Physical Geography examines the natural and physical systems of the Earth including the atmosphere, biosphere, cryosphere (ice and snow), hydrosphere (water) and lithosphere (land surface). Physical geographers also look at the connections between these systems, how they change over time, and the implications of these changes. Atmospheric science covers topics such as climate change, storms (including tornadoes), weather systems and other atmospheric phenomena. Biogeography is the study of the biosphere, and examines the geographic nature of plants, animals, and ecosystems. Hydrology is the study of the Earth’s water in its many forms including ice, snow, rivers, lakes, and groundwater. Lastly, geomorphology examines the nature of the Earth’s land surface features such as mountains and river.