Age refers to the time elapsed since the birth of a living being or an object. We understand the age of plants and animals quite well since we usually measure their age in human time.

However, when it comes to the age of objects, it can be challenging to determine.

For instance, we may estimate the age of antiques based on the time period they were created in, but it can be difficult for an average person to identify the age of an antique accurately.

Rocks are ubiquitous, and we often ignore them. However, rocks are valuable records of ancient Earth history and living fossils. They are also useful for studying the origin and evolution of Earth, as well as the evolution of humans.

Hence, it is essential to understand the age of rocks. During research, geologists have found that geological time is ordered and stable, and a timeline similar to the A.D. is required to describe events that occurred at a specific geological time. This timeline is known as a geological chronology, and it is crucial for studying the history of our planet.

Geologists and chemists have discovered that when rocks or minerals form during a geological event, radioactive isotopes enter the rocks and minerals in a specific form. These isotopes decay continuously, leading to a gradual metamorphosis into substrates.

Therefore, by accurately measuring the parent and daughter radioisotope content in a rock or mineral, we can calculate its geological age based on the law of radioactive decay. This age determination is called isotope timing or radioactive timing, and the age of a geological event or cosmic event is known as the "isotopic geological age."

We can identify which rock formations are older and which are newer based on the stratigraphic sequence and sedimentary structure, among other characteristics. Different strata contain different fossil organisms, and the order of their evolution can help identify the sequence of stratigraphic deposition.

Rocks are classified into three major categories based on their formation time: magmatic rocks, sedimentary rocks, and metamorphic rocks. Magmatic rocks formed during the early stages of Earth's formation when a considerable amount of heat was generated at the core, which slowly spilled over the Earth's surface, resulting in magma everywhere.

When the magma cooled down, magmatic rocks were formed. The age of magmatic rocks refers to the time since their formation to the present.

On the other hand, sedimentary rocks are formed due to the erosion of water and weathering. This results in the deposition of previously formed magmatic and metamorphic rocks in low-lying areas such as the sea floor, which gradually solidify into rocks after many years. The age of sedimentary rocks refers to the time elapsed since their formation to the present.

Metamorphic rocks are formed through metamorphism, which can occur through contact metamorphism or dynamic metamorphism. Contact metamorphism occurs when hot magma flows into cold rocks, leading to their metamorphism on the surface.

Dynamic metamorphism occurs when pressure generated by tectonic movements leads to the formation of fractured rocks. The age of metamorphic rocks is the time elapsed since their formation to the present.

Rocks have an age that can be determined by studying their formation and composition. Understanding the age of rocks is critical in studying the history of our planet and the evolution of humans.

It enables us to gain valuable insights into the Earth's origin and evolution, which is vital for understanding the planet we live on.