Definition

Noun: 1. A distinct, mappable body of rock or sediment with characteristic internal structure and composition: A geological formation is the fundamental unit of stratigraphy, used to describe and map layers of rock in the Earth's crust. It is defined by consistent physical properties (like rock type) and has recognizable boundaries. 2. Any natural, physical feature of the Earth's surface or subsurface created by geological processes: This broader sense refers to the structure, shape, and arrangement of rocks and landforms resulting from processes like erosion, deposition, folding, or volcanic activity.

Usage Examples

• As a stratigraphic unit:
  • The sandstone formation contains fossils from the Jurassic period.
  • Geologists identified a new limestone formation during the survey.
• As a natural feature:
  • The canyon is a spectacular geological formation created by river erosion over millions of years.
  • The unusual rock formations along the coast attract many tourists.

Advanced Usage

• "Caprock formation": A resistant layer of rock overlying a more easily eroded layer, often protecting underlying formations and influencing landscape shape (e.g., in mesas or buttes).
• In formal geological reports, a formation name typically combines a geographic location with the dominant rock type (e.g., , ).

Variants and Related Words

• Formation (n): The most common short form in geological context. (e.g., )
• Stratum (n, plural: strata): A single layer of sedimentary rock or soil.
• Bed (n): A specific layer within a rock formation, representing a distinct depositional event.
• Structure (n): Refers more to the arrangement or deformation of rocks (e.g., folds, faults) rather than the rock body itself.

Synonyms

• Rock unit
• Stratigraphic unit
• Bedding
• Stratum
• Landform (for surface features)

Related Phrases

• To map a formation: To determine and chart the surface extent and subsurface configuration of a geological formation.
  • The team's objective was to map the formation across the entire basin.
• Formation boundary: The surface or interface separating one geological formation from another.
  • The formation boundary is marked by a clear change in rock color and hardness.

Related Idioms

• A formation of...: While not a strict idiom, this phrasing is commonly used to describe groups of similar features.
  • We hiked through a formation of towering sandstone pinnacles.

Noun

1. (geology) the geological features of the earth