Volcanic plug

A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of pressure if rising volatile-charged magma is trapped beneath it, and this can sometimes lead to an explosive eruption. Glacial erosion can lead to exposure of the plug on one side, while a long slope of material remains on the opposite side. Such landforms are called crag and tail. If a plug is preserved, erosion may remove the surrounding rock while the erosion-resistant plug remains, producing a distinctive upstanding landform.Edinburgh Castle in Scotland is built upon an ancient volcanic plug.Taung Kalat, Burma.Pico Cão Grande, landmark volcanic plug peak on São Tomé Island (São Tomé and Príncipe), rising over 300 metres (980 ft) above the surroundings.Strombolicchio Island and its lighthouse, close to Stromboli Island (Aeolian Islands, Italy).Roque Nublo, symbol of Gran Canaria island.Dent de la Rancune, a challenging climbing site in the Chaîne des Puys, France.Slemish, a volcanic plug in Northern Ireland, is traditionally associated with St Patrick.Trosky Castle ('Panna' Tower), Czech Republic.Devils Tower, Wyoming, USA.Shiprock, New Mexico, USA.St. Paul's Rock, above Whangaroa Harbour, Northland, New Zealand. A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of pressure if rising volatile-charged magma is trapped beneath it, and this can sometimes lead to an explosive eruption. Glacial erosion can lead to exposure of the plug on one side, while a long slope of material remains on the opposite side. Such landforms are called crag and tail. If a plug is preserved, erosion may remove the surrounding rock while the erosion-resistant plug remains, producing a distinctive upstanding landform. An example of two volcanic plugs can be found at the Pitons, in Saint Lucia, as they rise abruptly out of the eastern Caribbean Sea. Near the village of Rhumsiki in the Far North Province of Cameroon, Kapsiki Peak is an example of a volcanic plug and is one of the most photographed parts of the Mandara Mountains. Spectacular volcanic plugs are present in the center of La Gomera island in the Canary Islands archipelago, within the Garajonay National Park. Borgarvirki is a volcanic plug located in north Iceland. A volcanic plug is situated in the town of Motta Sant'Anastasia in Italy. Saint Michel d'Aiguilhe chapel, whose construction started in 969, near Le Puy-en-Velay in France. The volcanic plug rises about 85 metres (279 ft) above the surroundings. Another building on a volcanic plug is the 14th century Trosky Castle in the Czech Republic. Strombolicchio, the northernmost of the Aeolian Islands, and Rockall, a small, uninhabited, remote islet in the North Atlantic Ocean, are also volcanic plugs. In the United Kingdom, two examples of a building on a volcanic plug are the Castle Rock in Edinburgh, Scotland, and Deganwy Castle, Wales. The Law, Dundee, Ailsa Craig, Bass Rock, North Berwick Law and Dumgoyne hill are other examples of volcanic plugs located in Scotland. There are over 30 volcanic plugs in Northern Ireland, including Slemish in Ballymena, Tievebulliagh, Scawt Hill, Carrickarede, Scrabo and Slieve Gallion. There are several volcanic plugs in the United States, including Morro Rock in California and Shiprock in New Mexico. Devils Tower in Wyoming and Little Devils Postpile in Yosemite National Park, California, are also believed to be volcanic plugs by many geologists.