The geologic time scale, back to the oldest rocks, some 4,280,000,000 years ago, can be quantified by isotopic dating techniques.
In other subdisciplines of geophysics, gravimetric techniques are used to determine the shape and size of underground structures; electrical methods help to locate a variety of mineral deposits that tend to be good conductors of electricity; and paleomagnetism has played the principal role in tracking the drift of continents.
Thus a few minerals such as the feldspars, quartz, and mica are the essential ingredients in granite and its near relatives.
Limestones, which are widely distributed on all continents, consist largely of only two minerals, calcite and dolomite.
Geologic history provides a conceptual framework and overview of the evolution of the Earth.
An early development of the subject was stratigraphy, the study of order and sequence in bedded sedimentary rocks.
The combination of weathering and erosion leads to the wearing down or denudation of mountains and continents, with the erosion products being deposited in rivers, internal drainage basins, and the oceans. The unconsolidated accumulated sediments are transformed by the process of diagenesis and lithification into sedimentary rocks, thereby completing a full cycle of the transfer of matter from an old continent to a young ocean and ultimately to the formation of new sedimentary rocks.