Geosphere
The geosphere is the solid Earth, including the crust, mantle, and core, along with all rocks, minerals, soil, and landforms.
Definition
The geosphere is the solid part of Earth, from the ground underfoot down through the crust, mantle, and core, including all rocks, soil, sediment, and landforms, and it makes up about $99.9\%$ of Earth's mass. It is structured both by composition, crust, mantle, and core, and by mechanical behavior, lithosphere, asthenosphere, mesosphere, and the outer and inner core, and its internal heat, left over from planetary formation and generated by the radioactive decay of uranium, thorium, and potassium, drives mantle convection, plate tectonics, and the geodynamo, releasing a total surface heat flow of about $47$ terawatts. The geosphere also serves as the long-term reservoir for the carbon, water, and nutrient cycles, since silicate weathering and carbonate burial remove atmospheric $CO_2$ over roughly $100{,}000$-year timescales while volcanic outgassing returns it, coupling the solid Earth to climate through the rock cycle.
Example
The Appalachian Mountains, the red clay in a Charlotte backyard, the sand at the Outer Banks, and the hot core at Earth's center are all parts of the geosphere, and when the Appalachians eroded, that sediment fed rivers that built the Coastal Plain now supporting farms and forests. Uplift of the Himalaya and Tibetan Plateau over the past $50$ million years increased silicate weathering and is a leading hypothesis for the long-term cooling that led into the Cenozoic ice ages, while isostatic rebound after the last ice sheets melted still raises parts of Canada and Scandinavia about a centimeter each year.
Key Insight
Water, air, and living things are just a thin coating over the far larger geosphere, and it changes on two very different clocks, earthquakes and landslides happening in seconds while mountain building and erosion take millions of years. The geosphere effectively sets the boundary conditions for everything else on the planet, since continental positions steer ocean currents, mountain ranges direct winds and rain, and volcanic and weathering fluxes fix the long-term $CO_2$ baseline within which climate can vary.