An erratic is a fragment of glacial till carried by ice, sometimes for hundreds of miles, and deposited on rocks of a different geologic composition. Erratics were once considered evidence of a biblical flood, but in the 19th Century scientists gradually came to accept that erratics pointed to an ice age in Earth's past. Many erratics found in the United States have their origin in Canada. Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...
Erratic Rock State Park in Oregon contains a 40 ton specimen, the largest erratic found in the Willamette Valley. A fern-covered erratic the size of a garage is found on Cougar Mountain near Seattle. State nickname: Beaver State Other U.S. States Capital Salem Largest city Portland Governor Ted Kulongoski (D) Senators Ron Wyden (D) Gordon Smith (R) Official language(s) None Area 255,026 km² (9th) - Land 248,849 km² - Water 6,177 km² (2. ... The Willamette Valley The Willamette Valley The Willamette Valley is the region in northwest Oregon in the United States that surrounds the Willamette River as it proceeds northward from its emergence from mountains near Eugene to its confluence with the Columbia River. ... // Cougar Mountain Cougar Mountain is a 22 square mile cluster of highlands in the suburbs of Seattle, Washington, southeast of the intersection of Interstate 90 and I-405. ... City nickname Emerald City City bird Great Blue Heron City flower Dahlia City mottos The City of Flowers The City of Goodwill City song Seattle, the Peerless City Mayor Greg Nickels County King County Area - Total - Land - Water - % water 369. ...
Sources
Imbrie, J. & K. P. Imbrie. Ice Ages, Enslow Publishers, Hillside, New Jersey, 1979.
Ice erosion is caused by movement of ice, typically as glaciers.
Glaciers can scrape down a slope and break up rock and then transport it, leaving moraines, drumlins, and glacial erratics in its wake typically at the terminus or during glacial retreat.
Ice wedging is the weathering process where water trapped in tiny rock cracks freezes and expands, causing the breakup of the rock.
Due to the positions of Greenland, Antarctica, and the northern portions of Europe, Asia, and North America in polar regions, the Earth today is considered prone to ice age glaciations.
Evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics.
Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret.
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