Definition

1. Noun:
   • A major division of geological time: A "geological period" is a fundamental unit of the geologic time scale, representing a span of time during which a specific system of rocks was formed. It is a subdivision of an era and is itself subdivided into epochs.

Usage

• The term "geological period" is used to discuss Earth's history in a formal, scientific context. It refers to a specific, named interval of time defined by major events in the rock record, such as mass extinctions or the appearance of dominant life forms.
• It is often preceded by the name of the period (e.g., the Jurassic Period, the Cretaceous Period).

Examples

Advanced Usage

• "to define a geological period": to establish the boundaries and characteristics of a specific time unit in Earth's history.
  • The extinction event helped define the end of the Cretaceous geological period.
• "spanning a geological period": lasting for the entire duration of a specific period.
  • The formation of these mountains spanned several geological periods.

Variants and Related Words

• Period (n): The common shortened form used in geology (e.g., the Devonian Period).
• Geologic time scale (n): The framework of chronological dating that relates geological strata to time, of which periods are a key part.
• Era (n): A larger division of geologic time, composed of multiple periods.
• Epoch (n): A subdivision of a geological period.

Synonyms

• Geologic period: An exact synonym.
• System (n): In stratigraphy, the "system" refers to the set of rocks deposited during a "period" of time. The terms are chronostratigraphic (system) and geochronologic (period) counterparts.

Related Phrases

• Phanerozoic geological periods: Refers to the periods (e.g., Cambrian, Ordovician) within the Phanerozoic Eon, the current eon of visible life.
• Boundary between periods: The transition point in the rock record marking the end of one period and the start of another.

Noun

1. a unit of geological time during which a system of rocks formed
   • ganoid fishes swarmed during the earlier geological periods