~ Mother Earth ~

last SG · 2005-03-28T01:23:34+00:00

Celtic Sea The Celtic Sea (Irish: An Mhuir Cheilteach) is the area of the Atlantic Ocean off the south coast of Ireland. It is bounded to the east by Saint...

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Canadian Shield

The Canadian Shield is a large craton in eastern and central Canada and adjacent portions of the United States, composed of bare rock dating to the Precambrian Era (between 4.5 billion and 540 million years ago). It is also called the Precambrian Shield, Laurentian Shield or Laurentian Plateau.

The Canadian Shield

Regional extent

The Shield is approximately U-shaped, with the U's points in the arctic. It covers much of Greenland; Labrador; most of Quebec north of the St. Lawrence River; much of Ontario outside the southern peninsula between the Great Lakes; the Adirondack Mountains of northern New York; parts of Michigan, Wisconsin, and Minnesota; the central portion of Manitoba away from Hudson Bay and the Great Plains; northern Saskatchewan; a small portion of north-eastern Alberta; and the mainland northern Canadian territories to the east of a line extended north from the Saskatchewan/Alberta border (Northwest Territories and Nunavut). In total it covers approximately 8 million square kilometers.

Geology

Such a large area of exposed, old rock requires some explanation. The current surface expression of the Shield is one of very thin soil lying on top of the bedrock, with many bare outcrops. This arrangement was caused by severe glaciation during the last ice age, which covered the Shield and scraped the rock clean. The multitude of rivers and lakes in the entire region is caused by the watersheds of the area being so young and in a state of sorting themselves out with the added effect of post-glacial rebound. The Shield was originally an area of very large mountains and much volcanic activity, but over the millennia the area was eroded to its current topographic appearance of relatively low relief.

Mountains have deep roots and float on the denser mantle much like an iceberg at sea. As mountains erode, their roots rise and are eroded in turn. The rocks that now form the surface of the Shield were once far below the earth's surface. The high pressures and temperatures at those depths provided ideal conditions for mineralization.

Mining and economics

The Shield is one of the world's richest areas in terms of mineral ores. It is filled with substantial deposits of nickel, gold, silver, and copper. Throughout the north of Canada there are many mining towns extracting these minerals. The largest, and best known, is Sudbury, Ontario. Sudbury is an exception to the normal process of forming minerals in the Shield since the Sudbury Basin is believed to be an ancient meteorite impact crater.

The Shield, particularly the portion in the Northwest Territories, has recently been the site of several major diamond discoveries. The kimberlite pipes in which the diamonds are found are of relatively recent origin, and one theory of their origin suggests that the Shield was at some time in the past above a hot spot in Earth's mantle (much like the one that formed Hawaii, but under land rather than ocean). The spot lifted the surrounding landscape as the continent drifted over it, forming the pipes in various locations. The line of subsurface mountains that runs from the eastern seaboard of the United States nearly to Europe before culminating in the Challenger Seamount would, if run backwards in time, follow a path that matches what is suggested.

The Shield is also covered by vast boreal forests that support an important logging industry.

Issue #71

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Mount Tambora

Mount Tambora is a volcano on the Indonesian island of Sumbawa. In 1815, the volcano of Tambora suffered the most violent eruption in modern times. Beginning in early April 1815 and continuing through the middle of July 1815, its explosion affected an immense area that included the Maluku Islands (Molucca Islands), Java, and portions of Sulawesi (Celebes), Sumatra, and Borneo. Heavy ashrains also specifically affected the islands of Bali and Lombok.

Mount Tambora, Indonesia, seen from space

Elevation: 2,850 metres (9,350 feet)
Coordinates: 8° 15' 0'' S 118° 0' 0'' E
Location: Lesser Sunda Islands (Indonesia)
Type: Stratovolcano

The most violent eruption in recorded history

Mount Tambora erupted on April 10, by most accounts, and the eruption lasted from April 10 to April 15. The explosion, of Volcanic Explosivity Index 6-7, ejected an estimated 100 cubic km of melted rock, weighing approximately 2-3 × 10^14 kg. This left a caldera 7 km (4 mi) across. Before the explosion, Mount Tambora was approximately 4200m (13,000 ft) high; after the explosion, it was only 2,851 m (about 9,000 ft) high. Tambora was not, however, the most violent volcanic eruption of all time. The eruption of Santorini (Thira) in Greece in about 1650 BC was greater, but no accounts of the explosion survive, possibly because it destroyed the nearby civilizations which might have recorded it. A much larger eruption of Toba roughly 75,000 years ago has been theorized to have reduced the worldwide population of mankind (Homo erectus, Homo neanderthalensis and Homo sapiens) at the time to just a few thousand individuals, though definite evidence is lacking. One of the greatest known eruptions was of the Yellowstone Caldera about 2,000,000 years ago, an event which almost certainly caused an extended period of volcanic winter with far-reaching effects. Even greater undiscovered cataclysmic eruptions have certainly occurred in the Earth's 4.7 billion year history.

Indonesia has more active volcanoes than any other nation.

Effects

All vegetation on several nearby islands was destroyed. About 10,000 people died immediately from the eruption, with about 82,000 dying from later consequences of the disaster. Worldwide deaths caused by starvation and disease due to climate change are more difficult to quantify.

The eruption sent so much volcanic ash into the atmosphere that weather patterns around the world were altered, causing the following year to be nicknamed the "Year Without a Summer".

Quotes from 1815 accounts of the eruption

Explosion

"The concussions produced by its explosions were felt at a distance of a thousand miles (1,600 km) all round; and their sound is said to have been heard even at so great a distance as seventeen hundred miles (2,700 km). In Java the day was darkened by clouds of ashes, thrown from the mountain to that great distance (three hundred miles or 500 km), and the houses, streets, and fields, were covered to the depth of several inches with the ashes that fell from the air. So great was the quantity of ashes ejected, that the roofs of houses forty miles (65 km) distant from the volcano were broken in by their weight. The effects of the eruption extended even to the western coasts of Sumatra, where masses of pumice were seen floating on the surface of the sea, several feet in thickness and many miles in extent."

Pyroclastic flow

"From the crater itself there were seen to ascend three fiery pyroclastic columns, which, after soaring to a great height, appeared to unite in a confused manner at their tops. Soon, the whole of the side of the mountain next to the village of Sang'ir seemed like one vast body of liquid fire. The glare was terrific, until towards evening, when it became partly obscured by the vast quantities of dust, ashes, stones, and cinders thrown up from the crater. Between nine and ten o'clock at night the ashes and stones began to fall upon the village of Sang'ir, and all round the neighbourhood of the mountain."

Atmospheric disturbance

"The heat triggered a 'dreadful whirlwind', which blew down nearly every house in the village, tossing the roofs and lighter parts high into the air. In the neighbouring sea-port the effects were even more violent, the largest trees having been torn up by the roots and whirled aloft. Before such a furious tempest no living thing could stand. Men, horses, and cattle were whirled into the air like so much chaff, and then dashed violently down on the ground. The sea rose nearly twelve feet above the highest tide-mark, sweeping away houses, trees, everything within its reach. This whirlwind lasted about an hour."

Gradual decrease

"The 'awful internal thunderings of the mountain' continued with scarcely any intermission until the 11th of July, when they became more moderate, the intervals between them gradually increasing till the 15th of July, when they ceased. Almost all the villages for a long distance round the mountain were destroyed. By far the greatest part of this destruction was wrought by the violence of the whirlwind which accompanied the eruption."

Issue #72

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Strait of Gibraltar

The Strait of Gibraltar (Spanish: Estrecho de Gibraltar) is the strait which separates the Atlantic Ocean from the Mediterranean Sea. On the northern side is Spain and Gibraltar, on the southern side Morocco and Ceuta (a Spanish exclave in North Africa). Its boundaries were known to antiquity as the Pillars of Hercules. There are some small islands, like the disputed Isla Perejil, that is claimed by Spain and Morocco.

The Strait of Gibraltar as seen from space.

The Strait of Gibraltar has a very strategic location. Ships that travel from the Atlantic to the Mediterranean and vice versa, pass through this strait overlooked by the Rock of Gibraltar. Also, very many people who travel from Europe to Africa and vice versa, travel through this strait. During World War II, the British controlled the straits from their nearby base. German submarines entering the Mediterranean Sea were effectively trapped, because they couldn't leave on the surface and the undersea currents were too strong to leave underwater.

The depth is about 300 m, and it is about 14 km wide at its narrowest point.

For a number of years the Spanish and Moroccan governments have been jointly investigating the feasibility of a tunnel underneath the strait, similar to the Channel tunnel between England and France. A new three-year study for a railway tunnel was announced in 2003.

Also, a group of American and British engineers have studied the feasibility of building a bridge to span the straits. Such a bridge would be of a combination suspension-truss design and would dwarf any existing bridge in height (over 3,000 feet) and length (15 km).

Issue #73

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Yosemite Falls

Yosemite Falls is the highest waterfall in North America. Located in Yosemite National Park in the Sierra Nevada mountains of California, it is a breathtaking sight best viewed in the late spring.

Yosemite Falls seen from the valley floor.

The total 2,425 foot distance from the top of the upper falls to the base of the lower falls qualifies Yosemite Falls as the sixth highest waterfall in the world. Although often referred to as a "two-stage drop", the falls actually consist of three sections:

-- The 1,430 foot plunge qualifies the Upper Falls alone as one of the twenty highest waterfalls in the world. Trails up from the valley floor and down from other regions of the park outside the valley proper lead to both the top and base of upper Yosemite Falls. The upper fall is formed by the swift waters of Yosemite Creek which, after meandering through Eagle Creek Meadow, hurls themselves over the edge of a hanging valley in a spectacular and deafening show of force.

-- Between the two obvious main plunges there are a series of cascades and smaller plunges generally referred to as "the cataracts". Taken together these account for another drop of 675 feet, nearly twice the height of the lower falls. Because of the layout of the area, the lack of any major drops in this section and the lack of public access they are all too easy to overlook. Most viewpoints in the valley miss them entirely. The best vantage points for the cataracts are found along the Yosemite Falls trail. Warning: Individuals climbing down from the falls trail towards the cataracts for a better look have required an expensive helicopter rescue due to steep and slippery terrain and features.

-- The final 320 foot drop of the Lower Falls, adjacent to an accessible viewing area provides countless park visitors with a close look at this spectacular waterfall. Yosemite Creek emerges from the base of the lower falls and flows into the Merced River nearby. Like many areas of Yosemite the plunge pool at the base of the lower falls is surrounded by dangerous jumbles of talus made even more treacherous by the high humidity and resulting slippery surfaces.

A photo which shows about 75% of Yosemitie Falls 2,425 foot drop, making the Falls higher than the Sears Tower and the Eiffel Tower combined.

In years of little snow, the falls may actually cease flowing altogether in late summer or fall. A very small number of rock climbers have taken the opportunity to climb the normally inaccessible rock face beneath the falls, although this is an extraordinarily dangerous undertaking; a single afternoon thunderstorm could restart the falls, sweeping the climbers off the face.

The Lower Falls are easily accessible near the Yosemite Lodge in Yosemite Valley. The top of the Upper Falls may be reached via a steep, strenuous, and usually crowded 3.5 mile hike beginning near the Sunnyside Walk-in Campground. The Upper Falls may also be reached via several routes from the Tioga Road to the north.

Issue #74

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Avon Gorge

The Avon Gorge is a 2.5 km (1.5 mi) long gorge on the River Avon in Bristol, South West England. The gorge runs south to north through a limestone ridge 2 km west of Bristol city centre and about 5 km 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.

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

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 the village and the National Trust forest it is situated in. There is an Iron Age hill fort on the side of the gorge in Leigh Woods.

The Clifton Suspension Bridge, designed by Isambard Kingdom Brunel, spans the gorge and is perhaps the best known landmark in Bristol. 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 railway to Portishead, which was closed by the Beeching Axe in the 1960s, but has now been reopened for freight traffic as far as Royal Portbury Dock, 4 km (2.5 mi) downstream.

At various times the sides of the gorge have been quarried, leaving steep gorge walls, now popular with climbers and a habitat for Peregrines.

Issue #75

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Novaya Zemlya

The archipelago of Novaya Zemlya (Russian: "New Land"; formerly known as Nova Zembla) consists of two major islands in the Arctic Ocean in the north of Russia, separated by the narrow Matochkin Strait, and a number of smaller ones. The two main islands are Severny (northern) and Yuzhny (southern). Novaya Zemlya separates the Barents Sea from the Kara Sea. The total area is about 90,650 km².

Location of Novaya Zemlya

The area is very mountainous, as geologically Novaya Zemlya is the continuation of the Ural Mountains. It is separated from the mainland by the Kara Strait. The mountains reach a height of 1,070 meters. The northern island contains many glaciers, while the southern one has a tundra climate. Natural resources include copper, lead and zinc. The islands have a small population, which subsists mainly on fishing, trapping and seal hunting.

The islands' indigenous population of about 100 persons are Nenetses, while the Russians knew of Novaya Zemlya from the 11th or 12th century, when traders from Novgorod visited the area. For western Europeans, the search for the Northeast passage in the 16th century led to its exploration. The first visit was by Hugh Willoughby in 1553. Willem Barents in 1596 rounded the north point of Novaya Zemlya, and wintered on the east coast near the northern tip. During this voyage the west coast was mapped.

Novaya Zemlya, satellite image from NASA

A nuclear testing site named North Test Site was constructed in the mid-1950s, and existed during much of the Cold War. "Site A", Chernaya Guba (70.7N 54.6E), was used mostly from 195562. "Site B", Matochkin Shar (73.4N 54.9E) was used for underground tests in 196490. "Site C", Sukhoy Nos (73.7N 54.0E), was used from 195762 and was the 1961 explosion site of Tsar Bomba, a record 50-megaton burst. Other tests occurred elsewhere throughout the islands, with an official testing range covering over half of the landmass. In 1989 glasnost helped make the Novaya Zemlya testing activities public knowledge and opened the door for environmental assessment, and only a year later Greenpeace activists staged a protest at the site.

The last nuclear test explosion was in 1990 (also the last of the Soviet Union and Russia anywhere). Today only a limited amount of systems research is done at Matochkin Shar.

Issue #76

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Cape Horn

Cape Horn is often said to be the southernmost point of South America. It is located in the Tierra del Fuego archipelago. The southernmost point on the mainland is Cape Froward.

Cape Horn

The cape was first rounded by a European on January 26, 1616, by the Dutch expedition of Willem Schouten and Jacob Le Maire. They named it Kaap Hoorn after the city of Hoorn, Schouten's birthplace. The Spanish name of the place is derived from the Dutch: Cabo de Hornos.

Cape Horn from the South

Cape Horn is notorious because of the poor weather conditions that made it difficult to round in sailing ships. The open waters of the Drake Passage, south of the Cape, offer ample sea room for maneuvering, while the narrow Strait of Magellan through the Tierra del Fuego islands can offer a slow and difficult passage.

The Cape lies within Chilean territorial waters, and the Chilean Navy supports a lighthouse keeper and his family. The government station consists of a residence, utility building, chapel, and lighthouse. A short distance from the main station is a large sculpture featuring the silhouette of an albatross. The terrain is entirely treeless, although quite lush due to the frequent precipitation.

Main building of Chilean station

Rounding Cape Horn is considered the sailing-equivalent of climbing Mount Everest. All major yacht races go around it with the prevailing winds except for the Global Challenge.

Approaching Cape Horn from the SW

Issue #77

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Tower Bridge

Tower Bridge is a bridge in London, England, over the River Thames. It is close to the Tower of London, which gives it its name. It is occasionally incorrectly referred to as London Bridge, which is in fact the next bridge upstream.

Tower Bridge over the River Thames, London, England.

Design

In the second half of the nineteenth century increased commercial development in the East End of London led to a requirement for a new river crossing downstream of London Bridge. However, a traditional bridge could not be built because it would cut off access to the port facilities situated at that time in the Pool of London, between London Bridge and the Tower of London. A tunnel beneath the Thames, the Tower Subway, was opened in 1870, but it could only accommodate pedestrian traffic.

The bridge is illuminated at night.

A Special Bridge or Subway Committee was formed in 1876 to find a solution to the river crossing problem. It opened the design of the new crossing to public competition. Over 50 designs were submitted, including one from civil engineer Sir Joseph Bazalgette. However, the evaluation of the designs was surrounded by controversy, and it was not until 1884 that a design submitted by Horace Jones, the City Architect, was finally approved.

Jones' design was for a bascule bridge 800 feet (244 m) in length with two towers each 213 feet (65 m) high, built on piers. The central span of 200 feet (61 m) between the towers is split into two equal bascules or leaves, which can be raised to an angle of 83 degrees to allow river traffic to pass through. Although each bascule weighs over 1,000 tons, they are counterbalanced to minimise the force and time required to raise them, and they can be raised in under one minute. The original hydraulic raising mechanism was powered by pressurised water stored in six accumulators. Water was pumped into the accumulators by steam engines. Although the bridge is raised today electrically, the original steam engines are preserved as a visitor attraction.

Construction

Construction of the bridge started in 1886 and took 8 years, employing 5 major contractors and 432 construction workers. Two massive piers containing over 70,000 tons of concrete were sunk into the river bed to support the construction. Over 11,000 tons of steel provided the framework for the towers and walkways. This was then clad in Cornish granite and Portland Stone, both to protect the underlying steelwork and to give the bridge a more pleasing appearance.

Tower Bridge under construction, September 28, 1892

Jones died in 1887, and his chief engineer, Sir John Wolfe-Barry, took over the project. Wolfe-Barry replaced Jones' original mediaeval style of facade with the more ornate Victorian gothic style that makes the bridge such a distinctive landmark.

The bridge was opened in 1894. The official opening ceremony was conducted by the Prince of Wales, the future King Edward VII of the United Kingdom and his wife, Alexandra of Denmark.

Tower Bridge today

The high-level walkways between the towers gained an unpleasant reputation as a haunt for prostitutes and pickpockets and were closed in 1910. They have now been reopened as part of the Tower Bridge Experience, a museum/historical exhibition mostly housed in the bridge's twin towers. The exhibition also includes photos, holograms and a film detailing the build, along with access to the original steam engines that once powered the Bridge bascules, housed in a building close to the south end of the Bridge.

A "Behind the Scenes" tour can be booked in advance, on which it is possible to see the bridge's command centre (where the raising of the bridge is controlled when a vessel passes underneath). The bascules of the bridge are raised around five hundred times a year.

Although river traffic is now a fraction of what it used to be, it still takes priority over road traffic. This nearly caused a diplomatic incident in 1997, when the motorcade of United States President Bill Clinton got stuck on Tower Bridge while the bascules were unexpectedly opened.

The bridge sits almost directly above the Tower Subway, the world's first underground tube railway (1870), which, until the Bridge was opened, was the shortest way to cross the river from Tower Hill to Tooley Street.

Nearby places

The bridge is near the Tower of London, St Katharine Docks, and Shad Thames.

The north end is near Tower Hill tube station, Tower Gateway DLR station (Docklands Light Railway). The south end is about 10 minutes' walk away from London Bridge station.

To the south of Tower Bridge is Tower Bridge Road which is part of the London Inner Ring Road.

Sequence of photos showing Tower Bridge opening

Issue #78

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Lake Chad

Lake Chad (in French: Lac Tchad) is a large, shallow lake in Africa. It is economically very important, providing water to more than 20 million people living in the countries which surround it - Chad, Cameroon, Niger and Nigeria. It is located mainly in the far west of Chad, bordering on northeastern Nigeria. The lake possesses many small islands and mudbanks, and its shorelines are largely comprised of marshes. Because it is very shallow - only 7 metres at its deepest - its area is particularly sensitive to small changes in average depth, and it consequently also shows seasonal fluctuations in size. It has no apparent outlet but its waters percolate into the Soro and Bodele depressions.

Map of Lake Chad and the surrounding region

The lake is believed to be a remnant of a former inland sea which is estimated to have covered an area of 300,000 km² 6,000 years ago. It was one of the largest lakes in the world when first surveyed by Europeans in 1823, but it has shrunk considerably since then. Climate change and increased demands on the lake's water have accelerated its shrinkage over the past 40 years. In the 1960s it had an area of more than 26,000 km², making it the fourth largest lake in Africa. By 2000 its extent had fallen to less than 1,500 km². This is due to reduced rainfall combined with greatly increased amounts of irrigation water being drawn from the lake and the rivers which feed it, the largest being the Chari/Logon system, which originates in the mountains of the Central African Republic. It seems likely that the lake will shrink further and perhaps even disappear altogether in the course of the 21st century.

Lake Chad in a 2001 satellite image, with the actual lake in blue, and vegetation on top of the old lake bed in green. Above that, the changes from 1973 to 1997 are shown.

Indeed, the lake dried up in 1908 and again in 1984 and has an average depth of only 1.5 metres. As it retreats every summer, recessional agriculture is practised, while the Buduma people fish from canoes. There are many floating islands in the lake, which is also home to hippopotamuses and crocodiles.

Lake Chad Watershed

Issue #79

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Orinoco

With a length of 2,140 km, the Orinoco is one of the largest rivers of South America. It flows through Venezuela, having its source in Parima on the Brazilian frontier, and from there making a wide arc, first flowing southwest, then west, north and finally northeast, into the Atlantic Ocean and the Gulf of Paria.

Bridge over the Orinoco at Ciudad Bolívar, Venezuela (2004)

At its mouth it forms a wide delta that branches off into hundreds of rivers and waterways that flow through 41,000 km² of swampy forests. In the rainy season it can swell to a breadth of 22 kilometres and a depth of 100 meters. Most of the important Venezuelan rivers are tributaries of the Orinoco, the largest being the Caroní, which joins the Orinoco at Puerto Ordaz, close to the Llovizna Falls. The river is navigable for most of its length, and dredging enables ocean ships to go as far as Ciudad Bolívar, 435 km upstream. You can find it at about 9 degrees north (latitude) and 60 degrees west (longitude).

Map of Lower Orinoco, 1897

A peculiarity of the Orinoco river system is the Casiquiare canal, which starts as an arm of the Orinoco, and finds its way to the Rio Negro, a tributary of the Amazon, thus forming a 'natural canal' between the Orinoco and the Amazon.

Irish singer Enya had a hit with Orinoco Flow (Sail Away). Also, The Boto, or Amazon River Dolphin, is known to inhabit the Orinoco River system.

This region also contains large tar sands which may be a source of future oil production.

The city of Guayana, and the Alcaldia Mayor de Caroní (ALMACARONÍ) has for the past 15 years conducted a swim race of the rivers Orinoco and Caroní where around 900 competitors meet. The "Paso a Nado Internacional de los Rios Orinoco-Caroní" is celebrated every year close to 19th of April and on a sunday. This competition has gained importance worldwide and is one of the swim meets with the most competitors worldwide.

Issue #80

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Banks Peninsula

Banks Peninsula is located in the Canterbury region on the east coast of the South Island of New Zealand, partly surrounded by the Pacific Ocean, and adjacent to the largest city in the South Island, Christchurch, which has approximately 340,000 residents. The peninsula has a land area of approximately 1,000 km². The Banks Peninsula District Council has 7,833 residents (2001 census).

Banks Peninsula, including Lyttelton Harbour and Akaroa Harbour, in Canterbury, New Zealand. The peninsula is roughly circular in shape, with many bays, and two deep harbours.

History

There were three phases of Maori settlement on the peninsula. Waitaha were the earliest inhabitants, followed by Kati Mamoe. Ngai Tahu took over in the 17th century.

The first European sighting of the peninsula was by Captain James Cook during his first circumnavigation of New Zealand in 1769, and he named it in honour of the Endeavour's botanist, Joseph Banks. It is famous as one of his two cartographical errors - unable to see the low plains adjoining the peninsula he charted it as an island. Distracted by a phantom sighting of land to the southeast, he sailed away before exploring any closer and never discovered the two good harbours.

By the 1830s, Banks Peninsula had become a European whaling centre, to the detriment of the Maori who succumbed in large numbers to disease and inter-tribal warfare exacerbated by the use of muskets. Two significant events in the assumption of British sovereignty over New Zealand occurred at Akaroa. First, in 1830 the Maori settlement at Takapuneke was the scene of a notorious incident. The Captain of the British brig Elizabeth, John Stewart, helped North Island Ngati Toa chief, Te Rauparaha, to capture the local Ngai Tahu chief, Te Maiharanui. The settlement of Takapuneke was sacked. Partly as a result of this massacre, an official British Resident, James Busby, was sent to New Zealand in an effort to stop such atrocities. The events at Takapuneke thus led directly to the signing of the Treaty of Waitangi. Then in 1838 Captain Langlois, a French whaler, decided that Akaroa would make a good settlement to service the whaling ships and "purchased" the peninsula in a dubious land deal with the local Maori. He returned to France, floated the Nanto-Bordelaise company, and set sail for New Zealand with a group of French and German families aboard the ship Comte de Paris, with the intention of forming a French colony on a French South Island of New Zealand.

However, by the time Langlois and his colonists arrived at Banks Peninsula in August 1840, the Treaty of Waitangi had already been signed (the signatories including two chiefs at Akaroa in May) and New Zealand's first Governor, William Hobson, had declared sovereignty over the whole of New Zealand. On hearing of the French plan for colonisation, Hobson quickly dispatched the HMS Britomart from the Bay of Islands to Akaroa with police magistrates on board. While Langlois and his colonists sheltered from unfavourable winds at Pigeon Bay on the other side of the peninsula, the British flag was raised at Greens Point between Akaroa and Takapuneke and courts of law convened to assert British sovereignty over the South Island.

From the 1850s, Lyttelton and then Christchurch outgrew Akaroa, which has developed into a holiday resort and retained many French influences as well as many of its nineteenth century buildings.

Historic harbour defenses dating from 1874 onwards may be found at Ripapa Island in Lyttelton Harbour and at Godley Head.

Geology

Banks Peninsula is the main volcanic feature of the South Island. Geologically, the peninsula is the eroded remnants of two large stratovolcanoes (Lyttelton formed first, then Akaroa). These were formed by intraplate volcanism between approximately eleven and eight million years ago (Miocene) on a continental crust. The peninsula formed as offshore islands, with the volcanoes reaching to about 1,500 m above sea level. Two dominant craters formed Lyttelton and Akaroa Harbours. The Canterbury Plains formed from the erosion of the Southern Alps (an extensive and high mountain range caused by the meeting of the Indo-Australian and Pacific tectonic plates) and from the alluvial fans created by large braided rivers, and are at their widest point where they meet the hilly sub-region of Banks Peninsula. The northern and western flanks of the peninsula are covered with a layer of loess, a layer of rather unstable fine silt deposited by the föhn winds which bluster across the plains. The portion of crater rim lying between Lyttelton Harbour and Christchurch city is known as the Port Hills.

Land use

It is estimated that 98% of the peninsula was once covered by native forest. However, Maori and European settlers successively denuded the forest cover and less than 2% remains today, although some reafforestation is under way. Many English trees, notably walnut, were planted by settlers.

Several sites off the coast of the peninsula are used for mariculture cultivation of mussels.

A large Marine Mammal Sanctuary, mainly restricting set net fishing, surrounds much of the peninsula. The principal aim of this is the conservation of Hector's dolphin, the smallest of all dolphin species. Eco-tourism based around the playful dolphins is now a significant industry in Akaroa.

A relatively small marine reserve called Pohatu is centred on Flea Bay on the south-east side of the peninsula.

A notable feature of the peninsula is the Summit Road. Built in the 1930s, the road is in two sections - one along the crest of the Port Hills from Godley Head (the northern head of Lyttelton Harbour) to Gebbies Pass at the head of the harbour. The second section runs around the crater rim of Akaroa Harbour from 'Hill Top' - the junction with the main Christchurch-Akaroa highway to a point above Akaroa. Both roads afford spectacular views as well as providing vehicular access to many parks, walkways and other recreational features.

Statistics

-- Highest point: Mount Herbert (919 m)
-- Permanent population : 7,600

Issue #81

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Namib Desert

The Namib Desert is a large desert in south western Africa. The name "Namib" is Nama for "enormous" and indeed the desert occupies an area of around 50,000 km²), stretching some 1,000 miles (1,600 km) along the Atlantic Ocean coast of Namibia. Its east-west width varies from 30 to 100 miles (50-160 km).

Dune 7, the highest sand dune in the world, in the Namib Desert, Namibia.

The area is considered to be the oldest desert in the world, having endured arid or semi-arid conditions for at least 80 million years. Its aridity is caused by the descent of dry air cooled by the cold Benguela current along the coast. It has less than 1 cm (0.4 inches) of rain annually and is almost completely barren.

Although the desert is largely unpopulated and inaccessible, there are year-round settlements at Sossusvlei, close to a huge group of sand dunes, which at up to 340 metres high are the tallest sand dunes in the world. Access is via light aircraft from Windhoek (the capital of Namibia, about 300 miles east of the centre of the desert), Swakopmund and Walvis Bay at the north end of the desert, or overland on gravel roads.

The interaction between the water-laden air coming from the sea and the dry air of the desert causes immense fogs and strong currents, causing sailors to lose their way. Along with the Skeleton Coast further north, it is notorious as the site of many shipwrecks. Some of these wrecked ships can be found as much as 50 metres inland, as the desert is slowly creeping westwards into the sea, reclaiming land over a period of many years.

A number of unusual species of plants and animals are found only in this desert.

A plant of the genus Welwitschia, native to the Namib Desert.

The Namib is an important location for the mining of tungsten, salt and diamonds.

Issue #82

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Persian Gulf

The Persian Gulf is an extension of the Gulf of Oman in between the Arabian Peninsula and Iran (Persia).

This inland sea of some 233,000 km² is connected to the Gulf of Oman in the east by the Strait of Hormuz, and its western end is marked by the major river delta of Arvand/Shatt al-Arab river, which carries the waters of the Euphrates and the Tigris. Its length is 989 kilometres separating mainly Iran from Saudi Arabia with the shortest divide of about 56 kilometres in the Strait of Hormuz. The waters are overall very shallow and do not exceed anywhere 60 metres in depth.

NASA satellite image showing the Persian Gulf

Countries with a coastline on the Persian Gulf, called the Persian Gulf States, are (clockwise, from the southeast): United Arab Emirates, Saudi Arabia, Qatar on a peninsula off the Saudi coast, Bahrain on an island, Kuwait and Iraq in the northwest, and Iran in the north. Various small islands lie within the Persian Gulf and some are contested between neighbouring states.

The Persian Gulf and its coastal areas are the largest single source of crude oil and related industries dominate the region.

The Persian Gulf was among the scenes of the Iraq-Iran War that lasted from 1980 to 1988, as with each side attacking the other's oil tankers. In 1991 the Persian Gulf again was the background for a Persian Gulf War as Iraq invaded Kuwait and was subsequently pushed back during what is now predominantly known as the Persian Gulf War, despite the fact that this conflict did not focus primarily on the Persian Gulf.

The natural environment of the Persian Gulf is very rich with good fish grounds, extensive coral reefs and pearl oysters in abundance, but has become increasingly under pressure due to the heavy industrialisation and in particular the repeated major oil spillages associated with the variuous recent wars fought in the region.

Issue #83

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Eyjafjallajökull

Eyjafjallajökull is one of the smaller glaciers of Iceland. It is situated to the north of Skógar and to the west of the bigger glacier Mýrdalsjökull.

Eyjafjallajökull, Iceland

The ice-cap of the glacier covers a volcano (1,666 m in height) which has erupted rather frequently since the ice-age. The last eruption was in 1821-23, causing a fatal glacier run. The crater of the volcano has a diameter of 3-4 km, the glacier covering an extension of about 100 km².

The southern end of the mountain was once part of the Atlantic coastline. The sea now being in a distance of about 5 km from there, the former coastline left behind sheer cliffs with a multitude of beautiful waterfalls, the best known of them being Skógafoss. In case of stark winds, the water of minor falls is even sometimes blown up the mountain.

Issue #84

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Corinth Canal

The Corinth Canal is a canal connecting the Gulf of Corinth with the Aegean Sea. It cuts through the Isthmus of Corinth and separates the Peloponnesus peninsula from the Greek mainland and therefore effectively makes it an island.

The Corinth Canal, Greece

The canal is 6.3 km in length and was built between 1881 and 1893. It saves the 400 km long journey around the Peloponnesus for smaller ships, but since it is only 21 m wide, it is too narrow for modern ocean freighters. The canal is nowadays mostly used by touristic ships; 11,000 ships per year travel through the waterway.

The first attempt to build a canal at the place was carried out in 67 by the Roman emperor Nero, who ordered 6,000 slaves to dig with spades. In the following year Nero died, and his successor Galba abandoned the project, since it appeared too expensive to him.

Bungy jumping at the Corinth Canal.

Issue #85

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Puerto Rico Trench

The Puerto Rico Trench is an oceanic trench located on the boundary between the Caribbean Sea and the Atlantic Ocean. The trench is associated with a complex transition between the subduction zone to the south along the Lesser Antilles island arc and the major transform fault zone or plate boundary that extends west between Cuba and Hispaniola through the Cayman Trench to the coast of Central America. Scientific studies have concluded that an earthquake occurring along this fault zone could generate a significant tsunami.

Location map of the Puerto Rico trench

The island of Puerto Rico lays immediately to the south of the fault zone and the trench. The trench has a maximum a depth of over 8,400 meters and is the deepest point in the Atlantic Ocean.

Geology

The Puerto Rico Trench is located at a boundary between two plates that pass each other along a transform boundary with only a small component of subduction. The Caribbean Plate is moving to the east while the North American Plate is moving to the west. The North American Plate is subducting the Caribbean Plate to the southeast of the trench. This subduction zone explains the presence of active volcanoes over the southeastern part of the Caribbean Sea. Volcanic activity is frequent along the island arc southeast from Puerto Rico to the Coast of South America.

Perspective view of the sea floor of the Atlantic Ocean and the Caribbean Sea. The Lesser Antilles are on the lower left side of the view and Florida is on the upper right. The purple sea floor at the center of the view is the Puerto Rico trench, the deepest part of the Atlantic Ocean and the Caribbean Sea.

Puerto Rico, the United States Virgin Islands, British Virgin Islands and the Dominican Republic do not have active volcanoes, however they are at risk from earthquakes and tsunamis.

Public awareness

Knowledge of the risks has not been widespread among the general public of the islands located near the trench, as governments have generally spoken little about the it for two main reasons. First: tourism is essential for those nations to survive; wider knowledge of the danger may cut revenue generated by the industry. Second: the governments want to prevent fear among the local population.

Since 1988, the Puerto Rican Seismic Society has been trying to use the Puerto Rican media to inform people about a future earthquake that could result in a catastrophic tragedy.

Following the 2004 tsunami that affected more than forty countries in the Indian ocean, many more now fear of the consequences that such an event would bring to the Caribbean. Local governments have begun emergency planning. In the case of Puerto Rico and the US Virgin Islands, the United States government which has been studying the problem for years (see USGS fact sheet from 2001) is increasing its seismic investigations and developing tsunami warning systems.

Earthquake history

In 1918, the city of Mayaguez was hit by the Mayaguez earthquake, which is famous in the area, and caused a tsunami. In 1953, Santo Domingo, Dominican Republic was affected by the Santo Domingo earthquake. Experts blame both tragic earthquakes on the Puerto Rico trench fault.

Puerto Rico in particular has always been an area of concern to earthquake experts because, apart from the 1918 episode, there are frequent cases of tremors in and around the island. A 1981 tremor was felt across the island, while another in 1985 was felt in the towns of Cayey and Salinas. The Mameyes slide, which also happened in 1985, killed dozens in the city of Ponce, but was caused by rains from Tropical Storm Isabel and not directly related to seismic activity.

Tectonic and seismic map of Puerto Rico Trench area. Arrows show direction of plate movements.

Large earthquakes near Puerto Rico and the Virgin Islands.

Earthquake location -- Date -- Magnitude
Hispaniola -- 1953 -- 6.9
Mona Canyon -- 1946 -- 7.5
Hispaniola -- 1946 -- 8.1
Mona Canyon -- 1918 -- 7.5
Anegada Trough -- 1867 -- 7.5
Puerto Rico Trench -- 1787 -- 8.1

Issue #86

poon cho tang SG

Pyrenees

The Pyrenees (French: Pyrénées; Spanish: Pirineos; Occitan: Pirenèus or Pirenèas; Catalan: Pirineus; Aragonese: Perinés; Basque: Pirinioak) are a range of mountains in southwest Europe that form a natural border between France and Spain. They separate the Iberian Peninsula from France, and extend for about 430 km from the Bay of Biscay on the Atlantic Ocean to Cap de Creus on the Mediterranean Sea.

Central Pyrenees, as seen from the summit of the Pic du Midi de Bigorre.

For the most part the main crest forms the Franco-Spanish frontier, with the principality of Andorra sandwiched between them. The principal exception to this rule is formed by the Val d'Aran, which belongs to Spain but lies on the north face of the range. Other minor orographical anomalies include the Cerdagne fall and the Spanish exclave of the town Llívia.

Geography

The Pyrenees are part of the following French départements, from east to west: Pyrénées-Orientales, Aude, Ariège, Haute-Garonne, Hautes-Pyrénées, and Pyrénées-Atlantiques.

Composite satellite image of the Pyrenees (NASA)

The Pyrenees are also part of the following Spanish provinces, from east to west: Girona, Barcelona, Lleida, Huesca, Zaragoza, Navarre, and Guipúzcoa.

Finally, the Pyrenees are also part of the independent principality of Andorra.

The Pyrenees are typically divided into three sections: the Central, the Atlantic or Western, and the Eastern.

The Central Pyrenees extend eastward from the Port de Canfranc to the Val d'Aran, and include the highest summits of the range:

- Aneto or Pic de Néthou (3,404 m) in the Maladetta ridge,
- Mont Posets (3,375 m),
- Mont Perdu or Monte Perdido or Mont Perdut (3,355 m).

In the Atlantic Pyrenees the average elevation gradually decreases from east to west. In the Eastern Pyrenees, with the exception of one break at the eastern extremity of the Pyrénées Ariégeoises, the mean elevation is maintained with remarkable uniformity until a sudden decline occurs in the portion of the chain known as the Albères.

Geology

The Pyrenees are older than the Alps: their sediments were first deposited in coastal basins during the Paleozoic and Mesozoic eras. In the Lower Cretaceous period, the Gulf of Gascony (Bay of Biscay) fanned out, pushing Spain against France and putting large layers of sediment in a vice grip. The intense pressure and uplifting of the Earth's crust first affected the eastern part and stretched progressively to the entire chain, culminating in the Eocene epoch.

The eastern part of the Pyrenees consists largely of granite and gneissose rocks, while in the western part the granite peaks are flanked by layers of limestone. The massive and unworn character of the chain comes from its abundance of granite, which is particularly resistant to erosion, as well as weak glacial development.

Landscape

Four conspicuous features of Pyrenean scenery are:

- the absence of great lakes, such as fill the lateral valleys of the Alps
- the rarity and great elevation of passes
- the large number of the mountain torrents locally called gaves, which often form lofty waterfalls, surpassed in Europe only by those of Scandinavia
- the frequency with which the upper end of a valley assumes the form of a semicircle of precipitous cliffs, locally called a cirque.

Lake of Artouste

The highest waterfall is that of Gavarnie (462 m), at the head of the Gave de Pau; the Cirque de Gavarnie, in the same valley, is perhaps the most famous example of the cirque formation. Not only is there a total lack of those passes, so common in the Alps, which lead across the great mountain chains at a far lower level than that of the neighbouring peaks, but between the two extremities of the range, where the principal highroads and the only railways run between France and Spain, there are only two passes practicable for carriages: the Col de la Perche, between the valley of the Têt and the valley of the Segre, and the Col de Somport or Port de Canfranc, on the old Roman road from Saragossa to Oloron.

A particularly notable feature is La Brèche de Roland, a gap in the ridge line, in tradition created by Roland.

Issue #87

poon cho tang SG

Pyrenees - Cont'd

Natural resources

The metallic ores of the Pyrenees are not in general of much importance, though there are considerable iron mines at Vie de Sos in Ariège and at the foot of Canigou in Pyrénées-Orientales. Coal deposits capable of being profitably worked are situated chiefly on the Spanish slopes but the French side has numerous beds of lignite.

Mineral springs are abundant and very remarkable, and specially noteworthy are the hot springs, in which the Alps, on the contrary, are very deficient. The hot springs, among which those of Bagnères de Luchon and Eaux-Chaudes may be mentioned, are sulphurous and mostly situated high, near the contact of the granite with the stratified rocks. The lower springs, such as those of Bagnères de Bigorre (Hautes-Pyrénées), Rennes les Bains (Aude) and Campagne (Aude), are mostly selenitic and not very warm.

Mountain stream in the summer.

Climate

The amount of the precipitation, including rain and snow, is much greater in the western than in the eastern Pyrenees, which leads to a marked contrast between these sections of the chain in more than one respect. In the first place, the eastern Pyrenees are without glaciers, the quantity of snow falling there being insufficient to lead to their development. The glaciers are confined to the northern slopes of the central Pyrenees, and do not descend, like those of the Alps, far down in the valleys, but have their greatest length in the direction of the mountain chain. They form, in fact, a narrow zone near the crest of the highest mountains. Here, as in the other great mountain ranges of central Europe, there are evidences of a much wider extension of the glaciers during the Ice age. The case of the glacier in the valley of Argelbs in the département of Hautes-Pyrénées is the best-known instance. The snow-line varies in different parts of the Pyrenees from 2,700-2,800 m. above sea-level.

Pyrenees summit in the summer.

Flora and fauna

A still more marked effect of the preponderance of rainfall in the western half of the chain is seen in the aspect of the vegetation. The lower mountains in the extreme west are very well wooded, but the extent of forest declines eastwards, and the eastern Pyrenees are peculiarly wild and barren, all the more since it is in this part of the chain that granitic masses prevail. There is a change, moreover, in the composition of the flora in passing from west to east. In the west the flora, at least in the north, resembles that of central Europe, while in the east it is distinctly Mediterranean in character, though the difference of latitude is only about 1°, on both sides of the chain from the centre whence the Corbières stretch north-eastwards towards the central plateau of France. The Pyrenees are relatively as rich in endemic species as the Alps, and among the most remarkable instances of that endemism is the occurrence of the sole European species of Dioscorea (yam), Dioscorea pyrenaica, at a single high site in the central Pyrenees, and that of the monotypic genus Xatardia, only on a high alpine pass between the Val d'Eynes and Catalonia. The genus most abundantly represented in the range is that of the saxifrages, several species of which are endemic here.

Pic de Bugatet in the Néouvielle Natural Reserve

In their fauna also the Pyrenees present some striking instances of endemism. The Pyrenean desman or water-mole (Galemys pyrenaicus) is found only in some of the streams of the northern slopes of these mountains, the only other member of this genus being confined to the rivers of the Caucasus in southern Russia. Among the other peculiarities of the Pyrenean fauna are blind insects in the caverns of Ariège, the principal genera of which are Anophthalmus and Adelops. The Pyrenean Ibex mysteriously became extinct in January of 2000, and the last female Pyrenaic bear was shot dead on November 2004.

Sports

Both sides of the Pyrenees are popular spots for winters sports, like alpine ski and mountaineering. Some resorts are Formigal, Panticosa, Baqueira-Beret. Pyrena is a mushing competition held in the Pyrenees.

Issue #87

poon cho tang SG

Sea of Okhotsk

The Sea of Okhotsk (from the Russian Okhotskoe more) is a part of the western Pacific Ocean, lying between the Kamchatka Peninsula and the disputed Russo-Japanese Kurile Islands on the east, the Japanese island of Hokkaido to the south and the island of Sakhalin, the Amur province of Siberia (or Outer Manchuria) and eastern Siberia from the Shantar Islands to Okhotsk on the west.

Sea of Okhotsk

The Sakhalin Gulf and the Gulf of Tartary connect it with the Sea of Japan on the west of the island of Sakhalin, and on the south of this island by the La Perouse Strait.

Most of the Sea of Okhotsk, except for the area around the Kuril Islands, is frozen during the winter. Aside from offshore islands, the only island is the remote, tiny St Jonas ("Ostrov Svyatovy Iony"). In the summer, the icebergs melt and the sea becomes navigable again.

Cities by the Sea of Okhotsk include:

- Palana, Russia
- Magadan, Russia
- Okhotsk, Russia
- Oktyabarsky, Russia
- Yuzhno Sakhalinsk (Toyohara), Sakhalin
- Abashiri, Japan
- Monbetsu, Japan
- Wakkanai, Japan

In the Japanese language, the sea was traditionally called Hokkai, or "north sea." However, because this term is now used to refer to the North Sea in Europe, the name has changed to Ohotsukukai, a transliteration of the Russian name.

Issue #88

poon cho tang SG

Karelian Isthmus

The Karelian Isthmus is the narrow stretch of land between the Gulf of Finland and Lake Ladoga in northwestern Russia. The city of Vyborg and the town of Priozersk are situated on the northwestern end of the isthmus. In the southeast it reaches to Saint Petersburg. Since World War II, when the fronts moved back and forth over the isthmus, it belongs to the Leningrad Oblast of Russia.

Map of the Karelian Isthmus. Shown are important towns, the current Finnish-Russian border in the North-West and the pre-Winter War border further South.

In the first millennium, Finnic people wandered to the Karelian Isthmus.

In 11th century, Sweden and Novgorod started to compete tax holding rights. Sweden gained them in area near Viipuri and Novgorod in other parts of isthmus.

During 17th century Sweden gained the whole isthmus and also Ingria. In this time many Karelians escaped to Tver's Karelia.

From 1721-1812 the isthmus belonged to the Russian Empire, won in the Great Northern War that started with the Russian conquest of Ingria where the new imperial capital, Saint Petersburg, was founded (1703) in the southern end of the isthmus, in place of old Swedish town Nyenskans. Then in 1812, the northwestern half was transferred, as a part of Old Finland, to the semi-autonomous Grand Duchy of Finland, created in 1809 and in a personal union with Russia.

Due to the rich soil, rich fishing waters and the proximity to Saint Petersburg, the Karelian Isthmus became the wealthiest part of Finland once the industrial revolution had gained momentum in the 19th century. When Finland declared its independence in 1917, the isthmus remained Finnish.

In November 1939, the Soviet Union invaded Finland in what became known as the Winter War. Soviet forces were able to penetrate the well-defended Mannerheim Line across the isthmus in early 1940. Finland ceded the Karelian isthmus to the Soviet Union in the Peace of Moscow.

One year later, in 1941, Germany invaded the Soviet Union in Operation Barbarossa which led to the Great Patriotic War for the Russians and the Continuation War for the Finns. Finland initially regained the lost territory (co-belligerent with Nazi Germany), reaching the Russian side of the border of 1939 and seen by the Russians as indirectly contributing to the Siege of Leningrad.

On 9 June 1944, strong Soviet forces opened a counter-offensive and pushed the front from Leningrad to Vyborg in ten days. In the Battle of Tali-Ihantala, 25 June9 July, the Finns concentrated their military strength and brought the offensive to a halt at the River Vuoksi, in the northwesternmost part of the isthmus, at the closest point only 40 kilometers from the border of 1940, that again was recognized by Finland in the Peace of Paris, 1947. Since then the isthmus has belonged to the Leningrad Oblast and been inhabited by Russian people.

After the wars most of the old Finnish names were renamed to Russian ones.

Issue #89

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