Absolute Age of Rocks Williams Class Potomac Elementary School Blackfoot Missoula Montana

Absolute Ages of Rocks
After you have shuffled through you stack of magazines looking for articles about your favorite subject, you decide that you need to restack them into a neat pile. By now, there a jumble and no longer in order of their relative age that you found them in at the bottom of your locker. How can you stack them so the oldest are on the bottom and the newest are on top? Fortunately we are in luck and the magazines have a date printed on their cover. Unfortunately for geologists, rocks don't have their age printed on them. Or do they? Absolute Dating: A method used by geologists to determine the age in years of a rock or other object. Absolute dating is a process that uses the properties of atoms in rocks and other objects to find their ages. Ways that absolute dating is done. Radioactive Decay: The decay (break down) of an atom of one element into another element. This occurs over a set amount of time. Half Life: This is the amount of time it takes for half of the atom to decay . Example of a half-life of carbon-14 The half-life of carbon-14 atoms is 5730 years. So it will take 5730 years for half the carbon-14 atoms in an object to decay into nitrogen-14 atoms. You might guess that in another 5730 years all the carbon-14 would be gone. This is not the case. Only another half of the remaining carbon-14 atom will decay in the next 5730 years. So after two half-lives, one-fourth of the original carbon-14 atom will remain. After many half-lives it will be so small it might not be measurable. Radiometric Dating: A dating method that uses the known decay rate times (half-life) of elements in rocks to determine the absolute age of the rock. Radiocarbon Dating: Remember that living organisms are made up of carbon. Carbon-14 is useful for dating fossils, bones and wood up to 50,000 years old. Organisms take carbon out of the environment to build tissue in their bodies. When the organism dies the carbon-14 decays and turns into nitrogen-14. The amount of carbon-14 can be measured to determine the age of fossils or when humans used a fire site. Uniformitarianism: This idea that was developed by Scottish scientist James Hutton in 1700's His idea states that the Earth's processes (events) occurring today are similar to those that occurred in the past on Earth. He made observations that Earths events like erosion took much longer than earlier scientists had stated. From this idea he said that the Earth and rocks had to be much older than originally thought.

Absolute Ages of Rocks

After you have shuffled through you stack of magazines looking for articles about your favorite subject, you decide that you need to restack them into a neat pile. By now, there a jumble and no longer in order of their relative age that you found them in at the bottom of your locker. How can you stack them so the oldest are on the bottom and the newest are on top? Fortunately we are in luck and the magazines have a date printed on their cover. Unfortunately for geologists, rocks don't have their age printed on them. Or do they?

Absolute Dating:

A method used by geologists to determine the age in years of a rock or other object.

Absolute dating is a process that uses the properties of atoms in rocks and other objects to find their ages.

Ways that absolute dating is done.

Radioactive Decay:

The decay (break down) of an atom of one element into another element. This occurs over a set amount of time.

Half Life:
This is the amount of time it takes for half of the atom to decay .

carbon 14 decay image middle school geology

Example of a half-life of carbon-14

The half-life of carbon-14 atoms is 5730 years. So it will take 5730 years for half the carbon-14 atoms in an object to decay into nitrogen-14 atoms.

You might guess that in another 5730 years all the carbon-14 would be gone. This is not the case. Only another half of the remaining carbon-14 atom will decay in the next 5730 years. So after two half-lives, one-fourth of the original carbon-14 atom will remain.

After many half-lives it will be so small it might not be measurable.

Radiometric Dating:
A dating method that uses the known decay rate times (half-life) of elements in rocks to determine the absolute age of the rock.

Radiocarbon Dating:
Remember that living organisms are made up of carbon. Carbon-14 is useful for dating fossils, bones and wood up to 50,000 years old.

Organisms take carbon out of the environment to build tissue in their bodies. When the organism dies the carbon-14 decays and turns into nitrogen-14. The amount of carbon-14 can be measured to determine the age of fossils or when humans used a fire site.

Uniformitarianism:
This idea that was developed by Scottish scientist James Hutton in 1700's

His idea states that the Earth's processes (events) occurring today are similar to those that occurred in the past on Earth.

He made observations that Earths events like erosion took much longer than earlier scientists had stated. From this idea he said that the Earth and rocks had to be much older than originally thought.

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