Relative dating stratigraphy

Stratigraphy: The branch of geology that catalogues Earth's successions of rock layers.Half-life is a measurement of the time it takes for one-half of a radioactive element to decay.The fossils of changing lifeforms found in the different strata also help geologists determine the long history of Earth.

relative dating stratigraphy-87

Because of this stable process, scientists are able to estimate when a particular element was formed by measuring the amount of original and transformed atoms in that element. The age of the whole Earth is deduced from the ages of other materials in the solar system, namely, meteorites.

Meteorites are pieces formed from the cloud of dust and debris left behind after the beginning of the solar system.

Geologic time describes the immense span of time—billions of years—revealed in the complex rock surface of Earth.

Geologists have devised a geologic time scale that divides Earth's history into units of time. A unit is defined in terms of the fossils or rock types found in it that makes it different from the other units.

An important feature of the radioactive decay process is that each element decays at its own rate.

The half-life of a particular element, therefore, is constant and is not affected by any physical conditions (temperature, pressure, etc.) that occur around it.

Many people believed Earth was only a few thousand years old.

They also believed that all the physical features of Earth—mountains, valleys, oceans, rivers, continents—were the same as they had always been.

Since that time, geologists have learned to study the strata, or the thousands of layers of sedimentary rock that make up the Earth's crust.

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