Earth sciences

Sediment delivery ratio

The sediment delivery ratio (SDR) is the fraction of soil eroded within a drainage basin that actually reaches the basin outlet, typically below 1 because sediment is deposited en route.

Sediment resuspension

Sediment resuspension is the mobilization of settled bed sediment back into the water column when bottom shear stress exceeds a critical value, driven mainly by wind, waves, and currents.

Sediment sorting

Sediment sorting is the process by which transport and deposition separate sediment grains of different sizes, producing downstream fining, armored streambeds, and graded deposits in rivers.

Sediment transport capacity

Sediment transport capacity is the maximum sediment load a flow can carry under given hydraulic conditions, defined by G. K. Gilbert in 1877 and 1914.

Sediment transport model

A sediment transport model is a mathematical or numerical model simulating sediment movement by water, wind, or ice, used in dredging assessment, coastal morphodynamics, and hazard studies.

Sediment trap

A sediment trap is an oceanographic instrument, typically a funnel with a collection cup, that catches particles sinking toward the sea floor to measure carbon and nutrient fluxes.

Sediment yield

Sediment yield is the amount of sediment delivered from a drainage area over time, typically the annual load passing a gauging station on the stream.

Sedimentary ancient DNA (sedaDNA) is genetic material from past organisms preserved in lake, marine, and cave sediments, used to reconstruct past ecosystems, with permafrost records reaching 2 million years.

Oct 20, 2026

Sedimentary basin

Sedimentary basin: a subsiding lithospheric depression filled with sediment, formed by plate-tectonic subsidence mechanisms (stretching, cooling, loading). Classified into rift, foreland, intracratonic and other types; hosts petroleum, groundwater, and CO2 storage.

Sedimentary rock

Sedimentary rock, also known as sedimentary stone or aqueous rock, forms at the Earth's surface from accumulated sediment consolidated by compaction and cementation, typically showing layers and containing fossils.

Sedimentation

Sedimentation is the deposition of loose sediments, rock and mineral fragments, or biological materials that settle out of water or air into layers, eventually becoming sedimentary rock.

Seeder-feeder mechanism

The seeder-feeder mechanism is an orographic precipitation process in which precipitation from an upper seeder cloud falls through a lower feeder cloud, enhancing rainfall on hills.

Seepage velocity

Seepage velocity, also called average linear velocity or interstitial velocity, is the rate groundwater moves through an aquifer's connected pores, defined as the Darcy flux divided by effective porosity.

Seiche

A seiche, also called a seiche wave, is a standing wave oscillating in a lake, bay, or harbor after wind or pressure changes displace the water.

Seismic anisotropy

Seismic anisotropy is the dependence of seismic wave speeds on propagation direction, observed from the crust to the inner core and used to image mantle flow.

Seismic attribute analysis

Seismic attribute analysis is a geophysics method that extracts quantitative measures from seismic reflection data to characterize subsurface structure, stratigraphy, and fluid content, revealing faults without hand picking.

Seismic attributes

A seismic attribute is a quantity extracted or derived from seismic data, such as amplitude or frequency, analyzed to enhance subtle information and improve geological interpretation.

Seismic facies

A seismic facies is the character of a group of seismic reflections, defined by amplitude, continuity, and configuration. Interpreters use seismic facies units to infer depositional environments and lithology.

Seismic facies analysis

Seismic facies analysis is a geophysical interpretation method that classifies groups of seismic reflections into mappable facies units, inferring depositional environments, lithofacies, and reservoir properties of the subsurface.

Seismic gap

A seismic gap is an active plate boundary segment with a history of large earthquakes that has stayed quiet long enough to be considered likely to rupture.

Seismic interferometry

Seismic interferometry, also known as noise interferometry, is a geophysical method that estimates the Green's function between two receivers by cross-correlating their recordings, introduced to seismology by Jon Claerbout.

Seismic inversion

Seismic inversion is a geophysical method that converts recorded seismic reflection amplitudes, constrained by well logs, into estimates of subsurface properties like velocity, density, and acoustic impedance.

Seismic microzonation

Seismic microzonation is a geotechnical and seismological method that divides a city or municipality into zones of similar seismic behavior, refining national hazard maps with local soil conditions.

Seismic migration

Seismic migration is a geophysical imaging method that repositions recorded seismic reflection events to their true subsurface locations, producing an image of geological structures in the Earth's interior.

Seismic moment

Seismic moment (symbol M0) is the physical quantity seismologists use to measure earthquake size: the product of rock rigidity, fault rupture area, and average slip.

Seismic network

A seismic network is a coordinated set of seismometers at distributed locations whose recordings are combined at a data center to detect, locate, and characterize earthquakes.

Seismic oceanography

Seismic oceanography applies multichannel seismic reflection, a technique developed to image sub-seabed geology, to the ocean's thermohaline fine structure, with the first results reported in 1988.

Seismic phase picking

Seismic phase picking is the task of determining the arrival times of P and S waves on seismograms, a prerequisite for earthquake location and early warning.

Seismic refraction

Seismic refraction is a geophysical surveying method that infers subsurface layer velocities, depths, and dips from refracted wave travel times; it was the first seismic technique used in oil exploration.