Geology

Geology is the study of the composition and physical properties of rocks, minerals, gems and other related earth materials, including diamonds and crystals. Scientists gain an understanding of the Earth's history by studying its composition.

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To honor their prehistoric pasts, most U.S. states have designated official state fossils, ranging from trilobites to dinosaurs. Take our quiz to learn more!

By Mark Mancini

Decades after the massive conflict, reminders of battles linger in pristine Pacific waters.

By Christopher Hassiotis

Decades of fossil discoveries have revealed much about the extinct members of our hominid family tree, but we're far from having all the answers. What have we learned from some of these fascinating finds?

By Jane McGrath

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The world of our far-future descendants may be as unrecognizable to us as our bustling, urbanized world would be to our bewildered ancient forefathers. Will energy drive many of those changes?

By Robert Lamb

The Doll's Theater of Carlsbad Caverns looks otherworldly and took ages to form. What other incredible sights await us below ground?

By Julia Layton

Diamonds are some of the most brilliant and expensive natural features Earth has to offer. This collection of images displays diamonds in all their uncut and polished shapes and sizes. Obligatory pictures of very large diamonds are included of course.

By HowStuffWorks.com Contributors

One grows from the ground and one from the ceiling, but sometime's it's hard to remember which is the stalactite and which is the stalagmite. How do they get there, anyway?

By John Fuller

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Nutty Putty Cave, near Salt Lake City, Utah, was discovered in 1960 and sealed up forever in 2009. But why?

By Dave Roos & Austin Henderson

Cinnabar's bright-red pigment has been used in jewelry, pottery and makeup for millennia. But cinnabar is also the primary ore for mercury, making it a dangerous mineral if the particles are inhaled.

By Allison Troutner

There are caves all over the world, but some are in places that are hard to explore — hidden by rocks, ruins or even under ice. We've found seven secret caves you probably never knew existed.

By Stephanie Parker

This ancient rock adorns King Tut's coffin and the Sistine Chapel. And at one time it was more precious than gold. What is it about this deep blue rock that has drawn us in for centuries?

By Carrie Whitney, Ph.D. & Austin Henderson

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Waterfalls are mainly reliant on precipitation to keep flowing. Here are six famous waterfalls that slowed to a trickle when drought set in.

By Laurie L. Dove

Sometimes dinosaur fossils are too large and heavy to display without damaging them. How are those enormous models built? And what makes them look so realistic?

By Tracy V. Wilson

Researchers think the Chicxulub crater was caused by the massive asteroid that also killed off the dinosaurs 66 million years ago. What else do we know about this peak-ring crater?

By Mark Mancini

Diamond engagement rings. Diamond anniversary bands. Diamond earrings and necklaces. And now, the right-hand diamond ring! The four Cs -- cut, clarity, carat and color. Find out what the fuss is all about.

By Kevin Bonsor

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Countless movies and television shows depict quicksand as some kind of living creature that sucks its victims down into a bottomless pit, never to be heard from again. Well, you can't believe everything Hollywood tells you.

By Kevin Bonsor

We all know the cartoons of prehistoric people running from dinosaurs aren't realistic. But many animals living today have ancestors from that time.

By Tracy V. Wilson

Everyone knows that once a bone has fossilized, it's hard as a rock, right? So how did scientists find soft tissue inside a broken dinosaur bone?

By Tracy V. Wilson

It's not a trick; before you are a number of reptilian footprints in the rock. They're dinosaur tracks, preserved for thousands of years. But how did they possibly get there?

By Tracy V. Wilson

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Some people believe that dinosaurs were relatives of today's birds. But, you might ask, if that's so, why didn't they have feathers? Funny you should ask.

By Tracy V. Wilson

Sand dunes belch, moan and hum. They roll across the desert, seeking out new locales. You might even say they breed. It's no wonder people call these giant sand formations lifelike.

By Debra Ronca

Hollywood makes T. rex seem fast and agile, but some scientists think it was a scavenger, like a vulture. So which was it?

By Tracy V. Wilson

Ever since its discovery in 2000, a dinosaur fossil named Leonardo has held the interest of paleontologists the world over. A 3-D model of the animal even toured the world. So what's the big deal?

By Tracy V. Wilson

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Fossils tell a story, much like the clues at the scene of a crime. Researchers look for evidence and paleontologists study that evidence to answer questions about the past.

By Tracy V. Wilson

Dinosaur eggs and the embryos inside can teach us a lot about dinosaur reproduction and behavior. But how do scientists get the rocky embryos out from the equally rocky shells?

By Tracy V. Wilson