Final answer:
Relative age of rocks is determined by comparing them to other rocks or events rather than using an absolute age. Geologists use relative dating to establish the order of events in Earth's history, based on the positions of fossils in rock layers. Relative dating is cost-effective and versatile, but it does not provide precise ages.
Step-by-step explanation:
Relative age of rocks refers to the geologic age of an organism, rock, or event that is defined in relation to other rocks or events rather than in years before present or an absolute age.
Geologists use relative dating to determine the comparative age of two objects or events. One method of relative dating is by examining the rock layers in which fossils formed. Lower layers are assumed to contain older fossils, while higher layers are assumed to contain younger fossils.
Relative dating has advantages such as being inexpensive and quick, and it can be used on various types of rocks. However, it does not provide an exact age for the rocks. Absolute dating, on the other hand, is the only method that can give an exact age to a particular rock, but it is limited to certain minerals or materials.