Scawt Hill from the Sallagh Road, Cairncastle
|Elevation||378 m (1,240 ft)|
|Location||County Antrim, Northern Ireland|
|Topo map||OSNI Discoverer 9|
|Mountain type||Volcanic plug|
Scawt Hill is a volcanic plug in County Antrim, Northern Ireland, in the borough of Larne, 5 km from the village of Ballygally.
It gets its name from the Ulster Scots 'scawd' meaning scaly, scabby or rugged.Alternatively, 'scawt' meaning scruffy and contemptible, and when applied to rocks, covered in barnacles.
Scawt Hill is notable for being the type locality for several hydrated calcium silicates,that is, the place where they were first identified. These minerals were formed when the existing chalk of the area was intensely altered by the intrusion of the feeder tube of an ancient volcano, now long since cooled and eroded to its roots.
Minerals that were first discovered at Scawt Hill:
In all, 28 minerals have been found at this site.
Over 30 volcanic plugs are dotted through Northern Ireland, mostly along the Antrim coast like Scawt Hill, although they are relatively rare throughout the rest of Ireland. Volcanic plugs are often easy to spot. Their harder rock erodes away more slowly than their surroundings so they rise above the landscape as a hill.
The largest volcanic plug in Northern Ireland is the oval-shaped Slemish. At its widest, Slemish is over 1 km in diameter. Scawt Hill is more of a typically sized example. This olivine dolerite plug is 270 m x 180 m wide and rises 30 – 60 m above the Cretaceous white limestone (chalk), although the Antrim plateau around it is typically basalt.
Due to the volcanic intrusion the chalk around Scawt Hill has been transformed by high temperature and low pressure thermal metamorphism, developing the large and unusual range of calc-siliate minerals that have attracted interest. The rocks inside the vent were also changed by the contact, producing a sequence of alkali mafic igneous rocks as the magma assimilated the chalk, reducing the silica in the magma and leading to larger grain size near the contact.
Cecil Edgar Tilley, writing for the Mineralogical Magazine in 1929, was the first to appreciate the potential of the dolerite-limestone contact at Scawt Hill. Tilley named scawtite and larnite, and later, rankinite, and his writings inspired many others to find similar relationships between rocks worldwide.
In 1995, Scawt Hill was categorised as an Area of Special Scientific Interest, not just for its international importance to geology, but for its plant life, where chalky and alkaline conditions are in close proximity, and for its conditions for breeding birds.
Scawt Hill is on the Ulster Way, part of a series of walking routes which encircle Ulster. It is passed by between the Black Hill and the Sallagh Braes.
Geology of Northern Ireland
Volcanic plugs of Northern Ireland
Larne from Irish: Latharna, the name of a Gaelic territory) Scots: Lairne is a seaport and industrial market town, as well as a civil parish, on the east coast of County Antrim, Northern Ireland, with a population of 18,755 people at the 2011 Census. The Larne Local Government District had a population of 32,180 in 2011. It has been used as a seaport for over 1,000 years, and is today a major passenger and freight roll-on roll-off port. Larne is administered by Mid and East Antrim Borough Council. Together with parts of the neighbouring districts of Antrim and Newtownabbey and Causeway Coast and Glens, it forms the East Antrim constituency for elections to the Westminster Parliament and Northern Ireland Assembly. The civil parish is situated in the historic barony of Glenarm Upper.
Diabase or dolerite or microgabbro is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite. Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of English-speaking world, where sometimes the name diabase is applied to altered dolerites and basalts. Some geologists prefer the name microgabbro to avoid this confusion.
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Whitehead is a small seaside town on the east coast of County Antrim, Northern Ireland, lying almost midway between the towns of Carrickfergus and Larne. It lies within the civil parish of Templecorran, the historic barony of Belfast Lower, and is part of Mid and East Antrim Borough Council. Before the Plantation of Ulster its name was recorded as both Whitehead and Kinbaine.
Slemish, historically called Slieve Mish, is a small mountain in County Antrim, Northern Ireland. It lies a few miles east of Ballymena, in the townland of Carnstroan. Tradition holds that Saint Patrick, enslaved as a youth, was brought to this area and tended sheep herds on Slemish, and that during this time he found God.
Ballygally or Ballygalley is a village and holiday resort in County Antrim, Northern Ireland which lies on the Antrim coast, approximately 3 miles north of Larne. It is also a townland of 769 acres and is situated in the civil parish of Carncastle and the historic barony of Glenarm Upper. It had a population of 821 in the 2011 Census. It is located within the Mid and East Antrim Borough Council area.
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Prof Cecil Edgar Tilley FRS HFRSE PGS was an Australian-British petrologist and geologist.
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Scawtite is a hydrous calcium silicate mineral with carbonate, formula: Ca7(Si3O9)2CO3·2H2O. It crystallizes in the monoclinic crystal system as thin plates or flat prisms.