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Utah Geological Survey: How Do Geologists Know How Old a Rock Is?
Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the...
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Bc Open Textbooks: Physical Geology: Crystallization of Magma
The minerals that make up igneous rocks crystallize at a range of different temperatures. The sequence in which minerals crystallize from magma is known as the Bowen reaction series. An explanation of the reaction series is provided...