Volcanic plug 1572073 225399245 2008-07-13T13:59:36Z AtulaSiriwardane 3191966 Added Sigiriya Rock fortress built on a Volcanic plug. [[Image:Edinburgh Castle From Princes Street Garden 001.jpg|right|300px|thumb|[[Edinburgh Castle]] in [[Scotland]] is built upon an ancient Volcanic Plug]] A '''volcanic plug''', also called a '''volcanic neck''' or '''lava neck''', is a [[volcano|volcanic]] landform created when [[lava]] hardens within a [[vent]] on an active volcano. When forming, a plug can cause an extreme build-up of [[pressure]] if [[Volatiles|volatile]]-charged [[magma]] is trapped beneath it, and this can sometimes lead to an explosive eruption. If a plug is preserved, [[erosion]] may remove the surrounding rock while the erosion-resistant plug remains, producing a distinctive landform. [[Image:Steins Pillar.jpg|thumb|left|200px|Volcanic plug in the [[Ochoco National Forest]] of [[Oregon]], USA]] [[Image:Rhumsiki Peak.jpg|thumb|right|200px|Volcanic plug near [[Rhumsiki]], [[Far North Province]], [[Cameroon]]]] Examples of landforms created in this way in the [[United States]] include [[Morro Rock]], [[California]]; [[Lizard Head]], [[Colorado]]; and [[Shiprock]], [[New Mexico]]. [[Devils Tower National Monument|Devils Tower]] in [[Wyoming]], as well as [[Little Devils Postpile]] located in Yosemite National Park, are also thought to be a volcanic plug by many [[geologist]]s. The only example of a volcanic plug in the eastern USA is the highly eroded [[Stark's Knob]] basaltic structure located along the [[Hudson River]] near [[Saratoga Springs]], [[New York]].{{Fact|date=February 2007}} However, some geologists believe Stark's Knob is not a plug at all, but merely an outcrop of an ancient submarine lava flow. The [[Ailsa Craig]], [[Bass Rock]] and [[North Berwick Law]] are examples of volcanic plugs located in [[Scotland]]. [[Borgarvirki]] is a volcanic plug located in north Iceland. Subsequent [[Glaciation|glacial]] erosion can lead to exposure of the plug on one side, while a long slope of material remains on the lee side. Such landforms are called [[crag and tail]]. Examples include the [[Edinburgh Castle|Castle Rock]] in [[Edinburgh]], Scotland. [[Image:Sigiriya AS1.jpg|400px|[[Sigiriya]] Rock Fortress.]] Another fine example is the famous [[Sigiriya]] (Lion's rock), an ancient rock fortress and ruins of a castle situated in central [[Matale District]] of [[Sri Lanka]]. It is a popular tourist destination and also popular for the ancient paintings (''frescos'') very similar to the paintings in [[Ajanta Caves]] of [[India]]. It was built during the reign of King Kasyapa (477 &ndash; 495 AD) and one of the seven [[World Heritage Site]]s (Ref:202) in Sri Lanka.<ref name="SIGIRIYA-1">{{cite web | title = UNESCO page - Ancient City of Sigiriya | publisher = UNESCO.org | url = http://whc.unesco.org/en/list/202 | format =html | accessdate = 2008-01-18}}</ref><ref>{{cite web|url=http://www.asiaexplorers.com/srilanka/sigiriya.htm|title=Exploring Sigiriya Rock|work=AsiaExplorers.com|accessdate=2008-05-05}}</ref>Sigiriya rock is the hardened [[volcanic plug|magma plug]] from an extinct and long-eroded [[volcano]]. It stands high above the surrounding plain, visible for miles in all directions. The rock rests on a steep mound that rises abruptly from the flat plain surrounding it. The rock itself rises 370m and is sheer on all sides, in many places overhanging the base. It is elliptical in plan and has a flat top that slopes gradually along the long axis of the ellipse.<ref name="SIGIRIYA-2">{{cite web | title = Encyclopædia Britannica Article about Sigiriya | publisher = Encyclopædia Britannica | url = http://www.britannica.com/eb/article-9067705/Sigiriya | format =html | accessdate = 2008-01-18}}</ref> Sigiriya consists of an ancient castle built by King Kasyapa during the 5th century AD. The Sigiriya site has the remains of an upper palace sited on the flat top of the rock, a mid-level terrace that includes the Lion Gate and the mirror wall with its frescoes, the lower palace that clings to the slopes below the rock, and the [[moat]]s, walls and gardens that extend for some hundreds of metres out from the base of the rock. The site is both a palace and fortress. Sufficient remains to provide the visitor with a stunning insight into the ingenuity and creativity of its builders. The upper palace on the top of the rock includes cisterns cut into the rock that still retain water. The moats and walls that surround the lower palace are still exquisitely beautiful.<ref>{{cite web|url=http://en.epochtimes.com/news/5-5-4/28449.html|title=Sri Lanka: Slip Into Antiquity|work=The Epoch Times|accessdate=2005-05-04}}</ref> [[Category:Volcanic plugs| ]] [[es:Cuello volcánico]] [[fr:Neck]] [[is:Gígtappi]] [[nl:Vulkanische plug]]