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 [ [http://wordnet.princeton.edu/perl/webwn?s=earth%20science 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 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.It is the study of earth and space.

Earth's spheres

Earth science generally recognizes 4 spheres, the lithosphere, the hydrosphere, the atmosphere, and the biosphere [http://www2.cet.edu/ete/hilk4/intro/spheres.html Earth's Spheres] . ©1997-2000. Wheeling Jesuit University/NASA Classroom of the Future. Retrieved November 11 2007.] ; 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.

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

* 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, structural geology, engineering geology and sedimentology [Adams 20] Smith 5] .
* Geophysics and Geodesy investigate the figure of the Earth, its reaction to forces and its magnetic and gravity fieldsFact|date=November 2007. Geophysicists explore the Earth's core and mantle as well as the tectonic and seismic activity of the lithosphere [ [http://wordnet.princeton.edu/perl/webwn?s=geodesy Wordnet Search: Geodesy] ] [ [http://www.oceanservice.noaa.gov/education/kits/geodesy/welcome.html NOAA 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) [ [http://soil.gsfc.nasa.gov/ped/pedosph.htm Elissa Levine, 2001, The Pedosphere As A Hub] ] . Major subdisciplines include edaphology and pedology [ [http://jan.ucc.nau.edu/~doetqp-p/courses/env320/lec1/Lec1.html 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, chemical, and biological oceanographyFact|date=November 2007.
* 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 (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 single-celled organisms to pine trees to 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 ranges, volcanoes, and earthquakes are geological phenomena that can be explained in terms of energy transformations in the Earth's crust. [ [http://okfirst.ocs.ou.edu/train/meteorology/EnergyBudget.html Earth's Energy Budget] ]

Beneath the earth's crust lies the 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 . This convection process causes the lithospheric plates to move, albeit slowly. The resulting process is known as plate tectonics. [Simison par. 7] Adams 94,95,100,102] [Smith 13-17,218,G-6] Oldroyd 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 316,323-325] [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).] 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 electromagnet field

An electromagnet is a magnet that is created by a current that flows around a soft-iron core. [American 576] The earth has a soft iron 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 . This is referred to as the dynamo theory of earth's magnetism.Oldroyd 160] cite web
url=http://setiathome.berkeley.edu/~pauld/etc/210BPaper.pdf
title=Dynamo Theory and Earth's Magnetic Field.
author=Demorest, Paul
date=2001-05-21
accessdate=2007-11-17] The fact that earth is an electromagnet helps with the earth's maintenance of an atmosphere suitable for life.

Atmosphere

The 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 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.fact|date=November 2007 And since earth is 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 diversity in the biosphere.fact|date=November 2007

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".fact|date=June 2008 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

*Atmospheric chemistry
*Climatology
*Meteorology
**Hydrometeorology
*Paleoclimatology

Biosphere

* Biogeography
* Paleontology
** Palynology
** Micropaleontology
* Geomicrobiology

Hydrosphere

* Hydrology
**Limnology
* Hydrogeology
* Oceanography
**Chemical oceanography
**Marine biology
**Marine geology
**Paleoceanography
**Physical oceanography

Lithosphere or geosphere

* Geology
** Economic geology
** Engineering geology
** Environmental geology
** Historical geology
*** Quaternary geology
** Planetary geology
** Sedimentology
** Stratigraphy
** Structural geology
* Geography
** Physical geography
* Geochemistry
* Geomorphology
* Geophysics
** Geochronology
** Geodynamics (see also Tectonics)
** Geomagnetics
** Gravimetry (also part of Geodesy)
** Seismology
* Glaciology
* Hydrogeology
* Mineralogy
** Crystallography
** Gemology
* Petrology
* Speleology
* Volcanology

Pedosphere

* Soil science
** Edaphology
** Pedology

ystems

* Environmental science
* Geography
** Human geography
** Physical geography
* Gaia hypothesis

Others

* Cartography
* Geoinformatics (GIS)
* Geostatistics
* Geodesy and Surveying
* NASA Earth Science Enterprise

ee also

* Earth sciences graphics software
* Environmental geoscience
* List of basic earth science topics
* List of geoscience organizations
* Structure of the Earth
* Glossary of geology terms

References

Further reading

* Allaby M., 2008. Dictionary of Earth Sciences, Oxford University Press, ISBN 978-0199211944
* cite book
title=Earth Science: An illustrated guide to science
first=Simon
last=Adams
coauthors=David Lambert
publisher=Chelsea House
location=New York NY 10001
date=2006
pages=pp. 20
isbn=0-8160-6164-5
ids=earth science
* cite book
title=American Heritage dictionary of the English language
edition=4th edition
publisher=Houghton Mifflin Company
location=222 Berkeley Street, Boston, MA 02116
isbn=0-395-82517-2
pages=pp. 572, 770
ids=american
* Korvin G., 1998. Fractal Models in the Earth Sciences, Elsvier, ISBN 978-0444889072
* cite web
url=http://okfirst.mesonet.org/train/meteorology/EnergyBudget.html
title=Earth's Energy Budget
date=1996-2004
accessdate=2007-11-17
publisher=Oklahoma Climatological Survey
id=okfirst
* cite web
url=http://wordnet.princeton.edu/perl/webwn?s=earth%20science
title=WordNet Search 3.0
accessdate=2007-11-10
work=WordNet a lexical database for the English language
publisher=Princeton University/Cognitive Science Laboratory /221 Nassau St./ Princeton, NJ 08542
first=George A.
last=Miller
coauthors=Christiane Fellbaum, and Randee Tengi, and Pamela Wakefield, and Rajesh Poddar, and Helen Langone, and Benjamin Haskell
date=2006
id=wordnet:earth science
* cite web
url=http://www.oceanservice.noaa.gov/education/kits/geodesy/welcome.html
title=NOAA National Ocean Service Education: Geodesy
date=2005-03-08
accessdate=2007-11-17
publisher=National Oceanic and Atmospheric Administration
id=oceanservice
* cite book
title=Earth Cycles: A historical prespective
first=David
last=Oldroyd
publisher=Greenwood Press
location=Westport, Connicticut
date=2006
isbn=0-313-33229-0
ids=earth cycles
* cite book
title=Earth Science: Decade by Decade
first=Christina
last=Reed
publisher=Facts on File
location=New York, NY
date=2008
isbn=978-0816055333
ids=earth-science history during the 20th century
* cite web
url=http://www.ucmp.berkeley.edu/geology/tecmech.html
title=The mechanism behind plate tectonics
date=2007-02-05
accessdate=2007-11-17
author=Simison, W. Brian
* cite book
title=How Does the Earth Work?
subtitle=Physical Geology "and the" Process of Science
first=Gary A.
last=Smith
coauthors=Aurora Pun
publisher=Pearson Prentice Hall
location=Upper Saddle River, NJ 07458
date=2006
pages=pp. 5
isbn=0-13-034129-0
ids=how does
* Tarbuck E. J., Lutgens F. K., and Tasa D., 2002. Earth Science, Prentice Hall, ISBN 978-0130353900
* Yang X. S., 2008. Mathematical Modelling for Earth Sciences, Dunedin Academic Press, ISBN 978-1903765920