Topic summary
Geologically
Extracted from the Wikipedia article Geology.
Absolute dating
Dating of lava and volcanic ash layers found within a stratigraphic sequence can provide absolute age data for sedimentary rock units that do not contain radioactive isotopes and calibrate relative dating techniques. These methods can be used to determine ages of pluton emplacement. Fractionation of the lanthanide series elements is used to compute ages since rocks were removed from the mantle. Other methods are used for more recent events. Optically stimulated luminescence and cosmogenic radionuclide dating are used to date surfaces and/or erosion rates. Dendrochronology can be used for the dating of landscapes. Radiocarbon dating is used for geologically young materials containing organic carbon.