This list includes 61 Earth science words that start with S, from “Salinity” to “Syncline”. These entries cover processes, landforms, rocks, and atmospheric or ocean phenomena used in education, research, and resource management.

Earth science words that start with S are concise entries that define processes, features, and materials within Earth’s systems. Many of these terms have long histories in exploration and study; for example, “salinity” played a central role in early oceanography.

Below you’ll find the table with Term, Definition, Category, and Further reading.

Term: The word itself, shown alphabetically so you can quickly scan and find a specific Earth science S-word.

Definition: A brief, plain-language explanation of the term so you can grasp its meaning without specialist background.

Category: The discipline or subfield for the term, such as geology or oceanography, so you see its typical use and context.

Further reading: Links to reputable articles or glossary entries where you can explore definitions, mechanisms, and examples in more depth.

Earth science words that start with S

Term Category Typical units/scale Typical context Description
Saltation Process Centimeters–meters hops Wind-blown dunes and river beds The hopping transport of sand and small particles by wind or water; a key process in dune and ripple formation (USGS).
Salinity Measurement PSU (practical salinity) or ‰ Oceans, estuaries, salt lakes How much dissolved salt is in water; a primary control on ocean density, circulation, and marine life (NOAA).
Sand Sediment 0.06–2.00 mm particles Beaches, deserts, river channels Coarse-grained sediment dominated by quartz or silica; builds dunes, beaches, and many sedimentary rocks (USGS).
Sandbar Landform Meters to kilometers River mouths, coastal surf zones A ridge of sand deposited by currents, often parallel to shore or across channels; can shift with waves and tides (USGS).
Sandstone Rock Outcrop units meters–kilometers Sedimentary basins and cliffs A common sedimentary rock made of sand-sized grains cemented together; records ancient environments (USGS).
Saprolite Rock Meters to tens of meters Warm, humid weathering profiles Deeply weathered bedrock that retains original structure but is chemically altered to clay-rich material (AGI/USGS).
Scarp Landform Meters to hundreds of meters Faults, eroding slopes, cliffs A steep slope or cliff created by faulting or erosion; “fault scarp” often signals recent tectonic movement (USGS).
Schist Rock Outcrop meters–kilometers Regional metamorphic belts A foliated metamorphic rock with visible mica and platy minerals, indicating medium- to high-grade metamorphism (USGS).
Seafloor Ocean Depths from 0–11,000 m Ocean basins, trenches, mid-ocean ridges The ocean bottom surface that includes plains, ridges, and trenches; central to plate tectonics (NOAA/USGS).
Seamount Landform Tens to thousands of meters high Oceanic volcanic features An underwater volcanic mountain that never reaches the sea surface; important habitats and bathymetric features (NOAA).
Seawater Ocean Temperature °C, salinity PSU Open ocean, coastal waters The saline water of Earth’s oceans; its chemistry and temperature drive circulation and marine ecosystems (NOAA).
Sediment Material Grain sizes μm–meters Rivers, coasts, continental shelves Loose particles of rock, mineral, or organic material transported and deposited by water, wind, or ice (USGS).
Sedimentology Discipline Local to basin scale Rivers, deltas, deep sea fans The study of sediments and their depositional processes to interpret past environments (AGI).
Seiche Ocean/Limnology Centimeters–meters amplitude; hours Enclosed bays and lakes A standing oscillation in a lake or bay caused by wind or pressure changes, like a sloshing effect (NOAA).
Seismograph Instrument Records time (s) and amplitude Earthquake monitoring stations An instrument that records ground motion from earthquakes and vibrations; produces seismograms (USGS).
Seismology Discipline Local to global scales Earthquakes, interior structure studies The scientific study of earthquakes and Earth’s internal structure using seismic waves (USGS).
Seismicity Measurement Magnitude, events per year Tectonic regions and faults The frequency, distribution, and strength of earthquakes in a region; used for hazard assessment (USGS).
Seismogram Measurement Time series (seconds) Instrument outputs from seismographs A recorded graph of ground motion over time produced by a seismograph; used to analyze earthquakes (USGS).
Sill Rock Centimeters–hundreds of meters thick Between sedimentary layers A horizontal or near-horizontal igneous intrusion that injects between rock layers (USGS).
Silica Mineral Percent or particle size μm Sand, igneous rocks, hydrothermal deposits Silicon dioxide (SiO2), a major component of sand and many rocks and minerals (USGS).
Silicate Mineral Chemical percent composition Rock-forming minerals in crust and mantle Minerals built from silicon-oxygen tetrahedra; the dominant mineral family in Earth’s crust (USGS).
Silt Sediment 0.004–0.062 mm particles Floodplains, deltas, suspended load Fine-grained sediment smaller than sand but coarser than clay; affects soil and water clarity (USGS).
Siltstone Rock Bed thickness centimeters–meters Low-energy sedimentary environments A fine-grained sedimentary rock made mainly of silt-size particles, often layered (USGS).
Sinkhole Landform Meters to hundreds of meters Karst limestone and evaporite terrains A collapse depression formed when soluble rock dissolves and surface material falls in (USGS).
Slab Structure Tens–1,000s km Subduction zones and mantle A subducting piece of oceanic lithosphere that sinks into the mantle; crucial in plate tectonics (USGS).
Slope Landform Degrees of incline, meters Hillslopes, escarpments, channel banks The inclination of the land surface that controls erosion, runoff, and landslide risk (geomorphology).
Soil Substance Centimeters–meters depth Terrestrial surfaces, agricultural land The upper weathered layer of Earth that supports plants and stores water and nutrients (USDA/USGS).
Solifluction Process Centimeters–meters per year Periglacial slopes with thawed topsoil Slow downhill flow of saturated soil over frozen subsoil common in cold, wet climates (geomorphology).
Solstice Climate/Astronomy Dates (June/December) Seasonal solar extremes Times when the Sun reaches its highest or lowest declination, marking longest and shortest days (NOAA/NASA).
Solute Chemistry mg/L concentration Groundwater, rivers, and seawater A dissolved substance in water; solute chemistry controls water quality and mineral reactions (USGS/EPA).
Solubility Property g/L or mg/L Mineral-water interactions How much of a substance dissolves in a solvent; controls mineral stability and water chemistry.
Spring Hydrology L/s or m3/s flow Hillsides, aquifers, fault zones A place where groundwater naturally flows out at Earth’s surface, forming streams or wetlands (USGS).
Stalactite Landform Centimeters–meters Cave ceilings and passages A speleothem hanging from cave ceilings formed by mineral-rich drip waters depositing calcite (NPS/USGS).
Stalagmite Landform Centimeters–meters Cave floors below drip sites A mineral mound that grows upward from cave floors from dripping mineral-rich water (NPS/USGS).
Stratum Structure Centimeters–meters Sedimentary rock layers A single layer of sediment or rock with distinct properties used to read Earth’s history (USGS).
Stratigraphy Discipline Local to regional Sedimentary basins, outcrops The study of rock layers and their relationships to interpret geologic time and environments (AGI/USGS).
Stratovolcano Volcano Hundreds of meters–kilometers Convergent plate margins A steep, layered volcano built from alternating lava and ash layers; often explosive (USGS).
Stratification Process Centimeters–meters Water columns, sediments, atmosphere The formation of distinct layers due to density or composition differences, e.g., in lakes or air (oceanography).
Stream Landform Width centimeters–kilometers Channelized surface water flow A natural watercourse carrying flowing water downslope; fundamental to landscape shaping (USGS).
Streamflow Measurement Cubic meters per second (m3/s) Rivers and gauging stations The volume of water passing a point in a river over time; key for water resources (USGS).
Storm Atmosphere Pressure hPa, wind m/s Weather systems from local to synoptic A disturbed state of the atmosphere with strong winds, precipitation, or severe weather (NOAA).
Subduction Process Tens–thousands km Convergent plate boundaries The process where one tectonic plate sinks beneath another, driving earthquakes and volcanism (USGS).
Subsidence Process mm–meters per year Delta regions, basins, urban areas The gradual or sudden sinking of Earth’s surface due to natural or human causes (USGS).
Sublimation Process mm/day or kg/m2 Cold, dry regions, glaciers, snowfields Direct phase change from solid (ice) to vapor without becoming liquid; important in polar mass balance (NOAA).
Sulfate Ion/Mineral mg/L or percent Seawater, evaporites, soils A common anion (SO4 2–) forming minerals like gypsum; important in water chemistry and sediments (USGS).
Sulfur Element/Mineral Percent in rocks/gases Volcanic gases, hot springs, sulfide ores Element commonly emitted by volcanoes and found in sulfide and sulfate minerals (USGS).
Supercontinent Tectonics Thousands of kilometers Deep geological time, plate reconstructions A very large landmass formed by continental collision, such as Pangea in Earth history.
Suspension Process mg/L concentration Rivers, estuaries, atmosphere Fine particles kept aloft in a fluid; suspended load controls turbidity and sediment transport (USGS).
Suture Structure Kilometers scale Orogenic belts and collision zones The welded boundary between formerly separate tectonic plates or terranes in mountain belts (geology).
Syncline Structure Meters–kilometers Folded sedimentary sequences A downward-curving fold in layered rocks where youngest beds lie at the core (structural geology).
Swell Ocean Meters height, seconds period Open ocean away from wind fetch Long-wavelength surface waves generated by distant storms that travel long distances (NOAA).
Swamp Landform/Ecosystem Hectares to tens of thousands Low-lying wetlands with woody plants A wetland dominated by trees or shrubs, important for biodiversity and carbon storage (USGS/NOAA).
Spit Landform Meters to kilometers Shorelines with longshore drift A narrow landform of sand or gravel projecting from shore, formed by sediment transport (USGS).
Smectite Mineral Percent clay-sized material Soils, sedimentary basins, bentonites A group of expandable clay minerals that swell with water and affect soil behavior (USGS).
Sapropel Sediment Centimeters–meters thick Anoxic marine basins and lake bottoms Organic-rich sediment layers formed under low-oxygen conditions, important in paleo-records.
Shear Measurement/Process Pascals (Pa) or s⁻¹ strain rate Fault zones, fluid flow, rock deformation Stress that causes layers to slide past one another; central to faulting and flow processes (geology).
Sinter Deposit Centimeters–meters Hot springs and geyser outflows A mineral crust (often silica or carbonate) deposited by mineral-rich thermal waters (USGS).
Strontium Element ppm in rocks/waters Geochemical tracing in carbonates and seawater A trace element used in dating and tracing sources in geology and oceanography.
Sphalerite Mineral Percent Zn in ore Hydrothermal veins and massive sulfide deposits The main ore mineral of zinc (ZnS), commonly associated with sulfide mineralization (USGS).
Stromatolite Rock/Structure Centimeters–meters Shallow marine tidal flats and reefs Layered, laminated carbonate or silicate structures built by microbial mats; among Earth’s oldest fossils (geology).
Sulfide Mineral group Percent metal content Hydrothermal veins, volcanic-hosted deposits Minerals composed of sulfur plus a metal (e.g., pyrite); major ore sources for many metals (USGS)

Descriptions

Saltation
Salinity
Sand
Sandbar
Sandstone
Saprolite
Scarp
Schist
Seafloor
Seamount
Seawater
Sediment
Sedimentology
Seiche
Seismograph
Seismology
Seismicity
Seismogram
Sill
Silica
Silicate
Silt
Siltstone
Sinkhole
Slab
Slope
Soil
Solifluction
Solstice
Solute
Solubility
Spring
Stalactite
Stalagmite
Stratum
Stratigraphy
Stratovolcano
Stratification
Stream
Streamflow
Storm
Subduction
Subsidence
Sublimation
Sulfate
Sulfur
Supercontinent
Suspension
Suture
Syncline
Swell
Swamp
Spit
Smectite
Sapropel
Shear
Sinter
Strontium
Sphalerite
Stromatolite
Sulfide
If you think there is a missing term, let us know using the contact form.