A volcanic plug, also called a volcanic neck or lava neck, is a volcano object created when magma hardens within a Volcanic vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged magma is trapped beneath it, and this can sometimes lead to an explosive eruption. In a plinian eruption the plug is destroyed and ash is ejected.
Glaciation 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.
Examples of volcanic plugs
Africa
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. The Pico Cão Grande (Portuguese for "Great Dog Peak") is a landmark needle-shaped volcanic plug peak in São Tomé and Príncipe, in the Caué District of São Tomé Island in Parque Natural Obô de São Tomé. Its summit is 663 m (2,175 ft) above sea level,1 and it rises about 370 m (1,210 ft) over the surrounding terrain.2
Asia
Sigiriya is an ancient rock fortress near the town of
Dambulla in
Sri Lanka. Approximately 180m high, it is now a UNESCO listed World Heritage Site.
Europe
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,
In the United Kingdom, two examples of a building on a volcanic plug are the Edinburgh Castle 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 Tower and Slieve Gallion.[Wilson, H E et al (1986) Geological Survey of Northern Ireland, HMSO]
North America and the Caribbean
There are several volcanic plugs in the
United States, including
Morro Rock in
California, Devils Elbow located in the Heceta Head Lighthouse Scenic State Park on the
Oregon coast, Thumb Butte in the
Sierra Prieta of Arizona, and
Shiprock in
New Mexico.
Devils Tower in
Wyoming and Little Devils Postpile in Yosemite National Park, California, are also believed, by many
, to be volcanic plugs. In Canada, the Northern Cordilleran Volcanic Province gives rise to several confirmed and suspected plugs. Chief among these is Castle Rock, located in
British Columbia, which last erupted during the
Pleistocene. The southern coast of
Saint Lucia is dominated by the iconic Pitons, a
UNESCO World Heritage Site. The twin peaks, Gros Piton and Petit Piton, steeply rise more than above the
Caribbean Sea.
South America
Pinnacle Rock, Galápagos, Ecuador.
Oceania
There are several volcanic plugs in the
North Island of
New Zealand, including:
-
the Pinnacles in the Coromandel Peninsula
-
Bream Head in Northland Region
-
Paritutu and the adjacent Sugar Loaf Islands in Taranaki
-
St. Paul's Rock at Whangaroa Harbour
-
Piha's Lion Rock, which hosted a fortified Maori pā
-
Mount Pohaturoa near the village of Ātiamuri, a distinctive sight for travelers along State Highway 1
In New Zealand's South Island, Onawe Peninsula on Banks Peninsula is a prominent volcanic plug, and erosion of Saddle Hill near Dunedin has also revealed a plug. Dunedin's Mount Cargill displays two plugs: its main summit and the subsidiary summit of Buttar's Peak.
In Australia, The Nut in Tasmania are further examples, along with Mount Warning and the several peaks in the Warrumbungles in New South Wales. The 11 peaks of the Glasshouse Mountains National Park including Mount Beerwah, Mount Tibrogargan, Mount Coonowrin, Mount Cooroora, Mount Ngungun, Mount Tibberoowuccum, Mount Tunbubudla, and Mount Beerburrum, in South East Queensland are volcanic plugs.[
]
Gallery
Edinburgh Castle From Princes Street Garden 001.jpg|Edinburgh Castle in Scotland is built upon an ancient volcanic plug.
Mt Popa.jpg|Mount Popa, Burma.
Strombolicchio2.jpg|Strombolicchio Island and its lighthouse, close to Stromboli Island (Aeolian Islands, Italy).
RoqueNublo2.jpg|Roque Nublo, symbol of Gran Canaria island.
Slemish (8) - geograph.org.uk - 834986.jpg|Slemish, a volcanic plug in Northern Ireland, is traditionally associated with St Patrick.
TroskyCastle.JPG|Trosky Castle ("Panna" Tower), Czech Republic.
Devils_Tower.jpg|Devils Tower, Wyoming, USA.
File:Shiprock.snodgrass3.jpg|Shiprock, New Mexico, USA.
File:Whangaroa_Harbour3.JPG|St. Paul's Rock, above Whangaroa Harbour, Northland, New Zealand.
São Tomé - Pico Cão Grande.jpg|Pico Cão Grande, landmark volcanic plug peak on São Tomé Island (São Tomé and Príncipe), rising over above the surroundings.
Dent_de_la_Rancune,_voie_normale.png|Dent de la Rancune, a challenging climbing site in the Chaîne des Puys, France.
File:Crater Bluff Warrumbungles.jpg|Crater Bluff in the Warrumbungles, New South Wales
