Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements, it is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, has two main oxidation states, +2 and the more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number of protons, it has two main allotropes: at room temperature, the stable allotrope is β-tin, a silvery-white, malleable metal, but at low temperatures it transforms into the less dense grey α-tin, which has the diamond cubic structure. Metallic tin does not oxidize in air; the first tin alloy used on a large scale was bronze, made of 1/8 tin and 7/8 copper, from as early as 3000 BC. After 600 BC, pure metallic tin was produced. Pewter, an alloy of 85–90% tin with the remainder consisting of copper and lead, was used for flatware from the Bronze Age until the 20th century.
In modern times, tin is used in many alloys, most notably tin/lead soft solders, which are 60% or more tin, in the manufacture of transparent, electrically conducting films of indium tin oxide in optoelectronic applications. Another large application for tin is corrosion-resistant tin plating of steel; because of the low toxicity of inorganic tin, tin-plated steel is used for food packaging as tin cans. However, some organotin compounds can be as toxic as cyanide. Tin is a soft, malleable and crystalline silvery-white metal; when a bar of tin is bent, a crackling sound known as the "tin cry" can be heard from the twinning of the crystals. Tin melts at low temperatures of about 232 °C, the lowest in group 14; the melting point is further lowered to 177.3 °C for 11 nm particles. Β-tin, stable at and above room temperature, is malleable. In contrast, α-tin, stable below 13.2 °C, is brittle. Α-tin has a diamond cubic crystal structure, similar to silicon or germanium. Α-tin has no metallic properties at all because its atoms form a covalent structure in which electrons cannot move freely.
It is a dull-gray powdery material with no common uses other than a few specialized semiconductor applications. These two allotropes, α-tin and β-tin, are more known as gray tin and white tin, respectively. Two more allotropes, γ and σ, exist at temperatures above 161 pressures above several GPa. In cold conditions, β-tin tends to transform spontaneously into α-tin, a phenomenon known as "tin pest". Although the α-β transformation temperature is nominally 13.2 °C, impurities lower the transition temperature well below 0 °C and, on the addition of antimony or bismuth, the transformation might not occur at all, increasing the durability of the tin. Commercial grades of tin resist transformation because of the inhibiting effect of the small amounts of bismuth, antimony and silver present as impurities. Alloying elements such as copper, bismuth and silver increase its hardness. Tin tends rather to form hard, brittle intermetallic phases, which are undesirable, it does not form wide solid solution ranges in other metals in general, few elements have appreciable solid solubility in tin.
Simple eutectic systems, occur with bismuth, lead and zinc. Tin was one of the first superconductors to be studied. Tin can be attacked by acids and alkalis. Tin can be polished and is used as a protective coat for other metals. A protective oxide layer prevents further oxidation, the same that forms on pewter and other tin alloys. Tin helps to accelerate the chemical reaction. Tin has ten stable isotopes, with atomic masses of 112, 114 through 120, 122 and 124, the greatest number of any element. Of these, the most abundant are 120Sn, 118Sn, 116Sn, while the least abundant is 115Sn; the isotopes with mass numbers have no nuclear spin, while those with odd have a spin of +1/2. Tin, with its three common isotopes 116Sn, 118Sn and 120Sn, is among the easiest elements to detect and analyze by NMR spectroscopy, its chemical shifts are referenced against SnMe4; this large number of stable isotopes is thought to be a direct result of the atomic number 50, a "magic number" in nuclear physics. Tin occurs in 29 unstable isotopes, encompassing all the remaining atomic masses from 99 to 137.
Apart from 126Sn, with a half-life of 230,000 years, all the radioisotopes have a half-life of less than a year. The radioactive 100Sn, discovered in 1994, 132Sn are one of the few nuclides with a "doubly magic" nucleus: despite being unstable, having lopsided proton–neutron ratios, they represent endpoints beyond which stability drops off rapidly. Another 30 metastable isomers have been characterized for isotopes between 111 and 131, the most stable being 121mSn with a half-life of 43.9 years. The relative differences in the abundances of tin's stable isotopes can be explained by their different modes of formation in stellar nucleosynthesis. 116Sn through 120Sn inclusive are formed in the s-process in most stars and hence they are the most common isotopes, while 122Sn and 124Sn are only formed in the r-process (rapid neutr
Desertification is a type of land degradation in which a dry area of land becomes a desert losing its bodies of water as well as vegetation and wildlife. It is caused by a variety of factors, such as through climate change and through the overexploitation of soil through human activity; when deserts appear automatically over the natural course of a planet's life cycle it can be called a natural phenomenon. Desertification is a significant global ecological and environmental problem with far reaching consequences on socio-economic and political conditions. Considerable controversy exists over the proper definition of the term "desertification" for which Helmut Geist has identified more than 100 formal definitions; the most accepted of these is that of the Princeton University Dictionary which defines it as "the process of fertile land transforming into desert as a result of deforestation, drought or improper/inappropriate agriculture". Desertification has been neatly defined in the text of the United Nations Convention to Combat Desertification as "land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities."Another major contribution to the controversy comes from the sub-grouping of types of desertification.
Spanning from the vague yet shortsighted view as the "man-made-desert" to the broader yet less focused type as the "Non-pattern-Desert". The earliest known discussion of the topic arose soon after the French colonization of West Africa, when the Comité d'Etudes commissioned a study on desséchement progressif to explore the prehistoric expansion of the Sahara Desert; the world's most noted deserts have been formed by natural processes interacting over long intervals of time. During most of these times, deserts have shrunk independent of human activities. Paleodeserts are large sand seas now inactive because they are stabilized by vegetation, some extending beyond the present margins of core deserts, such as the Sahara, the largest hot desert. Desertification has played a significant role in human history, contributing to the collapse of several large empires, such as Carthage and the Roman Empire, as well as causing displacement of local populations. Historical evidence shows that the serious and extensive land deterioration occurring several centuries ago in arid regions had three epicenters: the Mediterranean, the Mesopotamian Valley, the Loess Plateau of China, where population was dense.
Drylands occupy 40–41% of Earth’s land area and are home to more than 2 billion people. It has been estimated that some 10–20% of drylands are degraded, the total area affected by desertification being between 6 and 12 million square kilometres, that about 1–6% of the inhabitants of drylands live in desertified areas, that a billion people are under threat from further desertification; as of 1998, the then-current degree of southward expansion of the Sahara was not well known, due to a lack of recent, measurable expansion of the desert into the Sahel at the time. The impact of global warming and human activities are presented in the Sahel. In this area, the level of desertification is high compared to other areas in the world. All areas situated in the eastern part of Africa are characterized by a dry climate, hot temperatures, low rainfall. So, droughts are the rule in the Sahel region; some studies have shown that Africa has lost 650,000 km² of its productive agricultural land over the past 50 years.
The propagation of desertification in this area is considerable. Some statistics have shown that since 1900 the Sahara has expanded by 250 km to the south over a stretch of land from west to east 6,000 km long; the survey, done by the research institute for development, had demonstrated that this means dryness is spreading fast in the Sahelian countries. 70% of the arid area has deteriorated and water resources have disappeared, leading to soil degradation. The loss of topsoil means that plants cannot take root and can be uprooted by torrential water or strong winds; the United Nations Convention says that about six million Sahelian citizens would have to give up the desertified zones of sub-Saharan Africa for North Africa and Europe between 1997 and 2020. Another major area, being impacted by desertification is the Gobi Desert; the Gobi desert is the fastest moving desert on Earth. This has destroyed many villages in its path. Photos show that the Gobi Desert has expanded to the point the entire nation of Croatia could fit inside its area.
This is causing a major problem for the people of China. They will soon have to deal with the desert. Although the Gobi Desert itself is still a distance away from Beijing, reports from field studies state there are large sand dunes forming only 70 km outside the city; as the desertification takes place, the landscape may progress through different stages and continuously transform in appearance. On sloped terrain, desertification can create larger empty spaces over a large strip of land, a phenomenon known as "Brousse tigrée". A mathematical model of this phenomenon proposed by C. Klausmeier attributes this patterning to dynamics in plant-water interaction. One outcome of this observation suggests an optimal plan
Geography of Algeria
Algeria comprises 2,381,741 square kilometers of land, more than four-fifths of, desert, in northern Africa, between Morocco and Tunisia. It is the largest country in Africa, its Arabic name, Al Jazair, derives from the name of the capital Algiers, after the small islands found in its harbor. It has a long Mediterranean coastline; the northern portion, an area of mountains and plateaus between the Mediterranean Sea and the Sahara Desert, forms an integral part of the section of North Africa known as the Maghreb. This area includes Morocco and the northwestern portion of Libya known as Tripolitania. Land boundaries:Total: 6,764 km Border countries: Libya 989 km, Mali 1,359 km, Mauritania 460 km, Morocco 1,559 km, Niger 951 km, Tunisia 1,034 km, Western Sahara 41 km. Area – comparative: 3.5 times the size of Texas and twice the size of Ontario. Coastline: 1,622 km Maritime claims:Exclusive fishing zone: 32–52 nmi Territorial sea: 12 nmi Stretching from the Moroccan border the Tell Atlas, including the Djebel Babor formation, is the dominant northwestern mountain range.
Stretching more than 600 kilometers eastward from the Moroccan border, the high plateau area consist of undulating, steppe-like plains lying between the Tell and Saharan Atlas ranges. The elevation averages between 1,100–1,300 metres in elevation in the west, dropping to 400 metres in the east; the climate is so dry. The plateau area is covered by alluvial debris formed. An occasional ridge projects through the alluvial cover to interrupt the monotony of the landscape. Higher and more continuous than the Tell Atlas, the Sahara Atlas range is formed of three massifs: the Ksour Range near the Moroccan border, the Amour Range, the Ouled-Naïl Range south of Algiers; the mountains, which receive more rainfall than those of the High Plateaus, include some good grazing land. Watercourses on the southern slopes of these massifs disappear into the desert but supply the wells of numerous oases along the northern edge of the desert, of which Biskra, Béchar are the most prominent. Eastern Algeria consists of a massive area extensively dissected into mountains and basins.
It differs from the western portion of the country in that its prominent topographic features do not parallel the coast. In its southern sector, the steep cliffs and long ridges of the Aurès Mountains create an impenetrable refuge that has played an important part in the history of the Maghrib since Roman times. Near the northern coast, the Petite Kabylie Mountains are separated from the Grande Kabylie range at the eastward limits of the Tell by the Soummam River; the coast is predominantly mountainous in the far eastern part of the country, but limited plains provide hinterlands for the port cities of Bejaïa, Annaba. In the interior of the region, extensive high plains mark the region around Constantine. Near Constantine, salt marshes offer seasonal grazing grounds to seminomadic sheep herders; the Algerian portion of the Sahara extends south of the Saharan Atlas for 1,500 kilometres to the Niger and Mali frontiers. The desert is an otherworldly place, scarcely considered an integral part of the country.
Far from being covered wholly by sweeps of sand, however, it is a region of great diversity. Immense areas of sand dunes called areg occupy about one-quarter of the territory; the largest such region is the Grand Erg Oriental, where enormous dunes two to five metres high are spaced about 40 metres apart. Much of the remainder of the desert is covered by rocky platforms called humud, the entire southeastern quarter is taken up by the high, complex mass of the Ahaggar and Tassili n'Ajjer highlands, some parts of which reach more than 2,000 metres. Surrounding the Ahaggar are sandstone plateaus, cut into deep gorges by ancient rivers, to the west a desert of pebbles stretches to the Mali frontier; the desert consists of distinguishable northern and southern sectors, the northern sector extending southward a little less than half the distance to the Niger and Mali frontiers. The north, less arid than the south, supports most of the few persons who live in the region and contains most of the desert's oases.
Sand dunes are the most prominent features of this area's topography, but between the desert areas of the Grand Erg Oriental and the Grand Erg Occidental and extending north to the Atlas Saharien are plateaus, including the Tademaït and a complex limestone structure called the M'zab where the Mozabite Berbers have settled. The southern zone of the Sahara is totally arid and is inhabited only by the Tuareg nomads and by oil camp workers. Barren rock predominates, but in some parts of Ahaggar and Tassili n'Ajjer alluvial deposits permit garden farming. Northern Algeria enjoys a mild, Mediterranean climate, it lies within the same latitudes as southern California and has somewhat similar climatic conditions. Its broken topography, provides sharp local contrasts in both prevailing temperatures and incidence of rainfall. Year-to-year variations in climatic conditions are common; this area, the most inhabited in Algeria, is referred to as the Tell. In the Tell, temperatures in summer average between 21 and 42 °C (
Enclave and exclave
An enclave is a territory, or a part of a territory, surrounded by the territory of one other state. Territorial waters have the same sovereign attributes as land, enclaves may therefore exist within territorial waters. An exclave is a portion of a state or territory geographically separated from the main part by surrounding alien territory. Many exclaves are enclaves. Enclave is sometimes used improperly to denote a territory, only surrounded by another state. Vatican City and San Marino, enclaved by Italy, Lesotho, enclaved by South Africa, are enclaved states. Unlike an enclave, an exclave can be surrounded by several states; the Azerbaijani exclave of Nakhchivan is an example of an exclave. Semi-enclaves and semi-exclaves are areas that, except for possessing an unsurrounded sea border, would otherwise be enclaves or exclaves. Enclaves and semi-enclaves can exist as independent states, while exclaves always constitute just a part of a sovereign state. A pene-enclave is a part of the territory of one country that can be conveniently approached—in particular, by wheeled traffic—only through the territory of another country.
Pene-enclaves are called functional enclaves or practical enclaves. Many pene-exclaves border their own territorial waters, such as Point Roberts, Washington. A pene-enclave can exist on land, such as when intervening mountains render a territory inaccessible from other parts of a country except through alien territory. A cited example is the Kleinwalsertal, a valley part of Vorarlberg, accessible only from Germany to the north; the word enclave is French and first appeared in the mid-15th century as a derivative of the verb enclaver, from the colloquial Latin inclavare. It was a term of property law that denoted the situation of a land or parcel of land surrounded by land owned by a different owner, that could not be reached for its exploitation in a practical and sufficient manner without crossing the surrounding land. In law, this created a servitude of passage for the benefit of the owner of the surrounded land; the first diplomatic document to contain the word enclave was the Treaty of Madrid, signed in 1526.
The term enclave began to be used to refer to parcels of countries, fiefs, towns, etc. that were surrounded by alien territory. This French word entered the English and other languages to denote the same concept, although local terms have continued to be used. In India, the word "pocket" is used as a synonym for enclave. In British administrative history, subnational enclaves were called detachments or detached parts, national enclaves as detached districts or detached dominions. In English ecclesiastic history, subnational enclaves were known as peculiars; the word exclave, modeled on enclave, is a logically extended back-formation of enclave. Enclaves exist for a variety of historical and geographical reasons. For example, in the feudal system in Europe, the ownership of feudal domains was transferred or partitioned, either through purchase and sale or through inheritance, such domains were or came to be surrounded by other domains. In particular, this state of affairs persisted into the 19th century in the Holy Roman Empire, these domains exhibited many of the characteristics of sovereign states.
Prior to 1866 Prussia alone consisted of more than 270 discontiguous pieces of territory. Residing in an enclave within another country has involved difficulties in such areas as passage rights, importing goods, provision of utilities and health services, host nation cooperation. Thus, over time, enclaves have tended to be eliminated. For example, two-thirds of the then-existing national-level enclaves were extinguished on August 1, 2015, when the governments of India and Bangladesh implemented a Land Boundary Agreement that exchanged 162 first-order enclaves; this exchange thus de-enclaved another two dozen second-order enclaves and one third-order enclave, eliminating 197 of the Indo-Bangladesh enclaves in all. The residents in these enclaves had complained of being stateless. Only Bangladesh's Dahagram–Angarpota enclave remained. For illustration, in the figure, A1 is a semi-enclave. Although A2 is an exclave of A, it cannot be classed as an enclave because it shares borders with B and C; the territory A3 is both an exclave of A and an enclave from the viewpoint of B.
The singular territory D, although an enclave, is not an exclave. An enclave is a part of the territory of a state, enclosed within the territory of another state. To distinguish the parts of a state enclosed in a single other state, they are called true enclaves. A true enclave cannot be reached without passing through the territory of a single other state that surrounds it. Vinokurov calls this the restrictive definition of "enclave" given by international law, which thus "comprises only so-called'true enclaves'". Two examples are Büsingen am Hochrhein, a true enclave of Germany, Campione d'Italia, a true enclave of Italy, both of which are surrounded by Switzerland; the definition of a territory comprises territorial waters. In the case of enclaves in territorial waters, they are called maritime (those surrounded by ter
The Gambia River is a major river in West Africa, running 1,120 kilometres from the Fouta Djallon plateau in north Guinea westward through Senegal and the Gambia to the Atlantic Ocean at the city of Banjul. It is navigable for about half that length; the river is associated with The Gambia, the smallest country in mainland Africa, which consists of little more than the downstream half of the river and its two banks. From the Fouta Djallon, the river runs northwest into the Tambacounda Region of Senegal, where it flows through the Parc National du Niokolo Koba is joined by the Nieri Ko and Koulountou before entering the Gambia at Fatoto. At this point the river runs west, but in a meandering course with a number of oxbows, about 100km from its mouth it widens, to over 10km wide where it meets the sea. Near the mouth of the river, near Juffure, is Kunta Kinteh Island, a place used in the slave trade, now a UNESCO World Heritage Site. On the banks of the river, the Kaira Konko Lodge, a scout camp, is located there.
The aquatic fauna in the Gambia River basin is associated with that of the Sénégal River basin, the two are combined under a single ecoregion known as the Senegal-Gambia Catchments. Although the species richness is moderately high, only three species of frogs and one fish are endemic to this ecoregion. Oysters are harvested from the River Gambia by women and used to make oyster stew, a traditional dish in the cuisine of Gambia. Media related to Gambia River at Wikimedia Commons Gambia River Information & Photos
Whaling is the hunting of whales for their usable products such as meat and blubber, which can be turned into a type of oil which became important in the Industrial Revolution. It was practiced as an organized industry as early as 875 AD. By the 16th century, it had risen to be the principle industry in the coastal regions of Spain and France; the industry spread throughout the world, became profitable in terms of trade and resources. Some regions of the world's oceans, along the animals' migration routes, had a dense whale population, became the targets for large concentrations of whaling ships, the industry continued to grow well into the 20th century; the depletion of some whale species to near extinction led to the banning of whaling in many countries by 1969, to a worldwide cessation of whaling as an industry in the late 1980s. The earliest forms of whaling date to at least circa 3000 BC. Coastal communities around the world have long histories of subsistence use of cetaceans, by dolphin drive hunting and by harvesting drift whales.
Industrial whaling emerged with organized fleets of whaleships in the 17th century. By the late 1930s more than 50,000 whales were killed annually. In 1986, the International Whaling Commission banned commercial whaling because of the extreme depletion of most of the whale stocks. Contemporary whaling is subject to intense debate. Countries that support commercial whaling, notably Iceland and Norway, wish to lift the ban on certain whale stocks for hunting. Anti-whaling countries and environmental groups oppose lifting the ban. Under the terms of the IWC moratorium, aboriginal whaling is allowed to continue on a subsistence basis. Over the past few decades, whale watching has become a significant industry in many parts of the world; the live capture of cetaceans for display in aquaria continues. Whaling began in prehistoric times in coastal waters; the earliest depictions of whaling are the Neolithic Bangudae Petroglyphs in Korea, which may date back to 6000 BC. These images are the earliest evidence for whaling.
Although prehistoric hunting and gathering is considered to have had little ecological impact, early whaling in the Arctic may have altered freshwater ecology. Early whaling affected the development of disparate cultures – such as Norway and Japan, both of which continue to hunt in the 21st century; the Basques were the first to catch whales commercially, dominated the trade for five centuries, spreading to the far corners of the North Atlantic and reaching the South Atlantic. The development of modern whaling techniques was spurred in the 19th century by the increase in demand for whale oil, sometimes known as "train oil", in the 20th century by a demand for margarine and whale meat. Many countries which once had significant industries, such as the Netherlands and Argentina, ceased whaling long ago, so are not covered in this article; the primary species hunted are minke whales,belugas and pilot whales. Which are some of the smallest species of whales. There are smaller numbers killed of gray whales, sei whales, fin whales, bowhead whales, Bryde's whales, sperm whales and humpback whales.
Recent scientific surveys estimate a population of 103,000 minkes in the northeast Atlantic. With respect to the populations of Antarctic minke whales, as of January 2010, the IWC states that it is "unable to provide reliable estimates at the present time" and that a "major review is underway by the Scientific Committee."Whale oil is used little today and modern whaling is done for food: for pets, fur farms, sled dogs and humans, for making carvings of tusks and vertebrae. Both meat and blubber are eaten from narwhals and bowheads. From commercially hunted minkes, meat is eaten by humans or animals, blubber is rendered down to cheap industrial products such as animal feed or, in Iceland, as a fuel supplement for whaling ships. International cooperation on whaling regulation began in 1931 and culminated in the signing of the International Convention for the Regulation of Whaling in 1946, its aim is to: provide for the proper conservation of whale stocks and thus make possible the orderly development of the whaling industry.
The International Whaling Commission was set up under the ICRW to decide hunting quotas and other relevant matters based on the findings of its Scientific Committee. Non-member countries conduct their own management programs, it regulates hunting of 13 species of great whales, has not reached consensus on whether it may regulate smaller species. The IWC voted on July 23, 1982, to establish a moratorium on commercial whaling of great whales beginning in the 1985–86 season. Since 1992, the IWC's Scientific Committee has requested that it be allowed to give quota proposals for some whale stocks, but this has so far been refused by the Plenary Committee. At the 2010 meeting of the International Whaling Commission in Morocco, representatives of the 88 member states discussed whether or not to lift the 24-year ban on commercial whaling. Japan and Iceland have urged the organisation to lift the ban. A coalition of anti-whaling nations has offered a compromise plan that would allow these countries to continue whaling, but with smaller catches and under close supervision.
Their plan would completely ban whaling in the Southern Ocean. More than 200 scientists and experts have
Delaware is one of the 50 states of the United States, in the South-Atlantic or Southern region. It is bordered to the south and west by Maryland, north by Pennsylvania, east by New Jersey and the Atlantic Ocean; the state takes its name from Thomas West, 3rd Baron De La Warr, an English nobleman and Virginia's first colonial governor. Delaware occupies the northeastern portion of the Delmarva Peninsula. It's the sixth most densely populated. Delaware's largest city is Wilmington; the state is divided into the lowest number of any state. From north to south, they are New Castle County, Kent County, Sussex County. While the southern two counties have been predominantly agricultural, New Castle County is more industrialized. Before its coastline was explored by Europeans in the 16th century, Delaware was inhabited by several groups of Native Americans, including the Lenape in the north and Nanticoke in the south, it was colonized by Dutch traders at Zwaanendael, near the present town of Lewes, in 1631.
Delaware was one of the 13 colonies participating in the American Revolution. On December 7, 1787, Delaware became the first state to ratify the Constitution of the United States, has since been known as "The First State"; the state was named after the Delaware River, which in turn derived its name from Thomas West, 3rd Baron De La Warr, the ruling governor of the Colony of Virginia at the time Europeans first explored the river. The Delaware Indians, a name used by Europeans for Lenape people indigenous to the Delaware Valley derive their name from the same source; the surname de La Warr is of Anglo-Norman origin. It came from a Norman lieu-dit La Guerre; this toponymic could derive from the Latin word ager, from the Breton gwern or from the Late Latin varectum. The toponyms Gara, Gaire appear in old texts cited by Lucien Musset, where the word gara means gore, it could be linked with a patronymic from the Old Norse verr. Delaware is 96 miles long and ranges from 9 miles to 35 miles across, totaling 1,954 square miles, making it the second-smallest state in the United States after Rhode Island.
Delaware is bounded to the north by Pennsylvania. Small portions of Delaware are situated on the eastern side of the Delaware River sharing land boundaries with New Jersey; the state of Delaware, together with the Eastern Shore counties of Maryland and two counties of Virginia, form the Delmarva Peninsula, which stretches down the Mid-Atlantic Coast. The definition of the northern boundary of the state is unusual. Most of the boundary between Delaware and Pennsylvania was defined by an arc extending 12 miles from the cupola of the courthouse in the city of New Castle; this boundary is referred to as the Twelve-Mile Circle. Although the Twelve-Mile Circle is claimed to be the only territorial boundary in the United States, a true arc, the Mexican boundary with Texas includes several arcs, many cities in the South have circular boundaries; this border extends all the way east to the low-tide mark on the New Jersey shore continues south along the shoreline until it again reaches the 12-mile arc in the south.
To the west, a portion of the arc extends past the easternmost edge of Maryland. The remaining western border runs east of due south from its intersection with the arc; the Wedge of land between the northwest part of the arc and the Maryland border was claimed by both Delaware and Pennsylvania until 1921, when Delaware's claim was confirmed. Delaware is with the lowest mean elevation of any state in the nation, its highest elevation, located at Ebright Azimuth, near Concord High School, is less than 450 feet above sea level. The northernmost part of the state is part of the Piedmont Plateau with rolling surfaces; the Atlantic Seaboard fall line follows the Robert Kirkwood Highway between Newark and Wilmington. A ridge about 75 to 80 feet in elevation extends along the western boundary of the state and separates the watersheds that feed Delaware River and Bay to the east and the Chesapeake Bay to the west. Since all of Delaware is a part of the Atlantic coastal plain, the effects of the ocean moderate its climate.
The state lies in the humid subtropical climate zone. Despite its small size, there is significant variation in mean temperature and amount of snowfall between Sussex County and New Castle County. Moderated by the Atlantic Ocean and Delaware Bay, the southern portion of the state has a milder climate and a longer growing season than the northern portion of the state. Delaware's all-time record high of 110 °F was recorded at Millsboro on July 21, 1930; the all-time record low of −17 °F was recorded at Millsboro on January 17, 1893. The transitional climate of Delaware supports a wide variety of vegetation. In the northern third of the state are found Northeastern coastal forests and mixed oak forests typical of the northeastern United States. In the southern two-thirds of the state are found Middle Atlantic coastal forests. Trap Pond State Park, along with areas in other parts of Sussex County, for example, support