Geo Chap 10
principle of Continuity
allows us to assume that similar layers of rock or sediment that are separated by a valley or other erosional feature were once continuos
Relative dating
cannot tell us how long ago something took place, only that is followed one event and preceded another
William Smith
created the first geological map in 1793
isotope
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.
national parks with shared strata
grand canyon national park,
numerical dating
how long ago something took place or specifically how old something or someone is.
parent
material that undergoes decay
half-life
measurement of decay from parent to daughter/ time for 1/2 of unstable parent to decay
principle of superposition
oldest layers are always on bottom for sedimentary rocks
Principles of relative dating
principle of superposition, original horozontiality, lateral continuity, cross-cutting, inclusions, fossil successions,
daughter
product of the decay
James Hutton
proposed idea of uniformitrianism
principle of inclusions
relatively dates objects based on their placement within other earth materials
principle of cross cutting
states that any geologic feature that crosses other layers or rock must be younger then the material it cuts across.
principal of original horozontiality
states that due to the influence of gravity all sediment is originally deposited horizontally.
principle of fossil succession
states that groups of fossils (called fossil assemblages) proceed one another in a regular and determinable manner.
geologic time
the span of time since earths formation
chron=
time
lithologic correlation
A correlation based on similarities in rock type
fossil correlation
A determination of the stratigraphic relation between two sedimentary rock units, reached by studying fossils.
angular conformity
An unconformity in which the strata below were tilted or folded before the unconformity developed; strata below the unconformity therefore have a different tilt than strata above.
disconformity
An unconformity parallel to the two sedimentary sequences it separates.
fossil succession
The principle of fossil succession states that groups of fossils appear in a chronological order through their vertical placement in sedimentary rocks
uniformitarianism
Uniformitarianism is the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe. "present is key to the past"