Earth science or Geoscience is an all-embracing
term referring to the fields of science dealing
with planet Earth. It is arguably a special
branch of planetary science, though with a
much older history. There are both reductionist
and holistic approaches to Earth sciences.
The formal discipline of Earth sciences may
include the study of the atmosphere, hydrosphere,
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 Earth Sciences:
Geology describes the rocky parts of the Earth's
crust and its historic development. Major
subdisciplines are mineralogy and petrology,
geochemistry, geomorphology, paleontology,
stratigraphy, structural geology, engineering
geology, and sedimentology.
Physical geography covers aspects of geomorphology,
soil study, hydrology, meteorology, climatology,
and biogeography.
Geophysics and geodesy investigate the shape
of the Earth, its reaction to forces and its
magnetic and gravity fields. Geophysicists
explore the Earth's core and mantle as well
as the tectonic and seismic activity of the
lithosphere. Geophysics is commonly used to
supplement the work of geologists in developing
a comprehensive understanding of crustal geology,
particularly in mineral and petroleum exploration.
See Geophysical survey.
Soil science covers the outermost layer of
the Earth's crust that is subject to soil
formation processes. Major subdisciplines
include edaphology and pedology.
Ecology covers the interactions between the
biota, with their natural environment. This
field of study differentiates the study of
the Earth, from the study of other planets
in our Solar System; the Earth being the only
planet teeming with life.
Hydrology describe the marine and freshwater
domains of the watery parts of the Earth.
Major subdisciplines include hydrogeology
and physical, chemical, and biological oceanography.
Glaciology covers the icy parts of the Earth.
Atmospheric sciences cover the gaseous parts
of the Earth between the surface and the exosphere.
Major discipline are meteorology, climatology,
atmospheric chemistry, and atmospheric physics.
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.
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 convection. This convection
process causes the lithospheric plates to
move, albeit slowly. The resulting process
is known as plate tectonics.
Plate tectonics might be thought of as the
process by which the earth is resurfaced.
Through a process called seafloor spreading,
new crust is created by the flow of magma
from underneath the lithosphere to the surface,
through fissures, where it cools and solidifies.
Through a process called subduction, oceanic
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.
Areas of the crust where new crust is created
are called divergent boundaries, those where
it is brought back into the earth are convergent
boundaries and those where plates slide past
each other, but no new lithospheric material
is created or destroyed, are referred to as
transform boundaries Earthquakes result from
the movement of the lithospheric plates, and
they often occur near convergent boundaries
where parts of the crust are forced into the
earth as part of subduction.
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. Earth has a solid iron inner core surrounded
by semi-liquid materials of the outer core
that move in continuous currents around the
inner core; therefore, the Earth is an electromagnet.
This is referred to as the dynamo theory of
Earth's magnetism.
Atmosphere
The troposphere, stratosphere, mesosphere,
thermosphere, and exosphere are the five layers
which make up Earth's atmosphere. In all,
the atmosphere is made up of about 78.0% nitrogen,
20.9% oxygen, and 0.92% argon. 75% of the
gases in the atmosphere are located within
the troposphere, the bottom-most layer. The
remaining one percent of the atmosphere 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. This allows Earth's surface
to be warm enough to have liquid water and
support life.
The magnetic field created by the internal
motions of the core produces the magnetosphere
which protects the Earth's atmosphere from
the solar wind. As the earth is 4.5 billion
years old, it would have lost its atmosphere
by now if there were no protective magnetosphere.
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.
Methodology
Methodologies vary depending on the nature
of the subjects being studied. Studies typically
fall into one of three categories: observational,
experimental, or theoretical. Earth scientists
often conduct sophisticated computer analysis
or go to many of the world's most exotic locations
to study Earth phenomena.
A foundational idea within the study Earth
science is the notion of uniformitarianism.
Uniformitarianism dictates that "ancient geologic
features are interpreted by understanding
active processes that are readily observed."
In other words, any geologic processes at
work in the present have operated in the same
ways throughout geologic time. This enables
those who study Earth's history to apply knowledge
of how Earth processes operate in the present
to gain insight into how the planet has evolved
and changed throughout deep history.
Earth's spheres
Earth science generally recognizes four spheres,
the lithosphere, the hydrosphere, the atmosphere,
and the biosphere; these correspond to rocks,
water, air, and life. Some practitioners include,
as part of the spheres of the Earth, the cryosphere
as a distinct portion of the hydrosphere,
as well as the pedosphere as an active and
intermixed sphere.
Partial list of the major earth science topics
See: List of basic earth science topics
Atmosphere
Atmospheric chemistry
Climatology
Meteorology
Hydrometeorology
Paleoclimatology
Biosphere
Ecology
Biogeography
Paleontology
Palynology
Micropaleontology
Geomicrobiology
Geoarchaeology
Hydrosphere
Hydrology
Geohydrology
Limnology
Oceanography
Chemical oceanography
Physical oceanography
Biological oceanography
Geological oceanography
Paleoceanography
Lithosphere or geosphere
Pedosphere
Soil science
Edaphology
Pedology
Systems
Environmental science
Geography
Human geography
Physical geography
Gaia hypothesis
Others
Cartography
Geoinformatics
Geostatistics
Geodesy and Surveying
NASA Earth Science Enterprise
See also
Earth sciences graphics software
Environmental geoscience
GEO-LEO
Glossary of geology terms
List of unsolved problems in geoscience
List of geoscience organizations
List of Russian Earth scientists
Nanogeoscience
Structure of the Earth
References
Further reading
Allaby M., 2008. Dictionary of Earth Sciences,
Oxford University Press, ISBN 978-0-19-921194-4
Adams, Simon; Lambert, David. Earth Science:
An illustrated guide to science. New York,
NY: Chelsea House. ISBN 0-8160-6164-5. 
Joseph P. Pickett. American Heritage dictionary
of the English language. Boston, MA: Houghton
Mifflin Company. ISBN 0-395-82517-2. 
Korvin G., 1998. Fractal Models in the Earth
Sciences, Elsvier, ISBN 978-0-444-88907-2
"Earth's Energy Budget". Oklahoma Climatological
Survey. 1996–2004. Retrieved 2007-11-17. 
Miller, George A.; Christiane Fellbaum; and
Randee Tengi; and Pamela Wakefield; and Rajesh
Poddar; and Helen Langone; Benjamin Haskell.
"WordNet Search 3.0". WordNet a lexical database
for the English language. Princeton University/Cognitive
Science Laboratory /221 Nassau St./ Princeton,
NJ 08542. Retrieved 2007-11-10. 
"NOAA National Ocean Service Education: Geodesy".
National Oceanic and Atmospheric Administration.
2005-03-08. Retrieved 2007-11-17. 
Oldroyd, David. Earth Cycles: A historical
perspective. Westport, Connicticut: Greenwood
Press. ISBN 0-313-33229-0. 
Reed, Christina. Earth Science: Decade by
Decade. New York, NY: Facts on File. ISBN 978-0-8160-5533-3. 
Simison, W. Brian. "The mechanism behind plate
tectonics". Retrieved 2007-11-17. 
Smith, Gary A.; Pun, Aurora. How Does the
Earth Work? Physical Geology and the Process
of Science. Upper Saddle River, NJ 07458:
Pearson Prentice Hall. ISBN 0-13-034129-0. 
Tarbuck E. J., Lutgens F. K., and Tasa D.,
2002. Earth Science, Prentice Hall, ISBN 978-0-13-035390-0
External links
American Geosciences Institute
Earth Science Picture of the Day, a service
of Universities Space Research Association,
sponsored by NASA Goddard Space Flight Center.
Geoethics in Planetary and Space Exploration.
National Earth Science Teachers Association
Earth Sciences Degree Program Directory
