Geological Time
The Earth is approximately 4.6 ___________________ years old.
Scientists have divided this geological time scale into eons, eras,
periods, and epochs. Eons represent the _______________ time.
Eons are divided into __________. Each era is subdivided
into_________________. Finally periods are divided into still
smaller units called ____________________.
Below is the Geological Time Scale.
http://www.ucmp.berkeley.edu/help/timeform.php geological time
The geologic time scale is a visual record of Earth’s history, with
the individual units based on changes in the _______ and_______.
Notice that the geological time scale before 650 million years
doesn’t have epochs but has a super eon called the Precambrian
which includes 3 eons. This is because Precambrian time, there
were fewer _______________ forms. These life forms are more
difficult to identify and the rocks have been disturbed often.
(9,200,000 years equal one minute of time)
Measuring the Age of Earth and the Events That Shaped It
Time line of earth history of major events pictures http://exploringorigins.org/timeline.html
Time line hour clock 1 hour - http://www.youtube.com/watch?v=H2_6cqa2cP4
How understanding the principles of rock layers help to
determine the age of rocks.
In geology the principal laws are:
 Principle of Uniformitarianism: Processes that are
happening today also happened in the
__________________.
 Principle of Superposition – The rock on the
__________________ are older than the rock on the
_____________.
 Principle of Cross-Cutting Relations: A rock is
_________________________ than any rock it cuts across.
In the above picture a vertical column of magma called a
dike cooled into _____________ rock. The magma that
cooled into igneous rock that cut across the other three layers
of rock is ____________________ than the three other
layers.
Looking at the picture to the right
arrange rock layers A, B, C, E, F, G, H, J, K in order from the
oldest to the youngest. Ignore letters D and I.
Rock layers from the oldest to the youngest:
________________________________________________
Rock layer D (red) going into layers A and B is
_____________________ than A and B but
____________________ then _____, ______, _____and
_______. Rock layer D represents a pocket of magma that
traveled up from beneath layers A and B which hardened into
igneous rock.
Order the rock layers in order from the oldest to youngest.
_________________________________________________
_________________________________________________
__________________________________
 Unconformity: Is a place where _____________ layers are
missing. After a rock layer is formed, the area can be
uplifted to the Earth’s surface (uplifting can be caused by
______________________ and plate tectonics). After, the
process of __________________ and _____________ can
wear the rock layer away. Rock layers often occur above the
unconformity, but they are not the kind of rock that would
have formed in the same way as the _______________ layer
beneath the unconformity.
Example:
Order the rock layers in
order from the oldest to youngest.
_______________________________________________
Order the rock layers in order
from the oldest to youngest.
_______________________________________________
Two Types of Dating
Relative Age Dating: Is a way to describe the age of one
event compared to another object or event. Relative age
dating is based on comparisons of the age of_____________.
Thus, this method of dating objects always includes words
such as before, after, earlier, later, older, and younger.
Example using the principal of superposition:
If you found an arrow head in one sedimentary layer of rock
and a saber tooth tiger skull in a lower layer of rock, you can
use the law of superposition to conclude that the skull is
________________ than the arrow head.
Absolute Age: This describes the _______________ age of
an object or event. The absolute ages of objects from long
ago are found by analyzing the ____________________ in
the object or the rock layers in which they were found.
Radiometric Dating – This is the most accurate form of
dating. This method measures the ____________ (decrease
in size and/or energy) of naturally occurring
___________________ isotopes.
Example: Carbon-14 Dating (The 14 is the total number of
________________ and _____________ in the nucleus of
the atom).
http://science.howstuffworks.com/environmental/earth/ge
ology/carbon-14.htm
Most atoms of carbon have 6 _____________ and 6
_______________ in the nucleus of atom. A very few carbon
atoms have a different number of ___________________ and
are called isotopes. In conclusion, an isotope is an atom of
the same element with a different amount of
_________________in the___________________. Carbon-14 is an
_____________ of carbon and is radioactive. Carbon-14 is
produced in the upper atmosphere when the ________
element nitrogen-14 is hit by cosmic radiation from the sun
forming the ___________ radioactive element carbon-14.
The carbon-14 will _________ eventually back into the
stable element nitrogen-14. Radioactive describes an
element that gives off tiny particles and _____________from
inside its atom. Only about 1 in a 1,000,000,000,000
(_____________) carbon atoms are__________________,
the majority of the atoms are carbon-12. This means that it
tends to give off _____________________ and energy from
its nucleus.
Above picture show the decay of carbon-14 to nitrogen-14.
The antineutrino will destroy itself and give off energy.
The carbon-14 atom changes back into an atom of nitrogen14, which is not ___________________ but stable. This
change is called radioactive decay. The ________________
process compares the ratio of carbon-14 to carbon-12 in an
object.
All living things contain very small amounts of carbon-14.
The amount of carbon-14 remains about the same as we live
our lives. This amount remains steady throughout our lives
as we eat and obtain carbon-14 but at the same time the
carbon -14 is decaying to nitrogen-14. This carbon is
recycled as we live our lives (carbon in food is released as
________________ __________________ as we burn food
for___________________). When an organism dies no
more carbon-14 is obtained and the carbon-14
__________________ to a the stable element nitrogen-14.
As the carbon-14 decays, the ratio of carbon-14 to carbon12 in the organic object _____________ at a steady rate,
because the amount of carbon-14 decreases. Scientists have
figured out that it takes about 5730 ___________________
for half of the carbon-14 to change to nitrogen-14.
Picture of how carbon-14 is renewed or produced on the Earth.
Another important radioactive isotope is Uranium which
decays into the stable element______________. This
method has let scientists to determine the approximate age
of the Earth as ______ _______________ years old.
Below are 3 common radioactive isotopes that are used to
date objects. The parent or mother isotope is the
radioactive_______________ isotope and the daughter
isotope is the _____________________ element that forms
from decay.