Petroleum geology is an interdisciplinary field composed of geophysics, geochemistry, and paleontology. The term incorporates aspects of geophysics, geochemistry, mineralogy, geodesy, and cartography. There are four major disciplines in earth sciences, namely geography, geology, geophysics and geodesy. The terms are used in geology, paleontology, geophysics, astronomy, and physical cosmology. In the 1920s, departments formed in geology, petroleum engineering and geophysics. The precision maps are applicable to studies in geophysics, geology and atmospheric circulation. Volcanologists require a bachelor's degree at minimum in geology, geophysics, or earth science. Virtually all dynamos in astrophysics and geophysics are hydromagnetic dynamos. Other studies include actinometry, geophysics, medicine and climatology. Rheology has applications in materials science, engineering, geophysics, physiology, human biology and pharmaceutics. There are examples in atmospheric sciences and in geophysics. Magnetic surveying is one of a number of methods used in archaeological geophysics. Ground penetrating radar survey is one method used in archaeological geophysics. Soltec, captain of the geophysics science survey flying saucer "Phoenix". The word "wavelet" has been used for decades in digital signal processing and exploration geophysics.