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Concept
Geyser maritime
Résumé
In geology, a blowhole or marine geyser is formed as sea caves grow landward and upward into vertical shafts and expose themselves toward the surface, which can result in hydraulic compression of seawater that is released through a port from the top of the blowhole. The geometry of the cave and blowhole along with tide levels and swell conditions determine the height of the spray.
Blowholes are likely to occur in areas where there are crevices, such as lava tubes, in rock along the coast. These areas are often located along fault lines and on islands. As powerful waves hit the coast, water rushes into these crevices and bursts out in a high pressured release. It is often accompanied by a loud noise and wide spray, and for this reason, blowholes are often sites of tourism.
Marine erosion on rocky coastlines produce blowholes that are found throughout the world. They are found at intersecting faults and on the windward sides of a coastline where they receive higher wave energy from the open ocean. The development of a blowhole is linked to the formation of a littoral cave. These two elements make up the blowhole system. A blowhole system always contains three main features: a catchment entrance, a compression cavern and an expelling port. The arrangement, angle and size of these three features determine the force of the air to water ratio that is ejected from the port. The blowhole feature tends to occur in the most distal section of a littoral cave. As their name suggests, blowholes have the ability to move air rapidly. Strong reverse draughts in response to pressure changes in a connecting littoral cave can send wind speeds upwards of 70 km/h.
The formation of a blowhole system begins as a littoral cave is formed. The main factors that contribute to littoral caves formation are wave dynamics and the parent material’s rock property. A parent material property such as susceptibility or resistance to weathering plays a major role in the development of caves.
Source officielle
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