Glacial erratic boulders of King County are large

glacial erratic A glacial erratic is a glacially deposited rock (geology), rock differing from the type of country rock (geology), rock native to the area in which it rests. Erratics, which take their name from the Latin word ' ("to wander"), are carried by gla ...

boulders In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In c ...

of rock which were moved into King County,

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

by glacial action during previous

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...

s. The Pleistocene ice age glaciation of

Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...

created many of the geographical features of the region, including Puget Sound itself, and the erratics are one of the remnants of that age. According to Nick Zentner of

Central Washington University Central Washington University (CWU) is a public university in Ellensburg, Washington, United States. Founded in 1891, the university consists of four divisions: the President's Division, Business and Financial Affairs, Operations, and Academi ...

Department of Geological Sciences, "Canadian rocks restrewn all over the Puget lowland, stretching from the Olympic Peninsula clear over to the Cascade Range." Erratics can be found at altitudes up to about in the Enumclaw area, along with kames,

drumlin A drumlin, from the Irish word ("little ridge"), first recorded in 1833, in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated till or groun ...

s, and perhaps also the unique

Mima mounds Mima mounds are low, flattened, circular to oval, domelike, natural mounds that are composed of loose, unstratified, often gravelly sediment that is an overthickened A horizon. These mounds range in diameter from to more than ; in height to ...

. The soil of Seattle, the county's (and state's) largest city, is approximately 80%

glacial drift In geology, drift is a name for all sediment (clay, silt, sand, gravel, boulders) transported by a glacier and deposited directly by or from the ice, or by glacial meltwater. Drift is often subdivided into unstratified (unsorted) drift ( glac ...

, most of which is Vashon glacial deposits (

till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

), 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)., 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). Boulders greater than 3 meters in diameter are "rare" in the Vashon till, but can be found, as seen in the table below.

List of boulders

References

;Notes ;Sources * *. * * * * * * * * * *

External links

Washington glacial erratics project
at University of Washington dept. of earth and space sciences {{Washington erratics Landforms of King County, Washington King County

List of boulders

See also

References

Further reading

External links