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Boulder, city, United States


city (1990 pop. 83,312), seat of Boulder co., N central Colo.; inc. 1871. A Rocky Mountain resort and a suburb of Denver, it is the seat of the Univ. of Colorado (1876). Industries include aerospace and biological research; the manufacture of machinery, electric, electronic, and computer equipment, and medical supplies; and software development. Boulder is home to the National Center for Atmospheric Research and other government and private research operations and is known as a mountain sports and "New Age" mecca.

boulder, in geology


large rock fragment formed by detachment from its parent consolidated rock by weathering and erosion. In engineering and geology, especially in the United States, the term is applied to loose rocks having specific sizes according to various systems of classification, i.e. the Wentworth scale (for C. K. Wentworth, American geologist), where a boulder has one linear dimension of at least 10.1 in. (25.4 cm). Boulders transported by glacial ice are usually referred to as glacial erratics; glacial boulder fields, or felsenmeer, containing large blocks of angular rock broken from intense frost action are evidence that the region has experienced glacial action in the past. See driftdrift,
deposit of mixed clay, gravel, sand, and boulders transported and laid down by glaciers. Stratified, or glaciofluvial, drift is carried by waters flowing from the melting ice of a glacier.
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; morainemoraine
, a formation composed of unsorted and unbedded rock and soil debris called till, which was deposited by a glacier. The till that falls on the sides of a valley glacier from the bounding cliffs makes up lateral moraines, running parallel to the valley sides.
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A worn rock with a diameter exceeding 256 millimeters. Also spelled bowlder.


A naturally rounded rock fragment larger than 10 in. (25 cm) in diameter; used for crude walls and foundations, generally in mortar.


1. a smooth rounded mass of rock that has a diameter greater than 25cm and that has been shaped by erosion and transported by ice or water from its original position
2. Geology a rock fragment with a diameter greater than 256 mm and thus bigger than a cobble