Earth science

Geology Geography Atmosphere of Earth
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The rocky side of a mountain creek near Orosí, Costa Rica. (presumably metamorphic rocks)

Earth science or geoscience includes all fields of natural science related to the planet Earth. This is a branch of science dealing with the physical and chemical constitution of the Earth and its atmosphere. 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 Earth and its neighbors in space. Some Earth scientists use their knowledge of the planet 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 geology, chronology, physics, chemistry, geography, 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 understand where they will strike. Geologists study rocks and help to locate useful minerals. Earth scientists often work in the field—perhaps 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:

Earth's interior

A volcanic eruption is the release of stored energy from below Earth's surface.[8]

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.[9]

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.[10][11][12][13]

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.[11][13][14]

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[11][13][15] 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.[16]

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.[11][16]

Earth's atmosphere

The magnetosphere shields the surface of Earth from the charged particles of the solar wind.
(image not to scale.)

The troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five layers which make up Earth's atmosphere. 75% of the gases in the atmosphere are located within the troposphere, the lowest layer. In all, the atmosphere is made up of about 78.0% nitrogen, 20.9% oxygen, and 0.92% argon. In addition to the nitrogen, oxygen, and argon there are small amounts of other gases including CO2 and water vapor.[17] Water vapor and CO2 allow the Earth's atmosphere to catch and hold the Sun's energy through a phenomenon called the greenhouse effect.[18] 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—which are often incorrectly thought to be deflected by the magnetic field.[19] The magnetic field—created by the internal motions of the core—produces the magnetosphere which protects Earth's atmosphere from the solar wind.[20] As the Earth is 4.5 billion years old,[21] 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.[22] The Earth has a solid iron inner core surrounded by a fluid outer core that convects;[23] therefore, Earth is an electromagnet. The motion of fluid convection sustains the Earth's magnetic field.[23][24]


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 visit an interesting location to study earth phenomena (e.g. Antarctica or hot spot island chains).

A foundational idea in Earth science is the notion of uniformitarianism, which states that "ancient geologic features are interpreted by understanding active processes that are readily observed."[citation needed] 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 long history.

Earth's spheres

Earth science generally recognizes four spheres, the lithosphere, the hydrosphere, the atmosphere, and the biosphere;[25] 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


  1. ^ Adams & Lambert 2006, p. 20
  2. ^ a b Smith & Pun 2006, p. 5
  3. ^ "WordNet Search – 3.1".
  4. ^ "NOAA National Ocean Service Education: Global Positioning Tutorial".
  5. ^ Elissa Levine, 2001, The Pedosphere As A Hub broken link? Archived October 30, 2007, at the Wayback Machine
  6. ^ Gardiner, Duane T. "Lecture 1 Chapter 1 Why Study Soils?". ENV320: Soil Science Lecture Notes. Texas A&M University-Kingsville. Archived from the original on 2018-02-09. Retrieved 2019-01-07.
  7. ^ Craig, Kendall. "Hydrology of the Watershed".
  8. ^ Encyclopedia of Volcanoes, Academic Press, London, 2000
  9. ^ "Earth's Energy Budget".
  10. ^ Simison 2007, paragraph 7
  11. ^ a b c d Adams & Lambert 2006, pp. 94–95, 100, 102
  12. ^ Smith & Pun 2006, pp. 13–17, 218, G-6
  13. ^ a b c Oldroyd 2006, pp. 101,103,104
  14. ^ Smith & Pun 2006, p. 327
  15. ^ Smith & Pun 2006, p. 331
  16. ^ a b Smith & Pun 2006, pp. 325–26, 329
  17. ^ Adams & Lambert 2006, pp. 107–08
  18. ^ American Heritage, p. 770
  19. ^ Parker, Eugene (March 2006), Shielding Space (PDF), Scientific American
  20. ^ Adams & Lambert 2006, pp. 21–22
  21. ^ Smith & Pun 2006, p. 183
  22. ^ American Heritage, p. 576
  23. ^ a b Oldroyd 2006, p. 160
  24. ^ Demorest, Paul (2001-05-21). "Dynamo Theory and Earth's Magnetic Field" (PDF). Archived from the original (PDF) on February 21, 2007. Retrieved 2007-11-17.
  25. ^ Earth's Spheres Archived August 31, 2007, at the Wayback Machine. ©1997–2000. Wheeling Jesuit University/NASA Classroom of the Future. Retrieved November 11, 2007.