Potassium-Argon Dating

The process of calculating the ratio of radioactive argon to radioactive potassium of rock to find out its time of origin is called potassium argon dating or K Ar dating. This method is used in many fields to determine the age of a sample. The process in rocks is based on the decay of radioactive potassium-40 to radioactive argon-40. Some parts also decay to calcium-40. The ratio of these components in a sample or rock is the measure of its age. The potassium argon method calculates the ages of several objects like meteorites, volcanic rocks, different types of minerals, etc. Some meteorites have dated back to 450 crore years, and some volcanic rocks are aged just 20,000 years.

Potassium Argon Dating Formula

The potassium argon dating process follows a particular formula to determine the age of a rock or a sample. The decay profile of radioactive potassium determines the age and origin of radioactive argon. Radioactive potassium also decays to radioactive calcium. The radioactive form of potassium and argon are potassium-40 and argon-40. The ratio of radioactive potassium, radioactive argon, and radioactive calcium is measured. This ratio is compared with the time of radioactivity. The entire process is completed through a particular formula of radioactivity. Thus, the age of a rock or a sample can be found out. 

How Does K Ar Dating Work?

One of the most abundant components in the earth's crust is potassium, about 2.4% of the mass. Out of every 10,000 potassium atoms, one radioactive potassium is present there. 19 protons and 21 neutrons are present in the nucleus of the radioactive potassium. When a proton of the radioactive potassium collides with a beta particle, it becomes neutral and converts into a neutron. The number of neutrons and protons in the nucleus becomes 22 and 18. It is the nucleus structure of radioactive argon. Thus, radioactive potassium atoms convert into radioactive argon atoms. By observing the transformation of potassium into argon, the age of a sample can be determined. 

Importance of Radioactivity

The potassium argon dating process is mainly dependent on radioactivity. By observing the transformation of radioactive potassium into radioactive argon, the age of a sample is determined. Every radioactive atom has a particular life. Relating the ratio of the particles in the sample and their life, the age is calculated. Therefore, radioactivity is a vital matter to determine the age of a sample.

Limitations of Potassium Argon Method

As K Ar dating is a sensitive geological process, there are some limitations to the method. The limits are mentioned below. 

• The volcanic rocks leave no evidence of going through a heating- recrystallization process after initial formation. Expert geologists should process the entire method. If there is any fault in the sample collection process, it can create problems in determination.

• This process has a strong relationship with the time duration. As the transformation of radioactive atoms concerning time is observed in this process, the time duration of the sample and the ratio of the atoms should be measured correctly.

• When a sample becomes higher than one million years old, it is difficult to determine the actual age and origin. Therefore, the ratio of the radioactive potassium and radioactive argon atoms present in the sample should be measured sincerely. 

During a potassium argon dating process, the things mentioned above should be considered. Otherwise, the actual age and origin of a sample cannot be determined correctly. 

Did You Know?

Now, we are going to discuss some unknown facts about the potassium argon dating process. 

• K Ar dating is one of the most used processes in archaeology and geochronology. 

• The potassium argon dating process is dependent on the abundance of nonradioactive calcium, potassium, and argon in the earth. 

• This process is related to the atmosphere and its changes, and volcanism. 

• Many meteorites have been found, dating back to 4,500,000,000 years through the potassium argon method of dating objects. Some volcanic rocks have been found just 20,000 years old by examination by the same process.