Blow Holes

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In geology, a blowhole is formed as sea caves grow landwards and upwards into vertical shafts and expose themselves towards the surface, which can result in quite spectacular blasts of water from the top of the blowhole if the geometry of the cave and blowhole and state of the weather are appropriate.

A blowhole is also the name of a rare geologic feature in which air is either blown out or sucked into a small hole at the surface due to pressure differences between a closed underground cavern system and the surface. The blowholes of Wupatki National Monument are an example of such a phenomenon. It is estimated that the closed underground passages have a volume of at least seven billion cubic feet. Wind speeds can approach 30 miles per hour