Geochronology
![A schematic depiction of the major events in the history of Earth](/Images/godic/202501/15/Geological_time_spiral1911.png")
![Tephra horizons in south-central Iceland. The thick and light-to-dark coloured layer at the height of the volcanologists hands is a marker horizon of rhyolitic-to-basaltic tephra from Hekla.](/Images/godic/202501/15/Icelandic_tephra1911.JPG")
Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios. By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved.