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.
Mineral Picture Gallery
The mineral wing of the About Geology Picture Gallery.
The mineral wing of the About Geology Picture Gallery.
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.
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.
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.
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.
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
Erupting Lakes
Three African lakes share a rare property: they explode.
Three African lakes share a rare property: they explode.
Fossil Picture Gallery
Pictures of fossils, part of the About Geology Image Gallery.
Pictures of fossils, part of the About Geology Image Gallery.
About the San Andreas Fault
Home page for everything about the San Andreas fault.
Home page for everything about the San Andreas fault.
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.
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.
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.
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
Geyser
Photo of Castle Geyser, in Yellowstone National Park, Wyoming.
Photo of Castle Geyser, in Yellowstone National Park, Wyoming.
Pictures of Geologic Features and Processes
Pictures of geologic features and the processes of geology.
Pictures of geologic features and the processes of geology.
Cement and Concrete
Cement is an artificial stone--or maybe lava.
Cement is an artificial stone--or maybe lava.
Earthquake Lights
A new theory of earthquake lights looks promising
A new theory of earthquake lights looks promising
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.
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.
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.
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.
Glacier Picture Gallery
Pictures of glacial features and the processes of glaciers.
Pictures of glacial features and the processes of glaciers.
The Biggest Eruptions
The biggest eruptions in history and prehistory
The biggest eruptions in history and prehistory
Quartz
Quartz is classified as a rock-forming mineral.
Quartz is classified as a rock-forming mineral.
How to Look at a Rock
Notes on the most basic operation in geology.
Notes on the most basic operation in geology.
Olivine
Olivine is an important rock-forming mineral.
Olivine is an important rock-forming mineral.
Abrasive Minerals
A survey of the minerals whose properties make them useful abrasives.
A survey of the minerals whose properties make them useful abrasives.
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.
The Richter Scales
Nowadays, every earthquake magnitude scale is the Richter scale.
Nowadays, every earthquake magnitude scale is the Richter scale.
Chert Nodule Interior
Interior of a chert nodule.
Interior of a chert nodule.
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.
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.
Agate
Agate is a rock made of chalcedony or cryptocrystalline quartz.
Agate is a rock made of chalcedony or cryptocrystalline quartz.
Geologic Map of California
California geologic map, at four different scales.
California geologic map, at four different scales.
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.
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.
Global Seismic Hazard Map Index
First page of the Global Seismic Hazard Map gallery.
First page of the Global Seismic Hazard Map gallery.
How to Identify Minerals
First steps in mineral identification.
First steps in mineral identification.
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
Chalcedony or Cryptocrystalline Quartz
A fractured chert pebble displays silica in its cryptocrystalline form.
A fractured chert pebble displays silica in its cryptocrystalline form.
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
Mesa, Utah
Mesas are a type of erosional landform.
Mesas are a type of erosional landform.
Earthquake Statistics
A graph displays the numbers of quakes of different magnitudes.
A graph displays the numbers of quakes of different magnitudes.
Tectonic Plates with Topography, Eastern Hemisphere
Topography of the Eastern Hemisphere with tectonic plate boundaries.
Topography of the Eastern Hemisphere with tectonic plate boundaries.
Geologic Map of New York
New York geologic map, presented at four different scales.
New York geologic map, presented at four different scales.
Calcite
Calcite is a rock-forming mineral, most important in limestone.
Calcite is a rock-forming mineral, most important in limestone.
What Is Geology?
The whole of Earth sciences, compressed to a nutshell.
The whole of Earth sciences, compressed to a nutshell.
About Salt
Salt pervades the Earth and seas and, not least, our lives.
Salt pervades the Earth and seas and, not least, our lives.
Soil Creep
Diagram of soil creep, the gentlest kind of landslide
Diagram of soil creep, the gentlest kind of landslide
Gypsum Rose
Gypsum is one of the sulfate minerals.
Gypsum is one of the sulfate minerals.
Plagioclase in Anorthosite
Plagioclase is well displayed in a gravestone.
Plagioclase is well displayed in a gravestone.
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.
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.
Muscovite Mica
Muscovite is classed as a rock-forming mineral.
Muscovite is classed as a rock-forming mineral.
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.
Tectonic Plates with Topography, Western Hemisphere
Topography of the Western Hemisphere with tectonic plate boundaries.
Topography of the Western Hemisphere with tectonic plate boundaries.
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.
Talc
Talc is one of the silicate minerals.
Talc is one of the silicate minerals.
Cinder Cone or Scoria Cone, Hawaii
Puu ka Pele, a Hawaiian cinder or scoria cone.
Puu ka Pele, a Hawaiian cinder or scoria cone.
Native Copper
Copper, the element Cu, is found in nature in native form.
Copper, the element Cu, is found in nature in native form.
Native Platinum
Platinum, the element Pt, occurs in native form.
Platinum, the element Pt, occurs in native form.
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.
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
Amethyst
Amethyst specimen showing typical shapes of quartz crystals.
Amethyst specimen showing typical shapes of quartz crystals.
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.
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.
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.
Potassium Feldspar (Microcline)
Large grains of microcline in a stone park bench.
Large grains of microcline in a stone park bench.
About Sandstone
Sandstone is sand cemented together into rock.
Sandstone is sand cemented together into rock.
What Are Minerals?
Minerals meet four criteria, more or less strict.
Minerals meet four criteria, more or less strict.
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.
Gold Nugget
Gold nugget, in the gallery of minerals with metallic luster.
Gold nugget, in the gallery of minerals with metallic luster.
Anticline
Anticline.: rock sequences pore space rock beds antiform anticlines
Anticline.: rock sequences pore space rock beds antiform anticlines
What Are Fossils?
Fossils are precious gifts from the geologic past.
Fossils are precious gifts from the geologic past.
Common Rock Densities
Density, or specific gravity, of common rock types.
Density, or specific gravity, of common rock types.
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.
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.
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.
Slump Landslide
Slumps small and large, harmless and catastrophic.
Slumps small and large, harmless and catastrophic.
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.
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.
Magnetite
Magnetite is one of the oxide minerals.
Magnetite is one of the oxide minerals.
Corundum
Corundum is one of the oxide minerals.
Corundum is one of the oxide minerals.
Opal, Hydrated Silica
Opal is a hydrated form of amorphous silica.
Opal is a hydrated form of amorphous silica.
Tombolo, California
Tombolos are a type of depositional landform.
Tombolos are a type of depositional landform.
Spit, Washington
Spits are a type of depositional landform.
Spits are a type of depositional landform.
Delta, Alaska
Deltas are a type of depositional landform.
Deltas are a type of depositional landform.
Geologic Map of Colorado
The great USGS Colorado geologic map, presented at full size.
The great USGS Colorado geologic map, presented at full size.
Slate
Slate is the first metamorphic rock in the pelitic sequence.
Slate is the first metamorphic rock in the pelitic sequence.
Geologic Map of Michigan
Bedrock geologic map of Michigan, at three different scales, courtesy of the state of Michigan
Bedrock geologic map of Michigan, at three different scales, courtesy of the state of Michigan
Mercalli Earthquake Intensity Scale
The modified Mercalli intensity scale rates the impact of quakes from I to XII.
The modified Mercalli intensity scale rates the impact of quakes from I to XII.
Brachiopod
A typical brachiopod fossil.: permian extinction cambrian rocks bivalve shells brachiopod
A typical brachiopod fossil.: permian extinction cambrian rocks bivalve shells brachiopod
Hexagonal Jointing in Basalt
Basalt cracks into six-sided columns.
Basalt cracks into six-sided columns.
Lisbon Earthquake, 1 November 1755
Lisbon earthquake of 1 November 1755, images and notes.
Lisbon earthquake of 1 November 1755, images and notes.
Galena
Galena is one of the sulfide minerals.
Galena is one of the sulfide minerals.
Alluvial Fan, California
Alluvial fans are a type of depositional landform.
Alluvial fans are a type of depositional landform.
Mica Schist
A dark mica schist from Manhattan.
A dark mica schist from Manhattan.
Marble
Marble is metamorphosed limestone.
Marble is metamorphosed limestone.
Geologic Gift Ideas
A few suggestions for something to get your favorite geologist.
A few suggestions for something to get your favorite geologist.
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.
Actinolite
Actinolite is a major amphibole mineral.
Actinolite is a major amphibole mineral.
Biotite Mica
Biotite mica is classified as a rock-forming mineral.
Biotite mica is classified as a rock-forming mineral.
Calderas - World's Largest Calderas
Table of the world's largest known calderas: chinati mountains kari kari supervolcanoes awasa taupo new zealand
Table of the world's largest known calderas: chinati mountains kari kari supervolcanoes awasa taupo new zealand
Mud Volcano, California
Mud volcanoes are classified as depositional landforms.
Mud volcanoes are classified as depositional landforms.
Native Iron
Native iron, the element Fe, is almost entirely from meteorites.
Native iron, the element Fe, is almost entirely from meteorites.
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.
Feldspar (Orthoclase)
Feldspar is a major rock-forming mineral.
Feldspar is a major rock-forming mineral.
Native Silver
Silver, the element Ag, is sometimes found in nature in native form.
Silver, the element Ag, is sometimes found in nature in native form.
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
Doubly Terminated Quartz Crystal
Herkimer diamond, doubly terminated quartz crystal.
Herkimer diamond, doubly terminated quartz crystal.
Famous Stones
Real rock stars from around the world, from Plymouth Rock to the Blarney Stone to the Black Stone of the Ka'aba.
Real rock stars from around the world, from Plymouth Rock to the Blarney Stone to the Black Stone of the Ka'aba.
About Tsunamis
Introducing tsunamis or tidal waves--whatever you call them, watch out.
Introducing tsunamis or tidal waves--whatever you call them, watch out.
Pyrite
Pyrite is one of the sulfide minerals.
Pyrite is one of the sulfide minerals.
Cat's-Eye Agate
Cats-eye chalcedony has fibrous inclusions of reibekite.
Cats-eye chalcedony has fibrous inclusions of reibekite.
Sea Arch, California
Sea arches are a type of erosional landform.
Sea arches are a type of erosional landform.
Biotite
Biotite is an iron-rich member of the mica minerals.
Biotite is an iron-rich member of the mica minerals.
Cirque, California
Cirques are mountaiside bowls carved by glacial erosion.
Cirques are mountaiside bowls carved by glacial erosion.
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
Migmatitic Gneiss
Gneiss in the extreme displays plastic and fluid deformation.
Gneiss in the extreme displays plastic and fluid deformation.
Topaz
Topaz is one of the silicate minerals.
Topaz is one of the silicate minerals.
Columnar Jointing in Basalt
Thick basalt flows crack into pencil-shaped columns.
Thick basalt flows crack into pencil-shaped columns.
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
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.
Mountain, California
Mountains are a quintessential erosional landform.
Mountains are a quintessential erosional landform.
Barrier Island, New Jersey
Barrier islands are a type of depositional landform.
Barrier islands are a type of depositional landform.
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.
Tourmaline
Tourmaline is one of the silicate minerals.
Tourmaline is one of the silicate minerals.
Obsidian Blocks
The blocky surface of an obsidian flow.
The blocky surface of an obsidian flow.
Bajada, California
Bajadas are a type of depositional landform.
Bajadas are a type of depositional landform.
Earthquakes in a Nutshell
Start here for the seismic basics.
Start here for the seismic basics.
Erupting Seas
An awesome mix of fire and water--methane and seawater--may lie behind mass extinctions.
An awesome mix of fire and water--methane and seawater--may lie behind mass extinctions.
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.
Permian-Triassic Extinction
New evidence and old converges on a volcanic explanation for "the great dying."
New evidence and old converges on a volcanic explanation for "the great dying."
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.
Exfoliation
Exfoliation of granite in thick slabs, Yosemite Valley, California.
Exfoliation of granite in thick slabs, Yosemite Valley, California.
Serpentine (Chrysotile)
Serpentine is one of the silicate minerals.
Serpentine is one of the silicate minerals.
Pahoehoe Lava
Pahoehoe, a bubble-filled ropy kind of basalt lava.
Pahoehoe, a bubble-filled ropy kind of basalt lava.
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.
Schist in Outcrop
Mica Schist outcrop in New York City.
Mica Schist outcrop in New York City.
Muscovite
Muscovite is an aluminum-rich member of the mica minerals.
Muscovite is an aluminum-rich member of the mica minerals.
Ammonoid or Ammonite
Miniature ammonoid fossil, emblem of the Cretaceous.
Miniature ammonoid fossil, emblem of the Cretaceous.
Hanging Valley, Alaska
Hanging valleys are a type of erosional landform.
Hanging valleys are a type of erosional landform.
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.
Chondrite Meteorite
Chondrite, in the photo gallery of various meteorites.
Chondrite, in the photo gallery of various meteorites.