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Geology & Earth Sciences vocabulary · Geologic Time & Fossils

Unconformity

Meaning in geology & earth sciences, with examples

/ˌʌnkənˈfɔːrməti/nounAdvanced term

In geology & earth sciences, unconformity means: A surface between rock layers that marks a gap in the geological record, where erosion removed rock or no sediment was deposited for a long time.

In Turkish: uyumsuzluk, diskordans

How it is used

Types include the angular unconformity (tilted layers below flat ones), the disconformity and the nonconformity (sediment on igneous or metamorphic rock). Siccar Point in Scotland, described by James Hutton, is a famous example.

Example sentences

  1. The angular unconformity shows that the older rocks were folded and eroded before the sea returned.

  2. About 50 million years of record are missing at this unconformity.

Common collocations

  • angular unconformity
  • unconformity surface
  • major unconformity
  • lie above an unconformity
  • stratumA single layer of sedimentary rock or sediment with similar features throughout, separated from the layers above and below it. The plural is strata.
  • law of superpositionThe principle that in undisturbed layers of sedimentary rock, the oldest layer is at the bottom and each layer above it is younger.
  • erosionThe removal of soil and rock fragments from one place and their transport to another by water, wind, ice or gravity.
  • geologic time scaleThe system that divides the Earth's roughly 4.6-billion-year history into named units such as eons, eras, periods and epochs, based on rocks and fossils.

More terms: Geologic Time & Fossils

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