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98-426: The population of the atoll was 1,081 in 2000, on an area of 4.5 km. The islands constitute a double atoll forming the number eight, with a total length of 11.5 kilometers (7.1 mi; 6.2 nmi) and up to 7 kilometers (4.3 mi; 3.8 nmi) wide; however, most of reef on the southern rim is submerged or poorly developed. The northern and eastern rims have several relatively large islets. The western lagoon

196-415: A commensal relationship , for example brittle stars , who climb the coral to get themselves off the seafloor, helping them to catch food particles, or small zooplankton, as they drift by. This is in sharp contrast with the typical deep-sea habitat, where deposit-feeding animals rely on food they get off the ground. In tropical zones extensive coral growth results in the formation of coral atolls late in

294-406: A seaplane anchorage off the southwest corner of Woleai Islet and established a weather station on Mariaon island to the west. Allied aircraft bombed the atoll and its military facilities on numerous occasions until the middle of 1945, driving its defenders underground and isolating them from supplies or reinforcements. By the surrender of Japan on September 2, 1945, only 1,650 survivors remained of

392-411: A windsock beside a landing strip. Types of runway safety incidents include: The choice of material used to construct the runway depends on the use and the local ground conditions. For a major airport, where the ground conditions permit, the most satisfactory type of pavement for long-term minimum maintenance is concrete . Although certain airports have used reinforcement in concrete pavements, this

490-480: A 7 will indicate 7,000 ft (2,134 m) remaining. The runway threshold is marked by a line of green lights. [REDACTED] There are three types of runways: Waterways may be unmarked or marked with buoys that follow maritime notation instead. For runways and taxiways that are permanently closed, the lighting circuits are disconnected. The runway threshold, runway designation, and touchdown markings are obliterated and yellow "Xs" are placed at each end of

588-399: A certain pattern in terms of eruptive activity, first observed with Hawaiian seamounts but now shown to be the process followed by all seamounts of the ocean-ridge type. During the first stage the volcano erupts basalt of various types, caused by various degrees of mantle melting . In the second, most active stage of its life, ocean-ridge volcanoes erupt tholeiitic to mildly alkalic basalt as

686-692: A classic example being the Emperor Seamounts , an extension of the Hawaiian Islands . Formed millions of years ago by volcanism , they have since subsided far below sea level. This long chain of islands and seamounts extends thousands of kilometers northwest from the island of Hawaii . There are more seamounts in the Pacific Ocean than in the Atlantic, and their distribution can be described as comprising several elongate chains of seamounts superimposed on

784-437: A daunting task due to their sheer number. The most detailed seamount mappings are provided by multibeam echosounding ( sonar ), however after more than 5000 publicly held cruises, the amount of the sea floor that has been mapped remains minuscule. Satellite altimetry is a broader alternative, albeit not as detailed, with 13,000 catalogued seamounts; however this is still only a fraction of the total 100,000. The reason for this

882-405: A global understanding of seamount ecosystems, and the roles they have in the biogeography , biodiversity , productivity and evolution of marine organisms. Possibly the best ecologically studied seamount in the world is Davidson Seamount , with six major expeditions recording over 60,000 species observations. The contrast between the seamount and the surrounding area was well-marked. One of

980-479: A landing site for the Space Shuttle . Takeoff and landing distances available are given using one of the following terms: There are standards for runway markings. There are runway markings and signs on most large runways. Larger runways have a distance remaining sign (black box with white numbers). This sign uses a single number to indicate the remaining distance of the runway in thousands of feet. For example,

1078-626: A more or less random background distribution. Seamount chains occur in all three major ocean basins, with the Pacific having the most number and most extensive seamount chains. These include the Hawaiian (Emperor), Mariana, Gilbert, Tuomotu and Austral Seamounts (and island groups) in the north Pacific and the Louisville and Sala y Gomez ridges in the southern Pacific Ocean. In the North Atlantic Ocean,

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1176-464: A number of seamounts are active undersea volcanoes; two examples are Kamaʻehuakanaloa (formerly Lo‘ihi) in the Hawaiian Islands and Vailulu'u in the Manu'a Group ( Samoa ). The most apparent lava flows at a seamount are the eruptive flows that cover their flanks, however igneous intrusions , in the forms of dikes and sills , are also an important part of seamount growth. The most common type of flow

1274-420: A particular pattern of growth, activity, subsidence and eventual extinction. The first stage of a seamount's evolution is its early activity, building its flanks and core up from the sea floor. This is followed by a period of intense volcanism, during which the new volcano erupts almost all (e.g. 98%) of its total magmatic volume. The seamount may even grow above sea level to become an oceanic island (for example,

1372-542: A periodic basis. Fields with very low traffic of light planes may use a sod surface. Some runways make use of salt flats. For pavement designs, borings are taken to determine the subgrade condition, and based on the relative bearing capacity of the subgrade, the specifications are established. For heavy-duty commercial aircraft, the pavement thickness, no matter what the top surface, varies from 10 to 48 in (25 to 122 cm), including subgrade. Airport pavements have been designed by two methods. The first, Westergaard ,

1470-429: A result of a larger area melting in the mantle. This is finally capped by alkalic flows late in its eruptive history, as the link between the seamount and its source of volcanism is cut by crustal movement. Some seamounts also experience a brief "rejuvenated" period after a hiatus of 1.5 to 10 million years, the flows of which are highly alkalic and produce many xenoliths . In recent years, geologists have confirmed that

1568-456: A summit collapse on the northern edge of Vlinder Seamount resulted in a pronounced headwall scarp and a field of debris up to 6 km (4 mi) away. A catastrophic collapse at Detroit Seamount flattened its whole structure extensively. Lastly, in 2004, scientists found marine fossils 61 m (200 ft) up the flank of Kohala mountain in Hawaii . Subsidation analysis found that at

1666-415: A third parallel runway was opened at Phoenix Sky Harbor International Airport in 2000 to the south of existing 8R/26L—rather than confusingly becoming the "new" 8R/26L it was instead designated 7R/25L, with the former 8R/26L becoming 7L/25R and 8L/26R becoming 8/26. Suffixes may also be used to denote special use runways. Airports that have seaplane waterways may choose to denote the waterway on charts with

1764-475: A total area of 8,796,150 km (3,396,210 sq mi), have been mapped but only a few have been studied in detail by scientists. Seamounts and guyots are most abundant in the North Pacific Ocean, and follow a distinctive evolutionary pattern of eruption, build-up, subsidence and erosion. In recent years, several active seamounts have been observed, for example Kamaʻehuakanaloa (formerly Lōʻihi) in

1862-484: A wide variety of tectonic settings, resulting in a very diverse structural bank. Seamounts come in a wide variety of structural shapes, from conical to flat-topped to complexly shaped. Some are built very large and very low, such as Koko Guyot and Detroit Seamount ; others are built more steeply, such as Kamaʻehuakanaloa Seamount and Bowie Seamount . Some seamounts also have a carbonate or sediment cap . Many seamounts show signs of intrusive activity , which

1960-425: Is Bowie Seamount , which has also been declared a marine protected area by Canada for its ecological richness. The study of seamounts has been hindered for a long time by the lack of technology. Although seamounts have been sampled as far back as the 19th century, their depth and position meant that the technology to explore and sample seamounts in sufficient detail did not exist until the last few decades. Even with

2058-413: Is pillow lava , named so after its distinctive shape. Less common are sheet flows, which are glassy and marginal, and indicative of larger-scale flows. Volcaniclastic sedimentary rocks dominate shallow-water seamounts. They are the products of the explosive activity of seamounts that are near the water's surface, and can also form from mechanical wear of existing volcanic rock. Seamounts can form in

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2156-445: Is an extrapolation of the original test results, which are not applicable to modern aircraft pavements or to modern aircraft landing gear . Some designs were made by a mixture of these two design theories. A more recent method is an analytical system based on the introduction of vehicle response as an important design parameter. Essentially it takes into account all factors, including the traffic conditions, service life, materials used in

2254-463: Is based on the assumption that the pavement is an elastic plate supported on a heavy fluid base with a uniform reaction coefficient known as the K value . Experience has shown that the K values on which the formula was developed are not applicable for newer aircraft with very large footprint pressures. The second method is called the California bearing ratio and was developed in the late 1940s. It

2352-399: Is considered to have the longest takeoff distance of the more common aircraft types and has set the standard for runway lengths of larger international airports. At sea level , 3,200 m (10,500 ft) can be considered an adequate length to land virtually any aircraft. For example, at O'Hare International Airport , when landing simultaneously on 4L/22R and 10/28 or parallel 9R/27L, it

2450-533: Is deeper and larger than its eastern counterpart. Both components are part of the same seamount . The total land area for both components combined is only 4.5 square kilometers (1.7 sq mi). The Austronesian ancestors of the Micronesians who make up the indigenous population of the Caroline Islands arrived in the islands c.  0-200 CE . Woleai subsequently became culturally unique among

2548-418: Is generally found to be unnecessary, with the exception of expansion joints across the runway where a dowel assembly, which permits relative movement of the concrete slabs, is placed in the concrete. Where it can be anticipated that major settlements of the runway will occur over the years because of unstable ground conditions, it is preferable to install asphalt concrete surface, as it is easier to patch on

2646-490: Is helped by geochemical exchange between the seamounts and the ocean water. Seamounts may thus be vital stopping points for some migratory animals , specifically whales . Some recent research indicates whales may use such features as navigational aids throughout their migration. For a long time it has been surmised that many pelagic animals visit seamounts as well, to gather food, but proof of this aggregating effect has been lacking. The first demonstration of this conjecture

2744-406: Is hurt by the simple lack of information available. Seamounts are very poorly studied, with only 350 of the estimated 100,000 seamounts in the world having received sampling, and fewer than 100 in depth. Much of this lack of information can be attributed to a lack of technology, and to the daunting task of reaching these underwater structures; the technology to fully explore them has only been around

2842-408: Is included for all ICAO and some U.S. military airports (such as Edwards Air Force Base ). However, most U.S.  civil aviation airports drop the leading zero as required by FAA regulation. This also includes some military airfields such as Cairns Army Airfield . This American anomaly may lead to inconsistencies in conversations between American pilots and controllers in other countries. It

2940-604: Is likely to lead to inflation , steepening of volcanic slopes, and ultimately, flank collapse. There are also several sub-classes of seamounts. The first are guyots , seamounts with a flat top. These tops must be 200 m (656 ft) or more below the surface of the sea; the diameters of these flat summits can be over 10 km (6.2 mi). Knolls are isolated elevation spikes measuring less than 1,000 meters (3,281 ft). Lastly, pinnacles are small pillar-like seamounts. Seamounts are exceptionally important to their biome ecologically, but their role in their environment

3038-454: Is most nearly aligned with the wind. Airports with one runway are often constructed to be aligned with the prevailing wind . Compiling a wind rose is one of the preliminary steps taken in constructing airport runways. Wind direction is given as the direction the wind is coming from : a plane taking off from runway 09 faces east, into an "east wind" blowing from 090°. Originally in the 1920s and 1930s, airports and air bases (particularly in

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3136-452: Is poorly understood. Because they project out above the surrounding sea floor, they disturb standard water flow, causing eddies and associated hydrological phenomena that ultimately result in water movement in an otherwise still ocean bottom. Currents have been measured at up to 0.9 knots, or 48 centimeters per second. Because of this upwelling seamounts often carry above-average plankton populations, seamounts are thus centers where

3234-468: Is responsible for as much as 95% of ecological damage to seamounts. Corals from seamounts are also vulnerable, as they are highly valued for making jewellery and decorative objects. Significant harvests have been produced from seamounts, often leaving coral beds depleted. Individual nations are beginning to note the effect of fishing on seamounts, and the European Commission has agreed to fund

3332-567: Is routine for arrivals from East Asia , which would normally be vectored for 4L/22R (2,300 m (7,546 ft)) or 9R/27L (2,400 m (7,874 ft)) to request 28R (4,000 m (13,123 ft)). It is always accommodated, although occasionally with a delay. Another example is that the Luleå Airport in Sweden was extended to 3,500 m (11,483 ft) to allow any fully loaded freight aircraft to take off. These distances are also influenced by

3430-451: Is slow, runway designation changes are uncommon, and not welcomed, as they require an accompanying change in aeronautical charts and descriptive documents. When a runway designation does change, especially at major airports, it is often done at night, because taxiway signs need to be changed and the numbers at each end of the runway need to be repainted to the new runway designators. In July 2009 for example, London Stansted Airport in

3528-404: Is that often, in the late of stages of their life, extrusions begin to seep in the seamount. This activity leads to inflation, over-extension of the volcano's flanks, and ultimately flank collapse , leading to submarine landslides with the potential to start major tsunamis , which can be among the largest natural disasters in the world. In an illustration of the potent power of flank collapses,

3626-399: Is that the fishes that are targeted over seamounts are typically long-lived, slow-growing, and slow-maturing. The problem is confounded by the dangers of trawling , which damages seamount surface communities, and the fact that many seamounts are located in international waters, making proper monitoring difficult. Bottom trawling in particular is extremely devastating to seamount ecology, and

3724-463: Is that uncertainties in the technology limit recognition to features 1,500 m (4,921 ft) or larger. In the future, technological advances could allow for a larger and more detailed catalogue. Observations from CryoSat-2 combined with data from other satellites has shown thousands of previously uncharted seamounts, with more to come as data is interpreted. Seamounts are a possible future source of economically important metals. Even though

3822-459: Is usually adequate for aircraft weights below approximately 100,000 kg (220,000 lb). Larger aircraft including widebodies will usually require at least 2,400 m (7,900 ft) at sea level. International widebody flights, which carry substantial amounts of fuel and are therefore heavier, may also have landing requirements of 3,200 m (10,500 ft) or more and takeoff requirements of 4,000 m (13,000 ft). The Boeing 747

3920-557: Is very common in a country such as Canada for a controller to clear an incoming American aircraft to, for example, runway 04, and the pilot read back the clearance as runway 4. In flight simulation programs those of American origin might apply U.S. usage to airports around the world. For example, runway 05 at Halifax will appear on the program as the single digit 5 rather than 05. Military airbases may include smaller paved runways known as "assault strips" for practice and training next to larger primary runways. These strips eschew

4018-498: The 2009 eruption of Hunga Tonga ). After a period of explosive activity near the ocean surface , the eruptions slowly die away. With eruptions becoming infrequent and the seamount losing its ability to maintain itself, the volcano starts to erode . After finally becoming extinct (possibly after a brief rejuvenated period), they are ground back down by the waves. Seamounts are built in a far more dynamic oceanic setting than their land counterparts, resulting in horizontal subsidence as

Woleai - Misplaced Pages Continue

4116-615: The German Empire in 1899. In 1914, in the early weeks of World War I , the Empire of Japan seized German possessions in the Pacific, including Woleai. Assigned a League of Nations mandate to administer the islands after the war in accordance with the Treaty of Versailles of 1919, Japan subsequently administered Woleai under the South Seas Mandate . In 1944, as Allied forces closed in on

4214-451: The Hawaiian Islands . Because of their abundance, seamounts are one of the most common marine ecosystems in the world. Interactions between seamounts and underwater currents, as well as their elevated position in the water, attract plankton , corals , fish, and marine mammals alike. Their aggregational effect has been noted by the commercial fishing industry , and many seamounts support extensive fisheries. There are ongoing concerns on

4312-582: The International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft ". Runways may be a human-made surface (often asphalt , concrete , or a mixture of both) or a natural surface ( grass , dirt , gravel , ice , sand or salt ). Runways, taxiways and ramps , are sometimes referred to as "tarmac", though very few runways are built using tarmac . Takeoff and landing areas defined on

4410-613: The Mariana Islands during World War II , a contingent of 6,426 troops from the Imperial Japanese Army 's 50th Independent Mixed Brigade and the Imperial Japanese Navy 's 44th Base Guard Unit and 216th Base Construction Unit heavily fortified Woleai. They completely leveled Wolfe Islet and made it into an airfield with a single 3,290-foot (1,003 m) runway and 2,050-foot (625 m) taxiway. They also constructed

4508-733: The New England Seamounts extend from the eastern coast of the United States to the mid-ocean ridge. Craig and Sandwell noted that clusters of larger Atlantic seamounts tend to be associated with other evidence of hotspot activity, such as on the Walvis Ridge , Vitória-Trindade Ridge , Bermuda Islands and Cape Verde Islands . The mid-Atlantic ridge and spreading ridges in the Indian Ocean are also associated with abundant seamounts. Otherwise, seamounts tend not to form distinctive chains in

4606-835: The Trust Territory of the Pacific Islands , a United Nations trust territory , from 1947 until 1979, when Woleai became part of the independent Federated States of Micronesia . Public schools: Woleai Civil Airfield , administered by the Federated States of Micronesia Division of Civil Aviation is located at an altitude of 2 meters (6 ft 7 in) on Falalap at 7°22′36″N 143°54′30″E  /  7.37666°N 143.90833°E  / 7.37666; 143.90833  ( Woleai Civil Airfield ) , 681 kilometers (423 mi; 368 nmi) southeast of Yap International Airport and 0.44 kilometers (0.27 mi) northeast of

4704-635: The Caroline Islands because of a script in use among some speakers of the Woleaian language prior to 1913. Woleai was among islands to the southeast of Yap that became tributaries of the Yapese Empire from about 1500 CE. Woleai came under the control of the Spanish Empire in 1686, governed along with the rest of the Caroline Islands as part of the Spanish East Indies . Spain sold the islands to

4802-475: The Indian and Southern Oceans, but rather their distribution appears to be more or less random. Isolated seamounts and those without clear volcanic origins are less common; examples include Bollons Seamount , Eratosthenes Seamount , Axial Seamount and Gorringe Ridge . If all known seamounts were collected into one area, they would make a landform the size of Europe . Their overall abundance makes them one of

4900-513: The OASIS project, a detailed study of the effects of fishing on seamount communities in the North Atlantic . Another project working towards conservation is CenSeam , a Census of Marine Life project formed in 2005. CenSeam is intended to provide the framework needed to prioritise, integrate, expand and facilitate seamount research efforts in order to significantly reduce the unknown and build towards

4998-646: The United Kingdom changed its runway designations from 05/23 to 04/22 during the night. Runway dimensions vary from as small as 245 m (804 ft) long and 8 m (26 ft) wide in smaller general aviation airports, to 5,500 m (18,045 ft) long and 80 m (262 ft) wide at large international airports built to accommodate the largest jets , to the huge 11,917 m × 274 m (39,098 ft × 899 ft) lake bed runway 17/35 at Edwards Air Force Base in California – developed as

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5096-461: The United Kingdom) were built in a triangle-like pattern of three runways at 60° angles to each other. The reason was that aviation was only starting, and although it was known that wind affected the runway distance required, not much was known about wind behaviour. As a result, three runways in a triangle-like pattern were built, and the runway with the heaviest traffic would eventually expand into

5194-551: The aircraft tyres. To maintain the macrotexturing built into the runway by the grooves, maintenance crews engage in airfield rubber removal or hydrocleaning in order to meet required FAA , or other aviation authority friction levels. Subsurface underdrains help provide extended life and excellent and reliable pavement performance. At the Hartsfield Atlanta, GA airport the underdrains usually consist of trenches 18 in (46 cm) wide and 48 in (120 cm) deep from

5292-447: The airport's main runway, while the other two runways would be either abandoned or converted into taxiways. Runways are named by a number between 01 and 36, which is generally the magnetic azimuth of the runway's heading in deca degrees . This heading differs from true north by the local magnetic declination . A runway numbered 09 points east (90°), runway 18 is south (180°), runway 27 points west (270°) and runway 36 points to

5390-537: The ambiguity that would result with more than three parallel runways. For example, in Los Angeles, this system results in runways 6L, 6R, 7L, and 7R, even though all four runways are actually parallel at approximately 69°. At Dallas/Fort Worth International Airport , there are five parallel runways, named 17L, 17C, 17R, 18L, and 18R, all oriented at a heading of 175.4°. Occasionally, an airport with only three parallel runways may use different runway identifiers, such as when

5488-675: The average size of seamounts. Nearly 50% of guyot area and 42% of the number of guyots occur in the North Pacific Ocean, covering 342,070 km (132,070 sq mi). The largest three guyots are all in the North Pacific: the Kuko Guyot (estimated 24,600 km (9,500 sq mi)), Suiko Guyot (estimated 20,220 km (7,810 sq mi)) and the Pallada Guyot (estimated 13,680 km (5,280 sq mi)). Seamounts are often found in groupings or submerged archipelagos ,

5586-411: The construction, and, especially important, the dynamic response of the vehicles using the landing area. Because airport pavement construction is so expensive, manufacturers aim to minimize aircraft stresses on the pavement. Manufacturers of the larger planes design landing gear so that the weight of the plane is supported on larger and more numerous tires. Attention is also paid to the characteristics of

5684-750: The crust to the surface. Volcanoes formed near or above subducting zones are created because the subducting tectonic plate adds volatiles to the overriding plate that lowers its melting point . Which of these two process involved in the formation of a seamount has a profound effect on its eruptive materials. Lava flows from mid-ocean ridge and plate boundary seamounts are mostly basaltic (both tholeiitic and alkalic ), whereas flows from subducting ridge volcanoes are mostly calc-alkaline lavas. Compared to mid-ocean ridge seamounts, subduction zone seamounts generally have more sodium , alkali , and volatile abundances, and less magnesium , resulting in more explosive, viscous eruptions. All volcanic seamounts follow

5782-425: The effect of seamounts on endemicity. They have , however, been confidently shown to provide a habitat to species that have difficulty surviving elsewhere. The volcanic rocks on the slopes of seamounts are heavily populated by suspension feeders , particularly corals , which capitalize on the strong currents around the seamount to supply them with food. These coral are therefore host to numerous other organisms in

5880-465: The first two have any potential of being targeted by mining in the next few decades. Some seamounts have not been mapped and thus pose a navigational danger. For instance, Muirfield Seamount is named after the ship that hit it in 1973. More recently, the submarine USS San Francisco ran into an uncharted seamount in 2005 at a speed of 35 knots (40.3 mph; 64.8 km/h), sustaining serious damage and killing one seaman. One major seamount risk

5978-417: The fish that feed on them aggregate, in turn falling prey to further predation, making seamounts important biological hotspots. Seamounts provide habitats and spawning grounds for these larger animals, including numerous fish. Some species, including black oreo (Allocyttus niger) and blackstripe cardinalfish (Apogon nigrofasciatus) , have been shown to occur more often on seamounts than anywhere else on

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6076-575: The following: According to Transport Canada 's regulations, the runway-edge lighting must be visible for at least 2 mi (3 km). Additionally, a new system of advisory lighting, runway status lights , is currently being tested in the United States. The edge lights must be arranged such that: Typically the lights are controlled by a control tower , a flight service station or another designated authority. Some airports/airfields (particularly uncontrolled ones ) are equipped with pilot-controlled lighting , so that pilots can temporarily turn on

6174-453: The gap. There have been instances where naval vessels have collided with uncharted seamounts; for example, Muirfield Seamount is named after the ship that struck it in 1973. However, the greatest danger from seamounts are flank collapses; as they get older, extrusions seeping in the seamounts put pressure on their sides, causing landslides that have the potential to generate massive tsunamis . Seamounts can be found in every ocean basin in

6272-521: The initial 6,426-strong Japanese garrison, the rest having perished largely because of starvation and disease rather than directly in Allied air raids. The United States Navy destroyer escort USS  Sloat  (DE-245) picked up the surviving Japanese on September 17, 1945. Following World War II, the atoll came under the control of the United States . The United States administered Woleai as part of

6370-496: The lack of designated landing direction. If there is more than one runway pointing in the same direction (parallel runways), each runway is identified by appending left (L), center (C) and right (R) to the end of the runway number to identify its position (when facing its direction)—for example, runways one-five-left (15L), one-five-center (15C), and one-five-right (15R). Runway zero-three-left (03L) becomes runway two-one-right (21R) when used in

6468-432: The landing gear itself, so that adverse effects on the pavement are minimized. Sometimes it is possible to reinforce a pavement for higher loading by applying an overlay of asphaltic concrete or portland cement concrete that is bonded to the original slab. Post-tensioning concrete has been developed for the runway surface. This permits the use of thinner pavements and should result in longer concrete pavement life. Because of

6566-497: The last few decades. Before consistent conservation efforts can begin, the seamounts of the world must first be mapped , a task that is still in progress. Overfishing is a serious threat to seamount ecological welfare. There are several well-documented cases of fishery exploitation, for example the orange roughy ( Hoplostethus atlanticus ) off the coasts of Australia and New Zealand and the pelagic armorhead ( Pseudopentaceros richardsoni ) near Japan and Russia. The reason for this

6664-409: The lights when the relevant authority is not available. This avoids the need for automatic systems or staff to turn the lights on at night or in other low visibility situations. This also avoids the cost of having the lighting system on for extended periods. Smaller airports may not have lighted runways or runway markings. Particularly at private airfields for light planes, there may be nothing more than

6762-433: The main settlements on the island. The 1,200-foot (370 m) runway has not been maintained since 1992, and the airfield has closed due to severe deterioration of the runway and the government's decision not to perform repairs. The runway is now covered with vegetation. Before the airfield closed, Caroline Islands Air provided chartered flights to it. The runway was built by the Empire of Japan during World War II. After

6860-516: The most common, and least understood, marine structures and biomes on Earth, a sort of exploratory frontier. Most seamounts are built by one of two volcanic processes, although some, such as the Christmas Island Seamount Province near Australia, are more enigmatic. Volcanoes near plate boundaries and mid-ocean ridges are built by decompression melting of rock in the upper mantle . The lower density magma rises through

6958-458: The nearest 10°, this affects some runways sooner than others. For example, if the magnetic heading of a runway is 233°, it is designated Runway 23. If the magnetic heading changes downwards by 5 degrees to 228°, the runway remains Runway 23. If on the other hand the original magnetic heading was 226° (Runway 23), and the heading decreased by only 2 degrees to 224°, the runway becomes Runway 22. Because magnetic drift itself

7056-521: The need for "distinctly marked and carefully prepared landing places, [but] the preparing of the surface of reasonably flat ground [is] an expensive undertaking [and] there would also be a continuous expense for the upkeep." For fixed-wing aircraft , it is advantageous to perform takeoffs and landings into the wind to reduce takeoff or landing roll and reduce the ground speed needed to attain flying speed . Larger airports usually have several runways in different directions, so that one can be selected that

7154-439: The negative impact of fishing on seamount ecosystems, and well-documented cases of stock decline, for example with the orange roughy ( Hoplostethus atlanticus ). 95% of ecological damage is done by bottom trawling , which scrapes whole ecosystems off seamounts. Because of their large numbers, many seamounts remain to be properly studied, and even mapped. Bathymetry and satellite altimetry are two technologies working to close

7252-581: The north (360° rather than 0°). When taking off from or landing on runway 09, a plane is heading around 90° (east). A runway can normally be used in both directions, and is named for each direction separately: e.g., "runway 15" in one direction is "runway 33" when used in the other. The two numbers differ by 18 (= 180°). For clarity in radio communications, each digit in the runway name is pronounced individually: runway one-five, runway three-three, etc. (instead of "fifteen" or "thirty-three"). A leading zero, for example in "runway zero-six" or "runway zero-one-left",

7350-470: The ocean floor. Marine mammals , sharks , tuna , and cephalopods all congregate over seamounts to feed, as well as some species of seabirds when the features are particularly shallow. Seamounts often project upwards into shallower zones more hospitable to sea life, providing habitats for marine species that are not found on or around the surrounding deeper ocean bottom. Because seamounts are isolated from each other they form "undersea islands" creating

7448-470: The ocean makes up 70% of Earth's surface area, technological challenges have severely limited the extent of deep sea mining . But with the constantly decreasing supply on land, some mining specialists see oceanic mining as the destined future, and seamounts stand out as candidates. Seamounts are abundant, and all have metal resource potential because of various enrichment processes during the seamount's life. An example for epithermal gold mineralization on

7546-589: The opposite direction (derived from adding 18 to the original number for the 180° difference when approaching from the opposite direction). In some countries, regulations mandate that where parallel runways are too close to each other, only one may be used at a time under certain conditions (usually adverse weather ). At large airports with four or more parallel runways (for example, at Chicago O'Hare , Los Angeles , Detroit Metropolitan Wayne County , Hartsfield-Jackson Atlanta , Denver , Dallas–Fort Worth and Orlando ), some runway identifiers are shifted by 1 to avoid

7644-536: The primary ecological havens on the seamount is its deep sea coral garden, and many of the specimens noted were over a century old. Following the expansion of knowledge on the seamount there was extensive support to make it a marine sanctuary , a motion that was granted in 2008 as part of the Monterey Bay National Marine Sanctuary . Much of what is known about seamounts ecologically is based on observations from Davidson. Another such seamount

7742-399: The right technology available, only a scant 1% of the total number have been explored, and sampling and information remains biased towards the top 500 m (1,640 ft). New species are observed or collected and valuable information is obtained on almost every submersible dive at seamounts. Before seamounts and their oceanographic impact can be fully understood, they must be mapped,

7840-478: The runway grade (slope) such that, for example, each 1 percent of runway down slope increases the landing distance by 10 percent. An aircraft taking off at a higher altitude must do so at reduced weight due to decreased density of air at higher altitudes, which reduces engine power and wing lift. An aircraft must also take off at a reduced weight in hotter or more humid conditions (see density altitude ). Most commercial aircraft carry manufacturer's tables showing

7938-406: The runway and at 1,000 ft (305 m) intervals. A line of lights on an airfield or elsewhere to guide aircraft in taking off or coming in to land or an illuminated runway is sometimes also known as a flare path . Runway lighting is used at airports during periods of darkness and low visibility. Seen from the air, runway lights form an outline of the runway. A runway may have some or all of

8036-439: The same biogeographical interest. As they are formed from volcanic rock , the substrate is much harder than the surrounding sedimentary deep sea floor. This causes a different type of fauna to exist than on the seafloor, and leads to a theoretically higher degree of endemism . However, recent research especially centered at Davidson Seamount suggests that seamounts may not be especially endemic, and discussions are ongoing on

8134-720: The seafloor is Conical Seamount, located about 8 km south of Lihir Island in Papua New Guinea. Conical Seamount has a basal diameter of about 2.8 km and rises about 600 m above the seafloor to a water depth of 1050 m. Grab samples from its summit contain the highest gold concentrations yet reported from the modern seafloor (max. 230 g/t Au, avg. 26 g/t, n=40). Iron - manganese , hydrothermal iron oxide , sulfide , sulfate , sulfur , hydrothermal manganese oxide , and phosphorite (the latter especially in parts of Micronesia) are all mineral resources that are deposited upon or within seamounts. However, only

8232-575: The seafloor, characteristically of conical form. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea . During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface, such flat-top seamounts are called " guyots " or "tablemounts". Earth's oceans contain more than 14,500 identified seamounts, of which 9,951 seamounts and 283 guyots, covering

8330-475: The seamount moves with the tectonic plate towards a subduction zone . Here it is subducted under the plate margin and ultimately destroyed, but it may leave evidence of its passage by carving an indentation into the opposing wall of the subduction trench. The majority of seamounts have already completed their eruptive cycle, so access to early flows by researchers is limited by late volcanic activity. Ocean-ridge volcanoes in particular have been observed to follow

8428-529: The seamount's life. In addition soft sediments tend to accumulate on seamounts, which are typically populated by polychaetes ( annelid marine worms ) oligochaetes ( microdrile worms), and gastropod mollusks ( sea slugs ). Xenophyophores have also been found. They tend to gather small particulates and thus form beds, which alters sediment deposition and creates a habitat for smaller animals. Many seamounts also have hydrothermal vent communities, for example Suiyo and Kamaʻehuakanaloa seamounts. This

8526-678: The smallest seamounts found in the Arctic Ocean and the Mediterranean and Black Seas; whilst the largest mean seamount size, 890 km (340 sq mi), occurs in the Indian Ocean . The largest seamount has an area of 15,500 km (6,000 sq mi) and it occurs in the North Pacific. Guyots cover a total area of 707,600 km (273,200 sq mi) and have an average area of 2,500 km (970 sq mi), more than twice

8624-623: The standard numerical naming convention and instead employ the runway's full three digit heading; examples include Dobbins Air Reserve Base 's Runway 110/290 and Duke Field 's Runway 180/360. Runways with non-hard surfaces, such as small turf airfields and waterways for seaplanes , may use the standard numerical scheme or may use traditional compass point naming, examples include Ketchikan Harbor Seaplane Base 's Waterway E/W. Airports with unpredictable or chaotic water currents, such as Santa Catalina Island 's Pebbly Beach Seaplane Base, may designate their landing area as Waterway ALL/WAY to denote

8722-414: The suffix T; this is advantageous for certain airfields in the far north such as Thule Air Base (08T/26T). Runway designations may change over time because Earth's magnetic lines slowly drift on the surface and the magnetic direction changes. Depending on the airport location and how much drift occurs, it may be necessary to change the runway designation. As runways are designated with headings rounded to

8820-567: The suffix W; such as Daniel K. Inouye International Airport in Honolulu and Lake Hood Seaplane Base in Anchorage . Small airports that host various forms of air traffic may employ additional suffixes to denote special runway types based on the type of aircraft expected to use them, including STOL aircraft (S), gliders (G), rotorcraft (H), and ultralights (U). Runways that are numbered relative to true north rather than magnetic north will use

8918-633: The surface of water for seaplanes are generally referred to as waterways . Runway lengths are now commonly given in meters worldwide , except in North America where feet are commonly used. In 1916, in a World War I war effort context, the first concrete-paved runway was built in Clermont-Ferrand in France , allowing local company Michelin to manufacture Bréguet Aviation military aircraft. In January 1919, aviation pioneer Orville Wright underlined

9016-441: The susceptibility of thinner pavements to frost heave , this process is generally applicable only where there is no appreciable frost action . Runway pavement surface is prepared and maintained to maximize friction for wheel braking. To minimize hydroplaning following heavy rain, the pavement surface is usually grooved so that the surface water film flows into the grooves and the peaks between grooves will still be in contact with

9114-441: The time of their deposition, this would have been 500 m (1,640 ft) up the flank of the volcano, far too high for a normal wave to reach. The date corresponded with a massive flank collapse at the nearby Mauna Loa , and it was theorized that it was a massive tsunami, generated by the landslide, that deposited the fossils. Geology Ecology Geography and geology Ecology Runway According to

9212-547: The top of the pavement. A perforated plastic tube (5.9 in (15 cm) in diameter) is placed at the bottom of the ditch. The ditches are filled with gravel size crushed stone. Excessive moisture under a concrete pavement can cause pumping, cracking, and joint failure. In aviation charts, the surface type is usually abbreviated to a three-letter code. The most common hard surface types are asphalt and concrete. The most common soft surface types are grass and gravel. A runway of at least 1,800 m (5,900 ft) in length

9310-572: The war it was shortly US Naval Base Woleai , Fleet Post Office #3246. Seamount A seamount is a large submarine landform that rises from the ocean floor without reaching the water surface ( sea level ), and thus is not an island , islet , or cliff -rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to 1,000–4,000 m (3,300–13,100 ft) in height. They are defined by oceanographers as independent features that rise to at least 1,000 m (3,281 ft) above

9408-695: The world's oceans. Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges , mantle plumes , and island arcs . Overall, seamount and guyot coverage is greatest as a proportion of seafloor area in the North Pacific Ocean, equal to 4.39% of that ocean region. The Arctic Ocean has only 16 seamounts and no guyots, and the Mediterranean and Black seas together have only 23 seamounts and 2 guyots. The 9,951 seamounts which have been mapped cover an area of 8,088,550 km (3,123,010 sq mi). Seamounts have an average area of 790 km (310 sq mi), with

9506-415: The world, distributed extremely widely both in space and in age. A seamount is technically defined as an isolated rise in elevation of 1,000 m (3,281 ft) or more from the surrounding seafloor, and with a limited summit area, of conical form. There are more than 14,500 seamounts. In addition to seamounts, there are more than 80,000 small knolls , ridges and hills less than 1,000 m in height in

9604-822: Was published in 2008. The effect that seamounts have on fish populations has not gone unnoticed by the commercial fishing industry . Seamounts were first extensively fished in the second half of the 20th century, due to poor management practices and increased fishing pressure seriously depleting stock numbers on the typical fishing ground, the continental shelf . Seamounts have been the site of targeted fishing since that time. Nearly 80 species of fish and shellfish are commercially harvested from seamounts, including spiny lobster (Palinuridae), mackerel (Scombridae and others), red king crab ( Paralithodes camtschaticus ), red snapper ( Lutjanus campechanus ), tuna (Scombridae), Orange roughy ( Hoplostethus atlanticus ), and perch (Percidae). The ecological conservation of seamounts

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