Transcript Document

Determining a Fossil’s Age
Age of rock layers..
Scientists can’t date most fossils directlyInstead, they date the rocks the fossils
are found in
 The oldest rocks are
found in lower layers, and
the rocks get younger as
you move upwards
Relative-Age Dating
By comparing the age
of a rock layer to the
rock layers near it,
scientists can
determine the relative
age of the rock – and
the relative age of any
fossils found in that
rock layer.
Using Index Fossils
Index fossils can be used to determine
the relative ages of the rocks they were
found in
 Index fossils must follow 2 rules:
1. Must have been found over a large
2. Must have only lived for a short
period of time
Index fossils (cont.)
Fossil A – 250 – 200 mya
Fossil B – 400 – 100 mya
Fossil C – 400 mya – 100 mya
Fossil D – 100 mya - present