Geologic Time Flashcards
What is Relative Age
the occurrence of one event in
relation to another
What is Absolute Age
Places events or rocks at a specific time
What is the principal of superposition
when rocks were deposited, newer ones were placed or
formed on top of the older ones
What is Principle of Original Horizontality
sediments are deposited in nearly horizontal beds
What is Principle of Cords-Cutting Relationships
geologic features that cut across rock must be younger than the rock they cut through
What is Principle of Inclusions
objects enclosed in rock must be older than the time of rock formation
What is Principle of Lateral Continuity
layers are continuous until encountering an obstruction
What is Principle of Faunal Sequence
layers of sedimentary rocks contain fossils in a
definite sequence
What is angular Unconformity
younger sediments rest upon the eroded surface of tilted or folded older rocks
What is Unconformity
Surface between two layers that was not deposited in an unbroken sequence; record of missing time
What is nonconformity
Unconformity between stratified rocks above and unstratified igneous or metamorphic rocks below
Radiogenic Isotopes
Undergo spontaneous decay to form atoms of another element
Most Isotopes are..
Stable isotopes
What is a half-life
time required for one-half of the original # of
parent atoms to decay into daughter atoms
