Geology: Relative Age Dating Flashcards

Relative Age Dating

• Determines the age of rocks by comparing them to other nearby rocks and geological features.

Law of Superposition

• In undisturbed rock layers, the oldest rocks are found at the bottom, and the youngest at the top.

Inclusion

• Refers to a piece of older rock encapsulated within a newer rock, typically in sedimentary contexts.

Unconformity

• A surface indicating weathering and erosion that creates a gap in the geological record.

Types of Unconformities

• Disconformity: Younger sedimentary layers on eroded older horizontal layers.
• Angular unconformity: New layers deposited atop tilted or folded and eroded layers.
• Nonconformity: Younger sedimentary layers placed over older, eroded igneous or metamorphic rocks.

Correlation

• The process of matching rocks and fossils from different locations.

Index Fossil

• A fossil from a species that existed for a brief time, was abundant, and had a widespread distribution, aiding in dating geological layers.

Stratigraphy

• Involves mapping and interpreting various layers of rock.

Sedimentary Petrology

• The study dedicated to understanding sedimentary rocks and their characteristics.

Absolute Age Dating

• Involves assigning specific timeframes to geological events indicated by changes in rock types.

Erosion

• The geological process of wearing away or transporting sediments through wind, water, or gravity.

Deposition

• The process where sediments settle after being transported in a fluid medium.

Nicholas Steno

• Recognized as the father of stratigraphy, laying foundational concepts for relative age dating.

Law of Cross-Cutting Relationships

• States that geological features like faults and igneous intrusions must be younger than the features they cut through.

Law of Inclusions

• Developed by James Hutton, indicating that rock fragments within sedimentary rocks are older than the rocks themselves.

Law of Original Horizontality

• Most sedimentary layers are deposited horizontally, and any angularity implies post-depositional processes.

Law of Lateral Continuity

• Sedimentary rocks generally extend laterally over large areas until they thin out or encounter a barrier.

Law of Flora/Faunal Succession

• Developed by William "Strata" Smith; states that simpler organisms precede more complex ones in the fossil record.

Xenolith

• Refers to a fragment of country rock embedded within igneous rock.

Country Rock

• The older rock, typically igneous or metamorphic, that is altered or displaced by intrusive bodies.

Types of Igneous Intrusions

• Include batholiths, plutons, dikes, sills, and laccoliths, each characterized by their unique formation and structure.

Geological Features

• Examples such as igneous intrusions, faults, canyons, and unconformities can disrupt older geological structures and records.

Test your understanding of relative age dating and key geological principles with these flashcards. Learn about concepts such as the Law of Superposition and inclusions in rock layers. Perfect for geology students or enthusiasts looking to reinforce their knowledge.