Aqueous geochemists study the distribution of chemical elements in surface and subsurface water. Planetary geologists study the moon and other planets of our solar system for clues about the origin and possible future development of the Earth. Glaciologists study the properties of ice, the movement of glaciers and ice sheets, and the effects glaciations have on world climate. Paleontologists study fossils to document the origin and evolution of life and reconstruct past environments. Stratigraphers investigate and interpret the sources of sediment and the depositional environments of sedimentary rocks from their fossil and mineral content.
Economic geologists explore the world for deposits of valuable mineral resources.
Hydrogeologists study how subsurface water migrates and determine ways to prevent contamination of known subsurface water supplies. Environmental geologists study the hazards of flooding and erosional mass movement in urbanized areas and the threat of groundwater pollution from careless waste disposal. Seismologists study the Earth's interior from earthquake waves and monitor the risks to urbanized areas from nearby active fault zones. All cooperate in understanding the Earth.