Chapter 9 Flashcards
The first win of Precambrian time. The eon prece ding the protozoic. It extends between 4.5 and 2.5 billion years ago
Archean Eon
A time span on the geologic time scale beginning about 6.5 million years ago, following the Mesozoic era
Cenozoic Era
Rock layers that were deposited without interruption
Conformable
The process of establishing the equivalence of rocks of similar age in different areas
Correlation
A principle of relative dating. A rock or fault is younger than any rock (or fault) through which it cuts
Cross-Cutting Relationship
A type of unconformity in which the beds above and below are parallel
Disconformity
The largest unit of time on the geologic scale, next in order of magnitude above area
Eon
A unit of the geologic time scale that is a subdivision of a period
Epoch
A major division on the geologic time scale; are divided into shorter units called periods
Era
The remains of traces of organisms preserved from the geologic past
Fossil
The definite and determinable order in which fossil organisms occur. enables us to identify many time periods by their fossil content
Fossil succession, principle of
The division of Earth History into blocks of tie-eons, eras, periods, and epochs. The time scale was created using relative dating principles.
Geologic Time scale
The earliest time interval (eon) of Earth history. The time before the planet’s first rocks.
Hadean Eon
The time required for one half of the atoms of a radioactive substance to decay
Half-life
A piece of one rock unit that is contained within another. Are used in relative dating.
Inclusions
A fossil that is associated with a particular span of geologic time.
Index Fossil
A time span on the geologic time scale between the Paleozoic and Cenozoic eras from about 248 to 65.5 million years ago.
Mesozoic Era
An unconformity in which older metamorphic or intrusive igneous rocks are overall by younger sedimentary strata
Nonconformity
The number of years that have passed since an event occurred
Numerical (absolute) dating
Layers of sediment that are generally deposited in a horizontal or nearly horizontal position
Original horizontality, principle
The systematic study of fossils and the history of life on Earth
Paleontology
A time span on the geologic time scale between the Precambrian and Mesozoic eras - from about 542 million to 252 million years ago
Paleozoic Eon
A basic unit of the geologic time scale that is a subdivision of an era. May be divided into smaller units called epochs.
Period
An unconformity in which the older strata dip at an angle different from that of the younger beds
Angular unconformity
All geologic time prior to the Phanerozoic eon. A term encompassing both the Archean and Protozoic eons.
Precambrian
The eon following the Archean and preceding the Phanerozoic. It extends between 2500 and 542 million years ago.
Proterozoic Eon
The spontaneous decay of certain unstable atomic nuclei
Radioactivity
The procedure of calculating the absolute ages of rocks and minerals that contain certain radioactive slopes
Radiometric dating
A process of determining the chronological order of events by placing rocks and structures in the proper sequence or order
Relative dating
A surface that represents a break in the rock record, caused by erosion and non-deposition
Unconformity
Dating of events from the very recent geologic past (the past few tens of thousands of years) based on the facet that the radioactive isotope of carbon is produced continuously in the atmosphere
Carbon-14 dating
In an unreformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below
Superposition, principle of
