This list includes 61 Earth science words that start with F, from “Facies” to “Funnel cloud”. They cover landforms, rocks, geologic processes, and atmospheric and oceanic phenomena used in classrooms and fieldwork.
Earth science words that start with F are specialized terms you use to name Earth’s materials, processes, and features. Many have long histories in geology and meteorology, like “facies”, a 19th‑century term still common in stratigraphy.
Below you’ll find the table with ‘Term’, ‘Definition’, ‘Category’, ‘Example’, and ‘Further reading’.
Term: The official word as used in Earth sciences, so you can find and cross-reference it easily.
Definition: Gives a concise meaning in one or two sentences, so you quickly understand each term’s gist and use.
Category: Labels like “rock”, “process”, or “atmosphere” so you can group and filter terms by field or context.
Example: Shows a short real-world example or typical setting, helping you picture where the term applies.
Further reading: Links or references to deeper articles so you can explore definitions, data, and case studies in more detail.
Earth science words that start with F
| Term | Category | Context | Typical units/scale |
|---|---|---|---|
| Fault | Process/Structure | Geology | millimeters to kilometers (displacement) |
| Fault scarp | Landform | Geomorphology | meters to hundreds of meters |
| Fault zone | Structure | Seismology/Geology | meters to tens of kilometers |
| Fault plane | Structure | Seismology | n/a |
| Fault creep | Process | Seismology | millimeters to centimeters per year |
| Fault-block mountain | Landform | Tectonics | kilometers high, tens of kilometers wide |
| Foreshock | Seismology | Earthquakes | n/a |
| Fissure | Structure | Volcanology/Geology | meters to kilometers (length) |
| Fissility | Property | Sedimentology/Geology | n/a |
| Fjord | Landform | Glacial geomorphology/oceanography | kilometers long, hundreds of meters deep |
| Fold | Structure | Geology | meters to kilometers (wavelength) |
| Folding | Process | Structural geology | n/a |
| Flow | Process | Hydrology/Glaciology | m3/s, meters per second |
| Flowstone | Landform | Speleology | centimeters to meters thick |
| Flow rate | Measurement | Hydrology/Oceanography | m3/s, liters per second |
| Flood | Process/Landform | Hydrology | cubic meters per second; return periods |
| Floodplain | Landform | Fluvial geomorphology | meters to kilometers wide |
| Flash flood | Process | Hydrology | minutes to hours; local scale |
| Flood stage | Measurement | Hydrology | meters above gauge datum |
| Flood frequency | Analysis | Hydrology | years (return period) |
| Flood basalt | Geology | Volcanology | thousands to millions km3 (erupted) |
| Fluvial | Adjective/Process | Geomorphology/Hydrology | n/a |
| Fluvial terrace | Landform | Geomorphology | meters to hundreds of meters above channel |
| Flocculation | Process | Sedimentology/Water quality | minutes to hours; micrometers (particle size) |
| Facies | Concept | Sedimentology/Petrology | n/a |
| Field capacity | Measurement | Soil science | % volumetric water content |
| Firn | Material | Glaciology | meters to tens of meters thick |
| Firn line | Feature | Glaciology | meters elevation (varies) |
| Fumarole | Feature | Volcanology | temperature up to hundreds °C |
| Felsic | Composition | Igneous petrology | n/a |
| Feldspar | Mineral | Mineralogy | n/a |
| Ferromagnesian | Composition | Petrology | n/a |
| Fog | Atmospheric phenomenon | Meteorology | visibility <1 km typically |
| Foehn | Atmospheric phenomenon | Meteorology | wind speeds vary |
| Freezing rain | Precipitation | Meteorology | mm of liquid equivalent |
| Freeze-thaw | Process | Weathering/Geology | temperature cycles around 0 °C |
| Frost wedging | Process | Geomorphology | n/a |
| Frost heave | Process | Soil science/Permafrost | centimeters to meters |
| Frost line | Concept | Soil science/Permafrost | meters depth (seasonal varies) |
| Fetch | Oceanography | Meteorology | kilometers |
| Forearc basin | Landform | Tectonics | tens to hundreds of kilometers |
| Foreland basin | Landform | Tectonics | hundreds of kilometers wide |
| Fracture | Structure | Geology | micrometers to meters (crack size) |
| Fault gouge | Material | Structural geology | millimeters to meters thick |
| Fossil | Object | Paleontology | millimeters to meters |
| Fossil fuel | Resource/Process | Energy/Climate | BP, tons, EJ (consumed) |
| Fire regime | Concept | Ecology/Geomorphology | frequency, intensity metrics |
| Fire weather | Atmospheric condition | Meteorology | temperature, humidity, wind |
| Fluorite | Mineral | Mineralogy | n/a |
| Fractional crystallization | Process | Igneous petrology | temperature, percent crystallized |
| Fractionation | Process | Geochemistry/Isotope geology | per mil (‰), ratio changes |
| Flux | Measurement/Concept | Biogeochemistry/Climate | mass/time or mol/time |
| Fan delta | Landform | Sedimentology | kilometers across |
| Funnel cloud | Atmospheric phenomenon | Meteorology | meters to kilometers long |
| Front | Atmospheric phenomenon | Meteorology | kilometers to thousands of km |
| Frontogenesis | Process | Meteorology | hours to days |
| Flat-slab subduction | Tectonics | Geodynamics | tens to hundreds of kilometers horizontal |
| Foraminifera | Organism/Proxy | Paleoceanography | micrometers to millimeters |
| Freshwater lens | Hydrogeology | Coastal aquifers | meters thick |
| Flow banding | Texture | Igneous petrology | millimeters to meters |
| Fluorescence | Property/Tool | Mineralogy/Biology | n/a |
Descriptions
Fault
A fracture or zone of fractures in Earth’s crust where movement has occurred; a primary control on earthquakes and mountain building (USGS).
Fault scarp
A steep slope or cliff formed by vertical displacement along a fault, often visible after earthquakes.
Fault zone
A region of many closely spaced faults and deformed rock that accommodates crustal strain and seismicity.
Fault plane
The geometric surface along which slip occurs during faulting; used to describe fault orientation (strike and dip).
Fault creep
Slow, continuous displacement along a fault without large earthquakes; can reduce stress accumulation but damage infrastructure.
Fault-block mountain
Mountain formed when large crustal blocks move along normal faults, creating alternating uplifted and down-dropped blocks.
Foreshock
A smaller earthquake that precedes the mainshock in a sequence; can sometimes provide warning but are not reliably predictive.
Fissure
A crack or opening in Earth’s surface through which lava, gas, or water can erupt or be emitted.
Fissility
The tendency of a rock (like shale) to split along thin, planar layers due to aligned clay minerals and bedding.
Fjord
A deep, narrow coastal inlet carved by glaciers and flooded by the sea; common in high-latitude coastlines (USGS).
Fold
A bend in layered rock caused by ductile deformation under compression, forming anticlines and synclines.
Folding
The process by which rock layers bend under stress, producing various fold geometries important in mountain building.
Flow
Movement of fluids (water, lava, ice) governed by gravity and material properties; ‘flow’ describes many transport processes.
Flowstone
Mineral deposits (calcite or aragonite) formed by flowing water in caves that precipitates layered stalagmite-like sheets.
Flow rate
The volume of fluid passing a point per time; used to quantify river discharge, glacier meltwater, or ocean currents.
Flood
An overflow of water onto normally dry land, often caused by heavy rain, snowmelt, or dam failure (USGS).
Floodplain
Flat area adjacent to a river that is periodically inundated and accumulates sediment during floods.
Flash flood
A rapid, intense flood caused by heavy rainfall over a short period, typically in small watersheds or steep terrain.
Flood stage
A river level at which flooding of lowlands or property begins; used for public safety and warnings.
Flood frequency
Statistical estimate of how often floods of a given size occur (e.g., 100-year flood); guides planning and design.
Flood basalt
Extensive lava flows from fissure eruptions that form large igneous provinces and affect climate over geologic time.
Fluvial
Relating to rivers and streams; used to describe processes, deposits, and landforms produced by flowing water.
Fluvial terrace
Step-like flat surfaces along river valleys representing former floodplain or channel positions from river downcutting.
Flocculation
Aggregation of fine particles into clumps that settle faster in water, important in sediment transport and water treatment.
Facies
A body of rock with distinctive characteristics reflecting a particular depositional environment or conditions.
Field capacity
The amount of soil moisture retained after excess water drains away; important for plant water availability.
Firn
Compacted, granular snow that survives a melt season and gradually recrystallizes into glacier ice.
Firn line
The altitude on a glacier separating the accumulation zone (firn) from the ablation zone where net melting occurs each year.
Fumarole
An opening near volcanoes emitting steam and volcanic gases; indicates hydrothermal activity (USGS).
Felsic
Describes igneous rocks rich in silica and light-colored minerals (feldspar, quartz) like granite; contrasted with mafic.
Feldspar
A common group of rock-forming silicate minerals abundant in igneous, metamorphic, and sedimentary rocks.
Ferromagnesian
Describes dark, iron- and magnesium-rich minerals common in mafic and ultramafic rocks.
Fog
A low cloud formed near the ground when air cools to saturation; reduces visibility and affects transport (NOAA).
Foehn
A warm, dry downslope wind on the lee side of mountains caused by adiabatic warming (also spelled Föhn).
Freezing rain
Rain that freezes on contact with cold surfaces, forming glaze ice and hazardous conditions.
Freeze-thaw
A mechanical weathering process where water freezes in cracks, expands, and breaks rock apart.
Frost wedging
A form of freeze-thaw weathering where ice growth in fractures pries rock apart over repeated cycles.
Frost heave
Vertical uplift of soil and objects due to ice lens formation during freezing, impacting infrastructure.
Frost line
Depth to which ground water freezes seasonally; important for foundations and plant root survival.
Fetch
The distance over water that wind blows in a single direction, influencing wave size and energy.
Forearc basin
A sedimentary basin between a subduction trench and volcanic arc that accumulates sediments from erosion and tectonics.
Foreland basin
A downwarped basin adjacent to mountain belts that receives thick sedimentary deposits from erosion of the uplifting range.
Fracture
Any break or crack in rock; includes joints and faults and influences fluid flow and rock strength.
Fault gouge
Finely crushed rock produced by frictional grinding along a fault, affecting fault strength and permeability.
Fossil
Remains or traces of past life preserved in rock; used to reconstruct past environments and date rock layers.
Fossil fuel
Organic carbon-rich fuels (coal, oil, natural gas) formed from ancient biomass; combustion releases CO2 and affects climate.
Fire regime
The patterns of fire occurrence, size, severity, and seasonality in an ecosystem, shaping vegetation and landscapes.
Fire weather
Weather conditions that influence wildland fire behavior, including dryness, wind, and atmospheric stability.
Fluorite
A colorful halide mineral (calcium fluoride) used industrially and noted for its fluorescence under UV light.
Fractional crystallization
The sequential removal of minerals from cooling magma, changing melt composition and producing diverse igneous rocks.
Fractionation
Separation of elements or isotopes between phases (e.g., water/rock), used to interpret environmental and geologic processes.
Flux
The rate of transfer of a quantity (mass, energy, momentum) across a boundary, e.g., carbon flux between ocean and atmosphere.
Fan delta
A sedimentary deposit formed where a river enters a standing body of water, building a fan-shaped delta from coarse sediments.
Funnel cloud
A rotating cloud column extending from a thunderstorm that may become a tornado if it reaches the ground.
Front
A boundary between contrasting air masses (cold, warm, stationary) that drives weather systems and precipitation.
Frontogenesis
The formation or intensification of a weather front through convergence and sharpening of temperature gradients.
Flat-slab subduction
A subduction style where the downgoing plate moves nearly horizontally beneath the overriding plate, affecting volcanism and deformation.
Foraminifera
Microscopic shelled protists whose fossil assemblages and isotopes are key proxies for past ocean conditions and ages.
Freshwater lens
A lens-shaped freshwater body that floats atop denser seawater in coastal aquifers, vulnerable to overuse and saltwater intrusion.
Flow banding
Layering in volcanic rocks produced by flow during emplacement, reflecting changes in composition or crystal content.
Fluorescence
Emission of visible light by some minerals or organisms when exposed to ultraviolet light, used in identification and analysis.