Haig Fras is a 45 km long submarine

granitic A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

rocky outcrop in the southern part of the

Celtic Sea The Celtic Sea is the area of the Atlantic Ocean off the southern coast of Ireland bounded to the north by St George's Channel, Saint George's Channel; other limits include the Bristol Channel, the English Channel, and the Bay of Biscay, as wel ...

, lying about 95 km northwest of the

Isles of Scilly The Isles of Scilly ( ; ) are a small archipelago off the southwestern tip of Cornwall, England. One of the islands, St Agnes, Isles of Scilly, St Agnes, is over farther south than the most southerly point of the Great Britain, British mainla ...

. It covers an area of . At one point it reaches within 38 m of the sea surface. It is protected as a

Special Area of Conservation A special area of conservation (SAC) is defined in the European Union's Habitats Directive (92/43/EEC), also known as the ''Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora''. They are to protect the 220 habitats and ap ...

(SAC) because of the diverse fauna developed in its

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

habitat. It was discovered in 1962 and named by Smith and others in 1965.

Geology

The Haig Fras

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

consists mainly of

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

, forming a WSW-ENE trending elongate

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

. The granite outcrop is surrounded by an area of

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...

s. Evidence from gravity data suggests that the extent of the intrusion is greater than the observed outcrop, based on its association with a linear negative

gravity anomaly The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity meas ...

. It is dated at 277 Ma,

Early Permian 01 or 01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), ''01'' (Richard Müller album), 2001 * 01 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...

in age, within the range of intrusion ages for the granites that make up the

Cornubian batholith The Cornubian batholith is a large mass of granite rock, formed about 280 million years ago, which lies beneath much of Cornwall and Devon in the South West Peninsula of England. The main exposed masses of granite are seen at Dartmoor, Bodmin M ...

. Although the two intrusions have the same trend and are of similar age, they are not thought to be related. In detail, three separate outcrops have been identified using a combination of radiometric data and seabed sampling. The granite is fine to medium-grained, unlike the

megacryst In geology, a megacryst is a crystal or grain that is considerably larger than the encircling Matrix (geology), matrix. They are found in igneous rock, igneous and metamorphic rocks. Megacrysts can be further classified based on the nature of their ...

ic granite typical of the Cornubian batholith intrusions, although this may be due to the low level of sampling available. A foliated granite is locally developed as a marginal

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

. The granite is thought to be cut by a swarm of

basic Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...

dykes inferred from magnetic and seismic reflection data. This swarm is interpreted to be 56 km long and 2.5 km across and at least six separate intrusive bodies have been identified. The proposed intrusions are though most likely to be of

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

age.

Fauna

The bedrock reef at Haig Fras supports a range of fauna. Jewel anemones (''

Corynactis viridis ''Corynactis viridis'', the jewel anemone, is a brightly coloured anthozoan similar in body form to a sea anemone or a scleractinian coral polyp, but in the order Corallimorpharia. It is found in the northeastern Atlantic Ocean and the Mediter ...

'') and Devonshire cup corals ('' Caryophyllia smithii'') are found at the top of the outcrop. Encrusting sponges,

crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...

s and Ross coral ''

Pentapora fascialis ''Pentapora'' is a small genus of bryozoans in the family Bitectiporidae. Species The World Register of Marine Species lists the following species: *'' Pentapora americana'' (Verrill, 1875) *'' Pentapora fascialis'' (Pallas, 1766) *'' Pentapo ...

'' are found near base of the outcrop. Mobile fauna observed include urchins such as ''

Echinus esculentus ''Echinus esculentus'', the European edible sea urchin or common sea urchin, is a species of marine invertebrate in the Echinidae family. It is found in coastal areas of western Europe down to a depth of . It is considered "Near threatened" in th ...

'',

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

s and the

squat lobster Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. They are found in the two superfamilies Galatheoidea and Chirostyloidea, which form part of the decapod infraorder Anomura, alongs ...

Munida ''Munida'' is the largest genus of squat lobster Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. They are found in the two superfamilies Galatheoidea and Chirostyloidea, which ...

''.

Special area of conservation

The area of the proposed SAC is , which includes a margin of around the mapped bedrock area, derived from the maximum water depth of and an assumed length to depth ratio of a fishing warp (the cable used to tow the fishing gear) of 3:1. This is intended to protect the site from potential further damage from

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...

fishing. The area was first proposed in 2004 and was included in the first tranche of candidate SACs submitted to the

European Commission The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...

in August 2008. It was selected on the basis of being an ''Annex I'' habitat, 1170 (reefs), in the terms of the EU

Habitats Directive The Habitats Directive (more formally known as Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora) is a directive adopted by the European Community in 1992 as a response to the Berne Convention. The ...

References

{{coord, 50.2592, -7.7830, display=title Special Areas of Conservation in England Geology of England Celtic Sea Marine reserves of the United Kingdom