The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to 4,000 feet (1,200 m) deep, the canyon stretches for over 80 miles (130 km) as the river winds westward through the Cascade Range forming the boundary between the State of Washington to the north and Oregon to the south. Extending roughly from the confluence of the Columbia with the Deschutes River down to eastern reaches of the Portland metropolitan area, the gorge furnishes the only navigable route through the Cascades and the only water connection between the Columbia River Plateau and the Pacific Ocean.

The gorge holds federally protected status as a National Scenic Area called the Columbia Gorge National Scenic Area and is managed by the United States Forest Service. The gorge is a popular recreational destination.

Description

The western gorge is dominated by conifers, Bigleaf Maple, cottonwood, Oregon Ash, and Vine Maple. The eastern gorge is home to Bigleaf Maple and Garry Oak. The wide range of elevation and precipitation in the gorge creates a diverse collection of ecosystems from the temperate rain forest at Oneonta Gorge (with an average annual precipitation of 75 inches (1,900 mm)) to the Celilo grasslands (with average annual precipitation 12 inches (300 mm), with a transitional dry woodland between Hood River and The Dalles. A large variety of endemic wildflowers thrives throughout the gorge.

Atmospheric pressure differentials east and west of the Cascades create a wind tunnel effect in the deep cut of the gorge, generating 35 mph (56 km/h) winds that make it a popular windsurfing and kiteboarding location.

The gorge also contains a high concentration of waterfalls, with over 90 waterfalls on the Oregon side of the gorge alone. Many are along the Historic Columbia River Highway, including the notable 620-foot (190 m)-high Multnomah Falls.

Geology

The Columbia River Gorge began forming as far back as the Miocene, (roughly 12 - 17 million years ago), and continued to take shape through the Pleistocene, (700,000 - 2 million years ago). During this period the Cascades Range was forming, which slowly moved the Columbia River's delta about 100 miles (160 km) north to its current location.

Although the river slowly eroded the land over this period of time, the most drastic changes took place at the end of the last Ice Age when the Missoula Floods cut the steep, dramatic walls that exist today, flooding the river as high up as Crown Pointe. This quick erosion left many layers of volcanic rock exposed.

History

The gorge has supported human habitation for over 13,000 years. Evidence of the Folsom and Marmes people, who crossed the Bering land bridge from Asia, were found in archaeological digs. Excavations near Celilo Falls, a few miles east of The Dalles, show humans have occupied this salmon-fishing site for more than 10,000 years.

The gorge has provided a transportation corridor for thousands of years. American Indians would travel through the Gorge to trade at Celilo Falls, both along the river and over Lolo Pass on the north side of Mount Hood. In 1805, the route was used by the Lewis and Clark Expedition to reach the Pacific. Early European and American settlers subsequently established steamboat lines and railroads through the gorge. Today, the BNSF Railway runs freights along the Washington side of the river, while its rival, the Union Pacific Railroad, runs freights along the Oregon shore. Until 1997, Amtrak's Pioneer also used the Union Pacific tracks. The Portland segment of the Empire Builder uses the BNSF tracks that pass through the gorge.

The Columbia River Highway, built in the early 20th century, was the first major paved highway in the Pacific Northwest. Shipping was greatly simplified after Bonneville Dam and The Dalles Dam submerged the gorge's major rapids.

In November 1986, Congress made it the first U.S. National Scenic Area and established the Columbia River Gorge Commission as part of an interstate compact. In 2004, the gorge became the namesake of the Columbia Gorge American Viticultural Area, a 4,432-acre (1,794 ha) area located on both sides of the river.

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The Manawatu Gorge (in Maori Te Apiti, meaning 'The Narrow Passage') runs between the Ruahine and Tararua Ranges of the North Island of New Zealand, linking the Manawatu and Hawke's Bay regions. It lies to the northeast of Palmerston North - its western end is near the small town of Ashhurst, its eastern end is close to the town of Woodville.

The Manawatu Gorge is significant because, unlike most gorges, the Manawatu River is a water gap, that is it runs directly through the surrounding ranges from one side to the other. This was caused by the ranges moving upwards at the same time as the gorge was eroded by the river, instead of the more usual erosion of an already existing range.

The road through the Manawatu Gorge is on the south side, and was completed in 1872. It is the primary link between the two sides of the lower North Island. It is sometimes closed by slips, especially in inclement weather. Alternative road routes cross the ranges on both the northern and southern sides. A rail connection was established on the northern side of the gorge; it was completed in 1891.

A tramping track, the Manawatu Gorge Track, runs parallel to the gorge on the south side through native bush.

The Old Gorge Cemetery lays on the north side of the Manawatu Gorge. Public access is available, but the cemetery was closed many years ago to further burials. The road is located just a few km out of Woodville on the north side of the gorge.

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Komati Gorge is a river valley in the Mpumalanga Province in central South Africa, which features vertical sandstone cliffs that provide habitat for a wide diversity of wildlife. Komati Gorge is located near the communities of Carolina and Machadodorp. The Komati River flows through the gorge and provides riparian cover for many species of flora and fauna, including several endemic endangered species and big game animals. The geology of the vertical cliffs of the gorge offer a diverse set of colourful mineralized exposures. Within Komati Gorge are the Kromberg Formation and upper Hooggenoeg Formation; where the latter formation exists, debris flows, turbidites, and thin gray chert units are exhibited. There are also exposures of black and white banded cherts interbedded with basalt flows representing eastern faces of Black Reef Chert. Furthermore, there is a banded iron formation present in the bluffs.

Ecology and geology

The Komati Gorge contains a great diversity of flora and fauna, including many large mammalian species. There are several discrete types of habitat present, including riparian zone, bluff habitat, thorn bushveld and highveld grassland. The river provides not only water for wildlife and aquatic vegetation, but also supports a robust riverine trout fishery. The bluffs support a very specialized ecosystem including vegetation adapted to the steep rocky vertical landform of the gorge sides. In addition there are favourable opportunities for bird habitat, providing more protection from certain predators; for example the threatened Southern Bald Ibis inhabits these cliff habitats.

Mammal species include big game animals as well as smaller fauna; for example zebra and giraffe can be found on the bushveld. Eland, Impala and other bovids are numerous.

Approximately three million years ago the underlying geological formations took shape in the Komati Gorge area, producing one of the Earth's rarest and most endangered ecosystems, the ancient grasslands of Africa. With increasing rainfall on the lowlands, an invasion of trees ensued, constituting the bushveld of the lowveld ecosystems present here.

Access and present situation

Access is from the north, via the towns of Carolina or Machadodorp, which towns are near the main highway leading to Johannesburg. Most of the Komati Gorge has been historically privately owned wilderness, with some ranching arriving in the latter half of the 20th century. Since the late 20th century there has been limited development of a lodge and a few country homes. As of the year 2006, visitation to the Komati Gorge is not intense, although there has been a recent case of geo-vandalism in the form of illegal drilling of some of the rock outcrops. Geo-vandalism is a term meaning defacing, alteration or drilling in significant rock formations either for unauthorised fossil, collection, mineral exploration or malicious destruction.

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Cheddar Gorge is a limestone gorge in the Mendip Hills, near the village of Cheddar in Somerset, England. The gorge is the site of the Cheddar show caves, where Britain's oldest complete human skeleton, Cheddar Man, estimated to be 9,000 years old, was found in 1903. Older remains from the Upper Late Palaeolithic era (12,000–13,000 years ago) have been found. The caves, produced by the activity of an underground river, contain stalactites and stalagmites.

Cheddar Gorge, including the caves and other attractions, has become a tourist destination. In a 2005 poll of Radio Times readers, following its appearance on the 2005 television programme Seven Natural Wonders, Cheddar Gorge was named as the second greatest natural wonder in Britain, surpassed only by Dan yr Ogof caves. The gorge attracts about 500,000 visitors per year.

Geography

Cheddar is a gorge lying on the southern edge of the Mendip Hills. The maximum depth of the gorge is 137 m (449 ft), with a near-vertical cliff-face to the south, and steep grassy slopes to the north. The B3135 road runs along the bottom of the gorge.

The area is underlain by Black Rock Limestone, Burrington Oolite and Clifton Down Limestone of the Carboniferous Limestone Series, which contain ooliths and fossil debris, on top of Old Red Sandstone and by Dolomitic Conglomerate of the Keuper. Evidence for Variscan orogeny is seen in the sheared rock and cleaved shales. In many places weathering of these strata has resulted in the formation of immature calcareous soils.

The gorge was formed by meltwater floods during the cold periglacial periods which have occurred over the last 1.2 million years. During the ice ages permafrost blocked the caves with ice and frozen mud and made the limestone impermeable. When this melted during the summers water was forced to flow on the surface, and carved out the gorge. During warmer periods the water flowed underground through the permeable limestone, creating the caves and leaving the gorge dry, so that today much of the gorge has no river until the underground Cheddar Yeo emerges in the lower part from Gough's Cave. The river is used by Bristol Water, who maintain a series of dams and ponds which supply the nearby Cheddar Reservoir, via a 137-centimetre (54 in) diameter pipe that takes water just upstream of the Rotary Club Sensory Garden, a public park in the gorge opposite Jacob's Ladder.

Ecology

The gorge is part of a Site of Special Scientific Interest now called Cheddar Complex.

The south side of the gorge is owned and administered by the Marquess of Bath's Longleat Estate. The cliffs on the north side of the gorge are owned by The National Trust. Every year both of the gorge's owners contribute funds towards the clearance of scrub bush and trees from the area. Longleat Estate has fenced off a large part of its land and has introduced goats, as part of a programme to encourage the biodiversity of the area; the goats were intended to replace the sheep that grazed in the gorge until the 1970s. The National Trust announced in March 2007 that they plan to release a flock of sheep on its side of the gorge for the same purpose, but will first consult local residents and interested parties on whether to fence off the gorge or introduce cattle grids to prevent the sheep from straying. There is already a small flock of feral Soay sheep in the gorge. Other notable species at the gorge include dormice, yellow-necked mice, slow worms and adders and the rare large blue butterfly (Maculinea arion), and small pearl-bordered fritillary (Boloria selene).

A wide variety of wild birds can be seen in the gorge including Peregrine Falcons, buzzards, kestrels, ravens and the Grasshopper Warbler (Locustella naevia).

The flora include chalk grassland-loving species such as marjoram and wild thyme. The Cheddar pink, (Dianthus gratianopolitanus), also known as firewitch, a type of Dianthus only grows in the wild in the gorge. It was once common in the gorge but declined after being picked by collectors. Now, following legal protection, the flowers are making a slow comeback. The nationally rare little robin geranium (purpureum), and Cheddar bedstraw (Galium fleurotii) and the nationally scarce species include slender tare (Vicia tenuissima), dwarf mouse-ear (Cerastium pumilum) and rock stonecrop (Sedum forsteranum) also occur in the gorge. It is one of the very few areas in southern Britain where the lichens Solorina saccata, Squamaria cartilaginea and Caloplaca cirrochroa can be found.

The gorge is also an important site for whitebeams and in 2009 a survey was carried out by botanists from the Welsh National Herbarium as part of a nationwide survey of whitebeams. Among the eight secies identified were three new species previously unknown to science. Nineteen specimens with oval-shaped leaves, were named the "Cheddar whitebeam", Sorbus cheddarensis, fifteen specimens with roundish leaves and greyish brown bark were named the "Twin Cliffs whitebeam", Sorbus eminentoides, and thirteen with long, narrow leaves were named "Gough’s Rock whitebeam", Sorbus rupicoloides. The Cheddar whitebeam, which has evolved as a cross between the common whitebeam and the grey-leaved whitebeam, is unique to the gorge, but its survival is threatened by the goats that were introduced specifically to keep down the growth of new trees and encourage the proliferation of rare plant species such as the Cheddar pink. Cuttings have been taken from the trees to be grafted and grown on at the Welsh National Herbarium.

Caves

Two main caves are open to the public – the extensive Gough's Cave and the smaller Cox's Cave, named after their respective discoverers. Both are known for their geology, and it has been suggested that the caves were the site of prehistoric cheese-making. Gough's cave, which was discovered in 1903, leads around 400 m (437 yd) into the rock-face, and contains a variety of large rock chambers and formations. Cox's Cave, discovered in 1837, is smaller but contains many intricate formations. A further cave houses a children's entertainment walk known as the "Crystal Quest".

The Gorge's many caves are home to colonies of Greater and Lesser horseshoe bats.

In 1999 the Channel 4 Time Team television programme investigated Cooper's Hole to see if they could find evidence of Palaeolithic human activity.

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The Cataract Gorge is a river gorge in Launceston, northern Tasmania, Australia and is one of the region's premier tourist attractions.

A pathway, known as the King’s Bridge-Cataract Walk, and originally built by volunteers in the 1890s, runs along the north bank of the Cataract Gorge, and is a popular tourist destination.

The chairlift crossing the Gorge is the longest single span chairlift in the world, with the longest span being 308 m (924 ft). The chairlift, built in 1972, has a total span of 457m.

Before the Hydro Dam was built in the 1950s upstream, flood waters could rise up as high as 12 metres. In the past, there was a power station at Duck Reach, about 2.5 kilometres from the suspension bridge. It was washed away in the floods of 1929, rebuilt and then decommissioned when the new Hydro Dam was finished in 1955. The building is now an interpretive museum.

The First Basin on the southern side features a swimming pool and an open area surrounded by bushland.

At the lower end of the Gorge, the South Esk spills into the Tamar River going under King's Bridge on the way. This was the only bridge leading north out of the city for nearly 100 years.

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Gough's Cave is located in Cheddar Gorge on the Mendip Hills, in Cheddar, Somerset, England. The cave is 90 metres (295 ft) deep and is 2.135 kilometres (1.33 mi) long, and contains a variety of large chambers and rock formations. It contains the Cheddar Yeo, the largest underground river system in Britain.

History

The initial sections of the cave, previously known as Sand Hole, were accessible prior to the 19th century. Between 1892 and 1898 Richard Cox Gough, who lived in Lion House in Cheddar, found, excavated and opened to the public further areas of the cave, up to Diamond Chamber, which is the end of the show cave today. Electric lighting was installed in the show caves in 1899.

The extensive flooded parts of the cave system were found and explored between 1985 and 1990.

Human remains and occupation

In 1903 the remains of a human male, since named Cheddar Man, were found a short distance inside Gough's Cave. He is Britain’s oldest complete human skeleton, having been dated to approximately 7150 BCE. There is a suggestion that the man died a violent death, perhaps related to cannibalism, although this has not been proven. Mitochondrial DNA taken from the skeleton has been found to match that of Adrian Targett, a man living in the local area today, indicating that Cheddar Man is a very distant ancestor. The remains currently reside in the Natural History Museum in London, with a replica in the Cheddar Man and the Cannibals museum in the Gorge. Other human remains have also been found in the cave.

In 2007 a carving of a mammoth, estimated to be 13,000 years old, was found in the cave.

In 2010 further human bones from the cave were examined, which ultra-filtration carbon dating dated to around the end of the ice age 14,700 years ago. A second technique, using the Alicona 3D microscope, showed that the flesh had been removed from the bones using the same tools and techniques used on animal bones. According to Professor Chris Stringer of the Natural History Museum this supports theories about cannibalism amongst the people living or visiting the cave at that time.

Access and Description

The first 820 metres (2,690 ft) of the cave are open to the public as a show cave, and this stretch contains most of the more spectacular formations. The greater part of the cave's length is made up of the river passage, which is accessible only by cave diving.

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