8. Super Volcano

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Volcanoes happen with some regularity and we see them talked about on the news from time to time, especially when they happen in populated areas or disrupt human activity in some other way, like causing disruptions for air travel. Experts already know that there is a massive super volcano beneath Yellowstone Park that has probably not erupted for about 640,000 years. Since this super volcano is believed to erupt every 600,000 or so years, we may be overdue for a cataclysmic event that could belch out enough ash to block the sun for years, and result in an effect very similar to a “nuclear winter.”