relative and absolute dating Flashcards
relative dating
a method to determine the age of rocks in each layer by identifying the relative order of previous events
law of superposition
the youngest rocks are located at the top while the oldest rocks are at the bottom of an undisturbed sedimentary strata
law of cross-cutting relationship
states that the geological structure, such as fault, erosion, or intrusion, is younger than the rock it disrupts if it cuts across rock layer
law of inclusions
refers to fragments of one rock unit that are enclosed within another
condition of law of inclusions
these inclusions must be older than the rock containing it
law of faunal succession
states that fossil assemblages in sedimentary rocks follow a predictable sequence over time
law of original horizontally
suggests that sediments are originally deposited in horizontal layer
absolute dating
provides numerical ages for rock layers by measuring the decay of radioactive isotopes in minerals within those rocks
tree rings
the age of a tree is found by counting its rings
radiometric dating
calculating absolute ages of rocks and minerals that contain radioactive isotopes
varves
any sediment layer that shows a yearly cycle. varves are often seen in glacial lakes dating back to ice age