2. Think About It…
• How old is Earth?
• What are some tools or
methods that scientists
could use to figure out the
age of the Earth?
3. Remember:
Geologists use relative
dating to figure out if a
rock is older or younger
than other rock. The older
rocks are on bottom and
the younger rocks are on
top.
4. But What If You Want to
Know the Exact Age?
Geologists often also need to know the exact
age of a rock or fossil.
Finding the exact age of an object is called
absolute dating.
5. Absolute dating is the
method of measuring the
absolute age of an event
or object.
01
7. 02
Everything is made of
atoms. The original atom
is called the “parent
isotope." The new form is
called the "daughter
isotope."
8. Half-life is the time needed for half of
a sample of a radioactive substance to
undergo radioactive decay. After every
half-life, the amount of parent material
decreases by one-half.
So, in this afternoon we will going to explore and learn more about how old is earth and what are some tools or methods that scientists could use to figure out the age of the Earth? Let’s start!
As what you have seen in our example the formations of rock, the older rocks are at the bottom and the younger rocks is on the top. This method of identifying the rocks is what we called relative dating.
Remember: “ABSOLUTE” means exact or definite. Question: What is Absolute Dating?
As what you can see in the example picture, you can see the exact age of the volcanic ash which is ___________________. Again the top is the younger ones and at the bottom is the older.
Overtime, some of these atoms may change into a different type of atom. This breakdown of the unstable isotopes or other elements is called radioactive.
Example
A scientist knows that half of the parent atoms will turn into daughter isotopes every 10, 000 years. Originally, there is 16mg of parent isotopes. 10, 000 years go by, half of the 16mg of parents turn into daughter isotopes (16 divided by 2 = 8) So, there are 8mg of daughter isotopes now and there are 8mg of parent isotopes left. 16 – 8- 4- 2
Scientists have used absolute dating to figure out the age of the Earth. By counting the parent and daughter isotopes in some very old rocks, scientists say that the solar system including Earth is about 4.6 billion years old.
