Geomorphologists examine landforms and those forces, such as erosion and deposition, which cause them to change. Other geologists are primarily concerned with Earth history . Paleontologists study animal and plant fossils found in geological formations to trace the evolution and development of past life and to date sedimentary beds. Geochronologists determine the absolute ages of rocks and landforms by radioactive decay of their elements. Stratigraphers study the distribution and arrangement of sedimentary rock layers by examining their fossil and mineral content.
Many geologists specialize in new fields that require knowledge of another science as well.
Astrogeologists study geological conditions on other planets. Geological oceanographers study sediment transport, ocean sediments and other rocks on the ocean floor and continental shelf. Most geologists who work for petroleum companies explore for gas and oil. The majority are in the United States, but many work in other oil-producing areas, such as Canada, Australia, the Middle east, Africa, the North Sea, and Indonesia. They also conduct basic research in fields such as paleontology, geochemistry, and geophysics.