Two bus passengers in Seoul, South Korea, plummeted nearly 10 feet as an instant abyss opened up below them.
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Naturally occurring sinkholes happen when a surface layer of earth gives way due to the erosion of the bedrock below, while man-made ones can be caused by faulty construction. These sometimes result in city scenes akin to New York’s dreaded sidewalk grate collapses, and are a reminder to always tread lightly.