Earth System Science Vocabularies Part V:
Ways of Knowing About the Earth

OBSERVATION

remote sensing

The science of collecting, processing, and interpreting images that record the interaction between electro-magnetic energy and matter. Acquiring information about an object or phenomenon by a recording device that is not in physical contact with the subject being studied; e.g. aerial photography and imagery acquired from satellites. Including airborne imaging, aerial photography, LIDAR, side-looking airborne radar, satellite imaging (infrared, AVHRR), microwave imaging, radar imaging, visible light imaging.

geologic map

A map on which is recorded geologic information such as the distribution, nature, and age relationships of rock units, surficial deposits and the occurrence of structural features, mineral deposits and fossil localities.

sampling

Selection of a subset of a population that, if properly selected, may be used to estimate the parameters of the population (e.g. geochemical sampling)

MEASUREMENTS

Field Measurements

field experiments

including in situ monitoring, telemetry, networks, video monitoring, acquisition of images and photographs, weather monitoring

borehole logging

including temperature, electrical resistivity, gamma-ray measurements

geolocation

including altimetry, bathymetry, land surveying, global positioning systems (GPS)

Potential Fields

magnetic field

A region in which magnetic forces would be exerted on any magnetized bodies or electric currents present; the region of influence of a magnetized. body or an electric current.

electrical conductivity

A measure of the ease with which a conduction current can be caused to flow through a material under the influence of an applied electric field.

electrical resistivity

The electrical resistance per unit length of a unit cross-sectional area of a material.

gravitational field

A region associated with any mass distribution that gives rise to forces of gravitational attraction.

heat flow

Measurement of the amount of heat leaving the Earth. It involves measuring the geothermal gradient of rocks by accurate resistance thermometers in drill holes, and the thermal conductivity of rocks. Term used for subdisciplines of geophysics concerned with the measurement, reduction and interpretation of conductive heat flow through the Earth's surface.

geothermal gradient

The rate of change of temperature in the Earth with depth. The gradient differs from place to place depending on the heat flow in the region and the thermal conductivity of the rocks.

Seismology

The study of earthquakes, and of the structure of the Earth, by both natural and artificially generated seismic waves.

reflection

The return of a wave incident upon a surface to its original medium.

refraction

The deflection of an energy wave due to its passage from one medium to another of differing density, which changes its velocity.

tomography

A method for finding the velocity distribution from a multitude of observations using combinations of source and receiver locations.

Geoid/geodesy

The figure of the Earth considered as a sea-level surface extended continuously through the continents. It is a theoretically continuous surface that is perpendicular at every point to the direction of gravity. It is the surface of reference for astronomical observations and for geodetic leveling.

Mechanical Properties

bulk modulus

A modulus of elasticity which relates a change in volume to a change in hydrostatic state of stress; it is the reciprocal of compressibility.

Poisson's ratio

The ratio of the lateral unit strain to the longitudinal unit strain in a body that has been stressed longitudinally within its elastic limit.

rheology

The study of the deformation and flow of matter.

strain

The change in shape or volume of a body as a result of stress.

LABORATORY EXPERIMENTS

phase equilibria

In physical chemistry, the study of those phases, which under specified conditions, may exist in

equilibrium

equation of state

An equation interrelating the thermodynamic variables that define the state of a system. It is classically applied to simple gases and liquids in terms of pressure, volume and temperature, but in modern geochemistry and petrology it is commonly extended to solids and to solutions.

cell culture experiment

growth of life forms (e.g. microbes) in experimental culture media.

ANALYSIS

chemical analysis (bulk samples)

Including atomic absorption, chromatography, mass spectroscopy, neutron activation analysis, particle beam analysis (electron microprobe, energy dispersive spectrometry)

chemical analysis (material surfaces)

Including Auger Electron Spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry (dynamic and time-of-flight)

isotopic analysis-light stable isotopes

as indicators of paleoclimate, geothermometers

isotopic analysis-radioactive elements

for radiometric age determination and as petrogenetic indicators

microscopy

including optical microscopy (petrography), electron microscopy (scanning and transmission electron microscopy) and nanoscale analysis using scanning tunneling and variants of atomic force microscopy.

paleomagnetic analysis

including Curie temperature analysis, hysteresis, laboratory-induced magnetization analysis, magnetic susceptibility analysis, and natural remnant magnetism analysis.

geographic information system

A computer program and associated data bases that permit cartographic information to be queried by geographic coordinates of features. Usually the data are organized in layers representing different geographic entities such as hydrology, culture, topography, etc. allowing information from different layers to be easily integrated and analyzed.

MODELING

A working hypothesis or precise simulation by means of description, statistical data, or analogy, of a phenomenon or process that cannot be observed directly or that is difficult to observe directly. Models may be derived by various methods, e.g. by computer, or by scaled experiments; computational models, physical models, theoretical models. May produce visualizations or simulations.

computational methods

Including image analysis, mathematical modeling, statistical analysis, visualization methods

THEORY

An explanatory system of propositions, general principles or laws, inferred from the phenomena and linking known facts and observations; held to be true until contradicted or amended by new facts or observations (e.g. theory of evolution, plate tectonics, quantum mechanics).