Earth science
Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth science. The major historic disciplines use physics, geography, mathematics, chemistry, and biology to build a quantitative understanding of the principal areas or spheres of the Earth system:
Earth's spheres
- Geology describes the rocky parts of the Earth's crust (or lithosphere) and its historic development. Major subdisciplines are mineralogy and petrology, geochemistry, geomorphology, paleontology, stratigraphy and sedimentology.
- Geodesy and Geophysics (joined together in the IUGG) investigate the figure of the Earth, its reaction to forces and its potential fields (magnetic and gravity field). Geophysicists explore also the Earth's core and mantle and the natural deposits, Geodesists the movement of stars and satellites.
- Soil science covers the outermost layer of the Earth's crust that is subject to soil formation processes (or pedosphere). Major subdisciplines include edaphology and pedology.
- Oceanography and Hydrology (incl. Limnology) describe the marine and freshwater domains of the watery parts of the Earth (or hydrosphere). Major subdisciplines include hydrogeology and physical, chemical, and biological oceanography. Within the scientific union IUGG the disciplines are joined with Geophysics, except the chemical ones.
- Glaciology covers the icy parts of the Earth (or cryosphere)
- Atmospheric sciences cover the gaseous parts of the Earth (or atmosphere) between the surface and the exosphere (~1000 km). Major subdisciplines are Meteorology, Climatology and Aeronomy.
However, due to the numerous interactions between the spheres many modern fields take an interdisciplinary approach and thus do not sit "comfortably" in this scheme. Even the above specialisms do not operate in isolation. For example to understand the circulation of the oceans, the interactions between ocean, atmosphere and Earth rotation must be considered.
Interdisciplinary fields
Other types of research are even more interdisciplinary and interactions between different disciplines are central to them, for example:
- Biogeochemistry follows the cycling of elements through the spheres mediated by biological and geological processes, and especially their distribution and fluxes between reservoirs.
- Mineralogy and Mineral Physics consider the rock-forming minerals on the atomic length-scale, both as part of geosystems and increasingly with an eye towards technological applications (for instance, as catalysts or exploiting their potential ferroelectric properties); in this, there is extensive and increasing overlap with solid-state physics, crystal chemistry and Materials Science.
- Paleoceanography and Paleoclimatology use the properties of sediments, ice cores, or biological material to infer past states of the ocean, atmosphere or climate.
- Meteorology describes, explains and predicts the weather based on the interaction of principally the ocean and atmosphere.
- Climatology describes and explains the climate in terms of the interaction of the litho-, pedo-, hydro-, atmo-, cryo-, and bio- spheres.
- Atmospheric chemistry describes, explains and predicts the chemical composition of the atmosphere in principlly terms of the interactions of the ocean, atmosphere, biosphere and human influence.
Earth system science
Many scientists are now starting to use an approach known as Earth system science which treats the entire Earth as a system in its own right, which evolves as a result of positive and negative feedback between constituent systems. The systems approach, enabled by the combined use of computer models as hypotheses tested by global satellite and ship-board data, is increasingly giving scientists the ability to explain the past and possible future behaviour of the Earth system.
Complex computer models which seek to model several different parts of the Earth system and the interactions between them are known as Earth system models. Many are based on Global climate models and include sub models for the ocean, atmosphere, biosphere and other parts of the earth system. These interactions are of particular importance when trying to understand changes over decade to centuries and longer periods.
Gaia theories explain the behaviour of the Earth system in terms of the influence of the biosphere.
Methodology
Like all other scientists, earth scientists apply the scientific method: formulate hypotheses after observation of and gathering data about natural phenomena and then test those hypotheses. In earth science, data usually plays a critical role in testing and formulating hypotheses.
Partial list of the major Earth Science topics
Atmosphere
Biosphere
Hydrosphere
Lithosphere or geosphere
- Geology
- Geochemistry
- Geomorphology
- Geophysics
- Geochronology
- Geodynamics (see also Tectonics)
- Geomagnetics
- Gravimetry (also part of Geodesy)
- Seismology
- Hydrogeology
- Mineralogy
- Petrology
- Volcanology
