Natural disasters were things anyone would recognize. Regardless were you lived in the world, even if you lived in civilization or not. It was something that transcended even time itself.
Something that remained the same no matter how many generations have already passed. So long as you lived on Earth, you would have seen or heard of them. Mother nature for all her beauty and grace was a fucking bitch when she got angry.
Forest fires that refused to be snuffed out. Hurricanes that terrorized everything in their path. Tsunamis that bitch slapped mankind for its folly. Earthquakes that shattered even the ground one stood on.
Although they were diverse and occurred all over the play there was a single constant. They always made man feel insignificant and powerless.