Flashcards in Ch9 Deck (17):
dating describes age in relation to events or when something formed
determines age in exact units of time; given as a number.
ex- my dog is 3
Laws for determining (relative) age
1) Original horizontality
4) Cross Cutting
most sediments and lava flows are originally deposited in horizontal sheets. There horizontal rock layers are called beds, or strata
‐ in any sequences of undeformed sedimentary rocks or lava flows, oldest layers are at bottom of sequence, while youngest layers at top
a clast included in another rock must be older than the rock it is in
Any feature that cuts through a body of rock is younger than that rock
Gap, deposition without anything fucking it up
Consist of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata
a gap in the rock record that represents a period during which erosion rather than deposition occurred.
consists of younger sedimentary rocks that overlie older metamorphic or igneous rocks
Importance of fossils
determine geologic history and prehistoric environments.
Principle of fossil succession
states that fossils succeed each other in a definite and determinable order
-can be used to date stratas
interval in the rock for which a certain fossil is found is called a range zone
Radiometric Dating of rocks
Radioactive isotopes - emit particles from their nuclei that cause radiation.Ultimately, the process produces a stable nonradioactive and stable isotope
isotope that decays is the parent, while the isotopes it produces are the daughters