Chapter 10 Vocab Flashcards
Cambrian Explosion
The remarkable diversification of life, indicated by the fossil record, that occurred at the beginning of the Cambrian Period.
Closure Temperature
The temperature below which isotopes are no longer free to move.
Contact
The boundary surface between two rock bodies (as between two stratigraphic formations, between an igneous intrusion and adjacent rock, between two igneous rock bodies, or between rocks juxtaposed by a fault).
Correlation
The process of defining the age relations between the strata at one locality and the strata at another.
Cross-Cutting Relations
If one geologic feature cuts across another, the feature that has been cut is older.
Daughter Isotope
The decay product of radioactive decay.
Eon
The largest subdivision of geologic time.
Epoch
An interval of geologic time representing the largest subdivision of a period.
Era
An interval of geologic time representing the largest subdivision of the Phanerozoic Eon.
Fossil Assemblage
A group of fossil species found in a specific sequence of sedimentary rock.
Fossil Succession
In a stratigraphic sequence, different species of fossil organisms appear in a definite order; once a fossil species disappears in a sequence of strata, it never reappears higher in the sequence.
Geochronology
The science of dating geologic events in years.
Geologic Column
A composite stratigraphic chart that represents the entirety of the Earth’s history.
Geologic History
The sequence of geologic events that has taken place in a region.
Geologic Map
A map showing the distribution of rock units and structures across a region.
Geologic Time
The span of time since the formation of the Earth.
Geologic Time Scale
A scale that describes the intervals of geologic time.
Half-Life
The time it takes for half of a group of a radioactive element’s isotopes to decay.
Index Fossil
Widespread fossil species which survived only for a relatively short interval of geologic time.
Isotope
Different versions of a given element that have the same atomic number but different atomic weights.
Isotopic Dating
The science of dating geologic events in years by measuring the ratio of parent radioactive atoms to daughter product atoms.
Original Horizontality
Layers of sediment, when originally deposited, are fairly horizontal.
Parent Isotope
A radioactive isotope that undergoes decay.
Period
An interval of geologic time representing a subdivision of a geologic era.
Precambrian
The interval of geologic time between Earth’s formation about 4.57 Ga and the beginning of the Phanerozoic Eon 542 Ma.
Radioactive Decay
The process by which a radioactive atom undergoes fission or releases particles, thereby being transformed into a new element.
Relative Age
The age of one geologic feature with respect to another.
Stratigraphic Column
A cross-section diagram of a sequence of strata summarizing information about the sequence.
Stratigraphic Formation
A recognizable layer of a specific sedimentary rock type or set of rock types, deposited during a certain time interval, that can be traced over a broad region.
Stratigraphic Group
Several adjacent stratigraphic formations in a succession.
Superposition
In a sequence of sedimentary rock layers, each layer must be younger than the one below, for a layer of sediment cannot accumulate unless there is already a substrate on which it can collect.
Unconformity
A boundary between two different rock sequences representing an interval of time during which new strata were not deposited and/or were eroded.
Uniformitarianism
Theory that states that physical processes we observe operating today operated in the past, at roughly comparable rates so, the present is the key to the past.
