1. Relative Age The age of a rock unit or event __________ to the age of another rock unit or event. In other words which layer or event came __________, __________, __________… Ex. Mr. Jensen is older than you are or the sandstone was deposited before the fault occurred

2. Absolute Age An actual year or a range of years (sometimes expressed as a __________ __________) Can be determined with ____________ dating Can be determined with the use of ________ __________ and __________ __________ __________

9. Index Fossils Index fossils (like fads) can help us determine the __________ __________ __________ that the rock formed The best index fossils are those that lived for a relatively _________ period of time and over a __________ area.

10. Volcanic Time Markers Volcanic ash is sent into the __________ _______________ and is carried all over the Earth __________ of volcanic ash are created all over the Earth. They can be linked to the __________ and __________

13. Not every Fossil is an Index Fossil Some fossils are not useful for determining the age of a rock because they … –Lived for _____ ________ a period of time –Too __________ of an area