''For the cave phenomena sometimes referred to as a blowhole, see Breathing cave'' Blowhole1

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

, 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 Seawater, or sea water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximat ...

that is released through a port from the top of the blowhole. The

geometry Geometry (; ) is a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...

of the cave and blowhole along with

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

levels and swell conditions determine the height of the spray.

Mechanics

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 In geography and seamanship, windward () and leeward () are directions relative to the wind. Windward is ''upwind'' from the point of reference, i.e., towards the direction from which the wind is coming; leeward is ''downwind'' from the point ...

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. Littoral caves can be formed by one of two processes: caves made of limestone are produced by

karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...

(dissolution) processes, and caves made of igneous rock are produced by pseudokarst (non-dissolutional) processes. In time the littoral cave enlarges growing inland and vertically through weak joints in the parent material. As weathering continues the roof of the cave is exposed, and the blowhole continues to enlarge, eventually the roof of the littoral cave is weaken and collapses. This creates a steep-wall inlet that allows the next stage of coastal morphology to progress. La Bufadora is a large example of a blowhole located in the Punta Banda Peninsula of Baja California, Mexico. It consists of a littoral cave with a thin opening that has a recurrence eruption interval of 13 -17 seconds, ejecting water up to 100 ft. above sea level.

Images

File:Alofa'aga Blowholes - Savai'i.jpg, Alofaaga Blowholes on Savai'i Island in

Samoa Samoa, officially the Independent State of Samoa and known until 1997 as Western Samoa, is an island country in Polynesia, part of Oceania, in the South Pacific Ocean. It consists of two main islands (Savai'i and Upolu), two smaller, inhabited ...

File:Blowhole, Barbados coast.jpg, Blowholes, north coast of

Barbados Barbados, officially the Republic of Barbados, is an island country in the Atlantic Ocean. It is part of the Lesser Antilles of the West Indies and the easternmost island of the Caribbean region. It lies on the boundary of the South American ...

File:Kudawella-blowhole-sri-lanka.JPG, Hummanaya - A blowhole located in Southern Province,

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

File:Halona Blowhole a0002860.jpg, Hālona Blowhole, Oahu, Hawaii File:KiamaBlow.JPG, Kiama Blowhole,

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

File:BufadoraRafaga.jpg, La Bufadora, Ensenada, Baja California

References

{{authority control Cave geology Coastal geography Coastal and oceanic landforms

Mechanics

Images

See also

References