Geology: Most Popular Articles
These articles are the most popular over the last month.
Rock Picture Gallery | Photos of Rocks
Pictures and descriptions of rocks on About.com Geology
Pictures and descriptions of rocks on About.com Geology
Rock Identification Tables
Three tables cover 37 of the most common rock types, with simple ways to distinguish them.
Three tables cover 37 of the most common rock types, with simple ways to distinguish them.
About Igneous Rocks
The three great rock classes--igneous, sedimentary and metamorphic--are introduced with igneous rocks.
The three great rock classes--igneous, sedimentary and metamorphic--are introduced with igneous rocks.
Mineral Picture Gallery
The mineral wing of the About Geology Picture Gallery.
The mineral wing of the About Geology Picture Gallery.
About Sedimentary Rocks
The second of the three great rock classes is introduced with photos.
The second of the three great rock classes is introduced with photos.
About Metamorphic Rocks
The three great rock classes--igneous, sedimentary and metamorphic--are introduced with photos, finishing with metamorphic.
The three great rock classes--igneous, sedimentary and metamorphic--are introduced with photos, finishing with metamorphic.
Mohs Hardness Scale
The ten-mineral Mohs scale of relative hardness, based on what scratches what.
The ten-mineral Mohs scale of relative hardness, based on what scratches what.
Landform Picture Gallery
The landform wing of the About Geology Picture Gallery.
The landform wing of the About Geology Picture Gallery.
About the Earth's Core
How we study the Earth's core and what it's made of.
How we study the Earth's core and what it's made of.
Fossil Picture Gallery
Pictures of fossils, part of the About Geology Image Gallery.
Pictures of fossils, part of the About Geology Image Gallery.
Plate Tectonics - The World's Crustal Plates
The Earth's crustal plates, from the U.S. Geological Survey
The Earth's crustal plates, from the U.S. Geological Survey
About Granite
Granite is the signature rock of the continents.
Granite is the signature rock of the continents.
Pahoehoe and Aa Basalt
Basalt displays both pahoehoe and aa texture in one place.
Basalt displays both pahoehoe and aa texture in one place.
About the Earth's Mantle
A look at six different aspects of the Earth's mantle.
A look at six different aspects of the Earth's mantle.
What Is a Rock?
Everyone knows what a rock is, until you ask what it is exactly.
Everyone knows what a rock is, until you ask what it is exactly.
About the San Andreas Fault
Home page for everything about the San Andreas fault.
Home page for everything about the San Andreas fault.
Fault Types in a Nutshell
The three basic types of fault, with their nomenclature, in a nutshell.
The three basic types of fault, with their nomenclature, in a nutshell.
Quartz
Quartz is classified as a rock-forming mineral.
Quartz is classified as a rock-forming mineral.
Gems to Minerals, Minerals to Gems
Mineral names and their corresponding gem names.: microcline feldspar gemstone mineral rubellite tourmaline demantoid garnet taaffeite
Mineral names and their corresponding gem names.: microcline feldspar gemstone mineral rubellite tourmaline demantoid garnet taaffeite
How to Look at a Rock
Notes on the most basic operation in geology.
Notes on the most basic operation in geology.
Pictures of Geologic Features and Processes
Pictures of geologic features and the processes of geology.
Pictures of geologic features and the processes of geology.
Glacier Picture Gallery
Pictures of glacial features and the processes of glaciers.
Pictures of glacial features and the processes of glaciers.
Chert Nodule Interior
Interior of a chert nodule.
Interior of a chert nodule.
The Biggest Eruptions
The biggest eruptions in history and prehistory
The biggest eruptions in history and prehistory
Olivine
Olivine is an important rock-forming mineral.
Olivine is an important rock-forming mineral.
Geyser
Photo of Castle Geyser, in Yellowstone National Park, Wyoming.
Photo of Castle Geyser, in Yellowstone National Park, Wyoming.
Top 25 US Geology PhD Schools
These 25 American colleges grant the huge majority of the geology PhD's held by U.S. college faculty.
These 25 American colleges grant the huge majority of the geology PhD's held by U.S. college faculty.
Slate or Phyllite?
Slate and phyllite grade into each other, and sometimes the choice is arbitrary.
Slate and phyllite grade into each other, and sometimes the choice is arbitrary.
Mount St Helens Eruption
Remembering a scientist who died in the 1980 eruption of Mount St Helens.
Remembering a scientist who died in the 1980 eruption of Mount St Helens.
Chalcedony or Cryptocrystalline Quartz
A fractured chert pebble displays silica in its cryptocrystalline form.
A fractured chert pebble displays silica in its cryptocrystalline form.
Tectonic Plates with Topography, Eastern Hemisphere
Topography of the Eastern Hemisphere with tectonic plate boundaries.
Topography of the Eastern Hemisphere with tectonic plate boundaries.
Calcite
Calcite is a rock-forming mineral, most important in limestone.
Calcite is a rock-forming mineral, most important in limestone.
Geologic Map of Texas
Texas geologic map, courtesy of the state bureau of economic geology
Texas geologic map, courtesy of the state bureau of economic geology
The Crust
The Earth's crust is exceptionally important, and not just because we live on it.
The Earth's crust is exceptionally important, and not just because we live on it.
Plate Tectonics in a Nutshell
A simple starting point for the basics of plate tectonics.
A simple starting point for the basics of plate tectonics.
Global Seismic Hazard Map Index
First page of the Global Seismic Hazard Map gallery.
First page of the Global Seismic Hazard Map gallery.
Biotite Mica
Biotite mica is classified as a rock-forming mineral.
Biotite mica is classified as a rock-forming mineral.
Valley Glacier - or Mountain or Alpine Glacier
Bucher Glacier, a typical valley - or mountain or alpine - glacier.
Bucher Glacier, a typical valley - or mountain or alpine - glacier.
Geologic Map of California
California geologic map, at four different scales.
California geologic map, at four different scales.
The Tibetan Plateau
The largest highest place on Earth is a showcase of plate tectonics.
The largest highest place on Earth is a showcase of plate tectonics.
How to Identify Minerals
First steps in mineral identification.
First steps in mineral identification.
Uluru, Australia
Uluru sits in the great Australian peneplain.: uluru australia mount monadnock geoscience australia australia uluru australia photo
Uluru sits in the great Australian peneplain.: uluru australia mount monadnock geoscience australia australia uluru australia photo
What Are Fossils?
Fossils are precious gifts from the geologic past.
Fossils are precious gifts from the geologic past.
Surface Minerals
The thousands of minerals known in rocks become a mere handful at the Earth's surface.
The thousands of minerals known in rocks become a mere handful at the Earth's surface.
Muscovite Mica
Muscovite is classed as a rock-forming mineral.
Muscovite is classed as a rock-forming mineral.
Talc
Talc is one of the silicate minerals.
Talc is one of the silicate minerals.
Agate
Agate is a rock made of chalcedony or cryptocrystalline quartz.
Agate is a rock made of chalcedony or cryptocrystalline quartz.
Mesa, Utah
Mesas are a type of erosional landform.
Mesas are a type of erosional landform.
The Richter Scales
Nowadays, every earthquake magnitude scale is the Richter scale.
Nowadays, every earthquake magnitude scale is the Richter scale.
Geologic Map of Arkansas
Arkansas geologic map, presented at four different scales with notes.
Arkansas geologic map, presented at four different scales with notes.
Articles on Earthquakes
Features about earthquakes, seismology, and related phenomena from your About Geology Guide.
Features about earthquakes, seismology, and related phenomena from your About Geology Guide.
Gold Nugget
Gold nugget, in the gallery of minerals with metallic luster.
Gold nugget, in the gallery of minerals with metallic luster.
Actinolite
Actinolite is a major amphibole mineral.
Actinolite is a major amphibole mineral.
1906 San Francisco Earthquake
The Great San Francisco Earthquake was the stuff of legend, but it really happened.
The Great San Francisco Earthquake was the stuff of legend, but it really happened.
Feldspar (Orthoclase)
Feldspar is a major rock-forming mineral.
Feldspar is a major rock-forming mineral.
About Sandstone
Sandstone is sand cemented together into rock.
Sandstone is sand cemented together into rock.
Earthquake Statistics
A graph displays the numbers of quakes of different magnitudes.
A graph displays the numbers of quakes of different magnitudes.
Opal, Hydrated Silica
Opal is a hydrated form of amorphous silica.
Opal is a hydrated form of amorphous silica.
About Ophiolites
Not a rock type, it's a whole assemblage of crustal rocks.
Not a rock type, it's a whole assemblage of crustal rocks.
Geology Desktop Wallpaper Pictures
Free 800x600, 1024x768, 1280x1024 and 1600x1200 geology pictures for your computer's desktop wallpaper.
Free 800x600, 1024x768, 1280x1024 and 1600x1200 geology pictures for your computer's desktop wallpaper.
Geologic Map of Colorado
The great USGS Colorado geologic map, presented at full size.
The great USGS Colorado geologic map, presented at full size.
Common Rock Densities
Density, or specific gravity, of common rock types.
Density, or specific gravity, of common rock types.
Amethyst
Amethyst specimen showing typical shapes of quartz crystals.
Amethyst specimen showing typical shapes of quartz crystals.
Oldoinyo Lengai
Oldoinyo Lengai erupts sodium carbonate--not quite a big rock candy mountain, but then nothing else about it is quite like the song.
Oldoinyo Lengai erupts sodium carbonate--not quite a big rock candy mountain, but then nothing else about it is quite like the song.
Gypsum Rose
Gypsum is one of the sulfate minerals.
Gypsum is one of the sulfate minerals.
Tectonic Plate Boundaries, Eastern Hemisphere
Plate boundaries of the Eastern Hemisphere: divergent, convergent, and transform.
Plate boundaries of the Eastern Hemisphere: divergent, convergent, and transform.
Articles on Volcanoes
Articles about volcanoes and related phenomena, from your About Geology Guide.
Articles about volcanoes and related phenomena, from your About Geology Guide.
Earth Formation in a Nutshell
The straight story of how Earth began, as today's geologists tell it.
The straight story of how Earth began, as today's geologists tell it.
Soil Creep
Diagram of soil creep, the gentlest kind of landslide
Diagram of soil creep, the gentlest kind of landslide
Topaz
Topaz is one of the silicate minerals.
Topaz is one of the silicate minerals.
Tombolo, California
Tombolos are a type of depositional landform.
Tombolos are a type of depositional landform.
Plagioclase in Anorthosite
Plagioclase is well displayed in a gravestone.
Plagioclase is well displayed in a gravestone.
Sumatra 26 Dec 2004 M9.3
The greatest earthquake in 40 years killed 300,000 people.
The greatest earthquake in 40 years killed 300,000 people.
Anticline
Anticline.: rock sequences pore space rock beds antiform anticlines
Anticline.: rock sequences pore space rock beds antiform anticlines
Pyroxene (Augite)
Pyroxene is a rock-forming mineral.
Pyroxene is a rock-forming mineral.
Lisbon Earthquake, 1 November 1755
Lisbon earthquake of 1 November 1755, images and notes.
Lisbon earthquake of 1 November 1755, images and notes.
Dolomite
Dolomite is one of the rock-forming minerals.
Dolomite is one of the rock-forming minerals.
Geology Wallpaper Images - Rock Closeups
A selection of wallpaper images of rocks in loving detail.
A selection of wallpaper images of rocks in loving detail.
Coal in the Home
Americans don't burn coal at home any more, but it still works for most of the world.
Americans don't burn coal at home any more, but it still works for most of the world.
Brachiopod
A typical brachiopod fossil.: permian extinction cambrian rocks bivalve shells brachiopod
A typical brachiopod fossil.: permian extinction cambrian rocks bivalve shells brachiopod
Geologic Time Scale: Eons and Eras
The three eons and ten eras of the geologic time scale.
The three eons and ten eras of the geologic time scale.
The Lithosphere in a Nutshell
What you need to know about the lithosphere: earthquake faults rock slab plate tectonics surface rocks lithosphere
What you need to know about the lithosphere: earthquake faults rock slab plate tectonics surface rocks lithosphere
Geologic Time Scale: The Phanerozoic Eon
Eras, periods and epochs of the Phanerozoic, part of the geologic time scale.
Eras, periods and epochs of the Phanerozoic, part of the geologic time scale.
Geologic Map of Missouri
Missouri geologic map, courtesy of the state geological survey
Missouri geologic map, courtesy of the state geological survey
Native Carbon: Graphite
Carbon, the element C, occurs in native form as graphite.
Carbon, the element C, occurs in native form as graphite.
Magnetite
Magnetite is one of the oxide minerals.
Magnetite is one of the oxide minerals.
Tourmaline
Tourmaline is one of the silicate minerals.
Tourmaline is one of the silicate minerals.
What Is Geology?
The whole of Earth sciences, compressed to a nutshell.
The whole of Earth sciences, compressed to a nutshell.
Geologic Map of Georgia
Georgia geologic map, at three different scales, created from the USGS data.
Georgia geologic map, at three different scales, created from the USGS data.
Native Carbon: Diamond
Diamond is a rare form of carbon, the element C, in native form.
Diamond is a rare form of carbon, the element C, in native form.
Cirque Glacier
Cirque glacier in the Fairweather Range, southeast Alaska.
Cirque glacier in the Fairweather Range, southeast Alaska.
Marble
Marble is metamorphosed limestone.
Marble is metamorphosed limestone.
Profile of Aa Basalt Flow
Basalt grades from massive to aa texture within a lava flow.
Basalt grades from massive to aa texture within a lava flow.
About Salt
Salt pervades the Earth and seas and, not least, our lives.
Salt pervades the Earth and seas and, not least, our lives.
Present Plate Motions, Eurasia/Africa
Current tectonic plate motions, eastern hemisphere.
Current tectonic plate motions, eastern hemisphere.
Slump Landslide
Slumps small and large, harmless and catastrophic.
Slumps small and large, harmless and catastrophic.
Potassium Feldspar (Microcline)
Large grains of microcline in a stone park bench.
Large grains of microcline in a stone park bench.
Stop 5, Monticello Dam: The Glory Hole
An overflow structure helps drain Lake Berryessa in northern California.
An overflow structure helps drain Lake Berryessa in northern California.
Poison Sumac, Toxicodendron vernix
Poison sumac, Toxicodendron vernix.
Poison sumac, Toxicodendron vernix.
What Are Minerals?
Minerals meet four criteria, more or less strict.
Minerals meet four criteria, more or less strict.
Geologic Map of New York
New York geologic map, presented at four different scales.
New York geologic map, presented at four different scales.
How to Read a Geologic Map, part 2 - Symbolizing Geology on Paper
Reading geologic maps--the symbols and labels and lines.
Reading geologic maps--the symbols and labels and lines.
Native Gold
Gold, the element Au, is usually found in nature in native form.
Gold, the element Au, is usually found in nature in native form.
Native Copper
Copper, the element Cu, is found in nature in native form.
Copper, the element Cu, is found in nature in native form.
Rock-Forming Minerals ID Key
Quick identification table for the minerals that form the majority of rocks.
Quick identification table for the minerals that form the majority of rocks.
Gemstone Special Effects
The most important optical effects in gemstones, from fire to asterism.
The most important optical effects in gemstones, from fire to asterism.
Sea Arch, California
Sea arches are a type of erosional landform.
Sea arches are a type of erosional landform.
Deaths from Tsunamis, by Ocean
The deadliest tsunamis recorded in each ocean basin.
The deadliest tsunamis recorded in each ocean basin.
Delta, Alaska
Deltas are a type of depositional landform.
Deltas are a type of depositional landform.
Tree Affected by Soil Creep
A tree bends in response to the slow soil creep beneath it.
A tree bends in response to the slow soil creep beneath it.
Hornblende Schist, San Francisco Bay Area
Hornblende schist in the gallery of amphibole minerals.
Hornblende schist in the gallery of amphibole minerals.
Corundum
Corundum is one of the oxide minerals.
Corundum is one of the oxide minerals.
About Feldspar
Feldspar is the commonest mineral in the Earth's crust, but identifying it can be tricky.
Feldspar is the commonest mineral in the Earth's crust, but identifying it can be tricky.
About Quartz
Quartz is essential to the land as we know it.
Quartz is essential to the land as we know it.
BYB Rock Collection
Advice on what to look for in those 'candy boxes' full of little rocks.
Advice on what to look for in those 'candy boxes' full of little rocks.
Geologic Map of Alaska
Alaska geologic map, at three different scales.: aleutian island chain alaska department of natural resources highest mountains in north america alaska campgrounds alaska geology
Alaska geologic map, at three different scales.: aleutian island chain alaska department of natural resources highest mountains in north america alaska campgrounds alaska geology
Geologic Time Scale: The Cenozoic Era
Ages, epochs and periods of the Cenozoic Era, part of the geologic time scale.
Ages, epochs and periods of the Cenozoic Era, part of the geologic time scale.
Arete
A jagged arete in Alaska glacier country.: juneau icefield glaciated mountains u s geological survey ragged ridge fish bone
A jagged arete in Alaska glacier country.: juneau icefield glaciated mountains u s geological survey ragged ridge fish bone
Mica Schist
A dark mica schist from Manhattan.
A dark mica schist from Manhattan.
The Most Common Mineral
This question has several answers, depending on what a mineral is and what part of the Earth we're talking about.
This question has several answers, depending on what a mineral is and what part of the Earth we're talking about.
Doubly Terminated Quartz Crystal
Herkimer diamond, doubly terminated quartz crystal.
Herkimer diamond, doubly terminated quartz crystal.
Bedrock Geologic Map of Nevada
Nevada geologic map, courtesy of the U.S. Geological Survey, with notes.
Nevada geologic map, courtesy of the U.S. Geological Survey, with notes.
Halite
Halite is one of the halide minerals.
Halite is one of the halide minerals.
Serpentine (Chrysotile)
Serpentine is one of the silicate minerals.
Serpentine is one of the silicate minerals.
Cirque, California
Cirques are mountaiside bowls carved by glacial erosion.
Cirques are mountaiside bowls carved by glacial erosion.
Cinder Cone or Scoria Cone, Hawaii
Puu ka Pele, a Hawaiian cinder or scoria cone.
Puu ka Pele, a Hawaiian cinder or scoria cone.
Chlorite
Chlorite is one of the silicate minerals.
Chlorite is one of the silicate minerals.
Native Platinum
Platinum, the element Pt, occurs in native form.
Platinum, the element Pt, occurs in native form.
Cat's-Eye Agate
Cats-eye chalcedony has fibrous inclusions of reibekite.
Cats-eye chalcedony has fibrous inclusions of reibekite.
Bre-X Gold Scandal
First there is a mountain of gold, then there is no mountain, then there is no gold mining company named Bre-X.
First there is a mountain of gold, then there is no mountain, then there is no gold mining company named Bre-X.
Tuff from Green Valley
Photos of erupted igneous rocks.
Photos of erupted igneous rocks.
Siltstone
Siltstone, in the gallery of sedimentary rocks.
Siltstone, in the gallery of sedimentary rocks.
How to Read a Geologic Map, part 1 - Starting on the Ground
Introducing the art of reading a geologic map--contours and landforms.
Introducing the art of reading a geologic map--contours and landforms.
Ammonoid or Ammonite
Miniature ammonoid fossil, emblem of the Cretaceous.
Miniature ammonoid fossil, emblem of the Cretaceous.
Esker
A classic esker, covered with forest, winds across northern Manitoba.
A classic esker, covered with forest, winds across northern Manitoba.
Coal in a Nutshell
Introducing coal: how it forms, what's in it, what it tells us.
Introducing coal: how it forms, what's in it, what it tells us.
Galena
Galena is one of the sulfide minerals.
Galena is one of the sulfide minerals.
Lapillistone, Oakland Hills, California
Lapillistone in the Oakland Hills, in the volcanic rocks gallery.
Lapillistone in the Oakland Hills, in the volcanic rocks gallery.
QAP Diagram for Plutonic Rocks
QAP ternary diagram showing IUGS classification of phaneritic igneous rocks.
QAP ternary diagram showing IUGS classification of phaneritic igneous rocks.
Slate
Slate is the first metamorphic rock in the pelitic sequence.
Slate is the first metamorphic rock in the pelitic sequence.
Insect Fossil in Amber
An amber earring contains an insect fossil.: fossilized tree resin resin traps fossil insect amber fossils amber specimens
An amber earring contains an insect fossil.: fossilized tree resin resin traps fossil insect amber fossils amber specimens
Ice Cave
Ice cave in Guyot Glacier, southeastern Alaska.: guyot glacier u s geological survey stream sediment ice caves winding ridge
Ice cave in Guyot Glacier, southeastern Alaska.: guyot glacier u s geological survey stream sediment ice caves winding ridge
Pyrite
Pyrite is one of the sulfide minerals.
Pyrite is one of the sulfide minerals.
Amphibole (Hornblende)
Amphibole is classed as a rock-forming mineral.
Amphibole is classed as a rock-forming mineral.
Syncline
A syncline is perfectly exposed in Ellesmere Island.
A syncline is perfectly exposed in Ellesmere Island.
Age of the Ocean Floor
Seafloor age map for the woarld.: national geophysical data geophysical data center plate tectonic maps digital isochrons national geophysical data center
Seafloor age map for the woarld.: national geophysical data geophysical data center plate tectonic maps digital isochrons national geophysical data center
Tectonic Plate Boundaries, Western Hemisphere
Plate boundaries of the Western Hemisphere: divergent, convergent, and transform.
Plate boundaries of the Western Hemisphere: divergent, convergent, and transform.
Biotite
Biotite is an iron-rich member of the mica minerals.
Biotite is an iron-rich member of the mica minerals.
Fluorite
Fluorite is one of the halide minerals.
Fluorite is one of the halide minerals.
Geologic Time Scale: Eons, Eras and Periods
The periods of geologic time, part of the geologic time scale.
The periods of geologic time, part of the geologic time scale.