【国家地理】每日一图：4月21-30日（图） - 珍珠湾ART

April 21， 2008

Byzantine Coin, Sinop, Turkey, 2001

Photograph by Randy Olson

Explorers pulled this ancient Byzantine coin from a Black Sea wreck near Sinop, Turkey. Millennia ago, the Black Sea was a freshwater lake. When the last ice age waned some 12,000 years ago, salt water from the Mediterranean breached the Bosporus Valley, transforming the Black Sea into its current state—a toxic, brackish, oxygen-deficient pool, perfect for preserving ancient wrecks.

(Photo shot on assignment for, but not published in, "Deep Black Sea," May 2001, National Geographic magazine)

April 22， 2008

Cloudy Sky, Location Unknown, 2004

Photograph by Peter Essick

Piles of cotton-like cumulus clouds fill the sky on a clear day. Mid-level cumulus clouds form between 6,500 feet (2,000 meters) and about 20,000 feet (6,000 meters). They form when humid air cools enough for water vapor to condense into droplets or ice crystals. A single cloud can hold billions of pounds of water, but may not always produce rain.

Earth Day, celebrated annually on April 22, marks the anniversary of the 1970 birth of the environmental movement. Scientists warn that rising temperatures worldwide could fuel extreme weather—just one of many damaging effects of global warming.

(Photo shot on assignment for, but not published in, "Signs From Earth: Heating Up, Melting Down," September 2004, National Geographic magazine)

April 23， 2008

Women Carrying Firewood, Sudan, 2003

Photograph by Randy Olson

Women carry bundles of firewood on their heads in the Sudanese desert. In rural African cultures, the responsibility of foraging for firewood usually falls to the women. In Sudan's brutally dry desert, where little vegetation grows, it can take several hours each day to collect enough wood to cook with.

(Photo shot on assignment for, but not published in, "Shattered Sudan: Drilling for Oil, Hoping for Peace," February 2003, National Geographic magazine)

April 24， 2008

Cars Passing the Colosseum, Rome, Italy, 1981

Photograph by O. Louis Mazzatenta

Nearly 2,000 years ago, the Colosseum was built to host gladiator duels, battle reenactments, and other public spectacles. Now, the 50,000-seat stone-and-concrete amphitheater serves Rome in another capacity: as a traffic circle.

(Photo shot on assignment for, but not published in, "Down the Ancient Appian Way," June 1981, National Geographic magazine)

April 25， 2008

Red-and-Green Macaws, Bolivia, 2000

Photograph by Joel Sartore

A mated pair of red-and-green macaws soars above the forest in Bolivia's Madidi National Park. These long-lived birds mate for life, and couples spend nearly every minute together.

(Text adapted from and photo shot on assignment for, but not published in, "Madidi: Will Bolivia Drown Its New National Park?" March 2000, National Geographic magazine)

April 26， 2008

Mudbrick Houses, Shibam, Yemen, 2005

Photograph by George Steinmetz

The city of Shibam, Yemen, rises from the Rub al Khali, or Empty Quarter, a sea of sand that occupies one-fifth of the Arabian Peninsula. The distinctive mud-brick skyscrapers that house Shibam's 5,000 residents have earned the city its nickname: "Manhattan of the Desert."

(Text adapted from and photo shot on assignment for, but not published in, "Empty Quarter: Exploring Arabia's Legendary Sea of Sand," February 2005, National Geographic magazine)

April 27， 2008

Horse Herders, Darhad Valley, Mongolia, 2003

Photograph by Gordon Wiltsie

Mongolian herdsmen drive horses back into the Darhad Valley after wintering on the other side of the 10,000-foot (3,000-meter) mountains that rise in the background. People have moved their herds over these mountains for generations. But a government effort to transition Mongolia's nomadic people to more stable urban lives could soon mean the end of this twice-yearly trek.

(Text adapted from and photo shot on assignment for, but not published in, "Mongolian Crossing: Is Time Running Out on Timeless Migration?" October 2003, National Geographic magazine)

April 28， 2008

Irrigation Fields, Qatar, 2003

Photograph by Robb Kendrick

Irrigated crop fields stand out starkly against an expanse of Qatari desert. Such farms provide Qataris with some fruits and vegetables, but most of their food is imported. Government efforts to increase domestic agriculture are complicated by the paucity of fresh water in this parched desert nation.

(Photo shot on assignment for, but not published in, "Revolution From the Top Down: Qatar," March 2003, National Geographic magazine)

April 29， 2008

Lightning Behind Chimney Rock, Colorado, 1989

Photograph by James L. Amos

Trails of lightning backlight Chimney Rock in southwest Colorado's San Juan National Forest. Home to ancestors of the Pueblo Indians more than 1,000 years ago, the area around Chimney Rock has been a designated archaeological area and national historic site since 1970.

(Photo shot on assignment for, but not published in, "Life and Times of William Henry Jackson: Photographing the Frontier," February 1989, National Geographic magazine)

April 30， 2008

Paragliders in the Clouds, Mount Fuji, Japan, 2002

Photograph by Karen Kasmauski

Paragliders float through the clouds that surround snowcapped Mount Fuji in Japan. At 12,388 feet (3,776 meters), Fuji is Japan's highest peak. But its relatively easy-to-scale flanks draw flocks of amateur climbers to its summit—some 400,000 every year.

(Text adapted from and photo shot on assignment for, but not published in, "Fuji: Japan's Sacred Summit (Except When It's Not)," August 2002, National Geographic magazine)