This list includes 69 Earth science words that start with G that begin with G, organized from “Gabbro” to “Gyre”. They cover rocks, landforms, climate, and ocean processes, useful in classrooms, fieldwork, and popular science.

Earth science words that start with G are concise labels for geological materials, processes, and features. For example, gabbro is a classic teaching rock that shows coarse crystals from slow cooling underground.

Below you’ll find the table with Term, Definition, Category, and Example/Link.

Term: The word itself; use it to look up precise meanings or to match vocabulary to field notes and exam questions.

Definition: A short, clear description explaining what the term means so you can quickly grasp its scientific role.

Category: Shows the subject area like “rock”, “process”, or “climate”, helping you filter terms by topic or lesson plan.

Example/Link: Gives a brief example or a link to a deeper article so you can explore applications or further reading.

Earth science words that start with G

Term Category Typical units/scale Occurrence/example Description
Glacier Landform/process Meters–kilometers; years–thousands of years Alpine and polar regions worldwide A large body of perennial ice that flows under its own weight, carving landscapes and storing freshwater.
Glaciation Process Thousands–millions of years Pleistocene ice advances worldwide Periods when large ice sheets expand across continents, reshaping topography and climate.
Glacial moraine Landform Meters–kilometers Ridges beside or in front of glaciers Accumulated rock and sediment dropped by a glacier, forming ridges or mounds that mark former ice limits.
Glacial till Sediment Centimeters–meters Beneath and around glaciers Unsorted sediment directly deposited by glacier ice, containing mixed grain sizes from clay to boulders.
Glacial outwash Deposit Meters–kilometers; sorting by grain size Plains ahead of melting glaciers Sediment carried and sorted by meltwater streams, forming braided channels and flat outwash plains.
Glacial erratic Landform/material Centimeters–meters Large boulder on different bedrock A rock transported and deposited by a glacier long distances from its source bedrock.
Glacial valley Landform Hundreds of meters–kilometers U-shaped valleys in mountain ranges A broad, U-shaped valley carved by glacier flow, distinct from narrow V-shaped river valleys.
Glacial abrasion Process Meters–kilometers Smooth polished bedrock surfaces Scraping and sanding of bedrock by rock fragments in moving ice, producing striations and polish.
Glacial plucking Process Meters–kilometers Jagged bedrock cliffs below ice The removal of bedrock blocks by freezing and movement of glacial ice, creating rough surfaces.
Gully Landform Meters–tens of meters Eroded rills on hillsides after storms A small, steep-sided channel carved by running water from concentrated surface runoff.
Gorge Landform Tens–hundreds of meters deep River canyons in resistant rock A steep, narrow valley typically cut by rivers into bedrock, often with cliffs on both sides.
Geyser Hydrothermal feature Meters–tens of meters tall; °C near boiling Yellowstone and other volcanic areas A hot spring that intermittently erupts steam and hot water due to underground pressure cycles.
Groundwater Hydrology Meters–kilometers depth; days–millennia residence Aquifers beneath Earth’s surface Water stored in subsurface pore spaces and fractures that supplies wells and springs.
Groundwater recharge Process Millimeters–meters per year; time varies Rain infiltrating permeable soil and rock The process where surface water percolates into an aquifer, replenishing groundwater supplies.
Groundwater discharge Process Liters per second–m3/day; springs Springs, wetlands, baseflow to rivers Flow of groundwater to the surface or into streams, lakes, and oceans that sustains ecosystems.
Gravel Sediment Millimeters–centimeters grain size Riverbeds and glacial deposits Coarse rock fragments between 2 and 64 millimeters, commonly produced by mechanical weathering.
Grain size Property Micrometers–meters (grain) Sediment sorting in rivers and beaches A measure of individual particle diameter, influencing how sediments are transported and deposited.
Graben Tectonic landform Kilometers wide; tens–hundreds of kilometers long Rift valleys like the East African Rift A down-dropped block bounded by normal faults formed by crustal extension.
Granite Igneous rock Centimeters–kilometers bodies Continental crust and mountain roots A coarse-grained intrusive rock rich in quartz and feldspar, common in continental crust.
Gabbro Igneous rock Centimeters–kilometers bodies Oceanic crust and plutons A coarse-grained mafic intrusive rock, chemically similar to basalt but with larger crystals.
Gneiss Metamorphic rock Centimeters–kilometers layers Ancient continental crust terranes A banded, high-grade metamorphic rock formed by intense heat and pressure altering original rock.
Granodiorite Igneous rock Centimeters–kilometers bodies Plutons in continental crust An intrusive igneous rock intermediate between granite and diorite, with more plagioclase.
Greywacke Sedimentary rock Matrix-supported sandstone; meters thick Deep-sea turbidite deposits A poorly sorted sandstone with angular grains and fine matrix, often from rapid deposition.
Gypsum Mineral Crystals centimeters; °C stable near surface Evaporite beds and plaster material A soft sulfate mineral that commonly forms from evaporation of saline waters.
Graphite Mineral Microscopic–centimeter flakes Metamorphosed carbon-rich sediments A soft, conductive form of carbon used in pencils and industrial applications.
Galena Mineral Crystals millimeters–centimeters Lead ore in hydrothermal veins A dense lead sulfide mineral and the primary ore of lead.
Garnet Mineral Millimeters–centimeters crystals Metamorphic rocks like schists A group of silicate minerals common in metamorphic rocks, used as index minerals.
Goethite Mineral Micrometers–centimeters Weathering products of iron-rich rocks An iron oxyhydroxide mineral forming rusty-colored soils and iron ore deposits.
Glauconite Mineral Micrometers–millimeters pellets Marine shelf sediments A green, potassium-rich clay mineral that indicates slow sedimentation in shallow seas.
Gibbsite Mineral Micrometers–centimeters Bauxite and tropical soils An aluminum hydroxide mineral that is a major constituent of bauxite ore.
Gold Metal/resource Grams–tons; nuggets to dispersed grains Veins, alluvial placers, ores A dense, malleable metal concentrated by hydrothermal veins and sedimentary placer deposits.
Gas hydrate Sediment/chemical deposit Cubic meters of gas per cubic meter sediment Continental slopes and permafrost sediments Ice-like solids of water and gas (usually methane) that trap large amounts of natural gas.
Geology Discipline Time: years–billions of years; meters–kilometers Study of Earth’s rocks, structures, history The science of Earth’s composition, structure, processes, and history through rock and landform study.
Geomorphology Discipline Centimeters to continental scale; years–millions of years Rivers, coasts, mountains Study of landforms and the processes that shape Earth’s surface.
Geochemistry Discipline Atoms to planet; parts per million Element cycles in rocks, water, atmosphere Study of chemical composition and reactions in Earth materials and processes.
Geophysics Discipline Meters–planetary scale; seconds–millions of years Earthquakes, magnetic surveys, gravity maps Application of physics to study Earth’s interior, gravity, magnetic field, and seismic activity.
Geochronology Discipline/technique Years; radiometric ages in millions–billions Dating volcanic ash and igneous rocks Methods for determining the age of rocks and events using radioactive decay and stratigraphy.
Geodesy Discipline Meters–millimeters precision; planetary scale GPS, sea-level monitoring The study of Earth’s shape, gravity field, and precise positions on the planet.
Geobiology Discipline Microscopic to global Microbial mats, biogeochemical cycles Study of interactions between the biosphere and Earth’s chemistry and geology.
Geodynamo Process Years–millions of years Earth’s liquid outer core generating field The process by which fluid motions in a planetary core generate a magnetic field.
Geomagnetic reversal Process Thousands–millions of years between events Magnetic stripes on ocean floors When Earth’s magnetic field flips polarity, recorded in rocks and seafloor spreading patterns.
Geothermal gradient Parameter/process °C per kilometer Crustal temperature increases with depth The rate at which temperature increases downward in Earth’s crust, driving many subsurface processes.
Geothermal energy Resource/application °C; megawatts of power Steam fields and hot springs Heat from Earth used for power or heating by tapping hot rock, fluids, or steam.
Greenhouse effect Climate process °C warming; global scale Atmospheric trapping of longwave radiation Natural warming of Earth’s surface by atmospheric gases that trap heat; enhanced by human emissions.
Greenhouse gas Atmospheric component Parts per million or billion CO2, CH4, N2O in the atmosphere Gases that absorb outgoing infrared radiation, affecting Earth’s climate.
Gyre Ocean circulation feature Thousands of kilometers across North Pacific and North Atlantic gyres Large, circular ocean current systems driven by wind and Earth’s rotation.
Gulf Coastal landform Kilometers across; depth varies Large coastal inlets worldwide A broad coastal indentation where the sea extends into land, often sheltered and deep.
Gulf Stream Ocean current Kilometers per hour; thousands of kilometers long Western North Atlantic strong current A powerful, warm Atlantic ocean current that influences regional climates and marine transport.
Ground motion Seismic phenomenon Millimeters–meters displacement Earthquakes shaking buildings and ground Movement of Earth’s surface during seismic waves, critical for earthquake engineering.
Gravity anomaly Geophysical measurement Milligals (mGal) Local mass excesses or deficits in crust Variations in Earth’s gravity field caused by density differences in subsurface materials.
Glacial maximum Climate event Thousands–tens of thousands of years Last Glacial Maximum about 21,000 years ago The peak of ice-sheet extent during an ice age, when glaciers covered large parts of continents.
Grainstone Sedimentary rock/type Centimeters–meters beds Carbonate beach and channel deposits A grain-supported carbonate rock with little mud, indicating high-energy depositional settings.
Ground ice Permafrost feature Centimeters–meters thickness Ice lenses in Arctic soils Ice that forms within soil or rock in cold climates, affecting terrain stability when it melts.
Glaciofluvial deposit Sediment deposit Centimeters–meters thick; sorted Outwash plains and river terraces Sediment deposited by meltwater streams flowing from glaciers, often well sorted and stratified.
Gley Soil type/process Centimeters–meters horizon Waterlogged soils in wetlands Waterlogged, reduced soils with gray-blue colors caused by low-oxygen conditions and iron reduction.
Greenstone belt Geological terrane Hundreds–thousands of kilometers long Archean terranes with volcanic-sedimentary rocks Ancient sequences of metamorphosed volcanic and sedimentary rocks important for early-Earth studies and mineral deposits.
Gas vent Geological feature/process Liters per second to larger fluxes Mud volcanoes and seafloor seeps Places where subsurface gases escape to the surface, often linked to hydrocarbons or volcanic activity.
Gondwana Supercontinent Continental scale; existed for millions of years Included modern Africa, South America, India, Australia A former southern-hemisphere supercontinent whose assembly and breakup shaped global geology and biogeography.
Guadalupian Geologic time epoch ~272–260 million years ago Middle Permian epoch in geologic record A middle Permian time interval notable for reef building and certain fossil groups.
Givetian Geologic time stage ~393–387 million years ago Mid-Devonian marine fossils A subdivision of the Devonian Period characterized by diverse marine life and reef systems.
Geosyncline Historical geology term Hundreds–thousands of kilometers long Former idea for large sedimentary basins An older concept for deep sedimentary basins now largely replaced by plate tectonics, historically important.
Granulation (soil) Soil texture/structure Millimeters–centimeters aggregates Granular soil in surface horizons The crumbly soil structure formed by aggregation of particles, important for aeration and root growth.
Geothermal spring Hydrothermal feature °C from warm to boiling Hot springs and thermal pools A spring heated by geothermal energy where hot water reaches the surface from subsurface heat.
Gully erosion Process Meters depth; rapid over years Agricultural hillsides after heavy rain Intense water erosion that removes soil forming deep, often permanent channels.
Glacial isostatic adjustment Process Centimeters–meters uplift; thousands of years Post-glacial uplift in formerly glaciated regions Slow rise of Earth’s crust after ice mass removal, affecting sea level and land elevation.
Ground-penetrating radar Geophysical method Centimeters–meters resolution Detecting buried objects, permafrost studies A near-surface geophysical tool that uses radio waves to image subsurface structures.
Geobarometer Petrology tool GigaPascals (pressure); °C for temperature Estimating metamorphic pressure conditions A mineral- or chemistry-based method to estimate the pressure at which rocks metamorphosed.
Geomagnetic intensity Geophysical parameter Microteslas (µT) Earth’s magnetic field strength varies regionally The strength of Earth’s magnetic field at a location, important for navigation and past field studies.
Gully plug Erosion control feature Cubic meters of sediment Installed in gullies to slow erosion Material or structures used to fill and stabilize gullies and reduce soil loss.

Descriptions

Glacier
Glaciation
Glacial moraine
Glacial till
Glacial outwash
Glacial erratic
Glacial valley
Glacial abrasion
Glacial plucking
Gully
Gorge
Geyser
Groundwater
Groundwater recharge
Groundwater discharge
Gravel
Grain size
Graben
Granite
Gabbro
Gneiss
Granodiorite
Greywacke
Gypsum
Graphite
Galena
Garnet
Goethite
Glauconite
Gibbsite
Gold
Gas hydrate
Geology
Geomorphology
Geochemistry
Geophysics
Geochronology
Geodesy
Geobiology
Geodynamo
Geomagnetic reversal
Geothermal gradient
Geothermal energy
Greenhouse effect
Greenhouse gas
Gyre
Gulf
Gulf Stream
Ground motion
Gravity anomaly
Glacial maximum
Grainstone
Ground ice
Glaciofluvial deposit
Gley
Greenstone belt
Gas vent
Gondwana
Guadalupian
Givetian
Geosyncline
Granulation (soil)
Geothermal spring
Gully erosion
Glacial isostatic adjustment
Ground-penetrating radar
Geobarometer
Geomagnetic intensity
Gully plug
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