Sea-Floor Spreading – Mechanism by which new sea floor crust is created at ridges in divergence zones as magma wells up and forces previously formed crust apart.
Seamount – Tall isolated mountain on the sea floor that may extend more than 1 kilometer from base to peak.
Saltation – Movement of sand or fine sediment by short jumps above the ground or stream-bed under the influence of a current too weak to keep it permanently suspended.
Salt Lick – Natural or artificial deposit of exposed salt that animals lick for nutrients.
Sample – Small portion of rock or a mineral deposit taken so that the metal content can be determined by assaying or other form of testing.
Sandblasting – Physical weathering process in which rock is eroded by the impact of sand grains carried by the wind, frequently leading to ventifact formation of pebbles and cobbles.
Sandstone – Sedimentary rock composed of sand sized particles of mainly quartz and feldspar bound together by silica, carbonate, or clay minerals.
Saprolite – Rock chemically disintegrated in its original place as a result of deep weathering of the bedrock surface.
SASW – Spectral Analysis of Surface Waves is an in-situ seismic method that analyzes dispersion of surface waves and inverts it in terms of mechanical properties of the soil.
Saturation – Percentage of the pore space occupied by water in hydrologic applications.
Schist – Medium to coarse grained metamorphic rock with a strong foliation or schistosity allowing to split easily in one direction. Commonly displaying grains which have a generally parallel arrangement, usually caused by shearing.
Schistosity – Type of foliation that characterizes schist, resulting from the parallel arrangement of coarse-grained platy minerals, such as mica, chlorite and talc.
Scintillation Detector – Efficient detector used in nuclear-logging equipment whereby radiation causes flashes of light that are amplified and output in a crystal as electronic pulse.
Scissor Hole – Drillhole placed in a position to drill in a direction opposite to a previously drilled hole.
Scoria – Congealed lava with a large number of vesicles formed by gases coming out of solution.
Scree Slope – Steep slope, often referred to as a talus slope, consisting of loose, broken rock fragments.
Secondary Magnetic Field – Magnetic field that is generated by currents that are induced to flow in the ground by time variations in the primary magnetic field of the transmitter.
Secondary Porosity – Porosity developed in a rock after its deposition as a result of fracturing or solution.
Secondary Zone – Evidence of additional alteration.
Secular Variation – Slow changes in the orientation of the earth’s magnetic field that appear to be long lasting and internal in origin.
Sediment – Solid fragmented material such as gravel, sand or mud that has settled down from a state of suspension in a liquid, likely transported and deposited by wind, water or ice.
Sedimentary Rock – Rock formed by the accumulation and cementation of mineral grains transported by wind, water, ice or chemically precipitated at the deposition site.
Sedimentary Structure – Structure of a sedimentary or weakly metamorphosed rock that was formed at the time of deposition.
Seif Dune – Longitudinal dune that shows the sculpturing effect of cross-winds not parallel to its axis.
Sedimentation – Process of deposition of mineral grains or precipitates in beds or other accumulations.
Self-Potential – SP is a geophysical method measuring the natural, static voltage existing between sets of points on the ground surface.
Seismicity – Global or local distribution of earthquakes in space and time..
Seismic Profile – Data collected from a set of seismographs arranged in a straight line with an artificial seismic source.
Seismic Reflection – Mode of seismic prospecting in which the seismic profile is examined for waves that have reflected off of near-horizontal geologic strata below surface giving an idea of their depth and thickness.
Seismic Refraction – Mode of seismic prospecting in which the seismic profile is examined for waves that have been refracted upward from seismic discontinuities below the surface.
Seismic Surface Wave – Seismic wave that follows the earth’s surface only.
Seismic Transition Zone – Seismic discontinuity found in all parts of the earth at which the velocity increases rapidly with depth.
Seismogram – Record made by a seismometer of the ground motion as a function of time.
Serpentine – Greenish metamorphic mineral characterized by long, waxy or fibrous crystals. It is most often associated with ultramafic rocks.
Shale – Fine-grained, layered sedimentary rock formed from mud or clay.
Shale Base Line – Line drawn through the SP log deflections that represent shale.
Shear – Planar zone of deformed rock near areas of weakness along which a failure occurred whereby the portion of mass on one side slides past the portion on the opposite side.
Shear Modulus – Stress-strain ratio for simple shear in isotropic materials which obey Hooke’s law.
Shear Wave – Acoustic wave with direction of propagation at right angles to the direction of particle vibration.
Shear Zone – Geological term used to describe a geological area in which shearing has occurred on a large scale. Shear zones are commonly associated with Archean or Proterozoic copper deposits.
Short-Normal Log – One of a group of normal-resistivity logs usually with AM spacing of less than sixteen inches.
Short Ton – 2,000 pounds.
Sichelwannen – Curved grooves on rock surfaces formed by water that was under immense pressure at the base of a glacier.
Silcrete – Hardened rock formed when silica is dissolved from the soil and re-solidifies as a cement.
Siderite – Mineral, Also referred to as ironstone, it is a mineral composed of iron carbonate, symbol FeCO3.
Silica – Oxide of silicon with the chemical formula SiO2 commonly found in sand.
Silicate – Silica-rich igneous rock or magma such as granite and rhyolite.
Silicate Mineral – Mineral containing silicon and oxygen that makes up most of the earth’s crust.
Silicification – Process whereby silica, either amorphous or crystalline is introduced into a rock unit along a system of fractures or by permeating into porous permeable zones in the host rock and forms mineral deposits.
Sill – Sheet of igneous rock that has intruded along the layering that parallels the plane of sedimentary or metamorphic rock.
Silt – Unconsolidated sediment that contains particles larger than those in clay but smaller than those in sand.
Siltstone – Fine-grained sedimentary rock composed mostly of silt-size particles.
Single-Point Resistance Log – Single electrode device used to make measurements of resistance that cannot be used quantitatively.
Sinkhole – Natural depression in the surface of the earth’s surface caused by the collapse of the roof of a cavern or subterranean passage.
Skin Depth – Effective depth of penetration in a conducting medium of electromagnetic energy.
Slate – Fine-grained, metamorphic rock formed from shale that has excellent cleavage and commonly it tends to split easily into thin layers for use in roofing and flooring.
Soil – Unconsolidated materials situated above bedrock.
Soil Sampling – Systematic collection of soil samples at a series of different locations in order to study the distribution of soil geochemical values.
Sorosilicate – Mineral with isolated silicate tetrahedra linked in pairs.
Sounding – Survey method used in geophysics whereby the geometry and/or frequency of an array of sensors is varied so as to measure the physical properties of the earth as a function of depth beneath the configuration.
Spacing – In geophysics it is the distance between sources or transmitters and detectors or receivers on a logging probe.
Specific Conductance – Hydrogeology term referring to the conductivity of surface and ground water and expressed in micro Siemens per centimeter.
Spectral Induced Polarization – SIP is used in mineral exploration to assist in identifying graphite and clay from sulfide mineralization.
Spectral-Gamma Log – Log of gamma radiation as a function of its energy that permits the identification of the radioisotopes present.
Specular Hematite (or Specularite) – Sometimes referred to as Specularite it is a type of hematite or iron-oxide that is very hard, has a metallic luster and known in the jewelry industry as Alaska Black Diamond.
Sphalerite – Zinc mineral which is composed of zinc, sulphur and some iron and as its iron content increases its color alters from yellow to black. It is the main source of zinc.
Spinner Survey – Log made with an impeller flowmeter.
Spit – Sandy bar projecting from the mainland into open water formed by deposition of sediment moved by longshore currents.
Spontaneous Potential – SP, also called self-potential, is a naturally occurring electric potential difference in the Earth, measured by an electrode relative to a fixed reference electrode.
Spot Market – Market for buying and selling of commodities for delivery at an agreed upon future time, usually within a reasonably short period.
Spot Market Price – Price for quantities of commodities bought and sold in the spot market rather than under a firm long term contract. Usually, spot market pricing is higher than that of a contract price.
Stack – Pillar-shaped body of rock close to the shoreline that has been separated from the land by the erosion of intervening rocks.
Stacking – Adding together two or more signals. This process is often used in geophysics to improve the signal to noise ratio..
Stage – Succession of rock strata laid down in a single age on the geologic timescale.
Standard Deviation – Standard deviations represent the uncertainty of, or error in, the data and are an integral part of the survey. They have to be provided for each datum in order to determine the degree to which the model should reproduce, or fit, the data.
Standoff – In geophysics and diamond drilling it is the distance separating a probe from the wall of a borehole.
Statics – Time shift corrections to individual traces to compensate for the effects of variations in elevation, surface layer thickness or velocity, or datum references.
Staurolite – Brown, iron-rich silicate mineral found in metamorphic rocks that tends to form cross-shaped crystals.
Stock – Small, somewhat circular intrusion of igneous rock that is usually less than 100 square km.
Stockpile – Ore piled on the surface pending shipment or treatment.
Stoss and Lee – Arrangement of small hills or prominent rocks in glaciated terrain having gentle slopes on the stoss side and somewhat steeper, pitched slopes on the lee side. This is the reverse direction of crag and tail.
Strataform – Conforms to tabular shape.
Stratification – Structure of sedimentary rocks which have recognizable parallel beds of considerable lateral extent.
Stratified – Layered or bedded sedimentary rock.
Stratigraphic – Arrangement of strata with particular reference to their geographic position and chronologic order of sequence.
Stratigraphic Sequence – Set of beds deposited that reflects the geologic history of a region.
Stratigraphy – Study and description of rock layers and classification of strata in sedimentary rocks including the interpretation of the depositional environments of those strata in relation to the area.
Stratovolcano – Volcanic cone consisting of both lava and pyroclastic rocks that is often conical in shape.
Stratum – Layer of sedimentary rock of which the plural is strata.
Streak – Fine deposit of mineral dust left on an abrasive surface when a mineral is scraped across it.
Streak Plate – Ceramic abrasive surface for streak tests.
Stream Order – Hierarchical number of a stream segment in dendritic drainage with the smallest tributary streams having order one and at each junction of streams of equal order each a number higher by one.
Streaming Potential – Voltage resulting from flow of an ionic fluid.
Streamline – Curved line representing the successive positions of a particle in a flow as time passes.
Stress – Quantity describing the forces acting on each part of a body in units of force per unit area.
Striations – Scratches formed on a rock surface by rock fragments frozen into the bottom of a moving glacier.
Strike – Direction or bearing of a horizontal line on a plane. In geology, often used to describe the location of a secondary or separate outcrop or anomalous zone. Strike is perpendicular to the dip direction. It can also be used to describe the direction or trend of a geological structure.
Strike Length – Longest horizontal dimension of an orebody or zone of mineralization.
Strike-Slip Fault – Fault whose relative displacement is purely horizontal.
Stromatolite – Petrified layered structures created by sedimentation of microorganisms in shallow water.
Structure/Structural – Pertaining to a geological structure such as folds and faults.
Subduction – Geological process in which one edge of one crustal plate is forced below the edge of another.
Subduction Zone – Dipping planar zone descending away from a trench and defined by high seismicity. Usually interpreted as the shear zone between a sinking oceanic plate and an overriding plate.
Sublimation – Phase change from the solid to the gaseous state, without passing through the liquid state.
Submarine Canyon – Underwater canyon in the continental shelf.
Subsidence – Gentle sinking or gradual downward settling of the earth’s crust without appreciable deformation or horizontal motion.
Sulfide or Sulphide – Mineral compound characterized by the linking of sulphur with metal, containing sulphur in its non-oxidised form.
Sulphide/Sulphidation – Group of minerals in which one or more metals are found in combination with sulfur/rock that has been sulphidized.
Supergene – Near surface processes.
Supergroup – Group of rocks that are related by proximity but span a large time period.
Superposed Stream – Stream that flows through resistant formations because its course was established at a higher level on uniform rocks before down-cutting began.
Superposition, Principle of – Principle that, except in extremely deformed strata a bed that overlies another bed is always the younger.
Supersaturation – Unstable state of a solution that contains more solute than its solubility allows.
Surf Zone – Offshore belt along which the waves collapse into breakers as they approach the shore.
Surface Wave – Wave that travels along, or near to, the surface and its motion drops off rapidly with distance.
Surface Waves – Mechanical surface waves that are the slowest waves of an earthquake tremor but which cause the most destruction.
Survey Oil – Term used for the performance or result of an oil well-logging operation.
Suspended Load – Fine sediment kept suspended in a stream because the settling velocity is lower than the upward velocity of eddies.
Swash – Rush of water from a breaking wave moving up the slope of the beach.
S-Wave – Body seismic wave, traveling slower than the P-wave, and consisting of elastic vibrations transverse to the direction of travel. Also known as a shear wave, It cannot penetrate a liquid.
Swell – Oceanic water wave with a wavelength on the order of 30 meters or more and a height of up to two meters or less, that may travel great distances from its source.
SX/EW – Solvent Extraction Electrowinning.
Syenite – Intrusive igneous rock consisting of mostly feldspar with a little hornblende or biotite.
Symbiosis – Interaction of two mutually supporting species that do not compete with or prey upon each other.
Syncline – Fold of rock layers with a convex or trough of the fold that dips toward the earth. The youngest strata in the center.
Synform – Fold in which the limbs dip toward the axis of the fold. If the youngest rocks are in the central core of the fold, it is called a syncline.