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In geology and related fields, a stratum (plural: strata) is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. 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. 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. Eozoic strata pertains to rocks or strata older that the Paleozoic, in many of which the eozoön has been found.

Eozoic Strata

In geology and related fields, a stratum (plural: strata) is a layer of rock or soil with internally…

Vertical section of epidermis of the prepuce. Labels: a, stratum corneum, of very few layers, the stratum lucidum and stratum granulosum not being distinctly represented; b, c, d, and e, the layers f the stratum Malpighi, a certain number of the cells in layers d and e showing signs of segmentation; layers c consists chiefly of prickle or ridge and furrow cells; f, basement membrane; g, cells in cutis vera.

Epidermis

Vertical section of epidermis of the prepuce. Labels: a, stratum corneum, of very few layers, the stratum…

A genus of single-celled algae often forming a yellowish-green stratum on trees' damp walls, and in shallow pools.

Protococcus

A genus of single-celled algae often forming a yellowish-green stratum on trees' damp walls, and in…

"A sandy stratum, a a, acting as a filter, occupies an inclined position between two other strata impervious to water, such as clay, the water being absorbed by the superficial parts of the strata, as at a a (which may be of very great extent), will penetrate through its whole depth, and, finding no egress below on account of the basin-like form of the stratum, or from its resting at the lower termination upon a compact rock, will accumulate." — Wells, 1857

Sandy Stratum

"A sandy stratum, a a, acting as a filter, occupies an inclined position between two other strata impervious…

Simple or surface springs: (d) stratum, (e) clay, (c) pervious bed, (a) strata, (b) valley.

Simple Springs

Simple or surface springs: (d) stratum, (e) clay, (c) pervious bed, (a) strata, (b) valley.

An illustration of strata bent at a line of fault. In geology and related fields, a stratum (plural: strata) is a layer of rock or soil with internally consistent characteristics that distinguishes it from contiguous layers. Each layer is generally one of a number of parallel layers that lie one upon another, laid down by natural forces.

Strata with Fault Line

An illustration of strata bent at a line of fault. In geology and related fields, a stratum (plural:…

"Section of Stratified Thallus of Ricasolia herbacea. a, cortical stratum; b, gonidial stratum; c, medullary stratum." —The Encyclopedia Britannica, 1910

Thallus

"Section of Stratified Thallus of Ricasolia herbacea. a, cortical stratum; b, gonidial stratum; c, medullary…