chapter 9 geologic time
Terms
undefined, object
copy deck
- angular unconformity, p 275
- an unconformity where older strata dip at an angle different from that of younger beds.
- Archean eon, p 293
- OMIT
- Cenozoic era, p 293
- a time span on the geologic time scale following the Mesozoic era. The Ceonzoic began about 65 million years ago and continues to the present
- conformable, p 275
- rock layers that are deposited without interruption
- cross-cutting relationships, p 274
- a principle of relative dating of rocks. A rock or fault is younger than any rock or fault through which it cuts.
- disconformity, p 276
- a type of unconformity where the beds above and below are parallel
- eon, p 293
- the largest time unit on the geologic time swcale, next in order of magnitude above "era".
- epoch, p 293
- OMIT
- era, p 293
- a major division on the geologic time scale; eras are divided into shorter units called periods
- fossil succession, p 281
- Fossil organisms succeed one another in a definite and determinable order. Any time period can be recognized by its fossil content.
- fossil, p 277
- the remains or traces of organisims preserved from the geologic past
- geologic time scale, p 293
- The division of Earth history into blocks of time - eons, eras, and periods. The time scale was created using relative dating principles.
- Hadean eon, p 293
- OMIT
- half-life, p. 287
- the time required for one-half of the atoms of a radioactive substance to decay from parent to daughter product
- inclusions, p 275
- a piece of one rock unit contained within another. Inclusions are used in relative dating. The rock mass next to the one containing the inclusion must have been there first in order to provide the fragment.
- index fossils, p 281
- a fossil associated with a particular span of geologic time
- Mesozoic era, p. 293
- a time span on the geologic time scale between the Paleozoic and Cenozic ears - from about 248 to 64 million years ago.
- nonconformity, p 276
- an unconformity where older metamorphic or intrusive igenous rocks are overlain by younger sedimentary strata
- numerical date, p 273
- the numaber of years that have passed since an event occurred (sinced a rock formation was formed)
- original horizontality, p 273
- layers of sediment that are generally deposited in a horizontal or nearly horizontal position.
- paleontology, p 277
- the systematic study of fossils and the history of life on earth
- Paleozoic era, p 293
- a time span on the geologic time scale before the Mesozoic ear - from about 540 million to 248 million years ago
- period, p 293
- a basic unit of the geologic time scale that is a subdivision of an era.
- Phanerozoic eon, p 293
- That part of the geologic time represented by rocks containing abundant fossil evidence. The eon extending from the about 540 million years ago to the present,
- Precambrian, p 293
- All geologic time prior to the Paleozoic era.
- Protoerozoic eon, p 293
- OMIT
- radioactivity, p 285
- see radioactive decay
- radiocarbon dating, p 290
- the procedure of calculating the absolute ages of rocks and minerals that contain certain radioactive isotopes.
- relative dating, p 273
- rocks and structures are placed int their proper sequence or order. Only the chronological order of events is determined. No absolute ages are determined.
- superposition, law of - p 273
- in any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below.
- unconformity, p 275
- a surface representing a break in the rock record, caused by erosion, or nondeposition, or both.