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Avon Gorge

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

   The Avon Gorge and Clifton Suspension Bridge, looking south from the
   Downs
   Enlarge
   The Avon Gorge and Clifton Suspension Bridge, looking south from the
   Downs

   The Avon Gorge ( grid reference ST560743) is a 2.5km (1.5mi) long gorge
   on the River Avon in Bristol, South West England. The gorge runs south
   to north through a limestone ridge 2km west of Bristol city centre, and
   about 5km from the mouth of the river at Avonmouth. The gorge forms the
   boundary between the unitary authorities of North Somerset and Bristol.
   In the past, when Bristol was an important port, the gorge formed a
   spectacular defensive gateway to the city.

   On the east of the gorge is the town of Clifton, part of Bristol city,
   and The Downs, a large public park. To the west of the gorge is Leigh
   Woods, the name of both a village and the National Trust forest it is
   situated in. There are three Iron Age hill forts overlooking the gorge,
   as well as a more recent observatory. The Clifton Suspension Bridge, an
   icon of Bristol, crosses the gorge.
   Shown within Bristol (above) and England
   Shown within Bristol (above) and England.
                                            Bristol shown within England

Geology and formation

   Looking north from the bridge, with Leigh Woods on the left and the A4
   road on the right.
   Enlarge
   Looking north from the bridge, with Leigh Woods on the left and the A4
   road on the right.

   The gorge cuts through a ridge mainly of limestone, with some
   sandstone. This particular ridge runs from Clifton to Clevedon, ten
   miles away on the Bristol Channel coast, though limestone is found
   throughout the Bristol area. The fossil shells and corals indicate that
   the limestone formed in shallow tropical seas in the Carboniferous, 350
   million years ago. For a long time it was unclear what caused the Avon
   to cut through the limestone ridge, rather than run south west through
   the Ashton Vale towards Weston-super-Mare. However, Bristol was at the
   southern edge of glaciation during the last ice age, and it has been
   suggested that ice blocked the Ashton Vale, or a glacier carved the
   gorge.

   At various times the sides of the gorge have been quarried, leaving
   steep gorge walls. In the 18th century the gorge was quarried to
   produce building stone for the city. Stone was taken by boat into the
   floating harbour. In the 19th century celestite was discovered in Leigh
   Court estate, and the Wills family authorised quarrying. Between 1880
   and 1920 Bristol was producing 90% of the world's celestite, but the
   enterprise did not last long into the 20th century. Quarries on the
   Bristol side of the gorge are now popular with climbers and are a
   habitat for Peregrine falcons and other wildlife.

Ecology

   The bridge and river at low tide, from Observatory Green.
   Enlarge
   The bridge and river at low tide, from Observatory Green.

   The steep walls of the gorge support some rare fauna and flora,
   including species unique to the gorge. There are a total of 24 rare
   plant species and two unique trees: the Bristol and Wilmotts's
   whitebeams. Other notable plants include Bristol rock cress, Bristol
   onion, Spiked Speedwell, Autumn Squill and Honewort. Because of its
   steep sides, there are many parts of the gorge on which trees can not
   grow, making way for smaller plants. The gorge is also home to many
   rare invertebrate species. The gorge has a unique microclimate, around
   1 degree warmer than the surrounding land. The steep south-west facing
   sides receive the afternoon sunlight, but are partially sheltered from
   the prevailing winds. When winds come from the Bristol Channel in the
   north west they may be funnelled into the gorge, creating harsh and wet
   conditions.

   The steep gorge walls make an ideal habitat for peregrine falcons, with
   a plentiful supply of food nearby in the form of pigeons and sea gulls.
   Peregrines have a history of nesting in the gorge, but having become
   rare in the British Isles they did not breed and were rarely seen in
   the gorge after the 1930s. In 1990 Peregrines returned to the gorge,
   and have successfully bred in most of the following years. On warm days
   a strong uplift forms in the gorge, on which birds of prey soar while
   hunting. The gorge also houses large populations of Jackdaw and
   horseshoe bats, both of which find homes in the caves and bridge
   buttresses.

   Due to its geology and ecology, an area of 155.4 hectares of the gorge
   and surrounding woodland has been protected as a biological and
   geological Site of Special Scientific Interest (SSSI), the original
   notification taking place in 1952. The site may in future be protected
   as a Special Area of Conservation under the European Habitats
   Directive. The Leigh Woods side of the gorge is largely owned by the
   National Trust. The Downs on the city side of the gorge are owned by
   Bristol City Council and managed as a large public park. The actual
   gorge side is protected in partnership with Bristol Zoo, WWF and
   English Nature. The council's management of the gorge involves
   balancing the need to protect its ecology with recreational uses such
   as rock climbing.

History of human use

   The Portishead Railway runs through a short tunnel under the bridge
   buttress.
   Enlarge
   The Portishead Railway runs through a short tunnel under the bridge
   buttress.

   The gorge area was inhabited at least as early as the iron age,
   probably by the Dobunni tribe. In Leigh Woods above Nightingale Valley,
   a steep dry valley beside the suspension bridge, is Stokeleigh Camp,
   one of three iron age hill forts in the area. Stokeleigh was occupied
   from 3BCE to 1CE, and was also used in the Middle Ages. The camp was
   protected on two sides by the cliff faces of the gorge and Nightingale
   Valley, and was also protected by earthworks, and is now a scheduled
   ancient monument. A second hill fort was situated across Nightingale
   Valley, but has since been built on, and bridge road cuts through it.
   The third hill fort was situated on the opposite side of the gorge, in
   what is now observatory green. Archaeology, plus the configuration of
   the three forts, suggest they played a role in defending the gorge.

   During the Middle Ages and industrial revolution the area which now
   forms The Downs was used as common grazing land, was mined for lead,
   calamine, iron and limestone, and became home to a windmill which
   produced snuff from the tobacco which had become one of the city's
   principal imports. In 1777 the windmill bunt out in a storm, and the
   building was converted into the observatory, which houses a camera
   obscura. In the 18th and 19th centuries Bristol's economy boomed and
   Clifton became a desirable place to live. Mansion houses were built
   over looking the gorge, but after grazing was stopped, trees grew and
   obscured the view from these mansions. In the Victorian era, with
   houses creeping further onto the Downs, an Act of Parliament was passed
   to protect them as a park for the people of Bristol. In 1754 a bridge
   to span the gorge was proposed, but it was nearly 80 years before work
   began on Isambard Kingdom Brunel's Clifton Suspension Bridge, and a
   further 30 years of delays before it was completed. Today the bridge is
   perhaps the best known landmark in Bristol.

   Throughout Bristol's history the gorge has been an important transport
   route. It is the gateway to Bristol Harbour, and provided protection
   against storms or attack. The Bristol Channel and Avon estuary have a
   very high tidal range, and the gorge is relatively narrow and
   meandering, making it notoriously difficult to navigate and giving rise
   to the phrase ship shape and Bristol fashion.

   Today Bristol Harbour is no longer an important port, but the gorge is
   still a transport route. The A4 road runs through the gorge, linking
   Bristol city centre to the M5 motorway, which bypasses the city near
   Avonmouth. Two railways run through the gorge, on the east side the
   passenger railway to Avonmouth and Severn Beach runs through part of
   the gorge, and through a tunnel under the Downs, while on the west side
   is the former Portishead Railway, which was closed by the Beeching Axe
   in the 1960s, but has now been reopened for freight traffic as far as
   Royal Portbury Dock, 4km (2.5mi) downstream. Between 1893 and 1934, the
   Clifton Rocks Railway linked the passenger steamer pier at Hotwells
   with Clifton on the rim of the gorge.

   A footpath and National Cycle Network cycleway run alongside the
   Portishead Railway and along the old towpath.

Mythology

   The formation of the Avon Gorge is the subject of mediaeval mythology.
   The myths tell tales of two giant brothers, Vincent and Goram, who
   constructed the gorge. One variation holds that Vincent and Goram were
   constructing the gorge together and Goram fell asleep, to be
   accidentally killed by Vincent's pickaxe. Another variation tells of
   the brothers falling for Avona, a girl from Wiltshire, who instructs
   the giants to drain a lake which stretches from Rownham Hill to
   Bradford-on-Avon (i.e. the Avon valley). Goram began digging the nearby
   Hazel Brook Gorge in Blaise Castle estate, but consumed too much beer
   and fell asleep. Vincent dug the Avon Gorge and drained the lake,
   winning the affection of Avona. Upon waking Goram stamped his foot,
   creating "Goram's Chair" in the Blaise Castle estate, and threw himself
   into the Bristol Channel, turning to stone and leaving head and
   shoulder above water as the islands Flat Holm and Steep Holm.
   Retrieved from " http://en.wikipedia.org/wiki/Avon_Gorge"
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