The exact geographic center of the United States is near Lebanon, Kansas.
The Chesapeake Bay Bridge-Tunnel - which crossing Chesapeake near its mouth, at Norfolk, Virginia - uses a combination of bridge spans and tunnels. Manmade islands allow the roadway to enter the tunnels beneath the Bay's shipping channels.
The only nation whose name begins with an "A", but doesn't end in an "A" is Afghanistan.
Given their sheer volume, ninety-nine percent of the living space on the planet is found in the oceans. The average depth of the oceans is 2.5 miles (4 km). The deepest point lies in the Mariana Trench, 6.8 miles (10.9 km) down. By way of comparison, Mount Everest is only 5.5 miles (8.8 km) high.
Ninety percent of all volcanic activity occurs in the oceans. In 1993, scientists located the largest known concentration of active volcanoes on the sea floor in the South Pacific. This area, the size of New York state, hosts 1,133 volcanic cones and sea mounts. Two or three could erupt at any moment.
According to NASA, the U.S. has the world's most violent weather. In a typical year, the U.S. can expect some 10,000 violent thunderstorms, 5,000 floods, 1,000 tornadoes and several hurricanes.
Zion, Illinois - located on the shores of Lake Michigan north of Chicago - was founded by the followers of John Alexander Dowie, whose Christian Catholic Church disapproved of pharmacies, doctors, theaters or dance halls. Smoking, drinking and the eating of pork also was prohibited in town.
The U-S Park Service says the older Old Faithful gets, the more the geyser at Yellowstone National Park slows down. In the 1950s, it erupted every 62 minutes. Lately, it's been erupting every 77 minutes. Some experts say Old Faithful may someday just stop.
At 840,000 square miles, Greenland is the largest island in the world. It is 3 times the size of Texas. By comparison Iceland is only 39,800 square miles.
According to experts, large caves tend to "breathe"; they inhale and exhale great quantities of air when the barometric pressure on the surface changes, and air rushes in or out seeking equilibrium.
The surface area of the Earth is 197,000,000 square miles.
Forty six percent of the world's water is in the Pacific Ocean. The Atlantic has 23.9 percent; the Indian, 20.3; the Arctic, 3.7 percent.