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9 terms

The Relative Age of Rocks

Chapter 8-Section 2
STUDY
PLAY
relative age
the age of a rock compared to the ages of other rocks
absolute age
the number of years since the rock was formed
law of superposition
in horizontal sedimentary rock layers the oldest layer is at the bottom. Each higher layer is younger than the layers below it
extrusion
lava that hardens on the surface
intrusion
when magma cools and hardens into a mass of igneous rock
fault
a break in the Earth's crust
unconformity
a gap in the geological record
inclusion
a piece of rock that is contained in another rock
index fossil
a fossil that is used to match rock layers; it must be widely distributed and represent a type of organism that existed only briefly