The variance of the physical geography across the United States leads to unique weather phenomena. This makes disaster management more difficult than in countries where weather phenomena are more nearly uniform. Tornadoes are particularly powerful and frequent in the Midwest and Southeast United States. In fact, tornadoes are more numerous and more violent in the Great Plains region than anywhere else in the world. Droughts are common in the Southwest, while hurricanes hit the Gulf Coast and Atlantic Coast regions of the United States. All of these factors cause human deaths and property damage and are disruptive to commerce and the U.S. economy.
The western portion of the United States is prone to earthquakes and tsunamis due to its location on the most seismically active tectonic plates in the world. Northern California, Oregon, and Washington are situated within the Cascadia subduction zone, an area where the Juan de Fuca tectonic plate has slipped under the North American tectonic plate. This formation can cause megathrust earthquakes, which are the only earthquakes that produce magnitudes above 9.0 on a 10.0 scale. There is a high likelihood of a catastrophic earthquake affecting this region in the future. Offshore earthquakes in this region may produce tsunamis as well.
The latitudinal position of several regions of the United States can create unusual climate problems. For example, parts of Alaska experience six months of 24-hour sunlight, while those same parts experience six months of 24-hour darkness. This is because Alaska is the closest state to the Arctic Circle, which is the region that is closest to the sun during the summer months and the farthest from the sun during the winter months. In general, states closest to the North Pole experience extreme temperature fluctuation throughout the year, as well as extremely cold winters.
In certain parts of America, the physical geography of the region has contributed to stagnant growth when compared to the rest of the United States. For example, the narrow valleys and steep hillsides of the Appalachian region produce thin soil, which has hindered the region's agricultural growth. The steepness of the mountains in the Appalachia region also makes it difficult to build highways and adequate transportation systems. As a result, 38.6 percent of the counties of Appalachia are considered distressed economically or at-risk for becoming distressed. In the most northern parts of Alaska, the presence of permafrost has severely limited economic development.