Pebble
314610
221858646
2008-06-26T12:06:30Z
Hugo.arg
1456073
iw
{{wiktionary}}
[[Image:Wave Retreating from Pebbles.jpg|thumb|right|Sea wave polishing pebbles into rounded corners]]
[[Image:Pebbles-oliv-e.jpg|thumb|right|Pebbles]]
{{Otheruses}}
A '''pebble''' is a [[clastic rocks|clast]] of [[rock (geology)|rock]] with a [[particle size]] of 4 to 64 [[millimeter]]s based on the [[Krumbein]] phi scale of [[sedimentology]]. It is generally described to be larger than [[gravel]] and smaller than [[cobble]]. A rock made predominantly of pebbles is termed a [[conglomerate (geology)|conglomerate]].
Pebble [[tools]] are among the earliest known man-made artifacts, dating from the [[Palaeolithic]] period of human history. They have been found at [[Olduvai Gorge]] (1.85 million years ago{{Fact|date=April 2007}}) and at [[Longuopo]] in [[China]] (1.8 to 1.5 MYA{{Fact|date=April 2007}}).
A beach composed chiefly of surface pebbles is commonly termed a [[shingle beach]], which has [[armor (hydrology)|armoring characteristics]] with respect to wave [[erosion]]; moreover, this type of beach has unusual ecological niches that may provide [[habitat]] for a number of [[rare species|rare]] and [[endangered species]].
==See also==
* [[Gravel]]
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[[Category:Sedimentology]]
[[Category:Granular materials]]
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[[de:Kieselstein]]
[[et:Veeris]]
[[fr:Galet]]
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[[nl:Grind]]
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[[pl:Otoczak (geologia)]]
[[pt:Seixo (rocha)]]
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