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Roundness is the degree of smoothing due to abrasion of sedimentary particles. It is expressed as the ratio of the average radius of curvature of the edges or corners to the radius of curvature of the maximum inscribed sphere. ==Measure of roundness== Rounding, roundness or angularity are terms used to describe the shape of the corners on a particle (or clast) of sediment. Such a particle may be a grain of sand, a pebble, cobble or boulder. Although roundness can be numerically quantified, for practical reasons geologists typically use a simple visual chart with up to six categories of roundness: *Very angular: corners sharp and jagged *Angular *Sub-angular *Sub-rounded *Rounded *Well-rounded: corners completely rounded Rounding of sediment particles can indicate the distance and time involved in the transportation of the sediment from the source area to where it is deposited. Speed of rounding will depend on composition, hardness and mineral cleavage. For example, a soft claystone pebble will obviously round much faster, and over a shorter distance of transport, than a more resistant quartz pebble. The rate of rounding is also affected by the grain size and energy conditions. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Roundness (geology)」の詳細全文を読む スポンサード リンク
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