Geologists study physical earth materials and processes, including rocks, gases, minerals, sediment, and fossil fuels. Environmental geologists survey natural resources and advise mining, engineering, and petroleum sectors on how to find and safely extract earth materials and remediate human impact on groundwater supply and waste management. Geologists in research investigate patterns in earth phenomena hazardous to populations and ecosystems. Geologists conduct field studies for agencies like the USGS, model solutions for geological firms, and supervise environmental safety for city planning, conservation, and sustainability. They may specialize in fields like oceanography, seismology, and volcanology.