Geology Sitemap - Page 4 2016-09-26

Quakes and Other Events - Geological Phenomena
Geological events like earthquakes and volcanic eruptions are always newsworthy.

Geology - Maps,Pictures, Photos and Diagrams
Pictorial content of all kinds related to geology and Earth science.

North and South American Geology Webcams
Live geology-related webcams from North and South America.

Australian and Pacific Geology Webcams
Live geology-related webcams from Australia, New Zealand and the Pacific Ocean nations.

European and African Geology Webcams
Live geology-related webcams from European and African countries.

World Heritage Sites, Geology: Africa
UN World Heritage Sites that preserve geological treasures: South Africa, Kenya, Ethiopia, Algeria, Mali, Madagascar and more

World Heritage Sites, Geology: Australia and New Zealand
UN World Heritage Sites that preserve geological treasures: Australia and New Zealand

World Heritage Sites, Geology: Europe
UN World Heritage Sites that preserve geological treasures: Belgium, Bulgaria, Croatia, Hungary, Slovenia, Sweden and more

World Heritage Sites, Geology: Oceania
UN World Heritage Sites that preserve geological treasures: islands in the Atlantic, Pacific, Indian and Southern Oceans

Grades 9 - 12 Teachers' Resources
Lesson plans, standards, and inspiration for high-school teachers grades 9 through 12.

Geology Songs and Music
Songs, music and lyrics both light and serious that treat geology and geologic themes

What Makes a Planet a Planet?
Should geologists care what kind of planet Pluto is?

Seismic Hazard Map of Central Asia
The United Nations' map of seismic hazard for the countries of central Asia

Seismic Hazard Map of Turkey, Middle East, Iran and the Caucasus
The United Nations' map of seismic hazard for the countries of Turkey, the Middle East, Iran and the Caucasus

Seismic Hazard Map of Western Europe
The United Nations' map of seismic hazard for western Europe

Seismic Hazard Map of Japan and Korea
The United Nations' map of seismic hazard for Japan and the Korean Peninsula

Seismic Hazard Map of Eastern Canada
The United Nations' map of seismic hazard for eastern Canada

Seismic Hazard Map of Africa
The United Nations' map of seismic hazard for the countries of Africa

Seismic Hazard Map of Eastern Europe
The United Nations' map of seismic hazard for eastern Europe

Seismic Hazard Maps - Global Earthquake Threats
The United Nations' global map of seismic hazard

Seismic Hazard Map of India, the Himalaya and Bangladesh
The United Nations' map of seismic hazard for India, Bangladesh and the countries of the Himalaya

Seismic Hazard Map of China and Mongolia
The United Nations' map of seismic hazard for China and Mongolia

Seismic Hazard Map of Southeast Asia
The United Nations' map of seismic hazard for the countries of Southeast Asia

Seismic Hazard Map of Indonesia
The United Nations' map of seismic hazard for Indonesia

Seismic Hazard Map of Australia
The United Nations' map of seismic hazard for Australia

Seismic Hazard Map of Alaska and Western Canada
The United Nations' map of seismic hazard for Alaska and western Canada

Seismic Hazard Map of the 48 United States
The United Nations' map of seismic hazard for the 48 conterminous United States

Seismic Hazard Map of Mexico
The United Nations' map of seismic hazard for Mexico

Seismic Hazard Map of Central America and the Caribbean
The United Nations' map of seismic hazard for Central America and the Caribbean Sea countries

Seismic Hazard Map of Northern South America
The United Nations' map of seismic hazard for the north half of South America

Seismic Hazard Map of Southern South America
The United Nations' map of seismic hazard for the south half of South America

Seismic Hazard Map of Northern Europe
The United Nations' map of seismic hazard for northern Europe

What are Sedimentary Rocks?
Introducing sedimentary rocks, second of the three great rock classes (along with igneous and metamorphic rocks).

Deep Earthquakes - Why They Happen
Deep-focus quakes aren't supposed to happen, but they do.

Calderas - World's Largest Calderas
Table of the world's largest known calderas

Thrust Fault
The spectacular Keystone thrust is photographed from the air.

Product Summary - Rock Sets from Rocksandminerals.com
A brief review of the rock collections offered by rocksandminerals.com

A History of the Great Lisbon Earthquake of 1755
Lisbon earthquake of 1 November 1755, images and notes.

Sieberg-Ambraseys Tsunami Intensity Scale
The Sieberg-Ambraseys intensity scale rates the impact of tsunamis from 1 to 6.

Overview of focal Mechanisms: Earthquake Diagram in a Nutshell
The focal mechanism of an earthquake can derive from the solution of a

Bedrock Geology of Alberta
Alberta beneath its thick blanket of Ice Age debris, courtesy of the Alberta Geological Survey.

Geologic Time Scale for the Phanerozoic Eon
Explore the eras, periods, and epochs of the Phanerozoic Eon with this official geologic time scale, including the famous Paleozoic Era.

Dinosaur Park - Maryland Geological Attractions and Destinations
Dinosaur Park is one of Maryland's geological destinations. Page 5.

View of Mount Diablo, California from Morgan Territory
Mount Diablo is seldom seen from this vantage point in Morgan Territory Regional Preserve. Page 8.

'Hot Water Will Scald' Sign, Yellowstone
Hot springs can burn, depending on their temperature. A geological sign at Yellowstone National Park. Page 13.

'Underlooks' Geology Sign, Wisconsin
Overlooks are just pretty, but underlooks bring our attention to geological subjects. Page 3.

'Hot Water Can Kill' Sign, Yellowstone
Some of the attractions of Yellowstone are truly lethal. Page 14.

Quincy Quarries - Massachusetts Geological Attractions and Destinations
A selection of Massachusetts' geological attractions. Page 9.

Permian Stromatolite
Stromatolite from Permian rocks of the Czech Republic. Page 7.

Why Seismologists Don't Use the O-Word: 'Overdue'
Why don't seismologists ever talk about earthquakes being overdue? Everybody else does.

How to Look at a Rock
Notes on the most basic operation in geology.

Measuring Plate Motion in Plate Tectonics
The five ways we track the motion of the lithospheric plates.

Cement and Concrete - An Overview
Cement is an artificial stone--or maybe lava.

About Plate Tectonics - Introduction and Overview
Start here to learn the basics of plate tectonics.

What to Know Before You Buy a Magnifier
What to think about and look for when you set out to get a nice magnifier.

Picture Glossary of Geological Landforms
Find and see geological landforms at About.com Geology.

About Uranium-Lead Dating
Uranium-lead method is the oldest and, when done carefully, the most reliable isotopic dating method.

Minerals That Live on the Earth's Surface
The thousands of minerals known in rocks become a mere handful at the Earth's surface.

The Bowen Reaction Series in Geology
About this staple of igneous petrology.

Top 25 US College for Geology PhD Studies
These 25 American colleges grant the huge majority of the geology PhD's held by U.S. college faculty.

Mineral Pictures Index
My master guide to annotated pictures to help you identify minerals: typical examples of rock-forming, accessory, and rare or notable minerals.

What Are Minerals? Four Things That Define Them
Minerals meet four criteria, more or less strict.

Mineral Pictures A to Z
A-to-Z list of minerals shown on About.com Geology.

The San Andreas Fault in California
Home page for everything about the San Andreas fault: where it is, how it behaves, what it means.

Yellow and Yellowish Minerals
A guide to the most common and significant yellow minerals.

11 Types of Holes in Rocks
Geologists have named a variety of holes.

Red and Pink Minerals - Images and Descriptions
A guide to the most common and significant red and pink minerals.

Top 10 Gemstone Special Effects
The most important optical effects in gemstones, from fire to asterism.

Six 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.

Ma or Myr? How We Talk About Geologic Time
Geologists have a bit of awkwardness in their language in talking about the deep past: distinguishing dates from durations. None of us has a problem with the

The Best Place to Live for Geology
I'm going to repost this blog post from two years ago, because it's worth an update from those of you who missed it the first time—although anyone who

My Favorite Geological Word: Palinspastic (Accretionary Wedge #35)
It's time for the next iteration of the geo-blog thing known as The Accretionary Wedge! And the theme for AW#35 is,

Free Online Geology Courses
People have asked me for years if there are geology courses online. There are lots of places where you can see professors' lecture notes, but nothing exists

The Expanding-Earth / Plate-Tectonic Animation
The familiar expanding-Earth animation is an optical illusion based on a conceptual illusion.

Learn the Basics of Earthquakes
Start here for the seismic basics: faults that cause earthquakes, types of seismic waves, damages they cause and more.

10 Steps to Identify Minerals - Start with the Specimen
Mineral identification starts with picking a good specimen.

Mineral Identification - Step 3: Hardness
Hardness, as measured with the 10-point Mohs scale, is very important to know for mineral identification.

How to Identify Minerals - Step 4: Color
Be wary of using color to identify minerals, because in some cases it's misleading.

Mineral Identification - Step 6, Streak
Streak can be more reliable than color in identifying minerals. Here's how to do a streak test.

Identify Minerals Step 6: Crystal Form & Mineral Habit
Crystal form and habit are important for identifying minerals, but not necessary for the beginner.

Mineral Identification - Magnetism
Magnetism is a rare but interesting mineral property. Here's how to assess it.

Mineral Identification - Taste, Fizz, Heft
Other mineral properties include their taste, reaction to acid, and heft or density. Sometimes these are essential for an identification.

Contours - How to Read a Geologic Map
Contour lines are the key to visualizing topography on a geologic map.

Topography - How to Read a Geologic Map
Understanding geologic maps starts with topography.

Topographic Symbols - How to Read a Geologic Map
Symbols on topographic maps convey a great deal of information.

Symbolizing Geology on Geologic Maps
Introducing the symbols that convey geologic information on maps.

Contacts, Faults, Strikes and Dips on Geologic Maps
Rock orientation displayed by symbols on a geologic map.

Age and Formation Symbols on Geologic Maps
What the letters mean on a geologic map.

Colors on Geologic Maps
Colors and patterns add information to a geologic map.

Pleistocene Fossils of the Fairmead Landfill Site
A major collection of Irvingtonian fossils is growing near Fresno.

Mammoth Bones from the Fairmead Landfill Site
Mammoth bones sit on the 'Oversize' shelf in the MCPC archive in Madera, California.

Horse Skull from the Fairmead Landfill Site
A large horse fossil at the Madera County Paleontology Repository.

Horse Teeth from the Fairmead Landfill Site
Fossil horse teeth at the Madera County Paleontology Repository.

Pleistocene Camel from the Fairmead Landfill Site
A camel jaw fossil at the Madera County Paleontology Repository.

Harlan's Ground Sloth from the Fairmead Landfill Site
An extinct ground sloth fossil at the Madera County Paleontology Repository.

Dire Wolf Fossil from the Fairmead Landfill Site
An extinct large carnivore fossil at the Madera County Paleontology Repository.

Pleistocene Badger Fossil from the Fairmead Landfill Site
An extinct small carnivore fossil at the Madera County Paleontology Repository.

Geothermal Energy - Tapping the Earth's Heat Supply
Geothermal energy exploits the Earth's natural heat budget.

Fossilized or Petrified: What's the Difference?
What a petrified thing is as opposed to a fossilized thing.

Steno's Laws or Principles, the Basics of Geology
Steno (Niels Stensen) first set forth some of the basic principles that all geologists follow.

Geo-Quiz Number 5: General
Who wants to be a geo-whiz? The trivia game--subject: GENERAL.

Mineral Identification - The Next Step
Use your mineral's properties to identify it in a trusted source, preferably a book.

Mineral Identification - Cleavage and Fracture
Cleavage, the way a mineral breaks, is crucial for identifying minerals.

Mechanical Weathering Defined and Explained
A short explanation of mechanical weathering.

The San Francisco Earthquake of 1906
The Great San Francisco Earthquake was the stuff of legend, but it really happened.

Asbestos in a Nutshell
This mineral resource has been first a boon, then a bane in its century of commercial existence. Learn more about the minerals themselves.

Stoss Defined and Explained
The stoss side has a specific meaning in geomorphology.

Fossil Definition and Information
Fossils are precious gifts from the geologic past: signs and remains of ancient living things preserved in the Earth's crust.

Naked-Eye Sedimentary Textures in Words and Pictures
Sedimentary textures that can be seen in the field with the naked eye or a hand lens.

The Bre-X Gold Scandal, History and Resources
First there is a mountain of gold, then there is no mountain, then there is no mining company in the gold industry's greatest case of fraud.

The Scandal of Coltan: A Destructive Black Gold Rush
High prices for 'coltan' tantalum ore, essential for high-tech appliances, create devastation in central Africa.

A Brief History of Precambrian Time 1: Hadean and Archean
Four billion years condensed into two pages.

A Brief History of Precambrian Time 2: The Proterozoic
The Proterozoic Eon was Earth's middle age, the time of the great Oxygen Catastrophe and much else. Page 2.

Diagenesis - How Sediment Turns to Rock and Beyond
About diagenesis, the stage between sediment and rock.

How to Identify Minerals - Step 2: Luster
A mineral's luster is essential for identifying it.

Olivine, a Mineral with Many Names
Olivine is the most abundant mineral in the deep Earth, where it has several different identities.

1857 Earthquake Segment San Andreas Fault - San Emigdio Mountains Granite
Granite of the San Emigdio Mountains near the San Andreas fault. Page 34.

Hazardous Plants - Giant Hogweed Leaf
Leaf of giant hogweed, Heracleum mantegazzianum. Page 3.

Hazardous Plants - Giant Hogweed Plant and Flower
The giant hogweed, Heracleum mantegazzianum. Page 2.

Geologic Photography Tips - Indicating Scale with the GSA Scale Card
The Geological Society of America's handy scale card is recognized worldwide. Page 17.

Roaring Fork Valley - Geology of Glenwood Springs, Colorado
Roaring Fork River valley is the setting of Glenwood Springs, Colorado area.

Green and Round Lakes - New York Geological Attractions and Destinations
Green and Round Lakes are one of New York state's geological attractions. Page 7.

Gilboa Fossil Forest - New York Geological Attractions and Destinations
The Gilboa fossil forest is of New York state's geological attractions. Page 6.

Earthquake Lights
A new theory of earthquake lights looks promising

About Paleomagnetism
Home page for the basics of paleomagnetism: how it arises, how it's measured, what it means.

Metamorphic Fabrics
The six basic fabric types found in metamorphic rocks.

Platinum - Native Element Minerals
Platinum, the element Pt, occurs in native form. Page 6.

Introducing Rockhounding
Start a lifelong hobby from the ground up.

Peperite - Volcanic Rocks
When fire meets water in the shallow underground. Page 10.

Map of World Hotspots
A convenient map showing the most commonly accepted hotspots.

The Small-Comets Hypothesis
Little icy comets or processing errors? The story of a controversial theory.

The Small-Comets Hypothesis, page 2
Little icy comets or processing errors? The story of a controversial theory. Page 2.

Save the Geysers!
Thar they blow! a survey of geysers around the world.

How Basalt Got Its Name
The word 'basalt' goes back thousands of years, and it's meant different things throughout that time.

Manhattan Schist - Metamorphic Rock Gallery
Manhattan Schist is a classic mica schist. Page 6.

Obsidian Gallery - Pictures of Obsidian
Obsidian is an extreme variety of igneous rock with a glassy texture.

West Side Foothills - Geology of California's Great Central Valley
Steep, abrupt foothills run the length of the Central Valley's western side. Page 3.

Gypsum in the San Joaquin Valley - Geology of California's Great Central Valley
Gypsum is found and mined in California's Central Valley. Page 9.

Interstate 5 - Geology of California's Great Central Valley
Interstate 5 offers great views of the Central Valley in good weather. Page 5.

Kettleman Hills Arch - Geology of California's Great Central Valley
The Kettleman Hills rise gently within California's Central Valley. Page 4.

Lower Tuolumne River Valley - Geology of California's Great Central Valley
Geologic history is exposed along the rivers of California's Central Valley foothills. Page 21.

Fairmead Fossil Site, Chowchilla - Geology of California's Great Central Valley
The Fossil Discovery Center displays a wealth of fossils from California's Central Valley. Page 22.

Montezuma Hills - Geology of California's Great Central Valley
The Montezuma Hills mark the middle of the California Central Valley. Page 12.

Lava Flows, Oroville - Geology of California's Great Central Valley
Lava flows are found along the east side of California's Central Valley. Page 16.

San Joaquin River - Geology of California's Great Central Valley
Many natural streams now run dry in California's Central Valley. Page 7.

Sharktooth Hill - Geology of California's Great Central Valley
Sharktooth Hill is at the south end of California's remarkable Central Valley. Page 23.

Young Marine Fossils in California's Great Central Valley
Neogene and Quaternary fossils may be found in California's Central Valley. Page 10.

Sierra College Rock Walk - Geology of California's Great Central Valley
The rock walk at Sierra College in Rocklin, California, is a free museum of great specimens. Page 20.

Petroleum in California's Great Central Valley
Oil and gas are major resources of California's Central Valley. Page 8.

Gravel Quarries - Geology of California's Great Central Valley
Gravel and sand are major resources of California's Central Valley. Page 17.

Dunnigan Hills - Geology of California's Great Central Valley
The Dunnigan Hills are an anticline in California's Central Valley. Page 14.

Del Puerto Water Gap - Geology of California's Great Central Valley
The Del Puerto water gap is one of several in California's Central Valley. Page 11.

Sutter Buttes - Geology of California's Great Central Valley
The volcanic Sutter Buttes punctuate California's Central Valley. Page 15.

Berryessa Water Gap - Geology of California's Great Central Valley
The Berryessa water gap is one of several in California's Central Valley. Page 13.

Canals of the Central Valley - Geology of California's Great Central Valley
Canals handle most the water entering California's Central Valley. Page 6.

Entering the Central Valley - Geology of California's Great Central Valley
At first glance, the Central Valley appears to be an endless blank.

Geologic Map of California's Great Central Valley
Small-scale geologic map of California's Central Valley. Page 2.

Griffith Quarry - Geology of California's Great Central Valley
Granite was once quarried in parts of California's Central Valley. Page 19.

Yuba Dredge No. 17 - Geology of California's Great Central Valley
An antique gold dredge works the gold-bearing gravels of the northern Central Valley. Page 18.

Geology of California's Great Central Valley
Geological notes and photos of California's remarkable Central Valley.

Geology of California's Great Central Valley
Geological notes and photos of California's remarkable Central Valley.

Rock-Forming Minerals
A handful of very abundant minerals account for the great majority of the Earth's rocks.

Washington DC Geology
Pictures showing geology in Washington, DC.

Washington DC Geology
Pictures showing geology in Washington, DC.

What Are Crystals?
A clear explanation in everyday language of crystals as geologists see them.

Piemontite Picture - The Silicate Minerals
Piemontite is one of the silicate minerals, related to epidote. Page 21.

Benitoite Picture - The Silicate Minerals
Benitoite is one of the silicate minerals. Page 4.

Calcite and Aragonite in Earth's Carbon Cycle
Here's how these two closely related carbonate minerals matter in the Earth system.

The Great Permian-Triassic Extinction
The greatest mass extinction of the last 500 million years or Phanerozoic Eon happened 250 million years ago, ending the Permian Period and beginning the Triassic Period.

The Formation of the Earth in a Nutshell
The straight story of how Earth began, as today's geologists tell it.

The 1964 Good Friday Alaska Earthquake
Why the March 27, 1964 Alaskan earthquake was a landmark in geological science.

Earth Art in Waterfalls by Oscar Eliasson
Olafur Eliasson's 'Waterfalls' gave the urban landscape its own cataract. Page 13.

Basalt Artwork, Ellis Plaza, Seattle - Earth Art Gallery
The basalt sculpture at Seattle's Ellis Plaza is a worthy example of Earth art. Page 17.

Earth Art Gallery
Earth art photo gallery.

Cairngorm or Smoky Quartz
Cairngorm is brown crystalline quartz. Page 9.

'Herkimer Diamond' Doubly Terminated Quartz
Herkimer diamond, doubly terminated quartz crystal. Page 2.

Cone Penetrometer Testing or CPT
Cone penetrometer testing is carried out near an earthquake fault.

Gold Minerals and Geology
Basics of gold geology: where gold is found and why.

Geology of the Tibetan Plateau
The largest highest place on Earth is a showcase of plate tectonics.

Learn About Basalt
Basalt has a key role in Earth's tectonic cycle.

Diagram of the Rock Cycle - Geology
The rock cycle as I see it. Geology.

Rare Earth Elements in Geology
How the rare earths fit in today's geology.

Travertine of Ancient Lake Cahuilla, California - Travertine Picture Gallery
Ancient travertine crusts sit high above the Salton Sea. Page 12.

Travertine, Salton Sea, California - Travertine Picture Gallery
The nubbly travertine of ancient Lake Cahuilla. Page 13.

Hydrothermal Travertine, California - Travertine Picture Gallery
A former hot-sping deposit full of travertine. Page 7.

Tufa Detail, Trona Pinnacles, California - Travertine Picture Gallery
A closeup of the spongy travertine of Trona Pinnacles. Page 10.

Tufa Towers, Searles Lake, California - Travertine Picture Gallery
Travertine towers rise above a dead desert lake. Page 9.

Travertine Picture Gallery
A set of pictures exploring this rock type.

Tufa Towers, Mono Lake, California - Travertine Picture Gallery
Travertine mounds at Mono Lake in eastern California. Page 11.

Freshwater Tufa - Travertine Picture Gallery
Tufa forms as a carbonate crust around twigs and stems in a freshwater setting. Page 8.

Travertine Picture Gallery
A set of pictures exploring this rock type.

Geology of the California Coast
A survey of California's coastal geologic attractions, from north to south.

Where Things Come From: Rock Materials
Where rock materials (stone, gravel, clay and other basic natural substances) originate.

Where Things Come From: Rock Materials
Where rock materials (stone, gravel, clay and other basic natural substances) originate.

The Geoscience Handbook: AGI Data Sheets, 4th Edition
My review and advice for buying the Geoscience Handbook, a/k/a the AGI Data Sheets.

Supercontinents of the Past and Future
Several times in Earth history, plate tectonics has pushed all or most of the continents together into one big mass.

Measuring Paleomagnetism
Explaining the process by which a set of selected rock samples yields precious geological information about the Earth's deep past.

Epeirogeny Defined and Explained
Epeirogeny is the quiet sibling of orogeny: land-lifting as opposed to mountain-building.

GSSPs: Golden Spikes in Geologic Time
Global Boundary Stratotypes and Sections, or

Magnetic Reversals and Seafloor Stripes
How we track Earth's magnetism back in geologic time, and what that tells us.

Aeromagnetic Mapping
The basics behind aeromagnetic maps and what they show.

The Earth's Two Water Cycles
The Earth has not just one, but two water cycles, one for the surface and the other for the deep interior.

Living Fossil Plants - Ginkgo, Metasequoia, Wollemia
Three 'living fossils' from the plant kingdom.

About Thermal (Hot and Warm) Springs
About the minority of springs that yield warm water.

History of the Earth's Core
The latest thinking on how Earth's core has evolved over the last four billion years.

Shepard Sediment Classification Diagram
Triangular diagram to classify sediments by their sand, silt and clay content into categories specified by Shepard.

Folk Classification Diagram for Sediment - Sand, Silt, Clay
Triangular diagram to classify sediments by their sand, silt and clay content into categories specified by Folk.

Ultramafic Rock Classification Diagram
The standard ternary diagram for classifying ultramafic rocks.

Peridotites and Pyroxenites Classification Diagram
The standard ternary diagram for classifying peridotites and pyroxenites. Page 2.

Gabbroic Rocks Classification: Pl - Px/Hb - Ol Ternary
Classify the gabbroic rocks by their plagioclase, pyroxene-plus-hornblende and olivine composition.

Gabbroic Rocks Classification: Pl-Px-Hb Ternary
Classify the gabbroic rocks by their plagioclase, pyroxene and hornblende composition. Page 2.

Gabbroic Rocks Classification: Pl-Opx-Cpx Ternary
Classify the gabbronorites by their plagioclase and pyroxene composition. Page 3.

QAPF Diagram, Diamond Format
The conventional quartz-alkali feldspar-plagioclase-feldspathoid double ternary diagram.

QAPF Diagram, Square Format
An unconventional quartz-alkali feldspar-plagioclase-feldspathoid double ternary diagram. Page 2.

Australia's National Gemstone Emblem: Opal
The national gemstone of Australia, naturally, is opal.

New South Wales Gemstone Emblem: Black Opal
New South Wales dominates the world supply of black opal. Page 2.

Queensland State Gem: Sapphire
Queensland is known for its production of blue sapphires. Page 3.

South Australia Gemstone Emblem: Opal
South Australia is the dominant opal producer in Australia. Page 4.

Tasmania State Mineral Emblem: Crocoite
Tasmania is the principal source of this brillian orange-red specimen mineral. Page 5.

Western Australia State Fossil Emblem: Gogo Fish
The state fossil of Western Australia dates from the time when Australia was part of Gondwana. Page 6.

Photo Gallery of Rounded Clasts
Examples of clasts of well-rounded, rounded and subrounded shapes.

Basic Map of Earth's Tectonic Plates
The classic basic map from the U.S. Geological Survey.

Map of the Mid-Ocean Ridges
Schematic map showing the locations and names of the world's mid-ocean ridges.

Plate-Tectonic Features and Global Topography
A map showing the actual features that signify plate-tectonic entities.

Map of World Seafloor Ages
The evidence that made plate tectonics plausible: seafloor spreading.

Limestone with Coral Fossils - Treating Fossils and Rocks with Hydrochloric Acid
Step-by-step description of using HCl to dissolve rocks and clean fossils.

Day 2 of Acid Treatment - Treating Fossils and Rocks with Hydrochloric Acid
Limestone dissolving after treatment with HCl. Page 2.

Day 3 of Acid Treatment - Treating Fossils and Rocks with Hydrochloric Acid
Limestone half dissolved after several batches of HCl treatment. Page 3.

Acid-Etched Limestone Specimen - Treating Fossils and Rocks with Hydrochloric Acid
Fossils protrude from a half-etched limestone specimen. Page 4.

Harvested Fossils - Treating Fossils and Rocks with Hydrochloric Acid
Step-by-step description of using HCl to dissolve rocks and clean fossils. Page 5.

A Visit to Sharktooth Hill
I spent a day on Sharktooth Hill, famous for specimens of the shark C. megalodon.

Concretions on Sharktooth Hill
Large concretions litter the hillside at Sharktooth Hill. Page 10.

Vertebrae in a Sharktooth Hill Concretion
A concretion at Sharktooth Hill exposes large vertebrae. Page 11.

Hunting the Bone Bed at Sharktooth Hill
I stake my claim to the Sharktooth Hill bonebed. Page 12.

Sharktooth Hill Digging Tools
Typical tools used by Sharktooth Hill fossil diggers. Page 13.

Bonebed of Sharktooth Hill
First exposure of the great bonebed of Sharktooth Hill. Page 14.

Scapula Fossil on Sharktooth Hill
A mammal scapula emerges in the Sharktooth Hill bonebed. Page 15.

Field Preservation of a Sharktooth Hill Fossil
A coat of wood glue is the first step in trying to preserve a Sharktooth Hill fossil. Page 16.

End of the Day's Visit to Sharktooth Hill
The last digger works until the last minute at Sharktooth Hill. Page 17.

Sharktooth Hill Geologic Map
Geologic map of the Sharktooth Hill area near Bakersfield, California. Page 2.

Kern River Canyon Near Sharktooth Hill
The Kern River's base level controls erosion of the region. Page 3.

Sharktooth Hill: The Setting
View of the countryside around Sharktooth Hill. Page 4.

Buena Vista Museum
Sponsor and operator of the Sharktooth Hill fossil digs. Page 5.

Sharktooth Hill, Slow Curve Quarry
One of several digging spots on the Ernst family property on Sharktooth Hill. Page 6.

Rainwashed Sharktooth on Sharktooth Hill
Fossils may be exposed on bare ground as rain gently removes their matrix. Page 7.

First Sharktooth of the Day - A Visit to Sharktooth Hill
I spot my first sharktooth on a day's dig at Sharktooth Hill. Page 8.

My First Shark Tooth from Sharktooth Hill
Documented for the ages is my first shark tooth of many collected that day. Page 9.

Pseudofossils or Not-Fossils
Introducing the most common things that people mistake for fossils.

Shatter Cones - Common Pseudofossils
Shatter cones may be mistaken for fossils. Page 10.

Solution Features - Common Pseudofossils
Solution pits and grooves in limestone may be mistaken for fossils. Page 11.

Concretions - Common Pseudofossils
Concretions are commonly mistaken for fossils. Page 2.

Dendrites - Common Pseudofossils
Dendrites are commonly mistaken for fossils. Page 3.

Flint Nodules - Common Pseudofossils
Flint nodules are commonly mistaken for fossils. Page 4.

Geodes and Septarian Nodules - Common Pseudofossils
Geodes and septarian nodules are commonly mistaken for fossils. Page 5.

Liesegang Banding - Common Pseudofossils
Liesegang banding is commonly mistaken for fossils. Page 6.

Modern Objects - Common Pseudofossils
Modern objects may be mistaken for fossils. Page 7.

Pyrite Dollars and Sand Crystals - Common Pseudofossils
Pyrite dollars, sand crystals and other mineral formations are commonly mistaken for fossils. Page 8.

Sedimentary Structures - Common Pseudofossils
Sedimentary structures are commonly mistaken for fossils. Page 9.

Spheroidal Weathering - Common Pseudofossils
Spheroidal weathering may create shapes that are mistaken for fossils. Page 12.

Quick Sediment Testing: Particle Size
A simple procedure for analyzing the grain-size composition of sediment.

FAP Ternary Diagram of the Feldspathoid-Bearing Plutonic Rocks
Feldspathoid rocks get their own ternary classification diagram.

Fluorescence in Minerals
The basics of how minerals fluoresce and which ones do it.

Volcanic Gases
The gases in volcanoes aren't just vapors, but the very cause of volcanoes.

Metamorphic Facies Defined and Explained
How suites of certain minerals show the grade of metamorphism in a body of rock.

Gossan Defined and Explained
Gossans are weathering zones that can concentrate iron minerals.

Silica Tetrahedron Defined and Explained
The silica tetrahedron is the basis of the silicate minerals.

Index Minerals Defined and Explained
Minerals that are indicators of particular states of metamorphism.

Strain in Geology
Strain, like stress, has a definite meaning in geology.

The Japanese Seismic Intensity Scale - JMA Earthquake Scale
Details of the modern Japanese seismic intensity scale.

Dietary Minerals and Real Minerals
Nutritionists and geologists mean different things when they talk about minerals.

Microplate Definition
A short explanation of microplates, part of plate tectonics.

Triple Junction Defined and Explained
A short explanation of triple junctions, part of plate tectonics.

Rock Provenance by Petrologic Methods
Reconstructing former lands from the sediments they turn into.

How to Use a Rock Hammer Safely
Best practices for this powerful geological field tool.

How Earthquakes Disturb Streams and Groundwater
Earthquakes affect water even more than they do land.

Earthquakes and Solar Activity
Two researchers draw a line in the sand against inconclusive studies of a purported sun-quake connection.

Fossil Collecting Tools
What tools does the well-equipped geologist need to go fossil hunting?

Geologic Sayings and Proverbs
A collection of folk sayings about rocks, rivers and mountains.

The 2013 Geologic Time Scale for the Cenozoic Era
Ages, epochs and periods of the Cenozoic Era, part of the official 2013 geologic time scale.

The Rise and Fall of the Tertiary and Quaternary Periods
These two geologic time terms share a deep history.

Geologic Time Scale for the Precambrian
The Precambrian part of the official geologic time scale.

Volcano Movies of 1997 - 'Volcano' and 'Dante's Peak'
The leads in

Glacier Glossary - Definitions of Glacial Features
Definitions of glacial features and the processes of glaciers.

Aluminum Minerals and Geology
Where aluminum occurs in the Earth and how we extract the metal.

The Diamond Zone: Into the Mantle Part 1
Diamonds are actual pieces of the mantle that you can wear on your hand or ear.

Geo-Quiz Number 13: Earth Science "-ologies"
Who wants to be a geo-whiz? The trivia game--the subject: -OLOGIES.

Mystery Spots
Some roadside attractions claim strange geophysical effects, but those claims are hokum.

Why Don't More Rocks Have Fossils?
How can sedimentary rocks exist with no sign of ancient life in them?

Stilpnomelane in Schist, California Coast Range - Porphyroblast Gallery
Stilpnomelane forms dramatic porphyroblasts in high-grade schist with a mafic protolith. Page 11.

Fossil Wood Gallery - Cretaceous Wood, Drumheller, Alberta
Fossilized wood is abundant in Alberta. Page 7.

Folded Chert
Chert may be strongly folded. Geology. Page 10.

Green Metachert - Chert Gallery
Several different minerals may turn this siliceous rock type green. Page 15.

Jasper and Agate - Chert Gallery
Jasper and agate are varieties of chert. Page 3.

Jasper Beach Pebbles - Chert Gallery
Chert makes excellent pebbles. Geology. Page 17.

Metachert Outcrop - Chert Gallery
An outcrop of metamorphosed chert. Page 14.

Variegated Metachert - Chert Gallery
High-grade metamorphism lends a rainbow of color to chert. Page 16.

Geologic Wine Labels - Lava Cap Zinfandel
Lava Cap Winery was founded by a geologist. Page 10.

Black Organic-Rich Chert
Organic matter may color this siliceous rock type gray to black. Page 9.

Brown Chert
Iron oxides and clay can make chert brown. Page 8.

Gemstone Chert
Jasper and agate cabochons. Geology. Page 4.

Chert Diagenesis
Chert is subject to alteration as it lithifies. Page 11.

4 Diagnostic Features of Chert: Luster, Fracture, Hardness, Texture
How to identify this siliceous rock type.

Bedded Chert
Seafloor beds account for the majority of this siliceous rock type. Page 5.

Flint Nodule - Chert Gallery
Flint is a type of chert that forms in nodules. Page 2.

Chert Gallery
Some of the variety found in this siliceous rock type.

Chert Gallery
Some of the variety found in this siliceous rock type.

Picture Jasper
Picture jasper exemplifies the variety found in this siliceous rock type. Page 12.

Red Chert
Much deep-sea chert is red. Geology. Page 7.

Red Metachert - Chert Gallery
Metamorphosed chert is called metachert. Page 13.

White Chert
Outcrop of white chert. Geology. Page 6.

Mima Mounds - Organic or Biological Weathering Gallery
Mima mounds are thought to be built as gophers move sediment. Page 6.

Pressure Solution, Australia - Pictures of Sedimentary Structures
Pressure solution in a sedimentary rock from Australia. Page 20.

One Million Years by On Kawara - Earth Art Gallery
Artist On Kawara's attempt to visualize a million years is definitely Earth art. Page 15.

Tailings, California - Depositional Landform Pictures
Tailings are a widespread type of depositional landform. Page 15.

Wind Abrasion - Mechanical or Physical Weathering Gallery
Wind can sandblast stones, even landscapes. Page 13.

Strath - Erosional Landforms
Straths are a type of erosional landform. Page 24.

Pholad Borings - Organic or Biological Weathering
Pholad bivalves are significant eroders of beach rocks. Page 7.

Slickenside in a Chert Hand Specimen
Slickensides on a hand specimen of chert.

Slickensides on an Outcrop
Slickensides, fault-polished rock surfaces, appear on a rock face where the sun reflects off them. Page 2.

Hoodoos by Theo Nelson - Earth Art Gallery
A pair of geologically inspired ATCs in the Earth art photo gallery. Page 4.

Earth Art Gallery - Sentient Minerals of Phil McGaughy
The Earth art photo gallery features Phil McGaughy's speculation on the intentions of minerals. Page 27.

Tombolo at St. Catherine's Island, Wales
A tombolo connects this rocky islet to the mainland of Wales. Page 12.

Amazonite or Green Microcline Alkali Feldspar
Amazonite is a green variety of alkali feldspar. Page 10.

Sericite - Mica Minerals
Sericite is a silky, fine-grained variety of muscovite. Page 10.

Ilmenite - Oxide Minerals
Ilmenite is a titanium-iron oxide. Page 6.

Yorrike's Brick Clast - Geologists' Pet Rocks and Favorite Stones
Yorrike favors this well-eroded clast of brick. Page 10.

Stilpnomelane - Mica Minerals
Stilpnomelane is related to the mica minerals. Page 11.

Septarium or Septarian Nodule
Cross section of a septarium, or septarian nodule. Page 7.

Shungite - Mineraloids
Shungite is one of the mineraloids. Page 9.

Celadonite - Mica Minerals
Celadonite is a mica mineral well known to artists. Page 2.

Alkali Feldspar in Granite Pegmatite
Large alkali feldspar crystals in a boulder in Albany, New York. Page 7.

Moose Lake Agates - Minnesota Geological Attractions and Destinations
Moose Lake agates are one of Minnesota's geological attractions. Page 6.

Streak Tests for Goethite and Hematite
Goethite and hematite are distinguished by their streak. Page 9.

Tombolo or Oronsay, Vallay, Scotland
A tombolo connects the islet of Oronsay to the islet of Vallay. Page 10.

Tombolo at Elafonissos, Greece
Cape Elena is connected to the island of Elafonissos by a narrow tombolo. Page 11.

Rockfall - Gallery of Landslides
A small rockfall by a California roadside. Page 16.

Gabion Wall for Landslide Mitigation - Gallery of Landslides
A gabion wall protects a steep streambank from collapse. Page 32.

Glauconite - Mica Minerals
Glauconite is a dark-green mica found in marine rocks. Page 4.

Goethite - Oxide Minerals
Goethite is an iron oxide mineral similar to hematite. Page 4.

Mechanical or Physical Weathering Gallery
Processes that turn big particles into smaller particles.

The Pyroxene Minerals
The pyroxene minerals are major parts of the crust and mantle.

Sedimentary Rock Types - Pictures and Descriptions
The major types of sedimentary rocks.

Pictures and Descriptions of Igneous Rock Types
The major igneous rock types, plutonic, intrusive and extrusive.

Water Gap - Erosional Landforms
Water gaps are a type of erosional landform. Page 29.

Nannobacteria: A Bunch of Rot
The mysterious, extremely small particles dubbed nannobacteria may have an explanation as crumbs from the dinners of decay microbes

Preserving Geologic Heritage
Should we treat geological treasures like endangered species? A growing movement says yes.

Minerals That Are Native Elements
A look at some metals and other elements that are found in the nude.

Loch Ness Phenomenon - Not a Loch Ness Monster
A skeptical geoscientist throws more cold water on Scotland's liveliest legend, the Loch Ness Monster.

Oldoinyo Lengai, World's Weirdest Volcano
Oldoinyo Lengai erupts sodium carbonate--not quite a big rock candy mountain, but then nothing else about it is quite like the song.

Geo-Quiz Number 10: Volcanoes
Who wants to be a geo-whiz? The trivia game--subject: VOLCANOES.

Geo-Quiz Number 18: Space
Who wants to be a geo-whiz? The trivia game--subject: SPACE.

Geo-Quiz Number 12: Earth Extremes
Who wants to be a geo-whiz? The trivia game--subject: EXTREMES.

Geo-Quiz Number 15: Ores
Who wants to be a geo-whiz? The trivia game--subject: ORES.

Geo-Quiz Number 14: Geologists
Who wants to be a geo-whiz? The trivia game--subject: GEOLOGISTS.

Geo-Quiz Number 11: Water
Who wants to be a geo-whiz? The trivia game--subject: WATER.

Conflict Diamonds
The problem of clandestine gems has no geological solution.

Geo-Quiz Number 8: Seismology
Who wants to be a geo-whiz? The trivia game--subject: SEISMOLOGY.

Do Bombs Cause Earthquakes? Human-Triggered Earthquakes
Short answer: no. It depends on what you mean by earthquake and by cause.

The Bogeyman of Earthquake Prediction
A site selling weekly predictions gets a swift crackdown in a deep-rooted scientific allergic reaction.

Practicing Geology Without a License
How can this be a crime, and why should it be? Page 2.

Bleeding-Edge Earthquake Forecasting
Even the best seismology is worthless for predictions. Page 3.

How NOT to Forecast Earthquakes
GeoForecaster treats its data with smoke and mirrors. Page 4.

The Rise and Fall of Land Bridges
Giant causeways that link distant continents were handy ways around continental drift, but now they're mostly out of favor--mostly.

12-Point Tsunami Intensity Scale of Papadopoulos and Imamura
The 2001 Papadopoulos-Imamura intensity scale rates the impact of tsunamis from I to XII.

Damming the Mediterranean
An old man dreams of damming the Mediterranean Sea to save the world from global COOLING.

Fulgurites: Fossil Lightning
Sand fused by lightning strikes preserves evidence of ancient times.

Earthquake Odds for San Francisco Bay
Science bats against Nature in the next match of an endless series--San Francisco civilization versus earthquakes.

The Tokai Earthquake of 20xx
Japan has been preparing for it for over 25 years.

Evolution in a Nutshell
The theory of evolution grows out of common sense and a simple hypothesis.

The Strangelove Ocean
Strangelove oceans are nasty things no matter what they really are.

Jökulhlaups - Glacial Outburst Floods
Jökulhlaups are peculiar glacial floods, as impressive as the people who live with them.

Geo-Quiz Number 25: Gems
Who wants to be a geo-whiz? The trivia game: GEMS

Geology and Home Life
Is geology a lonely life? Geologists answer.

Geology and Home Life
Is geology a lonely life? Geologists answer. Page 2.

Geology and Home Life
Is geology a lonely life? Geologists answer. Page 3.

Geology and Home Life
Is geology a lonely life? Geologists answer. Page 4.

Great Stone Faces
Natural formations that resemble faces and more

The Global Seismic Hazard Map - World Map of Earthquake Hazard
The first map to show the entire world's seismic hazard consistently is all here on this site.

The Oklo Natural Nuclear Reactor
A spontaneous nuclear reactor made of uranium ore may be Earth's neatest trick.

About Radon
Radon is a minor health threat and a geological curiosity.

Unconformities: Gaps in the Record
In rocks, what is not there can be as informative as what is there.

Potassium-Argon Dating Methods - K-Ar and Ar-Ar Dating
Potassium-argon isotopic dating is especially useful for determining the age of lavas.

Geotourism - Touring the Earth
Get down to earth around the world through geologic tourism.

Infrasound: Air Seismology
Infrasound is the strange territory between sound and seismology.

The Core-Mantle Boundary - The End of D-Double-Prime?
The mantle's mysterious D-double-prime layer is offered a new name honoring a real Earth scientist instead of his outmoded model.

Geology of the Planet Mercury - Messenger Mission and Mercury
The planet Mercury is poised for an explosion of new information.

Meteorites from Other Planets
Rocks from the Moon and Mars are found on the ground on Earth.

Rock-Forming Mineral Formulas
Chemical formulas for the minerals that form the majority of rocks.

The Mohs Hardness of Coins
Experiments with using coins in your Mohs hardness kit.

Identification Key for the Rock-Forming Minerals
Quick identification table for the minerals that form the majority of rocks.

The Geology of Bricks
Brickmaking transforms low-strength mud into artificial stone.

Global Warming in a Nutshell Part 1 of 4 - Climate Forcings
A skeleton key to the enormous topic of global warming or climate change.

Global Warming in a Nutshell Part 2 of 4 - Internal Climate Variations
The decadal cycles affecting the climate. Page 2.

Global Warming in a Nutshell Part 3 of 4 - Proxy Measurements of Climate Data
Proxy measurements of climate data: documents, tree rings, ice cores and more. Page 3.

Global Warming in a Nutshell Part 4 of 4 - Climate in the Last 2000 Years
Global climate in the last two millennia--and the last century. Page 4.

Phosphate in a Nutshell
This underappreciated substance is more important than you know.

What Is Geology?
The whole of Earth sciences, compressed to a nutshell.

Mapping the Past - Paleogeographic Maps
Mapping a world we've never seen, as opposed to the Earth of today, takes a lot of imaginative work.

Types of Types - About Geologic Type Specimens
When geologists need some sort of precise standard for imprecise things, they revert to type--type specimens, that is.

Geology: Calling All Girls
It's a great time for women to be geologists, for girls to think about being one, and for men to do their part.

Petroleum in a Nutshell
The basics about this important geologic commodity.

Crysts, Blasts and Clasts - Large Particles in Rocks
There's a welter of terminology for large particles in various types of rocks.

MSK Earthquake Scale - European Seismic Intensity Scale
The Medvedev-Sponheuer-Karnik or MSK64 seismic intensity scale evolved into the European Macroseismic Scale.

Earthquake Intensities
Intensity scales measure how bad a quake is, on a scale from I to XII.

Black Smokers, Cold Seeps, Whale Falls
Three different seafloor communities have a worldwide connection.

List of Official State Minerals by State
The official state minerals of the United States, listed by state

List of Official State Rocks by State
Twenty-five states honor 17 different rocks as state rocks or state stones

Rock Collectors: A Collection
A look at several types of rock collectors, including my type.

Superfaults and Pseudotachylites
Faults can rub rocks together so hard, they melt.

Commercial Limestone and Marble Explained
An explanation of how different communities use the same words.

Earth's Most Ancient Places
Several localities of astonishing antiquities.

About Thin Sections
To geologists, thin sections are the greatest thing since sliced bread.

Geology of Venus
Introducing the mysterious cycles of Venus geology.

Venus Geology 2: The Hot Squeeze
What we know of Venus's deep interior and the process that renews its surface. Page 2.

Volcanism in a Nutshell
Volcanism is more than volcanoes: it's what recycles the Earth's crust.

Scientific Observation
Scientific observation is a refined version of an everyday skill.

Five Myths of Plate Tectonics
Even geologists are prone to these misconceptions about plate tectonics.

A Hotspot Alternative
Mantle plumes--those big burps of superhot magma from the deepest mantle--aren't the only theory in town any more when it comes to hotspots.

What Is an Ophiolite?
Not a rock type, it's a whole assemblage of crustal rocks.

Bioturbation by Earthworms - Organic or Biological Weathering
Earthworms process sediment by ingesting and excreting it. Page 4.

Bioturbation by Burrowing Bees - Organic or Biological Weathering
Bees and other insects can be significant movers of sediment. Page 3.

Weathering by Lichens - Organic or Biological Weathering
Lichens turn rock to soil by chemical and mechanical means. Page 10.

Bioturbation by Ants - Organic or Biological Weathering
By building anthills, ants are major agents of bioturbation.

Bioturbation by Benthic Organisms - Organic or Biological Weathering
Organic weathering by creatures living on and in the seafloor. Page 2.

Human Bioturbation - Organic or Biological Weathering
Humans are superb movers and transformers of rock and sediment. Page 9.

Bioturbation by Mammals - Organic or Biological Weathering
Moles, gophers and more animals move and transform rock and sediment. Page 5.

Bioturbation by Trees and Plants - Organic or Biological Weathering
Plants and tree roots are a major agent of organic weathering. Page 8.

Organic or Biological Weathering Gallery
Processes by which living things move and transform rock and sediment.

Hematite - Oxide Minerals
Hematite is one of the oxide minerals. Page 5.

Ringing Rocks County Park - Pennsylvania Geological Attractions and Destinations
Ringing Rocks County Park, Bucks County, is one of Pennsylvania's geological attractions. Page 8.

Don't Build Rock Piles Sign, Hawaii
A road sign forbids family fun for good reasons. Page 17.

No Rock Thieves Sign, Australia
Not all hazards related to rocks are geological. Page 15.

Rocks Sign, Burns, Oregon
A ROCKS road sign points out the obvious. Page 26.

Fault Zone Sign, Hawaii
A road sign in Hawaii calls our attention to a geological subject: faults. Page 22.

Tsunami Sign, Phuket, Thailand
A tsunami sign in English and Thai near Phuket. Page 20.

The Comeback of Noah's Flood Among Geologists
Once flame-war fuel in the 1800s, the bibilical flood story of Noah is now just another marvel of modern science.

Pictures and Descriptions of Igneous Rock Types
The major igneous rock types, plutonic, intrusive and extrusive.

Pictures and Descriptions of Igneous Rock Types
The major igneous rock types, plutonic, intrusive and extrusive.

Carbonate Minerals
Two major minerals and a host of popular minor ones.

Calcite - Carbonate Minerals
Calcite is one of the carbonate minerals. Page 2.

Obsidian Picture Gallery - Fresh Obsidian
Fresh glassy obsidian mined from a rhyolite dome. Page 5.

Obsidian Picture Gallery - Obsidian Chips
Obsidian chips from a prehistoric work site. Page 12.

Potassium Feldspar or Microcline
Large grains of microcline in a stone park bench. Page 5.

Spinel - Oxide Minerals
Spinel is one of the oxide minerals. Page 12.

Shelburne Falls - Massachusetts Geological Attractions and Destinations
Shelburne Falls is one of Massachusetts' geological attractions. Page 11.

QAP Diagram for Plutonic Rocks - Igneous Rock Classification Diagrams
QAP ternary diagram showing IUGS classification of phaneritic igneous rocks.

Exfoliation - Mechanical or Physical Weathering Gallery
How big rock domes peel off in shells. Page 6.

Granite Photo Gallery - Peninsular Ranges Granite 1
Granite from the Peninsular Range of southern California. Page 7.

Sedimentary Rock Types - Pictures and Descriptions
The major types of sedimentary rocks.

Feldspar in Gneiss, Estonia - Porphyroblast Gallery
Alkali feldspar forms porphyroblasts in gneiss.

Garnet in Amphibolite, Adirondack Mountains, New York - Porphyroblast Gallery
Garnet forms porphyroblasts in amphibolite. Page 2.

Porphyroblast Gallery
Porphyroblasts are distinctly large crystals in a metamorphic rock. Here are pictures of some of the minerals that form porphyroblasts.

Pyroxene in Serpentinite, Coast Ranges, California - Porphyroblast Gallery
Pyroxene forms porphyroblasts, or more precisely porphyroclasts, in serpentinite. Page 10.

Tombolo Gallery
Pictures of these rare sandbars that extend to a nearshore island.

Gallery of Mineraloids
A photo gallery of the mineraloids.

Pearl - Mineraloids
Pearl is one of the mineraloids. Page 8.

Drag Fold
Drag fold exposed along a thrust fault.: drag folds thrust fault minerals geology oakland hills

Articles on Earthquakes
Features about earthquakes, seismology, and related phenomena from your About Geology Guide.

Geologic Map Colors, US Geological Survey
Official colors for geologic maps, U.S. Geological Survey standard.

Sizes of Tectonic or Lithospheric Plates
Table listing the lithosphere's tectonic plates by oder of size.

QAP Diagram for Volcanic Rocks - Igneous Rock Classification Diagrams
Ternary diagram showing IUGS classification of volcanic rocks. Page 2.

TAS Diagram for Volcanic Rocks - Igneous Rock Classification Diagrams
Total-alkali-silica diagram for IUGS classification of aphanitic igneous rocks. Page 3.

Danger Erosion Sign, Scotland
Scotland assumes that you are geologically aware. Page 10.

Granite Curb Sign, Cazenovia, New York
A road sign calls attention to a granite curb. Page 6.

Typical Pillow Lava, Yuba County - Ophiolitic Rocks Photo Gallery
Lava pillow in the Smartville Ophiolite. Page 5.

Pillow Lavas, San Luis Obispo County - Ophiolitic Rocks Photo Gallery
Pillow lavas are part of a typical ophiolite. Page 3.

Ophiolitic Plagiogranite - Ophiolitic Rocks Photo Gallery
Plagiogranite is part of a typical ophiolite. Page 14.

Ophiolitic Pyroxenite, Nevada County - Ophiolitic Rocks Photo Gallery
Pyroxenite mixes with gabbro in a typical ophiolite. Page 12.

Serpentinized Peridotite, Nevada County - Ophiolitic Rocks Photo Gallery
Peridotite is usually serpentinized in a typical ophiolite. Page 18.

Serpentinite, Sign of Ophiolite - Ophiolitic Rocks Photo Gallery
Serpentinite is part of a typical ophiolite, but it may migrate. Page 20.

Sheeted Dikes, Yuba County - Ophiolitic Rocks Photo Gallery
Sheeted dike complexes are part of a typical ophiolite. Page 9.

Volcaniclastics, Yuba County - Ophiolitic Rocks Photo Gallery
Volcaniclastic rocks are part of a typical ophiolite. Page 6.

Metamorphosed Volcanics, Yuba County - Ophiolitic Rocks Photo Gallery
Metavolcanic rocks are part of a typical ophiolite. Page 7.

Loose Rocks Sign
A sign graphically warns of a quarry's hazard. Page 11.

Plate Crossing Sign, Parkfield, California
A plate crossing sign calls our attention to a geological subject. Page 4.