Geologic Time Flashcards

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Questions and Answers

What is an angular unconformity?

A geological time scale.

A type of metamorphic rock.

An unconformity with horizontal strata deposited on eroded layers. (correct)

A disorder in sedimentary layers.

What is the definition of disconformity?

A disconformity exists between sedimentary rocks and metamorphic or igneous rocks when sedimentary rock lies above and was deposited on pre-existing and eroded metamorphic or igneous rock.

What is correlation in geology?

Correlation involves using fossil remains of species to define time periods and relate strata based on fossil content.

What is a fossil?

The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock. Signup and view all the answers

What is the geological time scale?

A system of chronological dating that relates geological strata to time. Signup and view all the answers

What is half-life in geological dating?

The time required for one-half of the radioactive isotopes in a sample to decay to radiogenic isotopes. Signup and view all the answers

What is an index fossil?

A fossil that is useful for dating and correlating the strata in which it is found. Signup and view all the answers

What does the law of superposition state?

In any undisturbed sequence of rocks, the youngest layer is on top and the oldest on the bottom. Signup and view all the answers

What is a numerical date in geology?

A date or date range in years assigned to rocks using absolute dating methods. Signup and view all the answers

What is the principle of cross-cutting relationships?

An igneous intrusion is always younger than the rock it cuts across. Signup and view all the answers

What is the principle of fossil succession?

The observation that sedimentary rock strata contain fossilized flora and fauna that succeed each other in a reliable order. Signup and view all the answers

What does the principle of original horizontality state?

Layers of sediment are originally deposited horizontally under the action of gravity. Signup and view all the answers

What is radiometric dating?

A technique used to date materials such as rocks or carbon by measuring radioactive impurities. Signup and view all the answers

What is relative dating?

The science of determining the relative order of past events without necessarily determining their absolute age. Signup and view all the answers

What is uniformitarianism?

The theory that changes in the Earth's crust have resulted from continuous and uniform processes. Signup and view all the answers

What is nonconformity in geology?

A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks where sedimentary rock lies above eroded metamorphic or igneous rock. Signup and view all the answers

Study Notes

Geologic Time Concepts

Angular Unconformity: Represents a gap in the geological record where tilted and eroded sedimentary rock layers are overlain by horizontally deposited strata, highlighting a period of tectonic deformation.
Disconformity: Occurs when sedimentary rocks lie atop eroded metamorphic or igneous rocks, indicating a period where no sediment was deposited, leading to a significant age difference.
Correlation: Relates to the ability to date geological time periods based on the fossils found in sedimentary strata, linking them to corresponding time frames through paleontological studies.
Fossil: Refers to the preserved remains or traces of ancient organisms, including molds or casts, which provide crucial information about past life on Earth.
Geologic Time Scale (GTS): A chronological framework that categorizes Earth's history based on layers of rock, aiding scientists in understanding the timing and relationships of significant geological events.
Half-life: A fundamental concept in dating geological materials, indicating the time required for half of a radioactive isotope to decay, essential for understanding the age of fossils and rocks.
Index Fossil: A species of fossil that is widespread but only existed for a short geological timeframe, used to date and correlate the strata in which it is found.
Law of Superposition: A principle stating that in an undeformed sequence of sedimentary rocks, the oldest layers are at the bottom, with progressively younger layers above them.
Numerical Date: This method provides an actual date or date range for geological materials using absolute dating techniques, contrasting with relative dating which provides order without specific dates.
Principle of Cross-Cutting Relationships: Asserts that geological features, like igneous intrusions, must be younger than the rocks they disrupt, essential for understanding geological history.
Principle of Fossil Succession: Recognizes that fossilized remains in sedimentary rocks succeed each other in a consistent and identifiable sequence, allowing for dating across different locations.
Principle of Original Horizontality: States that sediment layers are deposited horizontally due to gravity, a key criterion for analyzing geological formations that have been folded or tilted.
Radiometric Dating: A technique for determining the age of rocks or organic materials based on the decay of radioactive isotopes present during their formation.
Relative Dating: Involves determining the chronological order of events without assigning exact ages, useful for understanding the sequence of geological formations.
Uniformitarianism: The principle that geologic processes today are similar to those in the past, suggesting that the present is key to understanding Earth's history.
Nonconformity: Exists where sedimentary rocks are deposited atop pre-existing eroded metamorphic or igneous rocks, indicating a significant interval of geological time without deposition.

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Description

Test your knowledge of geological terms with these flashcards. This quiz covers key concepts like angular unconformity and disconformity, essential for understanding the geological time scale. Perfect for geology students looking to reinforce their learning.