Stratum

Strata in Salta (Argentina).
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, or igneous rock that were formed at the Earth's surface,[1] 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.

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 processes. 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.

Other Languages
العربية: طبقة أرضية
asturianu: Estratu
azərbaycanca: Lay (təbəqə)
беларуская: Пласт (геалогія)
беларуская (тарашкевіца)‎: Пласт (геалёгія)
български: Пласт (геология)
català: Estrat
español: Estrato
euskara: Estratu
فارسی: چینه
Gaeilge: Srathú
한국어: 지층
hrvatski: Sloj
Bahasa Indonesia: Stratum
Nederlands: Gelaagdheid
日本語: 地層
norsk nynorsk: Lag i geologi
occitan: Estrat
português: Estrato geológico
Simple English: Strata
slovenčina: Vrstva (geológia)
Soomaaliga: Lakab dhul
српски / srpski: Слој (геологија)
Tagalog: Stratum
українська: Пласт (геологія)
Tiếng Việt: Địa tầng
中文: 地层