Earth science
Definition
Earth science or geoscience is a widely embraced term for the 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” is a broad term that encompasses four main branches of study, 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 magmawhich 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 CO2and 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 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
Atmosphere
- Atmospheric chemistry
- Geography
- Climatology
- Meteorology
- Hydrometeorology
- Paleoclimatology
Biosphere
- Biogeochemistry
- Biogeography
- Ecology
- Landscape ecology
- Geoarchaeology
- Geomicrobiology
- Paleontology
- Palynology
- Micropaleontology
Hydrosphere
- Hydrology
- Hydrogeology
- Limnology (freshwater science)
- Oceanography (marine science)
- Chemical oceanography
- Physical oceanography
- Biological oceanography (marine biology)
- Geological oceanography (marine geology)
- Paleoceanography
Lithosphere (geosphere)
- Geology
- Economic geology
- Engineering geology
- Environmental geology
- Historical geology
- Quaternary geology
- Planetary geology and planetary geography
- Sedimentology
- Stratigraphy
- Structural geology
- Geography
- Physical geography
- Geochemistry
- Geomorphology
- Geophysics
- Geochronology
- Geodynamics (see also Tectonics)
- Geomagnetism
- Gravimetry (also part of Geodesy)
- Seismology
- Glaciology
- Hydrogeology
- Mineralogy
- Crystallography
- Gemology
- Petrology
- Speleology
- Volcanology
Pedosphere
- Geography
- Soil science
- Edaphology
- Pedology
- Soil science
Systems
- Earth system science
- Environmental science
- Geography
- Human geography
- Physical geography
- Gaia hypothesis
- Systems ecology
- Systems geology
Others
- Geography
- Cartography
- Geoinformatics (GIS)
- Geostatistics
- Geodesy and Surveying
- NASA Earth Science Enterprise
- Remote Sensing