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Geologic Features and Processes Gallery

Special Galleries: Chemical Weathering, Concretions, Hydrothermal Features, Mechanical Weathering, Organic Weathering, Pseudofossils, Sedimentary Structures

Abrasion—How rocks break down against other rocks.
Alluvium—Young fresh waterborne sediment found alongside streams.
Amygdules—Mineral-filled bubbles in frozen lava.
Anticline—Folded rocks with the sides sloping away from each other.
Avulsion—Riverbeds shift, ignoring our political boundaries.
Basalt Columns—Hexagonal jointing makes pencil-stacks in cooling lava.
Bedding—The most common feature of sedimentary rocks.
Bioturbation—A desert anthill illustrates organic weathering.
Black Sand—Black sand is rare except in places like Hawaii.
Blocks—Blocks are boulders being born from solid rock.
Boudinage—Folding and stretching creates these sausage-y forms.
Braided Stream—Also called an anastomosing stream.
Cavernous Weathering—Mechanical forces carve hollows into solid rock.
Channel Cast—The fossil of a sand flow cutting into mud.
Colluvium—Weathered material carried down from hills ready for rivers.
Concretions—Pseudofossils bound with mineral cement in curious shapes.
Contact Metamorphism—Lava has baked mud into brick-red rock.
Convolute Lamination—Squirmy shapes in sedimentary rock beds.
Dendrite—Not fossils, but treelike mineral growths.
Desert Pavement—Deserts generally have a surface of stones like this.
Desert Varnish—A close-up and explanation of this dark rock coating.
Dikes—Examples of sandstone and basalt intrusions.
Drag Fold—Rock layers bent along a fault.
Exfoliation—This erosional process sends slabs down a granite slope.
Fiamme—Flamelike signs of extreme volcanic conditions.
Flame Structure—Wisps of clay drawn up into a heavy overflow.
Flint Nodules—Pseudofossils of pure chert found in chalk.
Flute Casts—Tracks left in sedimentary rocks by fast waters.
Folding—San Francisco's chocolate chert shows its wrinkles in an outcrop.
Foreset Beds—Sedimentary bedding laid down on a slope.
Frost Heave—Mechanical action of ice is a mover of sediment.
Gas-Escape Structures—They look similar to raindrop impressions.
Geodes—Rocky lumps with crystalline matter inside.
Geopetal Structure—A sign of the ancient horizontal direction.
Geyser—Everyone's favorite geologic personality.
Graded Bedding—A reliable indicator of up and down.
Grus—Granite weathers into this clean natural gravel.
Honeycomb Weathering—Small, close-spaced hollows carved into solid rock.
Hornito—Spurting lava builds little cones resembling old-fashioned ovens.
Hummocky Cross-Bedding—Stony evidence of sand-sweeping storms.
Imbrication—A stacking pattern that points to ancient currents.
Jointing—Organized cracks march in sets up a Sierra Nevada streambed.
Kink Folds—Sharply creased shale beds in a Canadian roadcut.
Knockers—A local name for the peculiar rocky knobs of mélange country.
Lamination—A finely layered form of sedimentary structure shown in siltstone.
Landslide Picture Gallery—Examples of several landslide types.
Lava Pillows—See Pillow Lava.
Liesegang Banding—Mysterious dark strips that overprint rocks.
Load Casts—Footprints in mud of a seafloor avalanche.
Meromictic Lake—Rare lakes whose waters never overturn.
Mudcracks—A stony mosaic documents a dry period in a wet place.
Pele's Hair—Wind stretches hot lava into blonde fibers.
Phenocrysts—Crystals that stand out in igneous rocks.
Pillow Lava—Common on the seafloor, here exposed on land.
Pseudofossils—A set of common items that fool fossil-hunters.
Retrograde Metamorphism—How a former garnet schist lost its garnets.
Ripples—Signs of an ancient, gentle limestone sea.
Rip-Up Clasts—Signs of an ancient seafloor avalanche.
Salt Spray—A constant corrosive mist of salt goes from sea to land.
Scour-and-Fill Structures—Typical signs of turbidites.
Shatter Cones—Distinctive shapes made in rocks by cosmic impacts.
Sill—An igneous intrusion within the beds of another rock.
Slickenside—The "fault mirror" or polished surface of a former fault.
Spheroidal Weathering—This near-surface process makes a basalt bulls-eye.
Stromatolitic Structure—Fossils of ancient bacterial mats.
Syncline—A spectacular giant fold in the Canadian Arctic.
Tafoni—Large hollows formed by cavernous weathering.
Talus—Call this rock debris scree, too, if you like.
Thrust Fault—Illustrated by the spectacular Keystone thrust of Nevada.
Vein—A crack with a story.
Vug—A hole with a story.
Xenoliths—Stones from strange places.

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Other galleries:
Glaciers and Ice
Geology and Society
Free Geologic Wallpaper Pictures

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