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44-453: The archipelago comprises 11 main islands forming an island arc running north–south, the largest being Montagu at 110 square kilometres (42 sq mi). It is divided into four groups, from north to south: The Traversay , Candlemas and Central Islands ( Saunders , Montagu , and Bristol ), and Southern Thule . The archipelago is prone to violent earthquakes . Over the previous century, nine M 7+ earthquakes have occurred here,

88-472: A crust which is either oceanic or intermediate between the normal oceanic crust and that typical of continents; heat flow in the basins is higher than in normal continental or oceanic areas. Some arcs, such as the Aleutians, pass laterally into the continental shelf on the concave side of the arc, while most of the arcs are separated from the continental crust. Movement between two lithospheric plates explains

132-574: A group of islands which he named "Sandwich Land" in honour of Lord Sandwich , then First Lord of the Admiralty . The word "South" was later added to distinguish them from the "Sandwich Islands", now known as Hawai'i . The Traversay Islands ( Zavodovski , Leskov and Visokoi ) were discovered by the Imperial Russian Navy expedition of Bellingshausen and Lazarev in the ships Vostok and Mirny in 1819. The United Kingdom formally annexed

176-538: A network of buoys in the central and eastern tropical Pacific Ocean helped study the El Niño-Southern Oscillation . Moored weather buoys range from 1.5–12 metres (5–40 ft) in diameter, while drifting buoys are smaller, with diameters of 30–40 centimetres (12–16 in). Drifting buoys are the dominant form of weather buoy in sheer number, with 1250 located worldwide. Wind data from buoys has smaller error than that from ships. There are differences in

220-496: A personal computer, and internet connection (or amateur radio) and are utilized by groups such as the National Weather Service (NWS) when generating forecast models . Each weather station submitting data to CWOP will also have an individual Web page that depicts the data submitted by that station. The Weather Underground Internet site is another popular destination for the submittal and sharing of data with others around

264-436: A significant amount. A weather instrument is any device that measures weather related conditions. Since there are a variety of different weather conditions, there are a variety of different weather instruments. Typical weather stations have the following instruments: In addition, at certain automated airport weather stations , additional instruments may be employed, including: More sophisticated stations may also measure

308-404: Is a plane that dips under the overriding plate where intense volcanic activity occurs, which is defined by the location of seismic events below the arc. Earthquakes occur from near surface to ~660 km depth. The dip of Benioff zones ranges from 30° to near vertical. An ocean basin may be formed between the continental margin and the island arcs on the concave side of the arc. These basins have

352-501: Is achieved. Island arcs can either be active or inactive based on their seismicity and presence of volcanoes. Active arcs are ridges of recent volcanoes with an associated deep seismic zone. They also possess a distinct curved form, a chain of active or recently extinct volcanoes, a deep-sea trench , and a large negative Bouguer anomaly on the convex side of the volcanic arc. The small positive gravity anomaly associated with volcanic arcs has been interpreted by many authors as due to

396-404: Is due to the present pattern of lithospheric plates. However, their volcanic history, which indicates that they are fragments of older island arcs, is not necessarily related to the present plate pattern and may be due to differences in position of plate margins in the past. Understanding the source of heat that causes the melting of the mantle was a contentious problem. Researchers believed that

440-451: Is lost, the reduction in pressure may cause pressure release or decompression partial melting . On the subducting side of the island arc is a deep and narrow oceanic trench, which is the trace at the Earth's surface of the boundary between the down-going and overriding plates. This trench is created by the downward gravitational pull of the relatively dense subducting plate on the leading edge of

484-404: Is related to the age of the subduction zone and the depth. The tholeiitic magma series is well represented above young subduction zones formed by magma from relative shallow depth. The calc-alkaline and alkaline series are seen in mature subduction zones, and are related to magma of greater depths. Andesite and basaltic andesite are the most abundant volcanic rock in island arc which is indicative of

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528-929: Is required for record keeping. Automatic transmission of data, in a format such as METAR , is also desirable as many weather station's data is required for weather forecasting. A personal weather station is a set of weather measuring instruments operated by a private individual, club, association, or business (where obtaining and distributing weather data is not a part of the entity's business operation). Personal weather stations have become more advanced and can include many different sensors to measure weather conditions. These sensors can vary between models but most measure wind speed, wind direction, outdoor and indoor temperatures, outdoor and indoor humidity, barometric pressure, rainfall, and UV or solar radiation. Other available sensors can measure soil moisture, soil temperature, and leaf wetness. The quality, number of instruments, and placement of personal weather stations can vary widely, making

572-426: Is the passage between Candlemas and Vindication islands. Island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth

616-695: The Richter Scale had its epicenter 205  km south-southeast of Bristol Island . On 30 June 2008, an earthquake of magnitude 7.0 struck the region. Its epicenter was at 283 km (176 mi) east-northeast (73 degrees) of Bristol Island. The northernmost of the South Sandwich Islands form the Traversay Islands and Candlemas Islands groups, while the southernmost make up Southern Thule . The three largest islands – Saunders , Montagu , and Bristol  – lie between

660-521: The ultraviolet index , leaf wetness , soil moisture , soil temperature, water temperature in ponds, lakes, creeks, or rivers, and occasionally other data. Except for those instruments requiring direct exposure to the elements (anemometer, rain gauge), the instruments should be sheltered in a vented box, usually a Stevenson screen , to keep direct sunlight off the thermometer and wind off the hygrometer. The instrumentation may be specialized to allow for periodic recording, otherwise significant manual labour

704-714: The weather and climate . The measurements taken include temperature , atmospheric pressure , humidity , wind speed , wind direction , and precipitation amounts. Wind measurements are taken with as few other obstructions as possible, while temperature and humidity measurements are kept free from direct solar radiation, or insolation . Manual observations are taken at least once daily, while automated measurements are taken at least once an hour. Weather conditions out at sea are taken by ships and buoys, which measure slightly different meteorological quantities such as sea surface temperature (SST), wave height, and wave period. Drifting weather buoys outnumber their moored versions by

748-538: The South Sandwich Islands through letters patent in 1908, grouping them with other British-held territory in Antarctica as the Falkland Islands Dependencies . Argentina claimed the South Sandwich Islands in 1938 and challenged British sovereignty in the islands on several occasions. From 25 January 1955 through the summer of 1956 Argentina maintained the summer station Teniente Esquivel at Ferguson Bay on

792-415: The amount of water present in the down-going slab is related to the melting temperature of the mantle. The greater the amount of water present, the more the melting temperature of the mantle is reduced. This water is released during the transformation of minerals as pressure increases, with the mineral carrying the most water being serpentinite . These metamorphic mineral reactions cause the dehydration of

836-494: The calc-alkaline magmas. Some Island arcs have distributed volcanic series as can be seen in the Japanese island arc system where the volcanic rocks change from tholeiite—calc-alkaline—alkaline with increasing distance from the trench. Several processes are involved in arc magmatism which gives rise to the great spectrum of rock composition encountered. These processes are, but not limited to, magma mixing, fractionation, variations in

880-427: The continents during the late Mesozoic or early Cenozoic . They are also found at oceanic-oceanic convergence zones, in which case the older plate will subduct under the younger one. The movement of the island arcs towards the continent could be possible if, at some point, the ancient Benioff zones dipped toward the present ocean rather than toward the continent, as in most arcs today. This will have resulted in

924-559: The deepest features of ocean basins; the deepest being the Mariana trench (approximately 11,000 m or 36,000 ft). They are formed by flexing of the oceanic lithosphere, developing on the ocean side of island arcs. Back-arc basin : They are also referred to as marginal seas and are formed in the inner, concave side of island arcs bounded by back-arc ridges. They develop in response to tensional tectonics due to rifting of an existing island arc. Benioff zone or Wadati-Benioff zone : This

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968-577: The deflected part of the plate coincides approximately with the Benioff zone beneath most arcs. Most modern island arcs are near the continental margins (particularly in the northern and western margins of the Pacific Ocean). However, no direct evidence from within the arcs shows that they have always existed at their present position with respect to the continents, although evidence from some continental margins suggests that some arcs may have migrated toward

1012-538: The depth and degree of partial melting and assimilation. Therefore, the three volcanic series results in a wide range of rock composition and do not correspond to absolute magma types or source regions. Remains of former island arcs have been identified at some locations. The table below mention a selection of these. Weather station A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study

1056-593: The determination of which stations collect accurate, meaningful, and comparable data difficult. There are a comprehensive number of retail weather stations available. Personal weather stations typically involve a digital console that provides readouts of the data being collected. These consoles may interface to a personal computer where data can be displayed, stored, and uploaded to websites or data ingestion/distribution systems. Open-source weather stations are available that are designed to be fully customizable by users. Personal weather stations may be operated solely for

1100-462: The enjoyment and education of the owner, while some owners share their results with others. They do this by manually compiling data and distributing it, distributing data over the Internet, or sharing data via amateur radio . The Citizen Weather Observer Program (CWOP) is a service which facilitates the sharing of information from personal weather stations. This data is submitted through use of software,

1144-479: The generalized features present in most island arcs. Fore-arc : This region comprises the trench, the accretionary prism, and the fore-arc basin. A bump from the trench in the oceanward side of the system is present (Barbados in the Lesser Antilles is an example). The fore-arc basin forms between the fore-arc ridge and the island arc; it is a region of undisturbed flat-bedded sedimentation. Trenches : These are

1188-435: The heat was produced through friction at the top of the slab. However, this is unlikely because the viscosity of the asthenosphere decreases with increasing temperature, and at the temperatures required for partial fusion, the asthenosphere would have such a low viscosity that shear melting could not occur. It is now believed that water acts as the primary agent that drives partial melting beneath arcs. It has been shown that

1232-555: The installations were demolished in December of that year. Since 1995, the South African Weather Bureau has maintained two automatic weather stations on the islands of Zavodovski and Thule. The territory of "South Georgia and the South Sandwich Islands" was formed in 1985; previously, both archipelagos had been governed as part of the Falkland Islands Dependencies . On 10 February 2008, an earthquake of magnitude 6.5 on

1276-439: The loss of ocean floor between the arc and the continent, and consequently, in the migration of the arc during spreading episodes. The fracture zones in which some active island arcs terminate may be interpreted in terms of plate tectonics as resulting from movement along transform faults , which are plate margins where the crust is neither being consumed nor generated. Thus the present location of these inactive island chains

1320-466: The major features of active island arcs. The island arc and small ocean basin are situated on the overlying plate which meets the descending plate containing normal oceanic crust along the Benioff zone. The sharp bending of the oceanic plate downward produces a trench. There are generally three volcanic series from which the types of volcanic rock that occur in island arcs are formed: This volcanic series

1364-640: The most recent being the M ;8.1 in August 2021. None of these earthquakes are known to have caused fatalities due to their remote location. The southern eight islands of the Sandwich Islands Group were discovered by James Cook in 1775. The northern three were discovered by Fabian Gottlieb von Bellingshausen in 1819. Departing from South Georgia, Captain Cook sailed to the southeast to discover Clerke Rocks and

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1408-508: The northern Pacific Ocean . The agreement of the weather ships ended in 1990. Weather ship observations proved to be helpful in wind and wave studies, as they did not avoid weather systems like merchant ships tended to and were considered a valuable resource. The last weather ship was MS  Polarfront , known as weather station M ("jilindras") at 66°N, 02°E, run by the Norwegian Meteorological Institute . MS Polarfront

1452-582: The northwest of Zavodovski Island is the Protector Shoal , a submarine volcano. Download coordinates as: The South Sandwich Islands from north to south are: A series of six passages separates each of the islands or island groups in the chain. They are, from north to south: Zavodovski Isl., Traverse passage , Visokoi Isl., Brown's passage , Candlemas Isl., Shackleton's passage , Saunders Isl., Larsen's passage , Montagu Isl., Biscoe's passage, Bristol Isl., Forsters Passage , Southern Thule. Nelson Channel

1496-444: The plate. Multiple earthquakes occur along this subduction boundary with the seismic hypocenters located at increasing depth under the island arc: these quakes define the Benioff zone . Island arcs can be formed in intra-oceanic settings, or from the fragments of continental crust that have migrated away from an adjacent continental land mass or at subduction-related volcanoes active at the margins of continents. Below are some of

1540-420: The presence of dense volcanic rocks beneath the arc. Inactive arcs are a chain of islands which contains older volcanic and volcaniclastic rocks . The curved shape of many volcanic chains and the angle of the descending lithosphere are related. If the oceanic part of the plate is represented by the ocean floor on the convex side of the arc, and if the zone of flexing occurs beneath the submarine trench , then

1584-411: The slab causing less viscous mantle to flow in behind it. It is the interaction of this down-welling mantle with aqueous fluids rising from the sinking slab that is thought to produce partial melting of the mantle as it crosses its wet solidus . In addition, some melts may result from the up-welling of hot mantle material within the mantle wedge. If hot material rises quickly enough so that little heat

1628-595: The southeastern coast of Thule Island . From 1976 to 1982, Argentina maintained a naval base named Corbeta Uruguay in the lee (southern east coast) of the same island. Although the British discovered the presence of the Argentine base in 1976, protested, and tried to resolve the issue by diplomatic means, no effort was made to remove them by force until after the Falklands War . The base was eventually removed on 20 June 1982 and

1672-539: The two. The Islands' highest point is Mount Belinda (1,370 m or 4,495 ft) on Montagu Island. The fourth highest peak, Mount Michael (990 m or 3,248 ft) on Saunders Island has a persistent lava lake , known to occur at only eight volcanoes in the world. The South Sandwich Islands are uninhabited, though a permanently staffed Argentine research station was located on Thule Island from 1976 to 1982 (for details, see § History above). Automatic weather stations are on Thule Island and Zavodovski . To

1716-411: The upper part of the slab as the hydrated slab sinks. Heat is also transferred to it from the surrounding asthenosphere. As heat is transferred to the slab, temperature gradients are established such that the asthenosphere in the vicinity of the slab becomes cooler and more viscous than surrounding areas, particularly near the upper part of the slab. This more viscous asthenosphere is then dragged down with

1760-701: The values of sea surface temperature measurements between the two platforms as well, relating to the depth of the measurement and whether or not the water is heated by the ship which measures the quantity. Synoptic weather stations are instruments which collect meteorological information at synoptic time 00h00, 06h00, 12h00, 18h00 ( UTC ) and at intermediate synoptic hours 03h00, 09h00, 15h00, 21h00 (UTC). Every weather station has assigned station unique code by WMO for identification. The common instruments of measure are anemometer, wind vane, pressure sensor, thermometer, hygrometer, and rain gauge. The weather measures are formatted in special format and transmit to WMO to help

1804-401: The world's oceans and lakes. Moored buoys have been in use since 1951, while drifting buoys have been used since the late 1970s. Moored buoys are connected with the seabed using either chains, nylon , or buoyant polypropylene . With the decline of the weather ship , they have taken a more primary role in measuring conditions over the open seas since the 1970s. During the 1980s and 1990s,

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1848-399: The world. As with CWOP, each station submitting data to Weather Underground has a unique Web page displaying their submitted data. The UK Met Office 's Weather Observations Website (WOW) also allows such data to be shared and displayed. A weather ship was a ship stationed in the ocean as a platform for surface and upper air meteorological measurements for use in weather forecasting. It

1892-492: Was also meant to aid in search and rescue operations and to support transatlantic flights. The establishment of weather ships proved to be so useful during World War II that the International Civil Aviation Organization (ICAO) established a global network of 13 weather ships in 1948. Of the 12 left in operation in 1996, nine were located in the northern Atlantic Ocean while three were located in

1936-519: Was removed from service January 1, 2010. Since the 1960s this role has been largely superseded by satellites , long range aircraft and weather buoys . Weather observations from ships continue from thousands of voluntary merchant vessels in routine commercial operation; the Old Weather crowdsourcing project transcribes naval logs from before the era of dedicated ships. Weather buoys are instruments which collect weather and oceanography data within

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