Earth's Evolution and Rock Dating

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Guided Notes

Relative Dating:

Determining
the order of
past events,
but NOT
exact dates.

The Law of Superposition

•In horizontal
layers of
sedimentary
rock, each layer
is older than
the layer above
it and younger
than the layer
below it.

Relative Dating Fossils

Younger fossils will
be found in the top
layers of rock.

Older fossils will be
found in the bottom
layers of rock.

Faulting:

• The arrow shows where
a fault line (earthquakes) moved the rock layers.

The breaking of rock layers by transform fault
lines.

Folding:

The bending of rock layers due to
pressure.

Absolute Dating:
Finding the approximate age of a
rock using the radioactive atoms
inside them.

Radioactive Dating

Radioactive dating is measuring the age of
the radioactive material inside of an object.

•Certain elements decay (break down) at certain
rates. (Ex. Carbon 14, Uranium)

•Scientists know how long certain atoms take to
decay.

•They compare the amount of atoms left to the
beginning amount to calculate its age.

Dating Fossils

Absolute dating methods, sometimes
called numerical dating, to give rocks an
actual date, or date range, in number of
years. For example, numerical dating tells
us the age of the Rock A in X numbers of
years.

Relative dating, compare how old
something is in comparison to something
else. For example, relative dating tells us
the age of Rock A compared to Rock B.

Earth’s Age

•Using radioactive dating,
scientists have identified rock as
old as 4.28 billion years old.

•With this evidence and more, the
approximate age of the Earth has
been calculated as 4.5 billion
years old.

Earth’s Evolution
The Earth’s surface has been slowly but
constantly changing in all of that time.

Earth used to be covered by a
supercontinent named Pangaea.

Evidence: Rock with the same composition
and the same age can be found on different
continents today.

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