Geochronology
A series of techniques to find the age when a surface was created or exposed. Exposure dating uses the concentration of nuclides like  10Be, 26Al, 36Cl. They are produced by cosmic rays interacting with Earth materials. The data show when a surface, such as an alluvial fan, was created. Burial dating uses the radioactive decay of two elements to find the age when a sediment was buried away from cosmic rays.