1.
Summit
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A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, a summit is a maximum in elevation. The topographic terms acme, apex, peak, and zenith are synonymous, the UIAA definition is that a summit is independent if it has a prominence of 30 metres or more, it is a mountain if it has a prominence of at least 300 metres. This can be summarised as follows, A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top, Summit may also refer to the highest point along a line, trail, or route. In many parts of the western United States, the term refers to the highest point along a road, highway. For example, the highest point along Interstate 80 in California is referred to as Donner Summit while the highest point on Interstate 5 is Siskiyou Mountain Summit, geoid Hill List of highest mountains Maxima and minima Nadir Summit accordance Peak finder
2.
Topographic prominence
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It is a measure of the independence of a summit. A peaks key col is a point on this contour line. By convention, the prominence of Mount Everest, the Earths highest mountain, is taken to equal the elevation of its summit above sea level, if the peaks prominence is P metres, to get from the summit to any higher terrain one must descend at least P metres. Together with the convention for Mount Everest, this implies that the prominence of any island or continental highpoint is equal to its elevation above sea level, for every ridge connecting the peak to higher terrain, find the lowest point on the ridge. The key col is defined as the highest of these cols, the prominence is the difference between the elevation of the peak and the elevation of the key col. The following mental exercise may illustrate the meaning of topographic prominence, imagine you are standing at the top of a peak and imagine that an imaginary sea level rises to your feet. Now slowly lower the sea level and an imaginary island appears beneath your feet. Your island will grow and will merge with other islands that emerge, the parent peak may be either close or far from the subject peak. The summit of Mount Everest is the parent peak of Aconcagua at a distance of 17,755 km, the key col may also be close or far from the subject peak. The key col for Aconcagua is the Bering Strait at a distance of 13,655 km, the key col for the South Summit of Mount Everest is about 100 m distant. Prominence is interesting to many mountaineers because it is a measurement that is strongly correlated with the subjective significance of a summit. Peaks with low prominences are either subsidiary tops of some higher summit or relatively insignificant independent summits, peaks with high prominences tend to be the highest points around and are likely to have extraordinary views. Only summits with a sufficient degree of prominence are regarded as independent mountains, for example, the worlds second-highest mountain is K2. While Mount Everests South Summit is taller than K2, it is not considered an independent mountain because it is a subsummit of the main summit, many lists of mountains take topographic prominence as a criterion for inclusion, or cutoff. John and Anne Nuttalls The Mountains of England and Wales uses a cutoff of 15 m, in the contiguous United States, the famous list of fourteeners uses a cutoff of 300 ft /91 m. Also in the U. S.2000 feet of prominence has become a threshold that signifies that a peak has major stature. This generates lists of peaks ranked by prominence, which are different from lists ranked by elevation. Such lists tend to emphasize isolated high peaks, such as range or island high points, one advantage of a prominence-ranked list is that it needs no cutoff, since a peak with high prominence is automatically an independent peak
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Geographic coordinate system
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A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection. The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead. Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before 1300, in 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the equator, the north pole is 90° N, the south pole is 90° S. The 0° parallel of latitude is designated the equator, the plane of all geographic coordinate systems. The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point. All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side. The antipodal meridian of Greenwich is both 180°W and 180°E, the combination of these two components specifies the position of any location on the surface of Earth, without consideration of altitude or depth. The grid formed by lines of latitude and longitude is known as a graticule, the origin/zero point of this system is located in the Gulf of Guinea about 625 km south of Tema, Ghana. To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0. 3% larger than the radius measured through the poles, the shorter axis approximately coincides with the axis of rotation
4.
American Samoa
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American Samoa is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of Samoa. American Samoa consists of five islands and two coral atolls. The largest and most populous island is Tutuila, with the Manuʻa Islands, Rose Atoll, All islands except for Swains Island are part of the Samoan Islands, located west of the Cook Islands, north of Tonga, and some 300 miles south of Tokelau. To the west are the islands of the Wallis and Futuna group, the 2010 census showed a total population of 55,519 people. The total land area is 199 square kilometers, slightly more than Washington, American Samoa is the southernmost territory of the U. S. and one of two U. S. territories south of the Equator, along with the uninhabited Jarvis Island. Tuna products are the exports, and the main trading partner is the United States. American Samoa is noted for having the highest rate of enlistment of any U. S. state or territory. Most American Samoans are bilingual and can speak English and Samoan fluently, Samoan is the same language spoken in neighboring independent Samoa. Contact with Europeans began in the early 18th century, dutchman Jacob Roggeveen was the first known European to sight the Samoan Islands in 1722. This visit was followed by French explorer Louis-Antoine de Bougainville who named them the Navigator Islands in 1768, contact was limited before the 1830s, when English missionaries and traders began arriving. The site of battle is called Massacre Bay. Mission work in the Samoas had begun in late 1830 when John Williams of the London Missionary Society arrived from the Cook Islands, by that time, the Samoans had gained a reputation for being savage and warlike, as violent altercations had occurred between natives and European visitors. In March 1889, an Imperial German naval force entered a village on Samoa, three American warships then entered the Apia harbor and prepared to engage the three German warships found there. Before any shots were fired, a typhoon wrecked both the American and German ships, a compulsory armistice was then called because of the lack of any warships. Forerunners to the Tripartite Convention of 1899 were the Washington Conference of 1887, the Treaty of Berlin of 1889, the following year, the USA formally occupied its portion, a smaller group of eastern islands, one of which contains the noted harbor of Pago Pago. The Navy secured a Deed of Cession of Tutuila in 1900, the territory became known as the US Naval Station Tutuila. On July 17,1911, the US Naval Station Tutuila, in 1918 during the final stages of World War I, the flu pandemic had taken its toll, spreading rapidly from country to country. The result of Poyers quick actions earned him the Navy Cross from the US Navy, with this distinction, American Samoans regarded Poyer as their hero for what he had done to prevent the deadly disease
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Topographic map
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Traditional definitions require a topographic map to show both natural and man-made features. A topographic map is published as a map series, made up of two or more map sheets that combine to form the whole map. A contour line is a line connecting places of equal elevation, however, in the vernacular and day to day world, the representation of relief is popularly held to define the genre, such that even small-scale maps showing relief are commonly called topographic. The study or discipline of topography is a broader field of study. Topographic maps are based on topographical surveys, performed at large scales, these surveys are called topographical in the old sense of topography, showing a variety of elevations and landforms. This is in contrast to older cadastral surveys, which primarily show property, the first multi-sheet topographic map series of an entire country, the Carte géométrique de la France, was completed in 1789. Topographic surveys were prepared by the military to assist in planning for battle, as such, elevation information was of vital importance. As they evolved, topographic map series became a resource in modern nations in planning infrastructure. Excluding borders, each sheet was 44 cm high and up to 66 cm wide, although the project eventually foundered, it left an indexing system that remains in use. TIGER was developed in the 1980s and used in the 1990, digital elevation models were also compiled, initially from topographic maps and stereographic interpretation of aerial photographs and then from satellite photography and radar data. Since all these were government projects funded with taxes and not classified for security reasons. Initial applications were mostly professionalized forms such as innovative surveying instruments, by the mid-1990s, increasingly user-friendly resources such as online mapping in two and three dimensions, integration of GPS with mobile phones and automotive navigation systems appeared. As of 2011, the future of standardized, centrally printed topographical maps is left somewhat in doubt, the various features shown on the map are represented by conventional signs or symbols. For example, colors can be used to indicate a classification of roads and these signs are usually explained in the margin of the map, or on a separately published characteristic sheet. Topographic maps are commonly called contour maps or topo maps. In the United States, where the national series is organized by a strict 7. 5-minute grid. Topographic maps conventionally show topography, or land contours, by means of contour lines, contour lines are curves that connect contiguous points of the same altitude. In other words, every point on the line of 100 m elevation is 100 m above mean sea level
6.
United States Geological Survey
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The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its resources. The organization has four science disciplines, concerning biology, geography, geology. The USGS is a research organization with no regulatory responsibility. The USGS is a bureau of the United States Department of the Interior, the USGS employs approximately 8,670 people and is headquartered in Reston, Virginia. The USGS also has major offices near Lakewood, Colorado, at the Denver Federal Center, the current motto of the USGS, in use since August 1997, is science for a changing world. The agencys previous slogan, adopted on the occasion of its anniversary, was Earth Science in the Public Service. Prompted by a report from the National Academy of Sciences, the USGS was created, by a last-minute amendment and it was charged with the classification of the public lands, and examination of the geological structure, mineral resources, and products of the national domain. This task was driven by the need to inventory the vast lands added to the United States by the Louisiana Purchase in 1803, the legislation also provided that the Hayden, Powell, and Wheeler surveys be discontinued as of June 30,1879. Clarence King, the first director of USGS, assembled the new organization from disparate regional survey agencies, after a short tenure, King was succeeded in the directors chair by John Wesley Powell. Administratively, it is divided into a Headquarters unit and six Regional Units, Other specific programs include, Earthquake Hazards Program monitors earthquake activity worldwide. The National Earthquake Information Center in Golden, Colorado on the campus of the Colorado School of Mines detects the location, the USGS also runs or supports several regional monitoring networks in the United States under the umbrella of the Advanced National Seismic System. The USGS informs authorities, emergency responders, the media, and it also maintains long-term archives of earthquake data for scientific and engineering research. It also conducts and supports research on long-term seismic hazards, USGS has released the UCERF California earthquake forecast. The USGS National Geomagnetism Program monitors the magnetic field at magnetic observatories and distributes magnetometer data in real time, the USGS operates the streamgaging network for the United States, with over 7400 streamgages. Real-time streamflow data are available online, since 1962, the Astrogeology Research Program has been involved in global, lunar, and planetary exploration and mapping. USGS operates a number of related programs, notably the National Streamflow Information Program. USGS Water data is available from their National Water Information System database
7.
Shield volcano
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A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their low profile, resembling a warriors shield lying on the ground and this is caused by the highly fluid lava they erupt, which travels farther than lava erupted from stratovolcanoes. This results in the accumulation of broad sheets of lava. The shape of shield volcanoes is due to the low viscosity of their mafic lava, Shield volcanoes are built by effusive eruptions, which flow out in all directions to create a shield like that of a warrior. Shield volcano itself is taken from the German term Schildvulkan, examples of pyroclastic shields include Billy Mitchell volcano in Papua New Guinea and the Purico Complex in Chile, an example of a felsic shield is the Big Obsidian Flow in Oregon. Active shield volcanoes experience near-continuous eruptive activity over long periods of time. Mount Everest, by comparison, is 8,848 m in height, the research has not yet been confirmed. Shield volcanoes feature a slope that gradually steepens with elevation before eventually flattening near the summit. In height they are typically about one twentieth their width, although the general form of a typical shield volcano varies little worldwide regional differences exist in their size and morphological characteristics. 4° and an average volume of 1.7 km3. Rift zones are a prevalent feature on shield volcanoes that is rare on other volcanic types, the large, decentralized shape of Hawaiian volcanoes as compared to their smaller, symmetrical Icelandic cousins can be attributed to rift eruptions. Fissure venting is common in Hawaiʻi, most Hawaiian eruptions begin with a wall of fire along a major fissure line before centralizing to a small number of points. These eruptions, the calmest of volcanic events, are characterized by the emission of highly fluid basaltic lavas with low gaseous content. These lavas travel a far greater distance than those of other types before solidifying, forming extremely wide. Low volumes of such lavas layered over long periods of time are what slowly constructs the characteristically low, central-vent eruptions, meanwhile, often take the form of large lava fountains, which can reach heights of hundreds of meters or more. If eruptive rates are enough, they may even form splatter-fed lava flows. Hawaiian eruptions are often extremely long lived, Puʻu ʻŌʻō, a cone of Kilauea, has been erupting continuously since 1983. These lava flows can be anywhere between 2 and 20 m thick, pāhoehoe flows, in contrast, move in more conventional sheets, or by the advancement of lava toes in snaking lava columns. Increasing viscosity on the part of the lava or shear stress on the part of local topography can morph a pāhoehoe flow into an aa one, although most shield volcanoes are by volume almost entirely Hawaiian and basaltic in origin, they are rarely exclusively so
8.
Types of volcanic eruptions
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Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed, some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions, the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of eruption, driven by the compression of gas within magma. Within these wide-defining eruptive types are several subtypes, the weakest are Hawaiian and submarine, then Strombolian, followed by Vulcanian and Surtseyan. The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions, subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that often correlates to eruptive types. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra, effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary widely in strength, on the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a crater near their peak. Some volcanoes exhibit lateral and fissure eruptions, notably, many Hawaiian eruptions start from rift zones, and some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to several thousands of years. But Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was likely triggered by magma that took a route from the mantle over just a few months. The volcanic explosivity index is a scale, from 0 to 8 and it is used by the Smithsonian Institutions Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes, the vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of events, characterized by the effusive eruption of very fluid basalt-type lavas with low gaseous content
9.
Manu'a
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Manuʻa, or the Manuʻa Islands Group, in the Samoan Islands, consists of three main islands, Taʻu, Ofu and Olosega. The latter two are now connected by a bridge over the shallow 137-meter-wide Asaga strait, Taʻu is the biggest island with its 44 square kilometres, and harbours the highest point of the Manuʻa at 931 metres. Politically, the form the Manua District, one of the three administrative divisions of American Samoa. All three islands are islands, volcanic remnants rising out of the sea 14° south of the equator. In contrast to most places in the world, the population of islands has been decreasing steadily for decades. In the 1930s some 20% of the population of American Samoa lived in the Manuʻa Islands, by the 1980s, only 6% were located there. Emigration is the consequence of a lack of opportunities and a desire of young people to participate in the more modern lifestyle offered on Tutuila. All the land of Manuʻa is owned communally by Samoan families of Manuʻa and this includes the National Parks lands which are only leased to the US National Parks system for 50 years. Samoan oral historical traditions state that Manua was a centre of a large Polynesian empire which included all of the Samoan archipelago. The traditional capital of Manuʻa is the village of Taʻū, on the island of Taʻū, the Manuʻa Group is now part of the US Protectorate of American Samoa. Samoa aligned its interests with the U. S. in a Deed of Succession, cession followed the Tripartite Convention of 1899 that partitioned the eastern islands of Samoa from the western islands of Samoa. The history of Manuʻa is said in Samoan oratory to contain the origins of Samoan and Polynesian culture, and this journey of the sun is strongly related to traditional beliefs and defines Samoa Sasae and Samoa Sisifo. The term Faasamoa describes The Samoan Way, or traditional Samoan way of life The sovereign of Manuʻa was called the Tui Manuʻa, the last Tui Manuʻa was Tuimanuʻa Elisara of the early 20th century. Tuimanuʻa Elisara died on July 2,1909, the title Tui Manuʻa technically still exists although there is no titleholder, Tuimanuʻa Elisara desired before his death that the title die with him. It was the U. S. government position at the time that his title changed to District Governor upon the hoisting of the U. S. flag at Taʻū on June 5,1900. However, titles and holdings were not obliterated when the became a U. S. territory. Today, many families of Manuʻa rely on income from family members working in Tutuila, the local diet is generally healthier than in Tutuila, with less reliance on imported American and New Zealand tinned foods, and a greater reliance on local fishing and farming. The people of Manuʻa speak the Samoan language and utilize the t, the high school on Taʻū, called Manuʻa High School, serves all of Manuʻa
