Geologic Time and Climate Change

Flashcards for key vocabulary terms from lectures on geologic time scale, dating methods, and climate change.

Numerical Dates

Specify the number of years that have passed since an event occurred.

Relative Dates

Place rocks in a sequence of formation.

Principle of Superposition

In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.

Principle of Original Horizontality

Layers of sediment are generally deposited in a horizontal position.

Principle of Lateral Continuity

Beds originate as continuous layers that extend in all directions until they eventually thin out or grade into a different sediment type.

Principle of Cross-Cutting Relationships

Younger features cut across older features; features that cut across rocks (faults, intrusions) must have formed after the rocks they cut through.

Principle of Inclusions

Inclusions are fragments of one rock unit that are enclosed within another rock unit; the rock containing the inclusion is younger.

Unconformity

A break in the rock record produced by non-deposition and erosion of rock units.

Angular Unconformity

Tilted rocks are overlain by flat-lying rocks.

Disconformity

Sedimentary strata on either side of the unconformity are parallel.

Nonconformity

Sedimentary strata overlay metamorphic or igneous rocks.

Fossils

Traces or remains of prehistoric life preserved in rock.

Paleontology

The study of fossils.

Permineralization

Mineral-rich groundwater flows through porous tissues and precipitates minerals.

Molds

Created when a shell is buried in sediment and then dissolved by underground water.

Casts

Created when the hollow spaces of a mold are filled with mineral matter.

Carbonization

Occurs when an organism is buried and compressed, which squeezes out gases and liquids leaving a thin film of carbon behind.

Impressions

Remain in the rock when the carbon film is lost.

Amber

Hardened resin of ancient trees.

Trace Fossils

Indirect evidence of prehistoric life, including tracks, burrows, coprolites, and gastroliths.

Principle of Faunal Succession

Fossils are arranged according to their age.

Index Fossils

Widespread geographically and limited to a short period of geologic time.

Fossil Assemblages

Can be used to identify a rock bed that does not contain an index fossil.

Atomic Number

The number of protons in the nucleus of an atom.

Mass Number

The number of protons and neutrons in a nucleus.

Isotopes

Atoms with the same number of protons but different numbers of neutrons.

Radioactivity

The spontaneous decay in the structure of an atom’s nucleus.

Parent Isotope

The unstable radioactive isotope in radiometric dating.

Daughter Product

The isotopes resulting from the decay of a parent isotope.

Half-Life

The amount of time required for half of the radioactive isotope to decay.

Eon

Represents the greatest expanse of time in the geologic time scale.

Era

A division of an eon in the geologic time scale.

Period

A division of an era in the geologic time scale.

Epoch

A division of a period in the geologic time scale.

Precambrian Time

The 4 billion years (88% of Earth’s history) prior to the Cambrian period, divided into the Proterozoic and Archean eons.

Climate System

A multidimensional system of interacting parts, including the atmosphere, hydrosphere, geosphere, biosphere, and cryosphere.

Paleoclimatology

The study of past climates.

Proxy Data

Indirect evidence of climate change used to reconstruct past climates.

Oxygen Isotope Analysis

The precise measurement of the ratio of 18O/16O used in climate studies.

Aerosols

Tiny solid and liquid particles found in the air.

Albedo

The percentage of solar radiation reflected back to space.

Greenhouse Effect

The selective absorption and reheating of Earth's atmosphere by gases like carbon dioxide and water vapor.

Climate-Feedback Mechanisms

Processes that can either reinforce (positive feedback) or offset (negative feedback) initial climate changes.

Positive-Feedback Mechanisms

Changes that reinforce the initial change in climate.

Negative-Feedback Mechanisms

Changes that produce results opposite of the initial change and offset it.