Planetary geologists study the moon and other planets to understand the evolution of the solar system. Structural geologists study deformation, fracturing and folding that has occurred in the Earth's crust. Stratigraphers investigate the time and space relationships of layered rocks and their fossil and mineral content. Sedimentologists study sedimentary rocks and the processes of sediment formation, transportation and deposition. Paleontologists study fossils to understand past life forms and their changes through time and to reconstruct past environments.
Marine geologists investigate the oceans and continental shelves.
Glaciologists study the physical properties and movement of glaciers and ice sheets. The long-range outlook is good at this time. Dwindling energy, mineral and water resources, increasing environmental concerns, global issues such as rising sea levels, and hazard assessment present new challenges to geoscientists. Career opportunities are increasing in environmental science and hydrogeology with the growing need to maintain Earth's natural environments and meet society's demands for Earth materials. According to the American Geological Institute's Geoscientific Employment and Hiring Survey - 1991, about 85,000 geoscientists work in the United States.