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* 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.
* 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==
[[Image:Volcano q.jpg|thumb|A [[volcano]] is the release of stored energy from below the surface of Earth, originating from radioactive decay and gravitational sorting in the Earth's core and mantle, and residual energy gained during the Earth`s formation.<ref>Encyclopedia of Volcanoes, Academic Press, London, 2000</ref>]]


[[Plate tectonics]], [[mountain|mountain range]]s, [[volcano]]es, and [[earthquake]]s are [[Geology|geological phenomena]] that can be explained in terms of [[energy transformation]]s in the [[Earth's crust]].<ref>[http://okfirst.ocs.ou.edu/train/meteorology/EnergyBudget.html Earth's Energy Budget]</ref>

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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]].<ref>Simison par. 7</ref><ref name="adams tectonics">Adams 94,95,100,102</ref><ref>Smith 13-17,218,G-6</ref><ref name="oldroyd tectonics">Oldroyd 101,103,104</ref>

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.<ref name="adams tectonics"/><ref name="oldroyd tectonics"/><ref>Smith 327</ref>

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''.<ref>Smith 316,323-325</ref><ref>There 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).</ref> [[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.<ref name="smith subduction">Smith 325,326,329</ref>

<!-- A diagram is needed here. -->
[[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.<ref name="adams tectonics"/><ref name="smith subduction"/>


== Earth's electromagnet ==
== Earth's electromagnet ==

Revision as of 18:32, 13 August 2008

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[1]. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth science. There are four major disciplines in earth sciences, namely geography, geology, geophysics and geodesy. These major disciplines use physics, chemistry, biology, chronology and mathematics to build a quantitative understanding of the principal areas or spheres of the Earth system.

Earth's spheres

Earth science generally recognizes 4 spheres, the lithosphere, the hydrosphere, the atmosphere, and the biosphere[2]; these correspond to 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.

Lava flows from the Kīlauea volcano into the ocean on the Island of Hawaii.

The following fields of science are generally categorised within the geosciences:


Earth's electromagnet

An electromagnet is a magnet that is created by a current that flows around a soft-iron core.[9] The earth has a soft iron core surrounded by semi-liquid materials from the mantle that move in continuous currents around the core;[10] therefore, the earth is an electromagnet. This is referred to as the dynamo theory of earth's magnetism.[11][12] The fact that earth is an electromagnet helps with the earth's maintenance of an atmosphere suitable for life.

Atmosphere

The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. It is compressed on the day (Sun) side due to the force of the arriving particles, and extended on the night side. (Image not to scale.)

The earth is blanketed by an atmosphere consisting of 78.0% nitrogen, 20.9% oxygen, and 1% Argon.[13] 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.[13]

The magnetic field created by mantle's internal motions produces the magnetosphere which protects the earth's atmosphere from the solar wind.[14] 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.[citation needed] And since earth is 4.5 billion years old,[15] 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.[13] Water vapors and CO2 allow the earth's atmosphere to catch and hold the sun's energy through a phenomenon called the greenhouse effect.[16] 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 diversity in the biosphere.[citation needed]

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. Uniformitarianism says that "ancient geologic features are interpreted by understanding active processes that are readily observed".[citation needed] 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.

Partial list of the major Earth Science topics

Atmosphere

Biosphere

Hydrosphere

Lithosphere or geosphere

Pedosphere

Systems

Others

Notes and references

  1. ^ Wordnet Search: Earth science
  2. ^ Earth's Spheres. ©1997-2000. Wheeling Jesuit University/NASA Classroom of the Future. Retrieved November 11 2007.
  3. ^ Adams 20
  4. ^ a b Smith 5
  5. ^ Wordnet Search: Geodesy
  6. ^ NOAA National Ocean Service Education: Geodesy
  7. ^ Elissa Levine, 2001, The Pedosphere As A Hub
  8. ^ Duane Gardiner, Lecture: Why Study Soils? excerpted from Miller, R.W. & D.T. Gardiner, 1998. Soils in our Environment, 8th Edition
  9. ^ American 576
  10. ^ The earth has a solid iron inner core surrounded by a liquid outer core (Oldroyd 160).
  11. ^ Oldroyd 160
  12. ^ Demorest, Paul (2001-05-21). "Dynamo Theory and Earth's Magnetic Field" (PDF). Retrieved 2007-11-17.
  13. ^ a b c Adams 107-108
  14. ^ Adams 21-22
  15. ^ Smith 183
  16. ^ American 770

References

  • Adams, Simon (2006). Earth Science: An illustrated guide to science. New York NY 10001: Chelsea House. pp. pp. 20. ISBN 0-8160-6164-5. {{cite book}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |ids= ignored (help)CS1 maint: location (link)
  • American Heritage dictionary of the English language (4th edition ed.). 222 Berkeley Street, Boston, MA 02116: Houghton Mifflin Company. pp. pp. 572, 770. ISBN 0-395-82517-2. {{cite book}}: |edition= has extra text (help); |pages= has extra text (help); Unknown parameter |ids= ignored (help)CS1 maint: location (link)
  • "Earth's Energy Budget". Oklahoma Climatological Survey. 1996–2004. okfirst. Retrieved 2007-11-17.{{cite web}}: CS1 maint: date format (link)
  • Miller, George A. (2006). "WordNet Search 3.0". WordNet a lexical database for the English language. Princeton University/Cognitive Science Laboratory /221 Nassau St./ Princeton, NJ 08542. wordnet:earth science. Retrieved 2007-11-10. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • "NOAA National Ocean Service Education: Geodesy". National Oceanic and Atmospheric Administration. 2005-03-08. oceanservice. Retrieved 2007-11-17.
  • Oldroyd, David (2006). Earth Cycles: A historical prespective. Westport, Connicticut: Greenwood Press. ISBN 0-313-33229-0. {{cite book}}: Unknown parameter |ids= ignored (help)
  • Reed, Christina (2008). Earth Science: Decade by Decade. New York, NY: Facts on File. ISBN 978-0816055333. {{cite book}}: Unknown parameter |ids= ignored (help)
  • Simison, W. Brian (2007-02-05). "The mechanism behind plate tectonics". Retrieved 2007-11-17.
  • Smith, Gary A. (2006). How Does the Earth Work?. Upper Saddle River, NJ 07458: Pearson Prentice Hall. pp. pp. 5. ISBN 0-13-034129-0. {{cite book}}: |pages= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |ids= ignored (help); Unknown parameter |subtitle= ignored (help)CS1 maint: location (link)
  • Tarbuck E. J., Lutgens F. K., and Tasa D., 2002. Earth Science, Prentice Hall, ISBN 978-0130353900
  • Korvin G., 1998. Fractal Models in the Earth Sciences, Elsvier, ISBN 978-0444889072
  • Yang X. S., 2008. Mathematical Modelling for Earth Sciences, Dunedin Academic Press, ISBN 978-1903765920
  • Allaby M., 2008. Dictionary of Earth Sciences, Oxford University Press, ISBN 978-0199211944

See also

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