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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.
Fast Links for Real-Time Info on Current...
Directions to information and data from earthquakes as fast as possible.
Use This Master Index of Rock Pictures
My master alphabetical guide to igneous, sedimentary and metamorphic rock pictures.
The Most Common Green Minerals in Nature
A guide to the most common and significant green and greenish minerals.
See the Densities of the Most Common Rock Types
Density, or specific gravity, of common rock types.
Where Are the Greatest Earthquake Threats in...
The United Nations' global map of seismic hazard
What to Know About Sedimentary Rocks
Introducing sedimentary rocks, second of the three great rock classes (along with igneous and metamorphic rocks).
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.
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
What Is My Blue or Purple Mineral?
A guide to the most common and significant blue and purple minerals.
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 a Black Mineral Is Most Likely to Be
A guide to the most common and significant black minerals.
Viewing Earth from on High
Satellite views of Earth's surface make possible geological discoveries never before imagined.
Schist
Schist is a major metamorphic rock type from regional metamorphism. Page 15.
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.
10 Steps to Help You Identify Any Mineral
Mineral identification starts with picking a good specimen.
Serpentinite
Serpentinite is a major metamorphic rock type from regional metamorphism. Page 16.
Siltstone
Siltstone is one of the major types of sedimentary rocks. Page 24.
Diorite
Diorite is one of the major igneous rock types. Page 4.
Igneous Rock Types
The major igneous rock types, plutonic, intrusive and extrusive.
Slate
Slate is a major metamorphic rock type from regional metamorphism. Page 17.
Quartzite
Quartzite is a major metamorphic rock type from regional metamorphism. Page 14.
Gneiss
Gneiss is a major metamorphic rock type from regional metamorphism. Page 6.
What Is Chemical Weathering?
A short explanation of chemical weathering.
Granite
Granite is one of the major igneous rock types. Page 8.
Pegmatite
Pegmatite is one of the major igneous rock types. Page 14.
Fossil Picture Gallery
Pictures of fossils, part of the About.com Geology gallery of images.
Why Granite is the Signature Rock of Earth
Granite is the signature rock of the continents. Here are the basics of this important stone.
Obsidian
Obsidian is one of the major igneous rock types. Page 13.
Peridotite
Peridotite is one of the major igneous rock types. Page 15.
Index Fossils: The Key to Telling Deep Time
The concept of index fossils is the very basis of geologic dating.
How to Look at a Rock Like a Geologist
Notes on the most basic operation in geology.
Where to Look for Rocks and Minerals
Rocks and minerals can be found everywhere, but there is a learning process involved.
Phyllite
Phyllite is a major metamorphic rock type from regional metamorphism. Page 13.
Sedimentary Rock Types
The major types of sedimentary rocks.
Gabbro
Gabbro is one of the major igneous rock types. Page 7.
Granodiorite
Granodiorite is one of the major igneous rock types. Page 9.
Pumice
Pumice is one of the major igneous rock types. Page 18.
Scoria
Scoria is one of the major igneous rock types. Page 22.
Porphyry
Porphyry is one of the major igneous rock types. Page 17.
Shale
Shale is one of the major types of sedimentary rocks. Page 23.
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.
Metamorphic Rock Types
The major metamorphic rock types, from regional, contact and mechanical metamorphism.
Pyroxenite
Pyroxenite is one of the major igneous rock types. Page 19.
How to Tell the Feldspar Minerals Apart
Feldspar is the commonest mineral in the Earth's crust, but identifying it can be tricky.
Exfoliation
How big rock domes peel off in shells. Page 6.
Fault Types in a Nutshell
The three basic types of fault, with their nomenclature, in a nutshell.
Sandstone: What It Is and What It Tells Us
Sandstone is sand cemented together into rock.
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.
Greenstone
Grenstone is a major metamorphic rock type from regional metamorphism. Page 8.
Quartz: How to Tell It, Different Kinds, What...
Quartz is essential to the land as we know it.
Perlite
Perlite is one of the major igneous rock types. Page 16.
Basalt
Basalt is one of the major igneous rock types. Page 3.
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.
Syenite
Syenite is one of the major igneous rock types. Page 23.
What Is My Red or Pink Mineral?
A guide to the most common and significant red and pink minerals.
Quartz Monzonite
Quartz monzonite is one of the major igneous rock types. Page 20.
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.
Tonalite
Tonalite is a felsic plutonic rock without alkali feldspar. Page 24.
Travertine
Travertine is one of the major types of sedimentary rocks. Page 25.
Dunite
Dunite is a plutonic rock consisting of olivine. Page 5.
Volcanic (Extrusive) Rock Types
Photos of the types of erupted igneous rocks.
Tuff
Tuff is one of the major igneous rock types. Page 26.
Chert
Chert is one of the major types of sedimentary rocks. Page 7.
Limestone
Limestone is one of the major types of sedimentary rocks. Page 17.
Sandstone
Sandstone is one of the major types of sedimentary rocks. Page 22.
Komatiite
Komatiite is a rare and ancient ultramafic lava. Page 11.
Soapstone
Soapstone is a major metamorphic rock type from regional metamorphism. Page 18.
Migmatite
Migmatite is a major metamorphic rock type from regional metamorphism. Page 11.
Dinosaur Eggs
Dinosaur eggs for sale at a high-end rock shop. Page 10.
Coquina
Coquina is one of the major types of sedimentary rocks. Page 11.
Graywacke or Wacke
Wacke or graywacke is one of the major types of sedimentary rocks. Page 15.
Andesite
Andesite is one of the major igneous rock types.
Troctolite
Troctolite is one of the gabbroid rocks: igneous, plutonic and mafic. Page 25.
Latite
Latite is the extrusive equivalent of monzonite. Page 12.
Claystone
Claystone is a type of sedimentary rock. Page 8.
Kimberlite
Kimberlite is the peculiar deep-seated ultramafic rock most famous as the ore of diamonds. Page 10.
Arkose
Arkose is one of the major types of sedimentary rocks. Page 2.
Quartz
Quartz is classified as a rock-forming mineral. Page 9.
Anorthosite
Anorthosite is one of the major igneous rock types. Page 2.
Rock Gypsum
Rock gypsum is one of the major types of sedimentary rocks. Page 20.
Calderas - World's Largest Calderas
Table of the world's largest known calderas: chinati mountains kari kari supervolcanoes awasa taupo new zealand
Dolomite Rock or Dolostone
Dolomite or dolostone is one of the major types of sedimentary rocks. Page 14.
Ironstone
Several types of sedimentary rocks are called ironstone. Page 16.
Greenschist
Greenschist is a major metamorphic rock type from regional metamorphism. Page 7.
More Than 50 Different Landforms in Pictures
Find and see geological landforms at About.com Geology.
Peat
Peat is one of the major types of sedimentary rocks. Page 18.
Geologic Maps of the 50 United States
Geologic maps of all 50 U.S. states.
Conglomerate
Conglomerate is one of the major types of sedimentary rocks. Page 10.
Mylonite
Mylonite is a major metamorphic rock type from mechanical metamorphism. Page 12.
What Is My Yellow Mineral?
A guide to the most common and significant yellow minerals.
Insect in Amber
An amber earring contains an insect fossil. Page 16.
Coal
Coal is one of the major types of sedimentary rocks. Page 9.
Mechanical Weathering
A short explanation of mechanical weathering.
Colorado Geologic Map
Geologic map of Colorado, part of a set of all 50 states. Page 6.
The Rock-Forming Minerals
A handful of very abundant minerals account for the great majority of the Earth's rocks.
Hornfels
Hornfels is a major metamorphic rock type from contact metamorphism. Page 9.
Rock Salt
Rock salt is one of the major types of sedimentary rocks. Page 21.
Shark Teeth
Shark teeth, fresh and fossil, from the U.S. east coast. Page 21.
Mammoth
Woolly mammoth skeleton mounted in the Lindsay Wildlife Museum. Page 17.
How to Use the Mohs Hardness Scale to Identify...
The 10-mineral Mohs scale of relative hardness is based on what scratches what.
Diamictite
Diamictite is a messy rock that is not quite conglomerate. Page 12.
Mineral Pictures A to Z
A-to-Z list of minerals shown on About.com Geology.
Foraminifers
Elphidium granti is a typical foraminifer. Page 13.
Dung Fossils
Fecal fossils are fruitful finds. Page 11.
Texas Geologic Map
Geologic map of Texas, part of a set of all 50 states. Page 43.
Breccia
Breccia is one of the major types of sedimentary rocks. Page 6.
Blueschist
Blueschist is a major metamorphic rock type from regional metamorphism. Page 3.
Blue Slag
Slag can take on many colors, like this sky blue. Page 23.
California Geologic Map
Geologic map of California, part of a set of all 50 states. Page 5.
Diatomite
Picture and notes about the sedimentary rock diatomite. Page 13.
North Carolina Geologic Map
Geologic map of North Carolina, part of a set of all 50 states. Page 33.
Horse Tooth Fossil
A fossil horse tooth from Miocene rocks in South Carolina. Page 15.
Trilobite
Trilobite fossil from Arizona. Geology. Page 23.
Tubeworm
Tubeworm fossil from a fossil seafloor cold seep. Page 24.
Sizes of Tectonic or Lithospheric Plates
Table listing the lithosphere's tectonic plates by oder of size.
The Scientific Definition of a Mineral
Minerals meet four criteria, more or less strict.
Fish
Fossil fish from Eocene lake beds. Page 12.
Eclogite
Eclogite is a major metamorphic rock type from regional metamorphism. Page 5.
Rock Cycle Diagram
The rock cycle as I see it. Geology.
Banded Iron Formation
Banded iron formation or BIF is one of the major types of sedimentary rocks. Page 4.
Stromatolite
Stromatolite cross-sections near Saratoga Springs, New York. Page 22.
Packrat Midden
An ancient packrat midden rests in a Great Basin rock shelter. Page 18.
Porcellanite
Porcellanite is a subtle sedimentary rock type. Page 19.
What Counts as a Rock to a Geologist?
Everyone knows what a rock is, until you ask what it is exactly.
Translate Names Between Gemstones and Minerals
Big list of mineral names and their corresponding gemstone names.
Natural Asphalt
Natural asphalt is one of the major types of sedimentary rocks. Page 3.
Gastropods
Tiny aquatic snail shells preserved in a southern California mudstone. Page 14.
Minerals with Metallic Luster
Minerals with metallic luster are easy to learn to identify.
Top 10 Action Steps to Take Against Earthquakes
Earthquake professionals list the elements of a quake-resistant society.
Holes in Rocks
Geologists have named a variety of holes.
North Dakota Geologic Map
Geologic map of North Dakota, part of a set of all 50 states. Page 34.
Weathering: Details of This Central Geologic...
A short description of weathering.
Petrified Wood and Fossil Trees
Fossil wood, or petrified wood. Geology. Page 19.
Is This Your Hat?
During my 2006 trip through the Sierra Nevada (at Stop 12 of the Subduction Tour, to be precise), I came upon a floppy water-resistant field hat lying on a
1 April 2014 Chile Earthquake Completes the Set
Yesterday's magnitude 8.2 earthquake off the coast of northern Chile was significant to scientists because it was widely anticipated and because it filled the
Huge Trove of Science Released to the Public
The American Geophysical Union is the world's largest publisher of Earth science research--and space science too. As an AGU member of long standing, I've
Gallery of Concretions
Concretions are cemented bodies of sediment that tend to erode free.
Georgia Geologic Map
Geologic map of Georgia, part of a set of all 50 states. Page 10.
Ohio Tightens Fracking Regulations
class="no-js" itemscope itemtype="http://schema.org/Article" > itemprop="description" >Hydraulic fracturing
Michigan Geologic Map
Geologic map of Michigan, part of a set of all 50 states. Page 22.
Quartz and Silica Minerals Gallery
Get familiar with quartz.
Measuring Plate Motion
The five ways we track the motion of the lithospheric plates.
Sedimentary Rock Classification Diagrams
Diagrams to help classify sedimentary rocks.
Argillite
A lightly metamorphosed claystone also called pipestone. Page 2.
Metamorphic Rock Gallery
A spectrum of metamorphic rocks, the pelitic sequence and the basaltic sequence.

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