Geomorphotogists examine landforms and processes that cause changes such as erosion and glaciation. Other geologists are primarily concerned with earth history. Paleontologists study plant and animal fossils found in geological formation to trace evolution and development. Geochronologists determine the age of rocks and landforms by the radioactive decay of their elements. Stratigraphers study the arrangements of sedimentary and rock layers by examining their fossil and mineral content.
Water is an increasingly scarce resource.
Hydrogeologists are concerned with groundwater - how to extract water from aquifers and how to avoid contaminating them by pollutants. They conduct surveys and trial drilling to find it and to provide wells and water supplies. Many geologists specialise in new fields that require knowledge of another science as well. Astrogeologists for example study geological conditions of other planets. Geological oceanographers study the sedimentary and other rocks on the ocean floor and continental shelf.