Genologic time: what is absolute dating/nurmerial age? describe this method and how it is used to evaluate genologic time?

http://en.wikipedia.org/wiki/Absolute_dating

Absolute dating, also known as numerical age dating, is a method used in geology to determine the exact age of rocks, fossils, and other geological materials. It involves assigning a specific numerical age to an event or object in the geological timescale. This is achieved by analyzing radioactive isotopes or other geological phenomena present in the material being studied.

The method of absolute dating relies on the principle of radioactive decay. Certain elements found in rocks, such as uranium and potassium, have unstable isotopes that spontaneously break down over time into more stable forms. This decay occurs at a consistent rate, known as the half-life, which is the time it takes for half of the parent isotopes to decay into daughter isotopes.

To use absolute dating, scientists typically measure the ratio of parent isotopes to daughter isotopes in a sample. By knowing the half-life and the current ratio, they can calculate how much time has passed since the beginning of radioactive decay within the material. This determination provides a numerical age.

Scientists also utilize other methods, like tree ring dating (dendrochronology), ice core dating, or varve analysis (counting layers in sedimentary rocks), to establish timeframes for specific periods and validate their findings.

In evaluating geological time, absolute dating helps explain the ages of rocks, the sequence of events in Earth's history, and the timing of important geological processes. It allows scientists to create a precise chronological order of events, such as the duration of geological periods, the formation of mountain ranges, the extinction of species, and other geological phenomena.

By studying different rock layers and fossils in various locations, scientists can correlate the ages of rocks and fossils from different regions, establishing a relative timeline of Earth's history. Absolute dating then provides specific ages for these events or materials, enabling a more accurate understanding of geological processes and the evolution of life on our planet.