blowhole

Blowhole is a term used for two related natural phenomena and the breathing opening of certain marine mammals. In geology, it refers to a coastal feature where a sea cave connects with the surface, expelling air and seawater through a vertical shaft when waves pressurize the interior. In marine biology, it denotes the nostril opening on the top of a cetacean’s head through which it breathes.

Geological blowholes form where sea caves are eroded upward by wave action in coastal cliffs. When ocean waves force air and water into a cave, pressure is released through the cave’s opening and up a vertical shaft, sometimes producing a spray or jet of seawater and air. The openings are typically located on or near the cliff tops and can range from small shafts to large chambers. Blowholes are dynamic features that can be active only during certain sea conditions and may pose hazards to visitors.

In cetaceans, the blowhole is the external nostril located on the top of the head. It provides the animal’s only exit and entry for air at the surface. The nostrils are controlled by muscular valves and can be closed underwater, allowing the whale to dive. When at the surface, whales exhale forcefully through the blowhole, producing a visible spout of air and water vapor, followed by a rapid inhalation. Most toothed whales have a single blowhole, while baleen whales typically have two. The blowhole’s position and function support efficient surface respiration in large, diving mammals.