Long after life first emerged from sea onto land, the early ancestors of whales began to reconsider the ocean. How these amphibious whales evolved to return to their aquatic habitat has long been a mystery — but some fascinating new fossils may help explain this transition. 

Earthworms play a major role in soil ecology — and, as Darwin discovered, many of them also leave crystals of calcite behind as they churn through the soil. But why they do it is still a mystery.

Some of the early precursors of planets in our solar system generated their own magnetic fields — a surprising feat for such small astronomical bodies.

Mars has no plate tectonics — but "shell tectonics" may help explain some of the puzzling features on the Red Planet's surface.

...but it isn't. Beneath the Taiwan Strait, scientists have discovered an underwater geological formation that closely resembles a fortress wall. It's not Atlantis, either.

Tiny nanoparticle-sized diamonds found in sediments dating to 13,000 years ago may hold a clue to why North America's mammoths disappeared about that time. The tiny gems suggest a cosmic impact, scientists say, that may have ultimately been behind the extinctions.

A series of minor earthquakes has shaken up Yellowstone National Park over the past week. Although scientists say the swarm probably doesn't foreshadow a volcanic eruption, they are keeping a close watch over the region.

At about 4,500 years old, Stonehenge is the world’s most iconic and mysterious prehistoric ruin, and archaeologists and geologists still wrangle over the origin of some of Stonehenge's stones: Did humans transport them hundreds of kilometers to southern England? Or were glaciers responsible, acting as a kind of natural conveyor belt?

After three and a half years of continuous eruption, the volcano has — for now — quieted.

Taxonomist Linneaus applied his classification system not only to living creatures but also to minerals. Although counterintuitive — iron doesn't have genes! — scientists say Linneaus may have been on to something: Like living organisms, minerals have evolved considerably over the course of Earth’s history.

For many tourists, Mountain Lake in southwestern Virginia has been an idyllic retreat. But in 2008, it vanished, leaving behind only cracked earth and a small pond. In this multimedia presentation, EARTH reporter Cassandra Willyard tells the geologic story behind the lake's disappearing act.

With Virginia's budget in the hole for $2.5 billion, the state is planning to lay off nearly half of the geologists in its Division of Geology and Mineral Resources.

“Giant Crystal Cave,” a new National Geographic Channel documentary on exploration beneath Mexico’s Naica Mountain, follows three scientists into a harrowing cave of wonders.

In addition to bullets and cannonballs, soldiers on either side of the Civil War fought a common enemy at the Battle of Antietam: carbonate rock. In fact, many of the Civil War’s bloodiest battles were fought on terrain formed from the sedimentary rock. And geologists say that’s not just a coincidence.

Media stories that granite countertops can emit dangerous radiation have sparked panic among consumers. But such fears are baseless, experts say.