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Irish Sea

2007 Schools Wikipedia Selection. Related subjects: Geography of Great
Britain

   Relief map of the Irish Sea. Major ports shown as red dots. Freight
   only ports as blue dots.
   Enlarge
   Relief map of the Irish Sea. Major ports shown as red dots. Freight
   only ports as blue dots.

   The Irish Sea ( Irish: Muir Éireann) separates the islands of Ireland
   and Great Britain. It is connected to the Atlantic Ocean by St George's
   Channel between the Republic of Ireland and Wales and Cornwall to the
   south and by the North Channel between Northern Ireland and Scotland to
   the north-east. The Isle of Man lies in the middle of the Irish Sea.
   The sea is of high economic importance to regional trade, shipping and
   transport, fishing and power generation in the form of wind power and
   nuclear plants. There has been long discussion of building a 80 km (50
   mile) rail tunnel to link Britain and Ireland; annual traffic between
   the two islands amounts to over 12 million passengers and 17 megatonnes
   of trade.

Shipping

   Ireland has no tunnel or bridge connection to a continent. Thus the
   vast majority of heavy goods trade is done by sea. Northern Irish ports
   handle 10 megatonnes of goods trade with Britain annually, while ports
   in the south handle 7.6 Mt, representing 50% and 40% respectively of
   total trade by weight.

   Liverpool and Birkenhead port handles 32 Mt cargo and 734 thousand
   passengers a year . Holyhead port handles most of the passenger traffic
   from Dublin and Dun Laoghaire port, as well as 3.3 million tonnes of
   freight.

   Ports in the Republic handle 3,600,000 travelers crossing the Irish sea
   each year, amounting to 92% of all sea travel . This has been steadily
   dropping for a number of years (20% since 1999), probably as a result
   of low cost airlines.

   Ferry connections between Britain to Ireland via the Irish Sea include
   the routes from Swansea to Cork, Fishguard and Pembroke to Rosslare,
   Holyhead to Dún Laoghaire, Stranraer to Belfast and Larne, and
   Cairnryan to Larne. There is also a connection between Liverpool and
   Belfast via the Isle of Man. The world's largest car ferry, Ulysses, is
   operated by Irish Ferries on the Dublin–Holyhead route.

Origin

   The Irish Sea has undergone a series of dramatic changes over the last
   20,000 years as the last ice age ended and was replaced by warmer
   conditions. At the height of the ice age the central part of the modern
   sea was probably a long freshwater lake. As the ice retreated 10,000
   years ago the lake reconnected to the sea, becoming brackish and then
   fully saline once again.

Environment

   The Irish Sea has been subject to heavy radioactive contamination by
   the first British weapons grade ^239Pu nuclear production plant and
   power station at Sellafield, also known as Windscale. (See the
   Sellafield page about the naming of this site.) An estimated 250 kg of
   plutonium have been deposited in marine sediments during the first
   decades of production. Another source of radioactive pollution may be
   the Dundrennan Range on the Solway Firth. Further north are the Holy
   Loch (the location of a United States Navy base [1960 to 1991]) and
   Faslane bases, where nuclear submarines were serviced during the cold
   war. After the Chernobyl disaster, rain containing Cs-137 and other
   radioactive material fell in the area. The area of the Beaufort's Dyke
   has been used as a dump for chemical weapons and possibly more nuclear
   waste.

   The Irish Sea Forum is an environmental forum concerned with the Irish
   Sea. Some elements of the Irish Sea fishery are subject to collapse,
   due to overfishing from worldwide population growth, and also due to
   marine pollution. In response, the UK government has created
   Biodiversity Action Plans related to the solea solea and other fishes.

U-boat Alley

   During the Great War the Irish Sea became known as “ U-boat Alley”.
   After the United States entered the war in 1917, the U-boats moved
   their emphasis from the Atlantic to the Irish Sea.

Oil and gas exploration

East Irish Sea Basin

   With 7.5 trillion cubic feet (210 km³) of gas and 176 million barrels
   (28,000,000 m³) of oil estimated by the field operators as initially
   recoverable reserves from eight producing fields (DTI, 2001), the East
   Irish Sea Basin is at a mature exploration phase. Early Namurian
   basinal mudstones are the source rocks for these hydrocarbons.
   Production from all fields is from fault-bounded traps of the Lower
   Triassic formation, principally aeolian Sherwood Sandstone reservoir,
   top-sealed by younger Triassic continental mudstones and evaporites.
   Future exploration will initially concentrate on extending this play,
   but there remains largely untested potential also for gas and oil
   within widespread Carboniferous fluvial sandstone reservoirs. This play
   requires intraformational mudstone seal units to be present, as there
   is no top-seal for reservoirs subcropping the regional base Permian
   unconformity in the east of the basin, and Carboniferous strata crop
   out at the sea bed in the west.

Caernarfon Bay Basin

   The Caernarfon Bay Basin contains up to 7 km of Permian and Triassic
   syn-rift sediments in an asymmetrical graben that is bounded to the
   north and south by Lower Paleozoic massifs. Only two exploration wells
   have been drilled so far, and there remain numerous undrilled targets
   in tilted fault block plays. As in the East Irish Sea Basin, the
   principal target reservoir is the Lower Triassic, Sherwood Sandstone,
   top-sealed by younger Triassic mudstones and evaporites. Wells in the
   Irish Sector to the west have demonstrated that pre-rift, Westphalian
   coal measures are excellent hydrocarbon source rocks, and are at peak
   maturity for gas generation (Maddox et al., 1995). Seismic profiles
   clearly image these strata continuing beneath a basal Permian
   unconformity into at least the western part of the Caernarfon Bay
   Basin. The timing of gas generation presents the greatest exploration
   risk. Maximum burial of, and primary gas migration from, the source
   rocks could have terminated as early as the Jurassic, whereas many of
   the tilted fault blocks were reactivated or created during Paleogene
   inversion of the basin. However, it is also possible that a secondary
   gas charge occurred during regional heating associated with intrusion
   of Paleogene dykes, such as those that crop out nearby on the coastline
   of north Wales. (Floodpage et al., 1999) have invoked this second phase
   of Paleogene hydrocarbon generation as an important factor in the
   charging of the East Irish Sea Basin’s oil and gas fields. It is not
   clear as yet whether aeromagnetic anomalies in the south-east of
   Caernarfon Bay are imaging a continuation of the dyke swarm into this
   area too, or whether they are instead associated with deeply buried
   Permian syn-rift volcanics. Alternatively, the fault block traps could
   have been recharged by exsolution of methane from formation brines as a
   direct result of the Tertiary uplift (cf. Doré and Jensen, 1996).

The Cardigan Bay Basin

   The Cardigan Bay Basin forms a continuation into UK waters of Ireland’s
   North Celtic Sea Basin, which has two producing gas fields. The basin
   comprises a south-easterly deepening half-graben near the Welsh
   coastline, although its internal structure becomes increasingly complex
   towards the south-west. Permian to Triassic, syn-rift sediments within
   the basin are less than 3 km thick and are overlain by up to 4 km of
   Jurassic strata, and locally also by up to 2 km of Paleogene
   fluvio-deltaic sediments. The basin has a proven petroleum system, with
   potentially producible gas reserves at the Dragon discovery near the
   UK/Ireland median line, and oil shows in a further three wells. The
   Cardigan Bay Basin contains multiple reservoir targets, which include
   the Lower Triassic (Sherwood Sandstone), Middle Jurassic shallow marine
   sandstones and limestone (Great Oolite), and Upper Jurassic fluvial
   sandstone, the reservoir for the Dragon discovery. The most likely
   hydrocarbon source rocks are early Jurassic marine mudstones (Lias
   Group). These are fully mature for oil generation in the west of the UK
   sector, and are mature for gas generation nearby in the Irish sector.
   Gas-prone, Westphalian pre-rift coal measures may also be present at
   depth locally. The Cardigan Bay Basin was subjected to two Tertiary
   phases of compressive uplift, whereas maximum burial that terminated
   primary hydrocarbon generation was probably around the end of the
   Cretaceous, or earlier if Cretaceous strata, now missing, were never
   deposited in the basin. Despite the Tertiary structuration, the Dragon
   discovery has proved that potentially commercial volumes of
   hydrocarbons were retained at least locally in Cardigan Bay. In
   addition to undrilled structural traps, the basin contains untested
   potential for stratigraphic entrapment of hydrocarbons near
   synsedimentary faults, especially in the Middle Jurassic section.

   The Liverpool Bay Development is BHP Billiton Petroleum's largest
   operated asset. It comprises the integrated development of five
   offshore oil and gas fields in the Irish Sea:
     * Douglas oil field
     * Hamilton gas field
     * Hamilton North gas field
     * Hamilton East gas field
     * Lennox oil and gas field

   Oil is produced from the Lennox and Douglas fields. It is then treated
   at the Douglas Complex and piped 17 kilometres to an oil storage barge
   ready for export by tankers.

   Gas is produced from the Hamilton, Hamilton North and Hamilton East
   reservoirs. After initial processing at the Douglas Complex the gas is
   piped by subsea pipeline to the Point of Ayr gas terminal for further
   processing. The gas is then sent by onshore pipeline to PowerGen's
   combined cycle gas turbine power station at Connah's Quay. PowerGen is
   the sole purchaser of gas from the Liverpool Bay development.

   First production
     * Hamilton North 1995
     * Hamilton 1996
     * Douglas 1996
     * Lennox (oil only) 1996
     * First contract gas sales 1996
     * Hamilton East 2001

   Facility details The Liverpool Bay development comprises:

   Four offshore platforms. Offshore storage and loading facilities. The
   onshore gas processing terminal at Point of Ayr.

Proposed tunnel projects

   Discussions of linking Britain to Ireland began in 1895, with an
   application £15,000 towards the cost of carrying out borings and
   soundings in the North Channel to see if a tunnel between Ireland and
   Scotland was viable. Sixty years later Harford Montgomery Hyde,
   Unionist MP for North Belfast, called for the building of such a
   tunnel. . A tunnel project has been discussed several times in the
   Irish Parliament,

   Several potential Irish Sea tunnel projects have been proposed, most
   recently the "Tusker Tunnel" between the ports of Rosslare and
   Fishguard proposed by The Institute of Engineers of Ireland in 2004. .
   A different proposed route is between Dublin and Holyhead, proposed in
   1997 by a leading British engineering firm, Symonds, for a rail tunnel
   from Dublin to Holyhead. Either tunnel, at 80 km, would be by far the
   longest in the world, and would cost an estimated €20,000,000,000.

   There could be an economic case for such a link. The Irish sea is one
   of the busiest shipping regions in the world and has the world's
   largest car ferry— Irish Ferries Ulysses . In addition, half of the air
   traffic at Dublin Airport is to Britain, with 8,300,000 passengers per
   annum. The Dublin-London air route is the busiest in the European Union
   and the second busiest in the world, with about 50 daily flights and
   4.5 million journeys per annum. The success of the 15 km Oresund
   Bridge, inaugurated in 2000 and linking Malmö, Sweden and Copenhagen,
   Denmark, which has led to important economic integration between the
   two cities, suggests that the Dublin–Holyhead route may be the most
   promising. With the addition of high speed rail, such a tunnel could
   cut journey times from the northern English cities of Liverpool and
   Manchester to Dublin to under an hour. The combined population of the
   three metropolitan areas is over 5 million. The question would have to
   be raised over what gauge to build a rail link as Ireland uses a
   different gauge to the UK.

   Despite this, and possibly due to the failure of the Channel Tunnel to
   generate adequate passenger numbers, various Irish government studies
   have concluded that an Irish Sea tunnel is, as yet, economically
   unfeasible.

Wind power

   The North Hoyle] site 4 - 5 miles off the coast from Rhyl and Prestatyn
   in north Wales, containing thirty 2 MW turbines.Built in 2003 , about
   10 km off the coast of County Wicklow in the south Irish Sea. The site
   currently has seven GE 3.6 MW turbines, each with 104 m rotor
   diameters, the world's first commercial application of offshore wind
   turbines over three megawatts in size. The operating company,
   Airtricity, has indefinite plans for nearly 100 further turbines on the
   site.

   Further wind turbine sites include:
     * (Link), NPower Renewables</ref>
     * A site in the Solway Firth is being developed
     * Turbines are being erected off the coast of Walney Island

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