Long-dormant volcanoes—including in Yellowstone—can awaken in a matter of hours, spewing a superheated, fast-moving mix of toxic gas and ash, according to a new study of a massive 2008 eruption in Chile.

Five big earthquakes struck in four days along the Pacific's Rim of Fire. Coincidence? Scientists aren't so sure.

Miners in South Africa recently found what may be one of the 20 largest diamonds ever uncovered—a 507.55-carat gem from the storied Cullinan Mine, which also produced the world's biggest diamond. Video.

See the latest, four-winged evidence that birds are dinosaurs in disguise, the guts of Nero's rotating dining room, a new Hubble stunner, and more.

A second earthquake shook western Indonesia Thursday as the death toll rose above 500 from Wednesday's powerful quake. Plus, see a computer simulation of Tuesday's Samoan quake and the resulting tsunami waves. Video.

Whole villages have been wiped out and scores are dead after an earthquake in the South Pacific triggered a tsunami that swept across several islands, including American Samoa, which has now been declared a major disaster area.

Tsunami waves, sparked by a powerful underwater earthquake, swept away people and cars and flattened villages in Samoa, American Samoa, and Tonga in the South Pacific on Tuesday—as seen in amateur video.

In light of Tuesday's Samoan islands tsunami, find out how tsunamis are caused, what the warning signs are, and how to respond.

A frog that eats birds and a catlike lizard are some of the 163 surprising new species discovered last year in the jungles of Southeast Asia's Greater Mekong region, WWF reports.

New species discovered along Asia's Mekong River in 2008—including a leopard gecko and a fanged frog that eats birds—are already under serious threat because of climate change, WWF says. Video.

The tiny island country of Palau has set aside a vast haven for sharks, which are plummeting due to rising demand for shark-fin soup.

The Beaufort Sea's coastline is disintegrating at alarming speed, thanks in part to warming Arctic temperatures, a new video of time-lapse photographs shows.

Increasingly powerful storms will devastate the country as rising temperatures add jolts of energy to typhoons in the western Pacific Ocean, scientists say.

See Ohio daredevils stage their own Burning Man festival, a planet take shape, whiskers go wild, and more in the week's best news pictures.

To help save South Australia's rare black-footed wallaby, researchers are taking joeys from the wild and placing them in surrogate pouches, encouraging wild moms to trigger "backup" pregnancies. Video.