Tell Whether A Rock Is Absolute Or Relative

Dig into the Earth’s surface to find rocks of different ages.

Determining the absolute or relative nature of rocks is essential for geologists. The most vital aspect of absolute and relative nature is that it provides clarity as to the age of the rock. The trick to understanding these two components is simple: absolute and relative natures exist at the same time. Absolute dating, according to the Utah Geological Survey, provides a specific era or year the rock was formed. Relative dating, on the other hand, places the age of rocks in a general chronological order.


1. Follow the law of superposition and crosscutting. Dig into the Earth’s surface and identify the shape, color, texture and type of rock you encounter by using geological charts. The law of superposition states that every rock you find closer to the Earth’s surface is younger than those deeper in the surface. The law of crosscutting states that every rock that cuts into or penetrates another rock is younger than the one it punctured. Identifying relative characteristics involves using the laws of superposition and crosscutting.

2. Compare fossil records against the rocks. Fossil imprints — plants or animals — on rocks offer assistance with relative dating. Matching a fossil record imprint on the body of a rock provides a clear idea of the rock’s relative age.

3. Use radiometric dating methods and a chart to determine a rock’s absolute nature. Radiometric dating identifies organic elements on individual rock crystals that help determine the age of a rock with greater specificity. Dating methods, such as Samarium-Neodymium, Lutetium-Hafnium and Rhenium-Osmium techniques, measure the decay of isotopes and their ratio against comparative organic elements to determine absolute age. Contact your local college geological department or state geological survey for specific information on dating techniques.

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