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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 (planet)|Earth.Wordnet Search: Earth science It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holism|holistic approaches to Earth sciences. The formal discipline of Earth sciences may include the study of the atmosphere, oceans and biosphere, as well as the solid earth. Typically Earth scientists will use tools from physics, chemistry, biology, chronology and mathematics to build a quantitative understanding of how the Earth system works, and how it evolved to its current state.

Fields of study

The following fields of science are generally categorized within the geosciences:
- Geology describes the Rock (geology)|rocky parts of the Earth's Crust (geology)|crust (or lithosphere) and its historic development. Major subdisciplines are mineralogy and petrology, geochemistry, geomorphology, paleontology, stratigraphy, structural geology, engineering geology and sedimentology.Adams 20Smith 5
- Geophysics and Geodesy investigate the figure of the Earth|shape of the Earth, its reaction to forces and its magnetic field|magnetic and gravity fields. Geophysicists explore the Earth's core and Earth's mantle|mantle as well as the Plate tectonics|tectonic and Seismology|seismic activity of the lithosphere.Wordnet Search: GeodesyNOAA National Ocean Service Education: Geodesy
- Soil science covers the outermost layer of the Earth's crust that is subject to soil formation processes (or pedosphere).Elissa Levine, 2001, The Pedosphere As A Hub Major subdisciplines include edaphology and Pedology (soil study)|pedology.Duane Gardiner, Lecture: Why Study Soils? excerpted from Miller, R.W. & D.T. Gardiner, 1998. Soils in our Environment, 8th Edition
- Oceanography and hydrology (includes limnology) describe the marine and freshwater domains of the watery parts of the Earth (or hydrosphere). Major subdisciplines include hydrogeology and Physical oceanography|physical, Chemical oceanography|chemical, and Marine biology|biological oceanography.
- Glaciology covers the ice|icy parts of the Earth (or cryosphere).
- Atmospheric sciences cover the gaseous parts of the Earth (or Earth's atmosphere|atmosphere) between the surface and the exosphere (about 1000 km). Major subdisciplines are meteorology, climatology, atmospheric chemistry and atmospheric physics.
- A very important linking sphere is the biosphere, the study of which is biology. The biosphere consists of all forms of life, from Microorganism|single-celled organisms to Pine|pine trees to Human|people. The interactions of Earth's other spheres - lithosphere/geosphere, hydrosphere, atmosphere and/or cryosphere and pedosphere - create the conditions that can support life.

Earth's interior

Plate tectonics, mountain|mountain ranges, volcanoes, and earthquakes are Geology|geological phenomena that can be explained in terms of energy transformations in the Earth's crust.Earth's Energy Budget Beneath the Earth's lithosphere|crust lies the Earth's mantle|mantle which is heated by the radioactive decay of heavy elements. The mantle is not quite solid and consists of magma which is in a state of semi-perpetual wiktionary:convection|convection. This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics.Simison par. 7Adams 94,95,100,102Smith 13-17,218,G-6Oldroyd 101,103,104 Plate tectonics might be thought of as the process by which the earth resurfaces itself. Through a process called ''spreading ridges'' (or seafloor spreading), the earth creates new crust by allowing magma underneath the lithosphere to come to the surface where it cools and solidifies--becoming new crust, and through a process called subduction, excess crust is pushed underground--beneath the rest of the lithosphere--where it comes into contact with magma and melts--rejoining the mantle from which it originally came.Smith 327 Areas of the crust where new crust is created are called ''divergent boundaries'', and areas of the crust where it is brought back into the earth are called ''convergent boundaries''.Smith 316,323-325There is another type of boundary called a transform boundary where plates slide in opposite directions but no new lithospheric material is created or destroyed (Smith 331). Earthquakes result from the movement of the lithospheric plates, and they often occur near covergent boundaries where parts of the crust are forced into the earth as part of subduction.Smith 325,326,329 Volcanoes result primarily from the melting of subducted crust material. Crust material that is forced into the Asthenosphere melts, and some portion of the melted material becomes light enough to rise to the surface--giving birth to volcanoes.

Earth's electromagnetic field

An electromagnet is a magnet that is created by a current that flows around a soft-iron core.American 576 Earth has a soft iron Earth core|core surrounded by semi-liquid materials from the mantle that move in continuous currents around the core;The earth has a solid iron inner core surrounded by a liquid outer core (Oldroyd 160). therefore, the earth is an Wiktionary:electromagnet|electromagnet. This is referred to as the dynamo theory of Earth's magnetism.Oldroyd 160 The fact that Earth is an electromagnet helps it maintain an atmosphere suitable for life.

Atmosphere

Earth is blanketed by an atmosphere consisting of 78.0% nitrogen, 20.9% oxygen, and 1% Argon.Adams 107-108 The atmosphere has five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere; and 75% of the atmosphere's gases are in the bottom-most layer, the troposphere. The magnetic field created by Earth's mantle|mantle's internal motions produces the magnetosphere which protects the Earth's atmosphere from the solar wind.Adams 21-22 It is theorized that the solar wind would strip away earth's atmosphere in a few million years were it not for the Earth's electromagnet. And since earth is Age of the earth|4.5 billion years old,Smith 183 earth would not have an atmosphere by now if there were no magnetosphere. The atmosphere is composed of 78% nitrogen and 21% oxygen. The remaining one percent contains small amounts of other gases including CO₂ and water vapors. Water vapors and CO₂ allow the Earth's atmosphere to catch and hold the sun's energy through a phenomenon called the greenhouse effect.American 770 This allows earth's surface to be warm enough to have liquid water and support life. In addition to storing heat, the atmosphere also protects living organisms by shielding the Earth's surface from cosmic rays. Note that the level of protection is high enough to prevent cosmic rays from destroying all life on Earth, yet low enough to aid the mutations that have an important role in pushing forward evolution|diversity in the biosphere.

Methodology

Like all other scientists, Earth scientists apply the scientific method. They formulate hypotheses after observing events and gathering data about natural phenomena, and then they test hypotheses from such data. A contemporary idea within earth science is uniformitarianism (science)|uniformitarianism. Uniformitarianism says that "ancient geologic features are interpreted by understanding active processes that are readily observed". Simply stated, this means that features of the Earth can be explained by the actions of gradual processes operating over long periods of time; for example, a mountain need not be thought of as having been created in a moment, but instead it may be seen as the result of continuous subduction, causing magma to rise and form continental volcanic arcs.

Earth's spheres

Earth science generally recognizes four spheres, the lithosphere, the hydrosphere, the atmosphere, and the biosphere Earth's Spheres. ©1997-2000. Wheeling Jesuit University/NASA Classroom of the Future. Retrieved November 11, 2007. ; these correspond to Rock (geology)|rocks, water, air, and life. Some practitioners include, as part of the spheres of the Earth, the cryosphere (corresponding to ice) as a distinct portion of the hydrosphere, as well as the pedosphere (corresponding to soil) as an active and intermixed sphere.