Geology Chapter 8 Flashcards

Questions and Answers

What is meant by geochronology?

The study of Earth Time, determining the timing of geological events and the ages of geological materials.

What is the approximate age of the Earth?

Approximately 4.6 billion years old.

Briefly explain the difference between relative and numerical dating.

Relative dating compares two entities to determine their age relation, while numerical dating provides exact ages in years.

What is the principle of uniformitarianism?

The scientific law stating that geological processes operating in the present occurred similarly in the past. Signup and view all the answers

What is the principle of original horizontality?

The scientific law stating that sediments are deposited in horizontal or nearly horizontal layers. Signup and view all the answers

What is the principle of superposition?

In an unaltered sequence of rock strata, each layer is younger than the one beneath it and older than the one above it. Signup and view all the answers

What is the principle of cross-cutting relationships?

A pluton is always younger than the rock that surrounds it. Signup and view all the answers

What are fossils?

The remains of ancient organisms or evidence of their existence preserved in geological material. Signup and view all the answers

Describe the principle of faunal succession.

Specific groups of animals have succeeded one another in a definite sequence through Earth history. Signup and view all the answers

What is an unconformity?

A boundary separating rocks of noticeably different ages, indicating a gap in geological records. Signup and view all the answers

What is correlation in geology?

The process of determining that geographically distant rocks originated in the same time period. Signup and view all the answers

What is a key bed?

A distinctive stratum appearing at several locations, marking a short-duration geological event. Signup and view all the answers

What is a half-life?

The time necessary for half of the atoms of a parent isotope to decay into the daughter isotope. Signup and view all the answers

Rubidium-strontium dating system: parent isotope is Rb-87 with a half life of ______ years.

47 billion Signup and view all the answers

Thorium-lead dating system: parent isotope is Th-232 with a half life of ______ years.

14.1 billion Signup and view all the answers

Carbon-14 dating system: parent isotope is C-14 with a half life of ______ years.

5730 Signup and view all the answers

Name three parent-daughter isotopic dating systems.

<ol> <li>Rubidium-strontium, 2. Thorium-lead, 3. Carbon-14.</li> </ol> Signup and view all the answers

Study Notes

Geochronology

Study of "Earth Time"; determines timing and ages of geological events and materials.
Earth is approximately 4.6 billion years old.

Dating Methods

Relative Dating: Compares entities to ascertain age order based on characteristics.
Numerical Dating (Absolute Dating): Provides actual time in years since rock formation or a geological event.

Key Geological Principles

Uniformitarianism: Geological processes currently observed also operated in the past, explaining past events.
Original Horizontality: Sediments are deposited in horizontal layers parallel to Earth's surface.
Superposition: In undisturbed rock strata, younger layers are on top; older layers are at the bottom.
Cross-Cutting Relationships: A rock intrusion (pluton) is younger than the surrounding rock.

Fossils and Faunal Succession

Fossils: Remains of ancient organisms preserved in geological materials; derived from the Latin "fossilus" meaning "something dug up".
Principle of Faunal Succession: Specific groups of animals succeed one another in a definite sequence, allowing relative dating through fossils (e.g., ammonites are younger than trilobites).

Geological Concepts

Unconformity: Boundary between rock layers of different ages, indicating a gap in the geological record due to erosion or lack of deposition.
Correlation: Process of linking geographically distant rock units from the same time period by identifying paleontological or geological similarities.

Key Bed

Distinct stratum visible at multiple locations, associated with a brief geological event (e.g., Mount Mazama eruption).

Half-Life

Time required for half of the parent isotope atoms to decay into the daughter isotope.

Isotopic Dating Systems

Rubidium-Strontium Dating: Parent isotope Rb-87 (half-life 47 billion years); dates potassium-rich minerals like biotite and feldspar.
Thorium-Lead Dating: Parent isotope Th-232 (half-life 14.1 billion years); dates materials like zircons and uraninite.
Carbon-14 Dating: Parent isotope C-14 (half-life 5730 years); dates any carbon-bearing material such as bones, wood, and shells.

Dendrochronology

A numerical dating method using tree rings to determine age and past climate conditions.

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Description

Test your knowledge on geochronology and the ages of geological materials with these flashcards. This quiz covers fundamental concepts of geological time and dating methods. Perfect for geology students looking to reinforce their understanding of Chapter 8.