The geosphere is the solid Earth that includes continental and oceanic crust as well as the various layers of the Earth's interior. Ninety-four percent of the earth is composed of the elements oxygen, iron, silica, and magnesium, and the interior of the earth is layered both chemically and mechanically. The geosphere is not static, but its surface (crust) is in a constant state of motion that gives rise to movement of the continents. The unifying theory that explains how continental drift is possible is called plate tectonics, which was developed by geologists in the 1960s.
Links to other components:
Atmosphere: Each year volcanism spews significant amounts of gases (water vapor, carbon dioxide, sulfur dioxide, hydrogen, hydrogen sulfide, etc) into the atmosphere. For example, explosive volcanism that injects large amounts of sulfur dioxide to the upper atmosphere is known to result in cooling of climate in the years immediate following the eruption.
Hydrosphere: Water is the main agent of chemical and mechanical erosion of the earth surface. When water flows over land it mechanically breaks rocks into finer particles and can chemically dissolve elements contained in rock-forming minerals. The sediment and chemical constituents are carried away downstream as the water makes its way back to the ocean. Consider, for example, the awesome depth of the Grand Canyon which was cut by the erosive power of the Colorado River. Over long periods of geologic time, erosion by water can wear down mountain ranges (process called peneplanation) and transport this material to be deposited in sedimentary basins.
Biosphere: The weathering of the geosphere to form soils provides terrestrial plants with a firm substrate and vital nutrients (phosphorous, nitrogen) and minerals needed for plant growth. In addition, the chemical weathering of the geosphere by water transports essential nutrients (phosphorous, nitrogen, silica, etc) to the oceans which are used by algae (marine plants) during photosynthesis.
Anthrosphere: Man has been exploiting the mineral resources of the geosphere by mining of raw materials. For example, the mining and subsequent combustion of fossil fuels represents a transfer of carbon from the geosphere to the atmosphere. By this process, man has accelerated the natural rate of transfer of carbon dioxide from the geosphere to the atmosphere. In turn, the increased concentration of carbon dioxide in the atmosphere will lead to global warming by enhancing the greenhouse effect.