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Geology: Most Popular Articles

These articles are the most popular over the last month.
Identify Almost Any Rock with This Table
Identify 43 of the most common rock types: igneous, sedimentary and metamorphic.
Use This Master Index of Rock Pictures
My master alphabetical guide to igneous, sedimentary and metamorphic rock pictures.
See the Densities of the Most Common Rock Types
Density, or specific gravity, of common rock types.
The Most Common Green Minerals in Nature
A guide to the most common and significant green and greenish minerals.
Identify Typical Minerals with This Master...
My master guide to annotated pictures to help you identify minerals: typical examples of rock-forming, accessory, and rare or notable minerals.
Fast Links for Real-Time Info on Current...
Directions to information and data from earthquakes as fast as possible.
10 Steps to Help You Identify Any Mineral
Mineral identification starts with picking a good specimen.
Fault Types in a Nutshell
The three basic types of fault, with their nomenclature, in a nutshell.
What to Know About Igneous Rocks
Introducing igneous rocks, first of the three great rock classes (along with sedimentary and metamorphic rocks).
Why the Earth's Crust Is So Important
The Earth's crust is exceptionally important, and not just because we live on it.
What Is My Blue or Purple Mineral?
A guide to the most common and significant blue and purple minerals.
What a Black Mineral Is Most Likely to Be
A guide to the most common and significant black minerals.
What to Know About Sedimentary Rocks
Introducing sedimentary rocks, second of the three great rock classes (along with igneous and metamorphic rocks).
Metamorphic Rock Types
The major metamorphic rock types, from regional, contact and mechanical metamorphism.
Pumice
Pumice is one of the major igneous rock types. Page 18.
What You Should Know About the San Andreas Fault
Home page for everything about the San Andreas fault: where it is, how it behaves, what it means.
Where to Look for Rocks and Minerals
Rocks and minerals can be found everywhere, but there is a learning process involved.
What Makes Metamorphic Rocks Special
Most of the thousands of rare minerals known to science occur in metamorphic rocks, which are formed by great heat and pressure. Introducing
Why Granite is the Signature Rock of Earth
Granite is the signature rock of the continents. Here are the basics of this important stone.
How to Look at a Rock Like a Geologist
Notes on the most basic operation in geology.
Basalt
Basalt is one of the major igneous rock types. Page 3.
About the Hayward Fault of California
The Hayward fault is America's greatest impending earthquake disaster.
Quartz: How to Tell It, Different Kinds, What...
Quartz is essential to the land as we know it.
Igneous Rock Types
The major igneous rock types, plutonic, intrusive and extrusive.
How to Tell the Feldspar Minerals Apart
Feldspar is the commonest mineral in the Earth's crust, but identifying it can be tricky.
Plate Tectonics Explains How the Earth's...
Start here to learn the basics of plate tectonics.
6 Things to Know About the Earth's Mantle
A six-part look at the basics of the Earth's mantle, the part between the crust and the core.
How to Use the Mohs Hardness Scale to Identify...
The 10-mineral Mohs scale of relative hardness is based on what scratches what.
Where Are the Greatest Earthquake Threats in...
The United Nations' global map of seismic hazard
Gneiss
Gneiss is a major metamorphic rock type from regional metamorphism. Page 6.
Obsidian
Obsidian is one of the major igneous rock types. Page 13.
Perlite
Perlite is one of the major igneous rock types. Page 16.
What Is Chemical Weathering?
A short explanation of chemical weathering.
What Is My Red or Pink Mineral?
A guide to the most common and significant red and pink minerals.
Quartzite
Quartzite is a major metamorphic rock type from regional metamorphism. Page 14.
Granite
Granite is one of the major igneous rock types. Page 8.
Gabbro
Gabbro is one of the major igneous rock types. Page 7.
Siltstone
Siltstone is one of the major types of sedimentary rocks. Page 24.
Schist
Schist is a major metamorphic rock type from regional metamorphism. Page 15.
Diorite
Diorite is one of the major igneous rock types. Page 4.
Serpentinite
Serpentinite is a major metamorphic rock type from regional metamorphism. Page 16.
California Geologic Map
Geologic map of California, part of a set of all 50 states. Page 5.
Pegmatite
Pegmatite is one of the major igneous rock types. Page 14.
What to Know Before You Buy a Magnifier
What to think about and look for when you set out to get a nice magnifier.
What Is the Most Common Mineral on Earth?
This question has several answers, depending on what a mineral is and what part of the Earth we're talking about.
Sandstone: What It Is and What It Tells Us
Sandstone is sand cemented together into rock.
Slate
Slate is a major metamorphic rock type from regional metamorphism. Page 17.
Sedimentary Rock Types
The major types of sedimentary rocks.
Andesite
Andesite is one of the major igneous rock types.
Geologic Maps of the 50 United States
Geologic maps of all 50 U.S. states.
Peridotite
Peridotite is one of the major igneous rock types. Page 15.
Felsite
Felsite is one of the major igneous rock types. Page 6.
Marble
Marble is a major metamorphic rock type from regional metamorphism. Page 10.
More Than 50 Different Landforms in Pictures
Find and see geological landforms at About.com Geology.
Porphyry
Porphyry is one of the major igneous rock types. Page 17.
Pyroxenite
Pyroxenite is one of the major igneous rock types. Page 19.
Viewing Earth from on High
Satellite views of Earth's surface make possible geological discoveries never before imagined.
Scoria
Scoria is one of the major igneous rock types. Page 22.
Sandstone
Sandstone is one of the major types of sedimentary rocks. Page 22.
Dunite
Dunite is a plutonic rock consisting of olivine. Page 5.
Phyllite
Phyllite is a major metamorphic rock type from regional metamorphism. Page 13.
Shale
Shale is one of the major types of sedimentary rocks. Page 23.
Chert
Chert is one of the major types of sedimentary rocks. Page 7.
Graywacke or Wacke
Wacke or graywacke is one of the major types of sedimentary rocks. Page 15.
Earthquake Odds for San Francisco Bay
Science bats against Nature in the next match of an endless series--San Francisco civilization versus earthquakes.
Granodiorite
Granodiorite is one of the major igneous rock types. Page 9.
Hayward Fault Map
Map showing the Hayward fault. Geology.
Syenite
Syenite is one of the major igneous rock types. Page 23.
The Great Cascadia Earthquake of 2xxx
Cascadia is America's tectonic version of Sumatra, where the great quake of 2004 occurred.
Translate Names Between Gemstones and Minerals
Big list of mineral names and their corresponding gemstone names.
Florida Geologic Map
Geologic map of Florida, part of a set of all 50 states. Page 9.
The Lithosphere in a Nutshell
What you need to know about the lithosphere.
Limestone
Limestone is one of the major types of sedimentary rocks. Page 17.
The Scientific Definition of a Mineral
Minerals meet four criteria, more or less strict.
Greenstone
Grenstone is a major metamorphic rock type from regional metamorphism. Page 8.
Tonalite
Tonalite is a felsic plutonic rock without alkali feldspar. Page 24.
Exfoliation
How big rock domes peel off in shells. Page 6.
Soapstone
Soapstone is a major metamorphic rock type from regional metamorphism. Page 18.
The Size Divisions of Sediment Particles
The grain sizes of sediments and sedimentary rocks are a matter of great interest to geologists. Here is a guide to sediment grades and grain sizes.
Rhyolite
Rhyolite is one of the major igneous rock types. Page 21.
Quartz
Quartz is classified as a rock-forming mineral. Page 9.
Mechanical Weathering
A short explanation of mechanical weathering.
Conglomerate
Conglomerate is one of the major types of sedimentary rocks. Page 10.
Arkose
Arkose is one of the major types of sedimentary rocks. Page 2.
Migmatite
Migmatite is a major metamorphic rock type from regional metamorphism. Page 11.
Measuring Plate Motion
The five ways we track the motion of the lithospheric plates.
The Rock-Forming Minerals
A handful of very abundant minerals account for the great majority of the Earth's rocks.
Mineral Pictures A to Z
A-to-Z list of minerals shown on About.com Geology.
Dike
Two dikes, one sedimentary and one igneous.: jack lockwood bedding planes u s geological survey volcano crater
Mylonite
Mylonite is a major metamorphic rock type from mechanical metamorphism. Page 12.
Hornfels
Hornfels is a major metamorphic rock type from contact metamorphism. Page 9.
What Is My Yellow Mineral?
A guide to the most common and significant yellow minerals.
Quartz Monzonite
Quartz monzonite is one of the major igneous rock types. Page 20.
Top 10 Gemstone Special Effects
The most important optical effects in gemstones, from fire to asterism.
Quartz and Silica Minerals Gallery
Get familiar with quartz.
Breccia
Breccia is one of the major types of sedimentary rocks. Page 6.
Komatiite
Komatiite is a rare and ancient ultramafic lava. Page 11.
Eclogite
Eclogite is a major metamorphic rock type from regional metamorphism. Page 5.
Holes in Rocks
Geologists have named a variety of holes.
The Promise of Geothermal Energy
Geothermal energy exploits the Earth's natural heat budget.
Weathering: Details of This Central Geologic...
A short description of weathering.
Earthquakes - The Basics in a Nutshell
Start here for the seismic basics: faults that cause earthquakes, types of seismic waves, damages they cause and more.
Texas Geologic Map
Geologic map of Texas, part of a set of all 50 states. Page 43.
Where the Top Geology Professors Get Their PhD's
These 25 American colleges grant the huge majority of the geology PhD's held by U.S. college faculty.
Tuff
Tuff is one of the major igneous rock types. Page 26.
Aftershocks Are Not Afterthoughts
Aftershocks can be nasty surprises, even worse than the main event.
Fossil Parks for Hands-On Digging
Public parks in the United States where you can collect fossils legally.
Map of Plates and Their Boundaries
Details of the world's major tectonic plates and their boundaries.
Calderas - World's Largest Calderas
Table of the world's largest known calderas: chinati mountains kari kari supervolcanoes awasa taupo new zealand
Amphibolite
Amphibolite is one of the major metamorphic rock types.
Dolomite Rock or Dolostone
Dolomite or dolostone is one of the major types of sedimentary rocks. Page 14.
Rock Gypsum
Rock gypsum is one of the major types of sedimentary rocks. Page 20.
Volcanic (Extrusive) Rock Types
Photos of the types of erupted igneous rocks.
Anorthosite
Anorthosite is one of the major igneous rock types. Page 2.
Plutonic Rocks
Plutonic rocks defined and explained.
Argillite
A lightly metamorphosed claystone also called pipestone. Page 2.
Latite
Latite is the extrusive equivalent of monzonite. Page 12.
Minerals with Metallic Luster
Minerals with metallic luster are easy to learn to identify.
The Official State Gemstones, In One List
Thirty-five states have official gemstones. Here they are, listed by state.
Learn to Read a Geologic Map
Understanding geologic maps starts with topography.
Lakeview Gusher of 1910, Maricopa, California
Visit the site of America's most spectacular oil gusher a hundred years later.
Geology, Earth Science: What's the Difference?
Is there a difference between Earth science and geology?
Expanding Earth Animation Really Shows Plate...
The familiar expanding-Earth animation is an optical illusion based on a conceptual illusion.
Fossil Picture Gallery
Pictures of fossils, part of the About.com Geology gallery of images.
Kimberlite
Kimberlite is the peculiar deep-seated ultramafic rock most famous as the ore of diamonds. Page 10.
Rock Hammers
Hammers that geologists and rockhounds use
The Geology Behind Asbestos Minerals
This mineral resource has been first a boon, then a bane in its century of commercial existence. Learn more about the minerals themselves.
How Earth Was Born: The Quick Story
The straight story of how Earth began, as today's geologists tell it.
Greenschist
Greenschist is a major metamorphic rock type from regional metamorphism. Page 7.
About Subduction in Plate Tectonics
Basics of plate tectonics: introduction to subduction.
What Counts as a Rock to a Geologist?
Everyone knows what a rock is, until you ask what it is exactly.
Gallery of Concretions
Concretions are cemented bodies of sediment that tend to erode free.
Gallery of Mineral Lusters
Gallery of this key attribute of minerals.
Mineral Streak
About this simple but effective field technique for mineral identification.
What You Should Know about the Earth's Core
The whole Earth on average consists of the same mixture of stuff we see elsewhere in the solar system, but the core has to be iron metal along with some nickel.
About Chert
This interesting sedimentary rock has a key role in the geochemical cycle.
Travertine
Travertine is one of the major types of sedimentary rocks. Page 25.
How Cement and Concrete Are Made
Cement is an artificial stone--or maybe lava.
Coquina
Coquina is one of the major types of sedimentary rocks. Page 11.
Identification Key for the Rock-Forming Minerals
Quick identification table for the minerals that form the majority of rocks.
Basic Map of Earth's Tectonic Plates
The classic basic map from the U.S. Geological Survey.
Olivine
Olivine is one of the silicate minerals. Page 20.
Claystone
Claystone is a type of sedimentary rock. Page 8.
About Divergent Zones in Plate Tectonics
Basics of plate tectonics: divergent zones are where plates move apart.
Sizes of Tectonic or Lithospheric Plates
Table listing the lithosphere's tectonic plates by oder of size.
What Rocks Erode Into: Minerals of the Earth's...
The thousands of minerals known in rocks become a mere handful at the Earth's surface.
Coal
Coal is one of the major types of sedimentary rocks. Page 9.
Colorado Geologic Map
Geologic map of Colorado, part of a set of all 50 states. Page 6.
Obsidian Gallery
Obsidian is an extreme variety of igneous rock with a glassy texture.
Fall Line Cities: Columbus, Macon, Milledgevill...
The Fall Line cities of Columbus, Macon, Milledgeville and Augusta are among Georgia's geological attractions. Page 3.

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