Earth science or geoscience includes all fields
of natural science related to the planet Earth.
It is the branch of science dealing with the
physical constitution of the earth and its
atmosphere. Earth science is the study of
our planet’s physical characteristics, from
earthquakes to raindrops, and floods to fossils.
Earth science can be considered to be a branch
of planetary science, but with a much older
history. “Earth science” encompasses four
main branches of study, the lithosphere, the
hydrosphere, the atmosphere, and the biosphere,
each of which is further broken down into
more specialized fields.
There are both reductionist and holistic approaches
to Earth sciences. It is also the study of
the Earth and its neighbors in space. Some
Earth scientists use their knowledge of the
Earth to locate and develop energy and mineral
resources. Others study the impact of human
activity on Earth's environment, and design
methods to protect the planet. Some use their
knowledge about Earth processes such as volcanoes,
earthquakes, and hurricanes to plan communities
that will not expose people to these dangerous
events.
The Earth sciences can include the study of
geology, the lithosphere, and the large-scale
structure of the Earth's interior, as well
as the atmosphere, hydrosphere, and biosphere.
Typically, Earth scientists use tools from
geography, chronology, physics, chemistry,
biology, and mathematics to build a quantitative
understanding of how the Earth works and evolves.
Earth science affects our everyday lives.
For example, meteorologists study the weather
and watch for dangerous storms. Hydrologists
study water and warn of floods. Seismologists
study earthquakes and try to predict where
they will strike. Geologists study rocks and
help to locate useful minerals. Earth scientists
mainly work “in the field”—climbing
mountains, exploring the seabed, crawling
through caves, or wading in swamps. They measure
and collect samples (such as rocks or river
water), then they record their findings on
charts and maps.
== Fields of study ==
The following fields of science are generally
categorized within the Earth sciences:
Physical geography, covers aspects of geomorphology,
soil study, hydrology, meteorology, climatology,
and biogeography.
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.
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.
Seismologists use geophysics to understand
plate tectonic shifting, as well as predict
seismic activity. See geophysical survey.
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.
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 the Solar System; the Earth being the only
planet teeming with life.
Hydrology, Oceanography and Limnology are
a study revolved around the movement, distribution,
and quality of the water and involves all
the components of the hydrologic cycle on
the earth and its atmosphere (or hydrosphere).
"Sub-disciplines of hydrology include hydrometeorology,
surface water hydrology, hydrogeology, watershed
science, forest hydrology, and water chemistry."
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
include 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 physical and
chemical processes 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. As the result
of seafloor spreading, new crust and lithosphere
is created by the flow of magma from the mantle
to the near surface, through fissures, where
it cools and solidifies. Through subduction,
oceanic crust and lithosphere returns to the
convecting mantle.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
(or conservative) 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 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 (all
but the nitrogen, oxygen, and argon) 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. In addition to storing heat,
the atmosphere also protects living organisms
by shielding some of the Earth's surface from
cosmic rays—of which are often incorrectly
thought to be deflected by the magnetic field.
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.
== Earth's magnetic field ==
An electromagnet is a magnet that is created
by an electric current. The Earth has a solid
iron inner core surrounded by fluid outer
core that convects; therefore, the Earth is
an electromagnet. The motion of fluid convection
sustains the Earth's magnetic field.
== 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 (e.g. Antarctica
or hot spot island chains).
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. Also included by some
are the cryosphere (corresponding to ice)
as a distinct portion of the hydrosphere and
the pedosphere (corresponding to soil) as
an active and intermixed sphere.
=== Partial list of the major Earth science
topics ===
== See also ==
== References ==
== Further reading ==
Allaby M., 2008. Dictionary of Earth Sciences,
Oxford University Press, ISBN 978-0-19-921194-4
Adams, Simon; Lambert, David (2006). Earth
Science: An illustrated guide to science.
New York, NY: Chelsea House. ISBN 0-8160-6164-5.
Joseph P. Pickett (executive editor) (1992).
American Heritage dictionary of the English
language (4th ed.). 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
(2006). "WordNet Search 3.0". WordNet a lexical
database for the English language. Princeton,
NJ: Princeton University/Cognitive Science
Laboratory. Retrieved 2007-11-10.
"NOAA National Ocean Service Education: Geodesy".
National Oceanic and Atmospheric Administration.
2005-03-08. Retrieved 2007-11-17.
Oldroyd, David (2006). Earth Cycles: A historical
perspective. Westport, CT: Greenwood Press.
ISBN 0-313-33229-0.
Reed, Christina (2008). Earth Science: Decade
by Decade. New York, NY: Facts on File. ISBN
978-0-8160-5533-3.
Simison, W. Brian (2007-02-05). "The mechanism
behind plate tectonics". Retrieved 2007-11-17.
Smith, Gary A.; Pun, Aurora (2006). How Does
the Earth Work? Physical Geology and the Process
of Science. Upper Saddle River, NJ: 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
