1. Absolute Age of Rocks Notes

2. Absolute Dating exact age properties atoms exact
When you find the ______ ____ of a rock.
Process uses the __________ of ______ in rocks to find their ______ ages.
exact
age
properties
atoms
exact

3. three particles neutrons same element same protons different neutrons
Atoms have _____ kinds of ________: protons, _________ and electrons
Atoms of the ______ ________ have the ______ number of ________, but can have a ________ number of _________
particles
neutrons
same
element
same
protons
different
neutrons

4. 6 7 8 element neutrons different
Isotope: atoms of an ________ that have ________ numbers of _________
Ex: These are some isotopes of carbon
Carbon-12 has __ neutrons
Carbon-13 has __ neutrons
Carbon-14 has __ neutrons
different
neutrons 6 7 8
Carbon-12
stable
Carbon-13
stable
Carbon-14
unstable

5. unstable isotope breaks down new elements
Radioactive Isotope: an _________ isotope
Radioactive Decay: when a radioactive ________ (parent isotope) _______ ______ into ____ isotopes (daughter isotope) of different _________.
unstable
isotope
breaks
down
new
elements
radioactive isotope
new isotope

6. radioactive isotope new
Parent isotope: another name for the ___________ isotope
Daughter isotope: ____ ________ formed when the parent isotope breaks down
radioactive
new
isotope
parent isotope
daughter isotope

7. Radiometric Dating exact ratio parent daughter radiometric only
The process of determining the ______ age of a rock sample based on the _____ of _______ isotope to _________ isotope is called ___________ dating.
Can _____ give _________ ages for rocks that have _____ been melted or __________
exact
ratio
parent
daughter
radiometric
only
accurate
NOT
weathered

8. calculate age rock amount parent amount daughter half-life parent
To _________ the ____ of a _____ you need to know:
1. The ________ of _______ isotope in the rock
2. The ________ of _________ isotope in the rock
3. The ________ of the _______ isotope
calculate
age
rock
amount
parent
amount
daughter
half-life
parent

9. % of parent isotope remaining Click here & scroll down for the demo
Half-life: amount of _____ it takes for ____ of the original amount of ______ isotope in the rock sample to ______, or change ____ the _________ isotope.
time
half
parent
decay
into
daughter
% of parent isotope remaining
Click here & scroll down for the demo
half-lives

10. 12 6 10,000 parent half parent left
When the rock formed it had 12mg of parent isotope (100%). 12
Ex: There are ___mg of _______ isotope in the rock to start and the ____-life of the parent is _______ years. After 10,000 years there would be ___mg of the _______ isotope ____ in the rock (half of the original amount).
parent
10,000 years pass (1 half-life)
half
10,000
Now there is 6mg (50%) of the parent left and 6mg (50%) of daughter isotope have formed. 6
parent
Another 10,000 years pass (2 half-lives)
left
Now 3mg (25%) of the parent left & 9mg (75%) of the daughter formed.

11. 1.3 two commonly used daughter argon-40 rocks 1 million
There are ____ parent isotopes __________ _____ in radiometric dating.
1. Potassium-40: Has a half-life of ___ billion years. Decays into the _________ isotope _________ Used to date ______ older than about ________ years.
two
commonly
used
1.3
daughter
argon-40
rocks
1 million

12. 4.5 Decays lead-206 older 10 million
2. Uranium-238: Has a half-life of ___ billion years. ________ into the daughter isotope _________. Used to date rocks _____ than about _________ years.
Decays
lead-206
older
10 million

13. Some of the Radioactive Isotopes Used in Radiometric Dating

14. Radiocarbon Dating
Carbon-14 is used to date fossils, ______, and wood up to _______ years old.
bones
75,000

15. used organisms bodies carbon constant
Carbon from the environment is _____ by ___________ to build tissue in their _______.
Throughout their lives, the amount of _______ remains _________.
used
organisms
bodies
carbon
constant

16. carbon-14 decays remaining measured age
After the organism dies, __________ slowly _______. The __________ carbon-14 can be __________ to determine the ____ of the fossil.
carbon-14
decays
remaining
measured
age

17. How Old is the Earth? age estimated meteorites rocks moon
The ____ of the earth is __________ by finding the absolute ages of ___________ from our solar system and ______ from the ______.
age
estimated
meteorites
rocks
moon

18. Based on this information, the ____ of the ______ is estimated to be around 4.6 ______ years old
age
earth
billion

19. Can’t rocks recycled history
______ use rocks on the earth to find the earth’s exact age because the ______ have been _________ or changed over the course of earth’s _______. (the rock cycle)
Can’t
rocks
recycled
history