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From its churning, sometimes stormy atmosphere to its shifting tectonic plates, Earth can be a dangerous place. Earthquakes, floods and other natural disasters killed more than 780,000 people between 2009 and 2009, according to the UN International Strategy for Disaster Reduction Secretariat. Millions more were injured or displaced. No one knows how the next decade will shape out, but some areas have more reason to worry than others.
Lake Nyos, CameroonSlide 2 of 15
Lake Nyos, Cameroon
A silent killer lurks beneath the surface of this West African lake. A pocket of magma deep below the lake bed leaks carbon dioxide into the lake above. Under the pressure of 650 feet (200 meters) of water, this carbon dioxide stays dissolved, much like the carbonation in a bottle of soda.
But on the night of August 21, 1986, the water in the lake abruptly turned over, and the now-depressurized carbon dioxide exploded upward like a shaken soft drink. The resulting carbon dioxide cloud rushed downhill, asphyxiating 1,700 people and thousands more animals. In the 15 miles (24 kilometers) of valleys below the lake, almost nothing survived.
Today, pipes are used to siphon carbon dioxide-rich water from the bottom of Lake Nyos. The pipes prevent carbon dioxide buildup, but that doesn't make Lake Nyos entirely safe, said George Kling, a University of Michigan geochemist who was on the team that originally investigated the 1986 disaster.
"We're keeping ahead of the game, but we're not drawing the gas down very quickly," Kling said. "That means that it still is a very dangerous lake."Slide 3 of 15
Naples, ItalySlide 4 of 15
In 79 A.D., Mount Vesuvius blew its top, burying the ancient cities of Pompeii and Herculaneum. More than 50 subsequent eruptions and the eerie human-shaped cavities left behind in the volcano's ash haven't dissuaded people from populating the slopes of this volcano by the sea. The city of Naples lies at its base, and up to 650,000 people may live on its slopes, according to Guido Bertolaso, the head of Italy's civil protection agency. An impending eruption could force the evacuation of more than a million people.
Vesuvius isn't the only active volcano threatening this densely-populated area. The Mediterranean Sea off the coast of Italy is littered with volcanoes. The most worrisome, according to Bertolaso, is the resort island of Ischia. An eruption there would affect Naples and "could be worse than a hypothetical Vesuvius eruption," Bertolaso said.Slide 5 of 15
Miami, FloridaSlide 6 of 15
No one can predict where a hurricane will hit next, but south Florida is always a reasonable bet. The U.S. Geological Survey estimates the southern tip of Florida can expect more than 60 hurricanes over a 100-year period. And in 2008, sustainability company SustainLane ranked Miami as the most risky city for natural disasters in the United States.
Hurricane destruction in Miami and the nearby Florida Keys is nothing new. In 1926, the Great Miami Hurricane destroyed or damaged every building in downtown Miami and killed at least 373 people, according to the Red Cross. Less than 10 years later, the Labor Day hurricane of 1935 killed 408 people in the Florida Keys. In 1960, Hurricane Donna roared through the Keys and South Florida, bringing with it 11 to 15-foot storm surges.
Perhaps the most famous hurricane to hit south Florida was 1992's Hurricane Andrew . Andrew blasted through Florida as a Category 4 storm with winds so high they broke measurement instruments. According to the National Oceanic and Atmospheric Administration, Andrew killed 23 people in the United States. The destruction totaled more than $26.5 billion.Slide 7 of 15
The Sahel region of AfricaSlide 8 of 15