What
is
relative
age
?
1
.
-
Two
ideas
that
help
scientists
determine
the
age
of
rock
layers
are
original
horizontality
and
____________________
.
2
.
-
Scientist
compare
the
age
of
one
rock
layer
to
the
age
of
another
to
find
its
____________________
____________________
.
3
.
-
Layers
of
rock
can
be
tilted
,
folded
,
or
____________________
by
forces
within
Earth
,
making
it
difficult
to
determine
their
relative
age
.
What
are
fossils
?
4
.
-
Fossils
can
form
when
organisms
die
and
are
buried
by
____________________
,
which
replaces
the
hard
parts
of
the
body
and
hardens
to
form
rock
.
5
.
-
Some
fossils
are
formed
when
organisms
are
trapped
in
flowing
tree
sap
,
which
hardens
to
form
____________________
.
6
.
-
Other
fossils
are
formed
when
footprints
or
other
____________________
quickly
dry
and
become
covered
with
sediment
and
preserved
.
What
is
absolute
age
?
7
.
-
The
discovery
of
____________________
allowed
scientists
to
determine
how
old
a
rock
layer
or
fossil
really
is
.
8
.
-
Rocks
contain
radioactive
elements
that
decay
into
other
elements
at
a
constant
rate
called
____________________
-
____________________
.
9
.
-
A
rock
layer´s
age
in
years
is
its
____________________
____________________
.
