2. Super Volcano
Even a run-of-the-mill volcano can cause havoc among the human population. Residents in proximity to an erupting volcano will probably have to evacuate the area if they are lucky enough to get out before being engulfed in a fast-moving cloud of super-heated ash. There can also be wide-ranging impact due to massive ash plumes that can disrupt air transportation and other human activities. A super volcano is in a class of its own and has the potential to cause global consequences. The most recent super volcano eruption was in Indonesia in the year 1815 and it resulted in the deaths of 92,000 people. Ash from the eruption spread as far as 800 miles.