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Relative Age. The age of a rock unit or event relative to the age of another rock unit or event. In other words which layer or event came first , second , third … Ex. Mr. Jensen is older than you are or the sandstone was deposited before the fault occurred. Absolute Age.
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Relative Age • The age of a rock unit or event relative to the age of another rock unit or event. • In other words which layer or event came first, second, third… • Ex. Mr. Jensen is older than you are orthe sandstone was deposited before the fault occurred
Absolute Age • An actual year or a range of years (sometimes expressed as a geologicperiod) • Can be determined with radiometric dating • Can be determined with the use of Index Fossils and Volcanic Time Markers
Index Fossils • Index fossils (like fads) can help us determine the specific time period that the rock formed • The best index fossils are those that lived for a relatively short period of time and over a largearea.
Volcanic Time Markers • Volcanic ash is sent into the upper atmosphere and is carried all over the Earth • Layers of volcanic ash are created all over the Earth. • They can be linked to the eruption and dated
Not every Fossil is an Index Fossil • Some fossils are not useful for determining the age of a rock because they … • Lived for too long a period of time • Too small of an area