This page lists 74 geological features that start with G, from “Gabbro” to “Gyre”. The list covers rocks, minerals, glacier landforms, caves, valleys, ocean features, and famous natural sites. Some are small enough to hold in your hand, while others stretch across whole continents. You can use the list for school projects, travel planning, hiking trips, rock collecting, or simple curiosity about how the planet is shaped.
Geological features are the natural formations, materials, and landforms that make up the Earth’s surface and the rock beneath it. They range from tiny crystals to giant mountain belts. The “Giant’s Causeway” in Northern Ireland, with its thousands of stone columns, is a well-known example that draws visitors from around the world.
Below you’ll find the table with each geological feature, its region, its main characteristics, and a short description.
Geological Feature: The name of each rock, mineral, landform, or natural site, listed alphabetically so you can quickly find a specific feature or browse through the full list.
Region: Where in the world you can find the feature, including countries, states, or whole continents, which helps you plan a visit or spot patterns.
Characteristics: A quick summary of what makes the feature stand out, such as its shape, color, or how it formed, so you can compare entries at a glance.
Description: A short, plain-language explanation of what the feature is and why it matters, giving you the key facts without needing a technical background.
Geological features
| Geological Feature | Region | Characteristics |
|---|---|---|
| Gabbro | Worldwide, especially oceanic crust | Coarse-grained, dark igneous rock |
| Galena | Worldwide, including Missouri, Australia, and Germany | Lead sulfide mineral, metallic silver cubes |
| Garnet | Worldwide, including India, Madagascar, and the United States | Hard silicate mineral, usually deep red |
| Gas Hydrate | Ocean floor and Arctic permafrost | Ice-like solid trapping natural gas |
| Geode | Worldwide, including Brazil, Uruguay, and Iowa | Hollow rock lined with crystals |
| Geological Fault | Worldwide | Fracture where rock blocks have moved |
| Geological Unconformity | Worldwide, including Siccar Point in Scotland | Gap in the rock record |
| Geomorphic Surface | Worldwide | Landscape surface of a particular age |
| Geosyncline | Mountain belts worldwide, including the Appalachians | Large, long-lived sedimentary basin |
| Geothermal Field | Iceland, New Zealand, California, Indonesia | Area of hot underground water and steam |
| Geyser | Yellowstone (USA), Iceland, New Zealand, Chile | Periodically erupting hot spring |
| Geyserite | Yellowstone, Iceland, New Zealand | Silica deposit around hot springs |
| Ghost Forest | Coastal North America and other coasts | Dead trees from sinking or flooded land |
| Giant’s Causeway | Northern Ireland | Basalt columns, mostly hexagonal |
| Giant’s Kettle | Scandinavia, Switzerland, and North America | Deep, round hole in bedrock |
| Gibber Plain | Central Australia | Stony desert surface |
| Gilgai | Australia and other regions with clay soils | Small mounds and depressions in clay soil |
| Glacial Cirque | Mountains worldwide | Bowl-shaped hollow carved by ice |
| Glacial Erratic | North America, Europe, and other glaciated regions | Boulder moved by ice |
| Glacial Lake | Canada, Scandinavia, Alps, Patagonia | Lake formed by glacial action |
| Glacial Moraine | Glaciated regions worldwide | Ridge of rock debris left by ice |
| Glacial Outburst Flood | Iceland, Himalayas, Andes, Alaska | Sudden release of glacial meltwater |
| Glacial Outwash Plain | Iceland, Alaska, Patagonia | Flat area of meltwater-laid sediment |
| Glacial Striations | Glaciated regions worldwide | Scratches on bedrock |
| Glacial Trough | Norway, Alps, Yosemite, New Zealand | U-shaped valley |
| Glacier | Antarctica, Greenland, Alaska, Himalayas, Alps | Slow-moving mass of ice |
| Glacier Cave | Iceland, Alps, Alaska | Tunnel inside or under ice |
| Glacier Mill | Greenland, Svalbard, Alaska | Vertical shaft in ice |
| Glacier Table | Alpine and polar glaciers | Boulder on a pedestal of ice |
| Glacis | Arid regions, including the American Southwest and Sahara | Gently sloping erosion surface |
| Glauconite | Worldwide marine sediments | Green iron-potassium mineral |
| Glossopteris Fossil Bed | Antarctica, India, Australia, South America, Africa | Fossil plant beds on separate continents |
| Gneiss | Canadian Shield, Scotland, Scandinavia | Banded metamorphic rock |
| Goethite | Worldwide | Iron oxide mineral, yellow-brown |
| Gold Placer Deposit | California, Alaska, Yukon, Australia | Gold concentrated in stream sediments |
| Gondwana | Southern Hemisphere | Ancient supercontinent |
| Gorge | Worldwide | Deep, narrow valley with steep walls |
| Graben | East Africa, Rhine Valley, Basin and Range (USA) | Down-dropped block between faults |
| Grabens of Canyonlands | Utah, USA | Faulted valleys in sandstone |
| Granite | Worldwide, including Yosemite and Dartmoor | Coarse-grained igneous rock |
| Granite Dome | Yosemite (USA), Brazil, Africa | Rounded mass of exposed granite |
| Granodiorite | Sierra Nevada, Andes, Scotland | Granite-like igneous rock |
| Granulite | Deep continental crust, Scotland, India, Scandinavia | High-grade metamorphic rock |
| Graphite | Sri Lanka, China, Canada, Brazil | Soft, dark carbon mineral |
| Graptolite Shale | Wales, Scotland, Scandinavia, North America | Fossil-bearing dark shale |
| Gravel Bar | Rivers worldwide | Ridge of stones in a river |
| Great Artesian Basin | Australia | Huge underground water reservoir |
| Great Barrier Reef | Queensland, Australia | World’s largest coral reef system |
| Great Basin | Nevada, Utah, western United States | Large region with no outlet to the sea |
| Great Blue Hole | Belize | Giant marine sinkhole |
| Great Dyke | Zimbabwe | Long, narrow igneous intrusion |
| Great Escarpment | Southern Africa | Steep edge of a high plateau |
| Great Rift Valley | East Africa | Chain of rift valleys where Africa is splitting |
| Great Sand Dunes | Colorado, USA | Tallest dunes in North America |
| Great Salt Lake | Utah, USA | Largest saltwater lake in the Western Hemisphere |
| Great Slave Lake Impact Zone | Northwest Territories, Canada | Deep lake in ancient crust |
| Greenstone Belt | Canada, Australia, South Africa, Zimbabwe | Ancient volcanic and sedimentary rock zone |
| Greisen | Cornwall, Germany, Czech Republic | Altered granite rich in tin |
| Grikes | Yorkshire (UK), Burren (Ireland), Karst regions | Cracks in limestone pavement |
| Grotto | Worldwide, including Capri in Italy | Small cave, often near water |
| Ground Ice | Arctic regions, Siberia, Canada, Alaska | Ice within frozen soil |
| Groundwater | Worldwide | Water stored beneath the surface |
| Gryke | Yorkshire (UK), Ireland, Karst regions | Fissure in limestone |
| Guyot | Pacific Ocean | Flat-topped underwater mountain |
| Gulch | Western United States | Deep, narrow ravine |
| Gulf | Worldwide, including Gulf of Mexico and Persian Gulf | Large inlet of the sea |
| Gully | Worldwide | Channel cut by running water |
| Gum Mountain Volcanic Field | Arizona, USA | Cinder cone and lava flow region |
| Gunnison Gorge | Colorado, USA | Narrow canyon in ancient rock |
| Gutter Rock Channels | Coastal regions worldwide | Grooves in rock cut by water |
| Gypsum | Worldwide, including New Mexico and Mexico | Soft sulfate mineral |
| Gypsum Dune Field | White Sands, New Mexico, USA | Dunes made of gypsum sand |
| Gypsum Cave | Mexico, Italy, Ukraine | Cave in soluble sulfate rock |
| Gyre | Oceans worldwide | Large circular ocean current system |
Descriptions
Gabbro
A dark, coarse-grained rock formed when magma cools slowly underground. It makes up much of the deep ocean crust and is chemically the same as basalt.
Galena
The main ore of lead, found as shiny gray cubic crystals. It often occurs in veins alongside silver and zinc minerals.
Garnet
A group of hard minerals found in metamorphic rocks, best known for their deep red color. They are used as gemstones and as industrial abrasives.
Gas Hydrate
A crystalline solid in which water molecules trap gas, usually methane. It forms under high pressure and low temperature in seafloor sediments and permafrost.
Geode
A rounded rock with a hollow center lined with crystals such as quartz or amethyst. They form when mineral-rich water deposits crystals inside a cavity.
Geological Fault
A crack in the Earth’s crust along which rocks have shifted. Sudden movement along faults causes earthquakes.
Geological Unconformity
A surface that marks missing time between two layers of rock, where erosion or a pause in deposition removed or prevented layers. It shows up as a visible break in the strata.
Geomorphic Surface
A land surface shaped by erosion or deposition at a particular time. Geologists use them to date landscapes and track changes in climate and uplift.
Geosyncline
An old term for a huge, elongated trough that fills with thick layers of sediment. The idea was replaced by plate tectonics, but it helped explain how mountain belts form.
Geothermal Field
A region where heat from deep within the Earth warms groundwater near the surface. Many are tapped for electricity and heating.
Geyser
A hot spring that shoots water and steam into the air at intervals. Eruptions happen when underground water boils under pressure.
Geyserite
A pale mineral crust left behind as hot spring water cools and drops dissolved silica. It builds up around geyser vents and pools.
Ghost Forest
A stand of dead trees killed when land subsides or floods with seawater. The best-known examples on the Pacific coast date to a large earthquake in 1700.
Giant’s Causeway
A coastline of about 40,000 interlocking basalt columns formed by an ancient volcanic eruption. It is a UNESCO World Heritage Site.
Giant’s Kettle
A smooth, circular pothole drilled into rock by stones swirling in meltwater beneath a glacier. Some are several meters deep.
Gibber Plain
A flat desert plain covered in a layer of tightly packed, wind-polished stones. The finer material between them has been blown away.
Gilgai
A pattern of small hollows and mounds formed as clay soils swell when wet and shrink when dry. It gives the ground a rippled look.
Glacial Cirque
An armchair-shaped valley head carved by a glacier high on a mountainside. Many hold small lakes called tarns after the ice melts.
Glacial Erratic
A large rock carried by a glacier and dropped far from where it originated. It often sits on land with very different rock beneath it.
Glacial Lake
A lake that fills a basin dug out or dammed by a glacier. Many of the world’s lakes in northern regions formed this way.
Glacial Moraine
A pile of rock, sand, and clay carried and dumped by a glacier. Moraines mark where a glacier once reached.
Glacial Outburst Flood
A flood caused when a lake held back by ice or debris suddenly drains. It can send huge volumes of water down a valley.
Glacial Outwash Plain
A broad, flat expanse of sand and gravel deposited by streams flowing out from a glacier. Also known as a sandur.
Glacial Striations
Parallel scratches in bedrock made by stones dragged along under a glacier. They show the direction the ice flowed.
Glacial Trough
A broad valley with steep sides and a flat floor, shaped by a glacier. It looks very different from the V shape of a river valley.
Glacier
A large body of ice that forms from compacted snow and flows slowly downhill under its own weight. Glaciers shape landscapes by eroding and carrying rock.
Glacier Cave
A passage formed by meltwater flowing through or beneath a glacier. Some are open to visitors in winter when they are stable.
Glacier Mill
A deep hole that meltwater drills through a glacier down to its base. Also called a moulin, it carries surface water to the bedrock below.
Glacier Table
A large rock perched on a column of ice. The rock shades the ice beneath it from the sun while the surrounding surface melts away.
Glacis
A gentle slope at the foot of a mountain or hill, usually formed by erosion. It is common in dry regions.
Glauconite
A green mineral that forms slowly on the seafloor, often in sandstone. Geologists use it to date rocks and to spot ancient marine settings.
Glossopteris Fossil Bed
Fossil leaves of an ancient seed fern found on continents now far apart. They were key evidence for the supercontinent Gondwana.
Gneiss
A coarse rock with light and dark bands, formed under intense heat and pressure. It is among the oldest rocks on Earth.
Goethite
A common iron mineral that gives many soils and rocks a rusty yellow-brown color. It forms when iron-bearing rocks weather.
Gold Placer Deposit
A deposit of gold flakes and nuggets washed from rock and settled in riverbeds. Prospectors have panned these since ancient times.
Gondwana
A massive landmass that once joined Africa, South America, India, Australia, and Antarctica. It broke apart over about 180 million years.
Gorge
A narrow, steep-sided valley, usually carved by a river cutting down through rock. Gorges often form where land has been uplifted.
Graben
A strip of land that has sunk between two parallel faults. The Rhine and East African rift valleys are famous examples.
Grabens of Canyonlands
A set of long, narrow valleys in Canyonlands National Park created as rock slid over salt beds below. The ground has dropped between parallel faults.
Granite
A hard, speckled rock that cools slowly from magma deep underground. It forms much of the continental crust and is widely used for building.
Granite Dome
A smooth, rounded hill of bare granite that forms as outer layers peel off in curved sheets. Half Dome and Sugarloaf Mountain are examples.
Granodiorite
A speckled rock similar to granite but with more plagioclase feldspar. It is one of the most common rocks in the continental crust.
Granulite
A rock changed by very high temperatures deep in the crust. It has interlocking grains and is found in the roots of ancient mountain ranges.
Graphite
A soft, slippery form of carbon used in pencils and batteries. It forms when carbon-rich rock is heated and compressed.
Graptolite Shale
A dark rock containing fossils of tiny colonial sea creatures that look like pencil marks. They are used to date rocks of the early Paleozoic era.
Gravel Bar
A bank of gravel deposited by flowing water, usually on the inside of a bend or in the middle of a channel. It shifts as water levels change.
Great Artesian Basin
One of the largest groundwater systems in the world, lying under about a fifth of Australia. Water seeps through porous rock and rises under pressure at artesian springs.
Great Barrier Reef
A reef of more than 2,900 individual reefs stretching about 1,400 miles along Australia’s coast. It is built from billions of tiny coral animals.
Great Basin
A dry region of the American West where rivers drain inward and never reach the ocean. It is known for its parallel mountain ranges and salt flats.
Great Blue Hole
A circular sinkhole about 1,000 feet wide and over 400 feet deep, in the Lighthouse Reef. It formed as a cave collapsed during lower sea levels.
Great Dyke
A 340-mile-long band of layered rock that cuts across Zimbabwe. It holds some of the world’s largest chromium and platinum reserves.
Great Escarpment
A long cliff-like edge that separates the high interior of southern Africa from the coastal lowlands. It runs for thousands of miles.
Great Rift Valley
A huge system of valleys, lakes, and volcanoes stretching thousands of miles from the Middle East to Mozambique. Africa is slowly splitting apart here.
Great Sand Dunes
A field of sand dunes up to about 750 feet high, piled against the Sangre de Cristo Mountains. Wind carries sand from the valley floor and traps it here.
Great Salt Lake
A shallow, very salty lake left over from the ancient Lake Bonneville. Its size changes a lot with rainfall and snowmelt.
Great Slave Lake Impact Zone
A huge, deep lake formed over some of the oldest rocks on Earth, in the Canadian Shield. It is one of the deepest lakes in North America.
Greenstone Belt
A band of very old rocks, often more than 2.5 billion years, that have been altered to a greenish tint. They are important sources of gold and records of early Earth.
Greisen
A rock formed when hot fluids alter granite, producing minerals such as quartz and mica. It often holds tin and tungsten ores.
Grikes
The deep cracks that separate the blocks, or clints, of a limestone pavement. They form as rainwater dissolves the rock along joints.
Grotto
A small cave, often formed by waves or dissolving rock. Some, like the Blue Grotto in Italy, are famous for their light.
Ground Ice
Ice that lies within frozen ground in cold regions. It can form wedges, lenses, or large masses and causes the ground to heave and sink.
Groundwater
Water that fills spaces in soil and rock below the ground. It feeds springs and wells and supplies drinking water for billions of people.
Gryke
A narrow, deep crack in limestone formed by rainwater dissolving the rock. Singular of grikes, it separates blocks of rock on a pavement.
Guyot
An extinct volcano under the sea whose top was flattened by waves when it was at the surface. It later sank beneath the water as the seafloor cooled.
Gulch
A steep-sided valley, usually cut by a fast-flowing stream. The term is often used in the American West.
Gulf
A large body of ocean water partly enclosed by land. Some formed as continents rifted apart or sea levels rose.
Gully
A small valley or ditch worn into soil or rock by water, often after heavy rain. Gullies can grow quickly where plants are sparse.
Gum Mountain Volcanic Field
A region of young volcanic features in the southwestern United States, with cones and lava fields formed in the last few million years.
Gunnison Gorge
A deep canyon cut by the Gunnison River through very old Precambrian rock. Its walls rise hundreds of feet above the river.
Gutter Rock Channels
Narrow channels on rock surfaces carved by flowing water or waves. They can funnel water and sediment toward lower ground.
Gypsum
A very soft mineral that forms when seawater evaporates. It is used to make plaster and drywall.
Gypsum Dune Field
A sea of white dunes made of gypsum rather than quartz. It is the largest gypsum dunefield in the world.
Gypsum Cave
A cave formed as water dissolves gypsum. Mexico’s Cave of Crystals contains some of the largest natural crystals ever found.
Gyre
A huge, slowly rotating system of ocean currents driven by wind and the Earth’s spin. The gyres shape sea life and where floating debris collects.