What is the Geosphere?
The geosphere is the Earth itself, the rocks, minerals and landforms of the surface as well as the interior. Below the crust which varies from about 5 km beneath the ocean to about 30 km below the land surface, temperatures are high enough for deformation and flow. The continents are lower in density then other crustal material and ride above the denser material. At one time, roughly 200 million years ago, the continents were joined together in a supercontinent called Pangaea, but since then the plates have slowly separated, creating the placement of the continents we are accustomed to today. Plate tectonics is still 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?
[click to launch animation]
Animation: 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)
The geosphere is an active player in the Earth system, affecting the atmosphere and the oceans, as well as critical processes such as the water cycle and the biogeochemical cycle. For instance, the types of minerals contained in soils--a factor of geologic processes--help to determine the vegetative cover of the surface. This vegetative cover influences the type and behavior of animals in the area, which in turn influences the composition of the ecosystem. Carbon bound in organic matter is carried to the ocean where eventually it becomes part of the ocean floor. Tectonic movement carries the ocean deposits into the earth's interior. On geologic timescales, volcanic activity can vent the carbon to the Earth's atmosphere as carbon dioxide. The outer core of the Earth contains liquid iron. Its motion drives the Earth's magnetic field which extends far beyond the atmosphere.
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 2004 earthquake in the Indian Ocean, along with the tsunami it triggered, is just one of many examples of the devastating impact of these forces. While we may never be able to stop earthquakes or volcanoes, our understanding of their mechanics may enable us to better predict them and adapt to them. Additionally, advances in geothermal technology will enable us to harness greater amounts of heat energy within the crust which can be converted to electricity at the surface.
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