnolia, West Seattle).[3][8] Boulders greater than 3 meters in diameter are "rare" in the Vashon till,[2] but can be found, as seen in the table below.

List of boulders

Name and description Height Image
Beaver Lake Preserve erratics are glacial erratics in and around protected space in Sammamish, weighing up to 100 tons.[9] The lake is a kettle lake also due to glaciation.[9] In the 1950s otters would reportedly rest on the large erratic at the north end of Beaver Lake.[10]

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Big Rock is a 8-foot (2.4 m) tall glacial erratic in the city of Duvall. A Duvall road, a park, and several businesses are named after it.[11][12] The rock, and two non-native sequoias adjacent to it probably planted by area pioneers, are a local landmark.[13] The erratic lies in what is said to be the smallest King County park, 20 by 70 feet (6.1 m × 21.3 m) in extent, that barely contains the rock and sequoias.[14] The two lanes of Big Rock Road used to split into a wye around the rock, until a shopping center was built nearby in the 1990s.[14][13]

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8 feet (2.4 m) File:Big Rock erratic in Duvall north face.JPG
Big Rock Park erratic is a glacial erratic in the eponymous city park in Sammamish. Sammamish considered naming the park "Bigger Rock Park" to distinguish it from the identically named park in Duvall.[15]

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Cascadia College erratic

Saved from destruction by sit-in conducted by Cascadia College environmental politics students, and relocated away from construction site.[16][17][18][19][20] The rock, which several students occupied during the sit-in, was about 2 meters across before being jackhammered to two thirds its original size.[19]

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3 feet (0.91 m) File:Cascadia College erratic 3.jpg
Des Moines Beach erratic near Des Moines Beach Park in Des Moines

8 by 6 by 4.5 feet (2.4 m × 1.8 m × 1.4 m)[21]

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4.5 feet (1.4 m) File:Des Moines Beach erratic front.JPG
Discovery Park beach erratics

Four or more erratics on beach below Discovery Park. Largest is 15.33 feet (4.67 m) high, 69.5 feet (21.2 m) in circumference.[22]

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15.33 feet (4.67 m) File:Eastern Discovery Park beach erratic, yardstick.jpg
Fantastic Erratic is a glacial erratic in Cougar Mountain Regional Wildland Park near Bellevue. It is approximately the size of a two-car garage, and 15 feet (4.6 m) high.[23][24]

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15 feet (4.6 m) File:Fantastic Erratic on Cougar Mountain.jpg
Four Mile Rock (also Fourmile Rock) is a round granite erratic, approximately 20 feet (6.1 m) across, in the intertidal zone below Seattle's Magnolia Bluff and 60 yards offshore.[25] It has had a navigational light placed on it and appears on nautical charts.[26]

Native Americans called the rock LE'plEpL, also written La'pub, and also called it Tele'tla (meaning "rock"). A legend says that a hero named Sta'kub could throw a giant cedar and hazel branch dragnet over the rock while standing at the beach.[27]

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15 feet (4.6 m) File:Fourmile Rock, Magnolia at low tide, with yardstick.JPG
Unnamed erratic at Highline Community College. Granitic with "textbook en echelon dikes". 21 by 12 feet (6.4 m × 3.7 m) and 9 feet (2.7 m) high.[29]

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9 feet (2.7 m) File:Highline CC erratic.jpg
Homage artwork boulders, three locations in Bridle Trails neighborhood of Bellevue,[30] using "local granite boulders".[31] Exposed granitic bedrock does not occur in western King County.[32]

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File:Bridle Trails boulders on 24th.jpg
Leschi Park erratic in Seattle's Leschi Park is a sandstone erratic with many embedded bivalve fossils. Analysis of the fossils and the rock's minerals shows it may have come from the Nooksack Group near Mount Baker, or from the Harrison Lake area of southern British Columbia.[33]

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5 feet (1.5 m) File:Leschi erratic east face, yardstick.JPG
Lone Rock in Tiger Mountain State Forest on Tiger Mountain[34][35]

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c. 15 feet (4.6 m) No image.png
Ravenna Park erratic in Ravenna Park in Seattle, a granodiorite stone three yards (2.75 meters) tall in Ravenna Creek with a wooden footbridge that wraps around it.[36][37]

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c. 10 feet (3.0 m) File:Ravenna park erratic east face, yardstick.JPG
Talus Rocks, a collection of piled erratics in Tiger Mountain State Forest on Tiger Mountain,[38][39][40] forming rock caves (called "Devil's Dens" in New England[41]) said to be among the largest in Washington.[42]

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c. 12 feet (3.7 m) File:Talus Rocks, Tiger Mountain, Washington - round boulder with yardstick.JPG
Thornton Creek erratic near 17th Ave. NE and NE 104th St., in Seattle Parks' Kingfisher Natural Area. A local conservation group calls the area containing the boulder "Erratic Flats".[43]

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c. 8 feet (2.4 m) File:Thornton Creek erratic with yardstick.JPG
Wedgwood Rock is a glacial erratic (and known to geologists as the "Wedgwood Erratic") near the neighborhood of Wedgwood in Seattle, Washington. It is 80 feet (24 m) in circumference and 19 feet (5.8 m) or 26 feet (8 m)[44] in height. Since 1970 it has been an offense punishable by a $100 fine to climb the rock.[45]

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26 feet (8 m) File:Wedgwood Rock, yardstick.JPG
Anonymous erratic in Wedgwood Square Park[46]

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c. 4 feet (1.2 m) File:Wedgwood Square erratic, yardstick.JPG

References

Notes
  1. Troost & Booth 2008, p. 12 "During the period that the Vashon-age ice sheet covered the region, a tremendous volume of pressurized water was carried by subglacial streams and was responsible for carving the deep troughs of the modern Puget Sound."
  2. 2.0 2.1 Booth, Troost & Shimel 2008.
  3. 3.0 3.1 Geology of Seattle and the Puget Sound on YouTube, narrated by Nick Zentner (Central Washington University Department of Geological Sciences). Uploaded March 2, 2015 by Hugefloods.com (Nick Zentner and Tom Foster: Discover the Ice Age Floods).
  4. Bretz 1913, p. 34.
  5. Goldstein 1994.
  6. Pailthorp, Bellamy, "Mima Mounds continue to mystify scientists", KPLU Wonders, KPLU<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. Troost & Booth 2008, p. 2.
  8. Troost & Booth 2008, p. 5.
  9. 9.0 9.1 D. Bruce Morgan, Beaver Lake Geology, Sammamish, Washington: Beaver Lake Community Club<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. Morgan 2012, p. 1.
  11. Dave Tucker (April 12, 2011), Dave Tucker, ed., "'Big Rock' (another one) in Duvall, Washington", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. Duvall Visitors Guide (PDF), Duvall Chamber of Commerce, 2015<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  13. 13.0 13.1 Louis T. Corsaletti (March 10, 1998), "Big Rock, Big Trees, Little Park -- New Safeway Being Built Near Tiny Duvall Landmark", The Seattle Times<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  14. 14.0 14.1 "Washington Rock is County Park", Reading Eagle, Reading, Pennsylvania, p. 42, May 15, 1977<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. http://www.issaquahreporter.com/news/193878931.html
  16. "Cascadia Community College students move into action to save a piece of geologic history", Bothell/Kenmore Reporter, February 22, 2010<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  17. http://www.komonews.com/communities/bothell/196330141.html
  18. Students Sit In to Save Boulder at Cascadia (Press release), Cascadia Community College, February 12, 2010, archived from the original on 2010-05-27<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  19. 19.0 19.1 Kristi O'Harran (February 23, 2010), "Cascadia College rock-solid about its boulder", Everett Herald<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  20. Micah Silke (September 26, 2012), "Construction: UWB 3 and the Sports and Recreation Complex", Husky Herald, University of Washington at Bothell<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  21. Bud Hardwick (c. 2011), Dave Tucker, ed., "Des Moines Beach erratic", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  22. https://nwgeology.wordpress.com/the-fieldtrips/glacial-erratic-field-trips/seattle-area-glacial-erratics/beach-erratics-at-discovery-park-seattle/
  23. Greg Kulseth (June 30, 2011), Dave Tucker, ed., "Fantastic Erratic, Cougar Mountain Regional Park, King County", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  24. Stekel 2009, p. 152.
  25. Ray 1891, p. 37.
  26. Puget Sound – Shilshole Bay to Commencement Bay (PDF) (Natucial chart), National Oceanic and Atmospheric Administration National Ocean Service, Office of Coast Survey, 2015, NOAA Chart 18474<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  27. Waterman 1922, p. 188.
  28. U.S. Geological Survey Geographic Names Information System: Fourmile Rock
  29. Magmatist (February 21, 2012), Dave Tucker, ed., "Thin en echelon dikes in the Highline Community College erratic", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  30. Bridle Trails art, City of Bellevue Department of Planning & Community Development, 2014<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  31. Bruce Myers, Bridle Trials Artist's Statement (Homage) (PDF), City of Bellevue Arts Program<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  32. Livingston 1971, p. 31 Figure 12, "Relation of metallic ore deposits to granitic rocks in King County, Washington"
  33. Dave Tucker; Doug McKeever; Wes Gannaway (2011), Dave Tucker, ed., "The fossil-rich erratic at Leschi Park", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  34. Alan Gibbs, Tiger Mountain Trail north, Washington Trails Association<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  35. Jon F. Stanley (November 1, 2008), Tiger Mountain State Forest trail map (PDF), switchbacks.com<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  36. Hutton 2012.
  37. Dave Tucker (May 6, 2011), Dave Tucker, ed., "Ravenna Park granodiorite erratic, Seattle", Northwest Geology Field Trips<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  38. Weber & Stevens 2010, p. 101.
  39. Dolan 2004, p. 167.
  40. Talus Rock trail, Washington Trails Association, retrieved 2015-04-20<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  41. Daniel V. Boudillion (2009), "Picture Glossary of New England Lithic Constructions", New England megaliths field journal<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  42. West Tiger Mountain NRCA, Washington State Department of Natural Resources, retrieved 2015-04-20<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  43. Kingfisher Forest Stewards (November 2, 2014), Kingfisher Natural Area events, Green Seattle Partnerships<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  44. Troost & Booth 2008.
  45. David Wilma (July 24, 2001), Seattle Neighborhoods: Wedgwood -- Thumbnail History, HistoryLink<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  46. http://wedgwoodinseattlehistory.com/2012/03/15/parks-in-wedgwood/
Sources

Further reading

External links