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| ==Origin== | | ==Origin== |
| New Latin, from [[Latin]], spread, bed, from neuter of ''stratus'', past participle of ''sternere'' to spread out | | New Latin, from [[Latin]], spread, bed, from neuter of ''stratus'', past participle of ''sternere'' to spread out |
− | *[http://en.wikipedia.org/wiki/16th_century 1599] | + | *[https://en.wikipedia.org/wiki/16th_century 1599] |
| ==Definitions== | | ==Definitions== |
| *1: a bed or layer artificially made | | *1: a bed or layer artificially made |
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| *5: a statistical subpopulation | | *5: a statistical subpopulation |
| ==Description== | | ==Description== |
− | In geology and related fields, a ''stratum'' (plural: '''strata''') is a layer of [http://en.wikipedia.org/wiki/Sedimentary_rock sedimentary rock] or [[soil]] with internally consistent characteristics that distinguish it from other layers. The "stratum" is the fundamental unit in a stratigraphic column and forms the basis of the study of [http://en.wikipedia.org/wiki/Stratigraphy stratigraphy]. | + | In geology and related fields, a ''stratum'' (plural: '''strata''') is a layer of [https://en.wikipedia.org/wiki/Sedimentary_rock sedimentary rock] or [[soil]] with internally consistent characteristics that distinguish it from other layers. The "stratum" is the fundamental unit in a stratigraphic column and forms the basis of the study of [https://en.wikipedia.org/wiki/Stratigraphy stratigraphy]. |
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− | When planning [http://en.wikipedia.org/wiki/Civil_engineering civil engineering] projects or other large constructions, the ''strata'' of the area where the construction takes place is a significant [[factor]] in [[design]] [[decisions]]. For example if a [http://en.wikipedia.org/wiki/Canal canal] is to be built on a route where the strata are not watertight, the canal will have to be lined with some form of waterproof material (usually [[clay]]). | + | When planning [https://en.wikipedia.org/wiki/Civil_engineering civil engineering] projects or other large constructions, the ''strata'' of the area where the construction takes place is a significant [[factor]] in [[design]] [[decisions]]. For example if a [https://en.wikipedia.org/wiki/Canal canal] is to be built on a route where the strata are not watertight, the canal will have to be lined with some form of waterproof material (usually [[clay]]). |
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− | Each layer is generally one of a number of [[parallel]] layers that lie one upon another, laid down by [[natural]] forces. They may extend over [http://en.wikipedia.org/wiki/1_E11_m² hundreds of thousands of square kilometers] of the [[Earth]]'s surface. Strata are typically seen as bands of different [[colored]] or differently structured material exposed in [http://en.wikipedia.org/wiki/Cliff cliffs], road cuts, [http://en.wikipedia.org/wiki/Quarry quarries], and [[river]] banks. Individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a specific mode of [http://en.wikipedia.org/wiki/Deposition_(sediment) deposition]: river silt, beach sand, coal swamp, sand dune, lava bed, etc. | + | Each layer is generally one of a number of [[parallel]] layers that lie one upon another, laid down by [[natural]] forces. They may extend over [https://en.wikipedia.org/wiki/1_E11_m² hundreds of thousands of square kilometers] of the [[Earth]]'s surface. Strata are typically seen as bands of different [[colored]] or differently structured material exposed in [https://en.wikipedia.org/wiki/Cliff cliffs], road cuts, [https://en.wikipedia.org/wiki/Quarry quarries], and [[river]] banks. Individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a specific mode of [https://en.wikipedia.org/wiki/Deposition_(sediment) deposition]: river silt, beach sand, coal swamp, sand dune, lava bed, etc. |
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− | Geologists [[study]] rock strata and categorize them by the material of beds. Each distinct layer is typically assigned to the name of sheet, usually based on a town, [[river]], [[mountain]], or region where the formation is [[exposed]] and available for study. For example, the [http://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale] is a thick exposure of dark, occasionally fossiliferous, shale exposed high in the [http://en.wikipedia.org/wiki/Canadian_Rockies Canadian Rockies] near Burgess Pass. Slight distinctions in material in a formation may be described as "members" (or sometimes "beds"). Formations are collected into "groups" while groups may be collected into "supergroups". | + | Geologists [[study]] rock strata and categorize them by the material of beds. Each distinct layer is typically assigned to the name of sheet, usually based on a town, [[river]], [[mountain]], or region where the formation is [[exposed]] and available for study. For example, the [https://en.wikipedia.org/wiki/Burgess_Shale Burgess Shale] is a thick exposure of dark, occasionally fossiliferous, shale exposed high in the [https://en.wikipedia.org/wiki/Canadian_Rockies Canadian Rockies] near Burgess Pass. Slight distinctions in material in a formation may be described as "members" (or sometimes "beds"). Formations are collected into "groups" while groups may be collected into "supergroups". |
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| [[Category: Earth Science]] | | [[Category: Earth Science]] |