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 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 blown through a small hole at the surface due to pressure differences between a closed underground 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.
Alofaaga Blowholes on Savai'i Island in Samoa
Blowholes, north coast of Barbados
Hummanaya - A blowhole located in Southern Province, Sri Lanka.
Nakalele blowhole, located near Nakalele Point in north western Maui, Hawaii.