stratum

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☒ The earth's crust contains stratas of hot, dry rock and natural aquifers—C. Wheater et al., 1990.

The singular of strata. See stratified sampling.

In geology, a layer of distinctive deposits with surfaces roughly parallel to those above and below.

A bed of sedimentary rock or earth.

Pl. strata [L.] a sheetlike mass of tissue of fairly uniform thickness; distinct layers making up various tissues or organs, as of the skin, brain, retina.

• s. avasculosum — the avascular stratum in the margin of the iris.
• s. basale — the mitotically active, basal layer of the epidermis, consisting of columnar to cuboidal keratinocytes on a basement membrane.
• s. corneum — the outer horny layer of the epidermis, consisting of cells that are non-nucleated, keratinized and desquamating.
• s. germinativum — in the epidermis, located between the stratum basale and the stratum granulosum. Together with the basal layer, called the malpighian layer. Called also germinative layer.
• s. granulosum — 1. the layer of cells between the stratum lucidum and the stratum spinosum of the skin, very thin and not always present. Called also the granular layer.
— 2. the deep layer of the cortex of the cerebellum. — 3. the layer of follicle cells lining the theca of the vesicular ovarian follicle. Called also granular layer.
• s. lamellatum — laminae of the hoof corium.
• s. lucidum — the translucent layer of the skin just beneath the stratum corneum. Called also clear layer. Present in the epidermis of the planum nasale of several species and footpads of carnivores.
• s. spinosum — the layer of the epidermis between the stratum granulosum and the stratum basale, marked by the presence of prickle cells; called also spinous layer and prickle-cell layer.
• s. tectorium — the layer of horny scales claimed to exist on the surface of the horse's hoof that gives it the smooth glossy appearance.

(n.pl strata) a layer of the epidermis or the epithelium of the oral mucosa.

• Materials, Formations, and Substances - stratum: sheetlike mass of sedimentary or igneous rock, usu. lying between other strata beds

This article is about the geologic use of the term, for other uses see Stratum (disambiguation)

The plural, "strata" redirects to this page. For other senses of that word, see Strata (disambiguation).

Goldenville strata in quarry in Bedford, Canada. These are Middle Cambrian marine sediments. This formation covers over half of Nova Scotia and is recorded as being 29,000 feet thick in some areas.

In geology and related fields, a stratum (plural: strata) is a layer of 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 stratigraphy.

When planning 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 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).

Contents 1 Characteristics 2 Naming 3 Gallery 4 See also 5 References 6 External links

Characteristics

The Permian through Jurassic strata in the Colorado Plateau area of southeastern Utah demonstrates the principles of stratigraphy. These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park. From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone. Picture from Glen Canyon National Recreation Area, Utah.

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 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 cliffs, road cuts, 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 deposition: river silt, beach sand, coal swamp, sand dune, lava bed, etc. it also is very important

Naming

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 Burgess Shale is a thick exposure of dark, occasionally fossiliferous, shale exposed high in the 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".

Gallery

Strata on a mountain face in the French Alps   Interstate road cut through limestone and shale strata in East Tennessee   Rock strata at Depot Beach, New South Wales   Rainbow Basin Syncline in the Barstow Formation near Barstow, California. Folded strata.   Outcrop of Upper Ordovician limestone and minor shale, central Tennessee; College of Wooster students.   Chalk Layers in Cyprus - showing classic layered structure.   Heavy minerals (dark) as thin strata in a quartz beach sand (Chennai, India).   Stratified Island near La Paz, Baja California Sur, Mexico.

See also

• Archaeological horizon
• Geologic map
• Geologic unit
• Geologic formation
• Law of superposition

References

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2010)

External links

Look up stratum in Wiktionary, the free dictionary.

• GeoWhen Database

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - lag

Nederlands (Dutch)
laag

Français (French)
n. - (Géol) strate, (Biol) couche, couche (sociale)

Deutsch (German)
n. - Schicht, Stratum

Ελληνική (Greek)
n. - στρώμα, διάστρωση, (γεωλ.) πέτρωμα

Italiano (Italian)
strato, falda

Português (Portuguese)
n. - camada (f)

Русский (Russian)
пласт, слой, уровень, страта

Español (Spanish)
n. - capa, estrato

Svenska (Swedish)
n. - skikt, lager, stratum

中文（简体）(Chinese (Simplified))
层, 组织层, 地层, 社会阶层

中文（繁體）(Chinese (Traditional))
n. - 層, 組織層, 地層, 社會階層

한국어 (Korean)
n. - 지층, (조직의) 층, 계층

日本語 (Japanese)
n. - 岩層, 地層, 階層

العربيه (Arabic)
‏(الاسم) طبقه (صخور), طور (تاريخ أو نمو)‏

עברית (Hebrew)
n. - ‮שכבה, רובד, מעמד חברתי‬

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