Geology, scientific study of the physical history and structure of earth. Branches of geology include geomorphology (the study of how natural forces shape and alter land forms), petrology (the study of rocks), and mineralogy (the study of minerals). Geochemistry bridges geology and chemistry, investigating the chemical composition of the earth and the origin and distribution of the elements within it. Structural geology studies mountain-building processes and the folding, jointing, and fracturing of rocks. Geophysics bridges geology and physics, applying the law of physics to the study of the earth's interior, atmosphere, and oceans; it includes the study of earthquakes (seismology), volcanoes (volcanology), radioactivity, geomagnetism, and geoelectricity. One of the newest branches of geology is the investigation of plate tectonics, which accounts for the shifting of great land masses that used to be called continental drifts.