Boulders

BOULDERS (EN: boulder, cobble; DE: Geroll; FR: cailloux, galets, blocs; ES: cantos rodados; RU: валуны) are the large rounded fragments and blocks of the rocks, which are having the dimensions from 10 to 100 centimetres. They distinguish the small (10-25 centimetres), medium (25-50 centimetres), and large (50-100 centimetres) boulders. Boulders acquire the rounded shape during the transfer by the water flows and glaciers. Boulders are distributed within the alluvial, glacial, proalluvial, and diluvial depositions. The boulders, which are formed by the rocks or useful minerals, which may be found relatively rarely, according to which there is possible to determine the directions of the ways for the transfer of the boulders, and the places of the bedrock outcrops of these rocks, are named as the governing boulders; the latter boulders may serve as the search indicator for the useful minerals. Boulders usually belong to the composition of the sand-gravel depositions, while in the individual cases, the boulder fraction may prevail (for example, at the Aksai gravel-boulder deposit within the Alma-Ata province of the Kazakh SSR, the content of the boulders reaches up to 60%). Boulders are used for the obtainment of the crushed gravel, for the construction of the foundations, for the strengthening of the earthen slopes, and as the stowing material within the body of the dams. In the individual cases, the clusters of the boulders may be of interest as the raw material for the facing stone.