Transcript Relative and Absolute Age Law of Superposition

Relative and Absolute Age
Law of Superposition
Relative and Absolute Dating
There are two major ways to date
geologic events:
Relative dating-how old a rock is
compared to surrounding rocks
Absolute dating-actual number
of years since the rock was
formed
Relative Dating
The various relative dating methods
tell you whether a specific rock or
layer of rocks is younger or older as
compared to surrounding rocks
This type of dating does not give an
exact age for the rock
• The Law of
Superposition
states that in an
undisturbed
sequence of
sedimentary rock:
Each layer is older
than the one above
Each layer is
younger than the
one below
Law of Superposition
• a vertical set of strata
(layers) is a
chronological record of
the geologic history of
that strata
• Youngest layers are on
top and oldest on
bottom
Law of Superposition
• Absolute Dating
– Absolute dating can give
you the exact age of a
rock
– This is accomplished
using radioactive dating,
which is also referred to
as radiometric dating
– Based on the regular
radioactive decay of
certain elements