Earth science

Earth science, or geoscience, is primarily the study of planet Earth. More specifically, 'Earth sciences' refers to those sciences that deal with the study of the Earth, its components and processes. Earth science includes those fields that study the firmament (the lithosphere or ground that makes up the land and the ocean floor), the waters (the hydrosphere which includes the oceans, the seas, rivers, lakes and so forth), and the atmosphere itself, the air around us. The study of other planet's atmospheres and lithospheres is often considered part of the Earth sciences, especially in the case of terrestrial planets. As a consequence, the Earth sciences have a strong multidisciplinary character.

Earth science also can encompass and is related to those disciplines that study the same topics on extra-terrestrial bodies such as the moon, the planets and asteroids.

Each aspect of these domains may be divided even further into separate but interrelated disciplines of study. Geology, which encompasses the lithosphere, includes vulcanology (the study of volcanoes), hydrology (the study of water through the atmosphere, surface, subsurface and oceans), mineralogy (the study of the composition of the geosphere, specifically the mineral composition of the geosphere), and geomorphology (the study of the forces that shape the geosphere and their different forms).

"Spheres" of study

There are three main ‘spheres’ of study in the earth sciences:

• atmosphere (from the Greek root atmos meaning 'vapor' and sphaira, meaning 'sphere'),
• lithosphere (Greek - lithos rock or 'stone'),
• hydrosphere (Greek – hydros, meaning 'water') correspond, respectively, to the gas, the solid ground, and the water of the earth.

There are other ‘spheres’ but these are subdivisions of the main ones. The pedosphere (Greek pedon or ‘soil’) refers to the outer layer of the lithosphere. It interacts directly with the atmosphere and the hydrosphere. The cryosphere (Greek root kryos, frost or ice) is the glacial layer, its study is called glaciology.

Disciplines and sub-disciplines

There are a large number of subdisciplines and related disciplines that involve overlapping fields of study. A perusal of university majors and journal topics demonstrates a fundamental characteristic of earth science: Although the geosciences are basically about the non-living aspects of the earth, the interaction non-living and living organisms, past and present, is also a very large area of study within earth sciences.

Geology

Astrogeology

As the study of the geology of other planets and extraterrestrial materials, it is concerned with the geology (the surface as well as interior processes) of all solid bodies in the solar system, including the major planets and their satellites, asteroids, comets, and meteorites. Astrogeology is synonymous with ‘exogeology’ and ‘planetary geology.’ Astrogeology utilises geological studies on Earth and incorporates remote sensing of planetary bodies (e.g. telescopy) to study such geological process as volcanism, floods, cratering, tectonics, and sand movement.

Crystallography and mineralogy

The study of crystals and minerals.

Economic geology

The study of economically valuable mineral and ore deposits.

Engineering geology

The study of the geological characteristics of sites where engineering operations are going to be carried out.

Environmental geology

The study of how geological processes affect environmental conditions.

Exploration geology

the search for new mineral deposits.

Geochemistry

The study of the impact of chemical reactions on geologic features.

Geochronology

The study of dating geological events. Events encompass such things as volcanic activity, seismic activity (earthquakes), flooding, drought, heavy rainfall, erosion, changes in the courses of rivers and the boundaries of bodies of water, meteor impacts, glaciation, extinctions, other catastrophic events such as major fires, proliferation of specific life forms (e.g. the Cambrian explosion), changes in the magnetic orientation of the earth, and changes in the atmosphere and climate. Researchers in the field employ methods that provide dates such as measuring the evidence left from radioactive decay, primarily the ratios of uranium, lead and thorium.

Gemology

the study of gemstones.

Geological heritage

The study of conservation of geologically important sites.

Geomagnetism

The study of changes in the magnetic orientation of the earth.

Geomorphology

The study of landforms. Fluvial geomorphology, for example, studies how human use impacts natural settings in a watershed and determines the shape of river channels. Fluvial geomorphology attempts to predict what physical changes will occur to a water channel in response to alterations in watershed conditions; and how changes will impact human infrastructure and fish habitat.

Geophysics

The study of the physical properties of the Earth.

Glaciology

The study of glaciers, their formation, movement and environmental impact

Hydrogeology

the study of the movement of water through the Earth.

Mining geology

the study of the geology of a mine site.

Petroleum geology and coal geology

The study of ancient organic deposits (fossil fuels).

Physical geography

A field within geography which studies patterns and processes of the hydrosphere, biosphere, atmosphere, and lithosphere to understand the physical topography and weather and the global patterns of life on Earth. An inter-related discipline, it draws upon geology, ecology, and climatology particularly with regard to the study of the impact of weathering and erosion. Physical geography is usually contrasted with and complemented by its sister science human geography.

Paleogeography and paleogeology

Paleogeography is the study of the earth’s surface in the distant past. “The study of paleogeography has two principle goals. The first goal is to map the past positions of the continents. The second goal is to illustrate the changing distribution of mountains, lowlands, shallow seas, and deep ocean basins through time.”

Paleogeology is the study of geologic conditions in the past which are manifest in the features of subterranean layers. Both employ analyses of long cylinders of bored rock or cores drilled from the earth which are charted and subjected to analytic comparisons.

Paleomagnetism

Paleomagnetism studies magnetic fields of the Earth in the past. Paleomagnetism measures the remnant magnetic field often preserved in iron-bearing rock formations. Paleomagnetic analysis can determine whether a rock was magnetized near the Pole or near the Equator and provides direct evidence of a continent's N-S (latitudinal) position, but not the E-W (longitudinal) position.

By reconstructing the positional drift of masses of bedrock, geologists have been able to determine that the the Earth's magnetic field has reversed polarity several times in the last 3 billion years.

Petrology

the study of rocks (igneous, metamorphic and sedimentary)

Sedimentary geology

Sedimentary geology encompasses the subdisciplines of sedimentology & stratigraphy. The field addresses all aspects of research into sediments and sedimentation processes at all spatial and temporal scales, sedimentary systems and basin analysis, subsurface analysis of sedimentary sequences, diagenesis (processes involving biological, physical and chemical changes in sediment which may then culminate in lithification), chemical sedimentology and numerical modelling (analysis of stratification facies).

Sedimentology is the study of the production, composition, transport, and deposition of sediment.

Stratigraphy is the study of existing layers or rocks and minerals and the process of layering (stratification). The primary focuses are the process of sedimentation encompassing such dynamics as changes in sea level, tectonic activity, and climatic effects on the production of sediment (e.g. particulates carried in water runoff due to flooding) and material sequentially layered through volcanic activity. (see Geologic ages of earth history)

There are other subfields as well. Lithostratigraphy is the study of strata to determine the history of geological processes and events through lithology, using well logs, mineral composition and quantity, grain size, texture and color. Chronostratigraphy is the study of the ages of strata through comparison, and correlation of separated strata to elucidate their relative and absolute ages. The interdisciplinary biologic stratigraphy (or biostratigraphy), employs the analysis of plant and animal fossils using principles of paleontology and stratigraphy to date and correlate strata using evidence as may be presented by such organisms as pollen and spores, marine microfossils (e.g. diatoms, foraminifera, and nannofossils) to determine the absolute and relative age and the environment that existed during deposition of a particular formation.

Seismology

The study of earthquakes and wave propagation through the earth.

Structural geology

The study of geological structures.

Tectonics

Structural geology on a continental scale, primarily concerned with the movement of crustal plates.

Soil science

The study of properties of soils from

Vulcanology

the study of volcanoes.

Oceanography

The study of the earth’s oceans.

Limnology

The branch of hydrology that pertains to the study of fresh water bodies: lakes, ponds, and streams, reservoirs, rivers, wetlands, and groundwater. Limnology also encompasses salt water in-land lakes. Limnology is derived from the Greek word limne - 'marsh' or 'pond' and the Latin limnaea – 'thing pertaining to a marsh'.

Integrating physical, chemical, and biological components, limnology studies the biogeochemical changes of standing (lentic) water ecosystems: their interactions within and water movement through drainage basins and their exchanges with the atmosphere. Inland water ecosystems are an integral component of a system that encompasses drainage area and atmosphere, running (lotic) waters and ground waters, chemical changes and interactions that occur en route, and includes components of the land being transported to the water.

Hydrology

The interdisciplinary study of the movement, characteristics and distribution of water, surface-water (fresh water and salt water), groundwater, and water-quality Subdisciplines include:

• Chemical hydrology: the study of the chemical characteristics of water. Also called hydrochemistry, chemical hydrology deals with the chemical characteristics of the surface water (freshwater and marine) and subterranean water. Water is a chemical solvent and, interacting chemically with materials with which it comes into contact, can dissolve many elements.
• Drainage basin management hydrology.
• Ecohydrology (the study of interactions between organisms and the hydrologic cycle.
• Engineering Hydrology
• Global hydrology
• Groundwater Hydrology
• Hydrobiology
• Hydrogeology is the study of the presence and movement of water in aquifers.
• Hydroinformatics is the adaptation of information technology to hydrology and water resources applications.
• Hydrometeorology is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.
• Isotope hydrology is the study of the isotopic signatures of water.
• Operational Hydrology
• Qualitative Hydrology
• Sedimentology
• Surface hydrology is the study of hydrologic processes that operate at or near the Earth's surface.
• Water resources development and management

Atmospheric sciences

Meteorology

The study of the weather - the day to day movements of air masses and airborne water.

Climatology

The study of the climate - the long-term patterns in the weather and changes therein.

See also effect of sun angle on climate.

Paleoclimatology

Paleoclimatology is the study of ancient climates. Different types of rock and minerals form under specific climatic conditions: wet and dry, warm and cool. This is also true of ancient life forms whose presence may be determined from the fossil record. As the earth’s surface changes climatically and continents move tectonically, the amount of sunlight will vary and effect conditions on the surface, leading to changes which then become buried in the strata. Coal deposits develop under wet conditions, bauxite deposits are evident where it was warm and wet, evaporites and calcretes occur under warm and dry conditions, and tillites where it was wet and cool. The ancient distribution of different rock types provide evidence of how the global climate has changed through time and how the continents have travelled across climatic belts.

Interdisciplinary divisions

Geomicrobiology

Studies microbes and their interactions in geologic systems

Paleobiogeography

Paleobiogeography studies microbial fossils and their interactions in geologic systems. The distribution of plants and animals in the ancient past helps reveal the latitudinal and relative position of the continents. Ancient plant organisms reflect temperature and rainfall in the distant past. The similarity or dissimilarity of life on different continents can be used to estimate their geographic proximity and may reveal when these continents were connected or isolated from each other.

Paleobotany

the study of ancient plant life. Paleontology may be divided further into vertebrate, invertebrate and micropaleontology

Paleoecology

the study of ancient environments.

Paleontology

the study of ancient life forms.

Biostratigraphy

This field involves the identification of fossils and their position relative to their occurrences in space and time. Fossil groups are confined to specific sedimentary layers which reflect changes in the earth’s environment. Fossils only occur in the lithosphere having been formed in the terrestrial (land), freshwater and marine (sea) environments. Biostratigraphy employs fossils of larger animals but the predominant area of study concerns microfossils such as foraminifera, calcareous nannofossils, and palynomorphs. Microfossils are also used in paleoclimatology, biogeography, and studies of thermal maturation.

Biostratigraphy can also be employed to ascertain ancient land forms in that seismic and tectonic activity may have shifted large areas of deposited materials and corresponding layers lying at varying depths may show specific fossils known to have been deposited at the same time. By correlating these fossil depositions, strata which appears to be deposited at different times may be shown to been formed at the same time and then later shifted through gradual or sudden changes. An example would be the fossils found in mountain ranges that may also occur in adjacent lower lying plains. Biostratigraphical studies can then be used to show that the mountains originally were contiguous with the plains and later thrust upward by tectonic activity.

Palynology

The science of the study of contemporary and fossil palynomorphs as well as associated particulate organic matter (POM) in sedimentary strata. Palynology is an interdisciplinary field overlapping with geological and biological sciences. Palynomorphs are microscopic, decay-resistant remains of certain plants and animals. Micro-fossils classed as palynomorphs include acritarchs, chitinozoans, dinoflagellate cysts (dinoflagellates are marine organisms, comprising the red algae which make up the "red tides" in modern oceans), pollen, spores and scolecodonts. Palynomorphs posses an organic outer wall which then render distinctive fossils.

Pollen and spores can be dispersed by wind and water and may be deposited over a very wide range. Since pollen and spores are transported over extensive distances before deposition, they are not consistently good sources of information for the environment in which they were deposited having originated elsewhere. They can however be used for the study of ancient climates (e.g. they may be used to study glacial and interglacial periods) and biostratigraphy. Organic chemicals become darker in hotter environments. This characteristic can be used to assess the temperature of the strata during the deposition of the palynomorphs. The color of fossils is useful in determining the possible presence of petroleum or gas since heat from burial in the Earth is a critical component of the process of forming oil and gas from organic deposits.

Stratigraphical palynology

Stratigraphical palynology involves identification, distribution, and abundance of palynomorphs to correlate the sequence of sedimentary depositions in time and place, and to provide chronological references for these sequences. Stratigraphic palynology is applied to sediments of all ages. It is considered a subdiscipline or inter-disciplinary field of biostratigraphy, micropalaeontology, paleobotany, paleopalynology.

Interdisciplinary Links in Citizendium

• Stage (geology)
• Age (geology)
• Geologic ages of earth history
• Chronostratigraphy
• Geochronology
• Geochronometry

Resources

• Australian Museum of Geosciences [1]
• Geoscience Information Society [2]
• American Geological Institute [3]
• Geological Society of New Zealand [4]
• University of Missouri-Kansas City, Geoscience Department [5]
• Kansas University Geology Department [6]
• Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian [7]
• United States Geological Services (USGS) Gazetteer of Planetary Nomenclature [8]
• Minerology Database [9] contains 4,442 individual mineral species descriptions with links and a comprehensive image library.
• Minerology Database [10] localities, photos and data
• Links for Minerologists Introduction to Crystallography Institute of Mineralogy, University of Würzburg,
• University of Texas, Austin Paleomap Project
• Division of Earth Sciences National Science Academies Press. Retrieved 17 April, 2007