What is the Geosphere?
The geosphere is the earth itself: the rocks, minerals, and landforms of the surface and interior. Below the crust - which varies in depth from about 5 km beneath the ocean floor to up to 70 km below the land surface, temperatures are high enough for deformation and a paste-like flow of elements. At one time, roughly 200 million years ago, the continents were joined together in a supercontinent called Pangaea, but since then tectonic plates have slowly separated, creating the arrangement of the continents we are accustomed to today.
Plate tectonic movement is ongoing, and humans can witness its sometimes violent activity in the form of earthquakes and volcanoes. More regularly, however, human interaction with the dynamic geosphere comes in the form of surface erosion, our use of arable land for farming, and excavations for the construction of buildings, roads, and mines.
How does the geosphere interact in the earth system?
While seemingly static, the geosphere is in fact a very active player in the earth's systems, affecting the atmosphere and the oceans, as well as critical processes such as the water cycle and biogeochemical cycles. For instance, the types of minerals contained in soils - the results of geologic processes - help to determine the vegetative cover and ecosystems on the soil surface. Carbon – an essential element of life – is bound in organic matter and is carried to the ocean via wind and water erosion where eventually it becomes part of the ocean floor. Tectonic movement carries ocean deposits into the earth's interior. On geologic timescales, volcanic activity can vent the stored carbon to the Earth's atmosphere as carbon dioxide. The carbon cycle is one of the key cycles linking the geosphere, atmosphere, hydrosphere, and biosphere.
The inner core of the earth contains liquid iron. Its motion is thought to drive the earth's magnetic field – the magnetosphere - which extends far beyond the atmosphere, protecting Earth and its biosphere from solar wind and cosmic radiation. This layer is extremely hot and advances in geothermal technology could some day enable us to harness greater amounts of heat energy from within the crust and convert it to electricity at the surface.
Evolution of the continents.Fast-forward 200 million years from the time of Pangaea to the creation of the modern-day continents. (Credit: ARC Science Simulations)
How do humans interact with the geosphere?
Soy Plantation, Amazon Brazil.With the aid of fossil fuel-powered machinery, man can make sweeping changes to the natural landscape. In Brazil, for instance, the drive to produce more and more soybeans for food and biofuels leads to deforestation of the Amazon rainforest.
Aside from surface disturbances such as excavations and agriculture, humans have a fairly minor impact on the workings and scale of the geosphere. Humans still live largely at the mercy of powerful geologic forces. The 2010 Haiti earthquake is just one of many examples of the impact of these forces. While we may never be able to stop earthquakes or volcanoes, studying their mechanics can enable us to better understand their dynamics so that we may continue to develop means for reducing risk to homes and people when they occur.
Geosphere
There are several conflicting definitions for geosphere.
The geosphere may be taken as the collective name for the lithosphere, the hydrosphere, the cryosphere, and the atmosphere.[1] The different collectives of the geosphere are able to exchange different mass and/or energy fluxes. Fluxes being the measurable amount of change. The exchange of these fluxes affects the balance of the different spheres of the geosphere. An example is how the soil acts as a part of the biosphere.[2] While also acting as a source of flux exchange.
In Aristotelian physics, the term was applied to four spherical natural places, concentrically nested around the center of the Earth, as described in the lectures Physica and Meteorologica. They were believed to explain the motions of the four terrestrial elements: Earth, Water, Air and Fire.
In modern texts and in Earth system science, geosphere refers to the solid parts of the Earth; it is used along with atmosphere, hydrosphere, and biosphere to describe the systems of the Earth (the interaction of these systems with the magnetosphere is sometimes listed). In that context, sometimes the term lithosphere is used instead of geosphere or solid Earth. The lithosphere, however, only refers to the uppermost layers of the solid Earth (oceanic and continental crustal rocks and uppermost mantle).[3]
Since space exploration began, it has been observed that the extent of the ionosphere or plasmasphere is highly variable, and often much larger than previously appreciated, at times extending to the boundaries of the Earth's magnetosphere or geomagnetosphere.[4] This highly variable outer boundary of geogenic matter has been referred to as the "geopause",[5] to suggest the relative scarcity of such matter beyond it, where the solar wind dominates.