The geosphere includes the rocks and minerals on Earth – from the molten rock and heavy metals in the deep interior of the planet to the sand on beaches and peaks of mountains. The geosphere also includes the abiotic (non-living) parts of soils and the skeletons of animals that may become fossilized over geologic time.
Beyond these parts, the geosphere is about processes. The processes of the rock cycle such as metamorphism, melting and solidification, weathering, erosion, deposition, and burial are responsible for the constant recycling of rocks on Earth between sedimentary, igneous, and metamorphic states.
- Sedimentary rocks are formed via weathering and transport of existing rocks, and then deposition, cementation, and compaction into sedimentary rock.
- Igneous rocks are formed by the cooling and crystallization of molten rock.
- Metamorphic rocks are formed when heat or pressure is applied to other rocks.
The primary agent driving these processes is the movement of Earth’s tectonic plates, which creates mountains, volcanoes, and ocean basins. Changes in the rate that rocks are made and destroyed can have a profound effect on the planet. As the rate of plate tectonic movements has changed over geologic time scales, the rock cycle has changed as well, and these changes have been able to affected climate. For example, at times when the rate of plate movements has been high, there is more volcanic activity, which releases more particles into the atmosphere. Faster plate tectonic movements also mean more mountains are built in areas where plates converge. As rocks are uplifted into mountains, they start to erode and dissolve, sending sediments and nutrients into waterways and impacting the ecosystems for living things.