According to the National Severe Storms Laboratory, the central United States experiences more tornadoes than any other location in the world. Its flat, wide expanse fosters combinations of weather conditions favorable for tornado formation. Texas, Kansas, Nebraska, Oklahoma, Iowa and southern Minnesota are particularly prone to tornadoes. Tornados are powerful windstorms characterized by a funnel cloud, which is a quickly rotating column of air that stretches from the ground up to a cumulonimbus cloud. Newly formed tornadoes have invisible funnels. As the storm gains speed and power, debris sucked into the tornado give the funnel cloud its characteristic gray color. The whirling column of debris also contributes to the roaring sound associated with large tornadoes. The National Severe Storms Laboratory reveals that 90 percent of American tornadoes are small, weak and cause little to no property damage. The remaining storms are huge, immensely powerful and cause huge swaths of destruction. These tornadoes topple skyscrapers, toss trucks into the air and present extreme threats to ground-based life. Although the central United States has the world's highest concentration of tornadoes, the storms occur on every continent except Antarctica. After the contiguous United States and Canada, the areas that experience the most tornadoes are central Asia, South America, South Africa, Australia, New Zealand and Europe.