The Demerara River is a river in eastern Guyana that rises in the central rainforests of the country and flows to the north for 346 kilometres until it reaches the Atlantic Ocean. Georgetown, Guyana's largest seaport and capital, is situated on the east bank of the river's mouth; the river divides Essequibo Islands-West Demerara on the west bank from Demerara-Mahaica to the east. The Demerara's estuary is narrow and the flowrate is rapid; this scouring action maintains a 5-to-6-metre-deep direct channel to the ocean. The river's deep brown color is the result of the massive quantities of silt carried from upriver by the powerful currents. So powerful are these currents, that the ocean retains the Demerara's brown color for a considerable distance out to sea; the Demerara's width and depth allow oceangoing vessels up to 5,000 t to navigate up to Linden, while smaller vessels may reach up to Malali. Beyond Malali, numerous rapids make further upstream travel impossible. A floating bridge, the Demerara Harbour Bridge, crosses the river 6 kilometres south of Georgetown from Peter's Hall, East Bank Demerara to Schoon Ord, West Bank Demerara.
Tributaries of the Demerara River include the Haiama River, Kuruabaru River, Haiakwa Creek and Haianari Creek. The islands Inver and Biesen are found 25 to 30 kilometres from the mouth. Borselem was once the location of the Dutch capital of Demerara. A Dutch colony of the same name was situated along the river's banks; the colony founded the sugarcane industry. Bauxite is mined around the Demerara, Linden is a major export centre
Biodiversity refers to the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic and ecosystem level. Terrestrial biodiversity is greater near the equator, the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, is richest in the tropics; these tropical forest ecosystems cover less than 10 percent of earth's surface, contain about 90 percent of the world's species. Marine biodiversity is highest along coasts in the Western Pacific, where sea surface temperature is highest, in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity tends to cluster in hotspots, has been increasing through time, but will be to slow in the future. Rapid environmental changes cause mass extinctions. More than 99.9 percent of all species that lived on Earth, amounting to over five billion species, are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described.
More in May 2016, scientists reported that 1 trillion species are estimated to be on Earth with only one-thousandth of one percent described. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC. In July 2016, scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor of all organisms living on Earth; the age of the Earth is about 4.54 billion years. The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago, during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland. More in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia.
According to one of the researchers, "If life arose quickly on Earth.. it could be common in the universe."Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon marked a rapid growth in biodiversity via the Cambrian explosion—a period during which the majority of multicellular phyla first appeared; the next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of animal life; the Permian–Triassic extinction event, 251 million years ago, was the worst. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has attracted more attention than others because it resulted in the extinction of the dinosaurs; the period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity. Named the Holocene extinction, the reduction is caused by human impacts habitat destruction.
Conversely, biodiversity positively impacts human health in a number of ways, although a few negative effects are studied. The United Nations designated 2011–2020 as the United Nations Decade on Biodiversity. 1916 - The term biological diversity was used first by J. Arthur Harris in "The Variable Desert," Scientific American, JSTOR 6182: "The bare statement that the region contains a flora rich in genera and species and of diverse geographic origin or affinity is inadequate as a description of its real biological diversity." 1975 - The term natural diversity was introduced 1980 - Thomas Lovejoy introduced the term biological diversity to the scientific community in a book.. It became used. 1985 -The contracted form biodiversity was coined by W. G. Rosen 1985 - The term "biodiversity" appears in the article, "A New Plan to Conserve the Earth's Biota" by Laura Tangley. 1988 - The term biodiversity first appeared in a publication. The present - the term has achieved widespread use. "Biodiversity" is most used to replace the more defined and long established terms, species diversity and species richness.
Biologists most define biodiversity as the "totality of genes and ecosystems of a region". An advantage of this definition is that it seems to describe most circumstances and presents a unified view of the traditional types of biological variety identified: taxonomic diversity ecological diversity morphological diversity functional diversity This multilevel construct is consistent with Datman and Lovejoy. An explicit definition consistent with this interpretation was first given in a paper by Bruce A. Wilcox commissioned by the International Union for the Conservation of Nature and Natural Resources for the 1982 World National Parks Conference. Wilcox's definition was "Biological diversity is the variety of life forms...at all levels of biologi
Niagara Falls is the collective name for three waterfalls that straddle the international border between the Canadian province of Ontario and the US state of New York. They form the southern end of the Niagara Gorge. From largest to smallest, the three waterfalls are the Horseshoe Falls, the American Falls and the Bridal Veil Falls; the Horseshoe Falls lie on the border of the United States and Canada while the American Falls lie on the United States' side, separated by Goat Island. The smaller Bridal Veil Falls are on the United States' side, separated from the American Falls by Luna Island. Located on the Niagara River, which drains Lake Erie into Lake Ontario, the combined falls form the highest flow rate of any waterfall in North America that has a vertical drop of more than 50 metres. During peak daytime tourist hours, more than 168,000 m3 of water goes over the crest of the falls every minute. Horseshoe Falls is the most powerful waterfall in North America; the falls are 27 kilometres north-northwest of Buffalo, New York, 121 kilometres south-southeast of Toronto, between the twin cities of Niagara Falls and Niagara Falls, New York.
Niagara Falls was formed when glaciers receded at the end of the Wisconsin glaciation, water from the newly formed Great Lakes carved a path through the Niagara Escarpment en route to the Atlantic Ocean. Niagara Falls is famed both as a valuable source of hydroelectric power. Balancing recreational and industrial uses has been a challenge for the stewards of the falls since the 19th century; the Horseshoe Falls drop about 57 metres, while the height of the American Falls varies between 21 and 30 metres because of the presence of giant boulders at its base. The larger Horseshoe Falls are about 790 metres wide; the distance between the American extremity of the Niagara Falls and the Canadian extremity is 3,409 feet. The peak flow over Horseshoe Falls was recorded at 6,400 cubic metres per second; the average annual flow rate is 2,400 cubic metres per second. Since the flow is a direct function of the Lake Erie water elevation, it peaks in late spring or early summer. During the summer months, at least 2,800 cubic metres per second of water traverses the falls, some 90% of which goes over the Horseshoe Falls, while the balance is diverted to hydroelectric facilities.
This is accomplished by employing a weir – the International Control Dam – with movable gates upstream from the Horseshoe Falls. The falls' flow is further halved at night, during the low tourist season in the winter, remains a minimum of 1,400 cubic metres per second. Water diversion is regulated by the 1950 Niagara Treaty and is administered by the International Niagara Board of Control; the verdant green colour of the water flowing over the Niagara Falls is a byproduct of the estimated 60 tonnes/minute of dissolved salts and "rock flour" generated by the erosive force of the Niagara River itself. The features that became Niagara Falls were created by the Wisconsin glaciation about 10,000 years ago; the same forces created the North American Great Lakes and the Niagara River. All were dug by a continental ice sheet that drove through the area, deepening some river channels to form lakes, damming others with debris. Scientists argue there is an old valley, St David's Buried Gorge, buried by glacial drift, at the approximate location of the present Welland Canal.
When the ice melted, the upper Great Lakes emptied into the Niagara River, which followed the rearranged topography across the Niagara Escarpment. In time, the river cut a gorge through cuesta; because of the interactions of three major rock formations, the rocky bed did not erode evenly. The top rock formation was composed of erosion-resistant Lockport dolostone; that hard layer of stone eroded more than the underlying materials. The aerial photo on the right shows the hard caprock, the Lockport Formation, which underlies the rapids above the falls, the upper third of the high gorge wall. Below the hard-rock formation, comprising about two-thirds of the cliff, lay the weaker, sloping Rochester Formation; this formation was composed of shale, though it has some thin limestone layers. It contains ancient fossils. In time, the river eroded the soft layer that supported the hard layers, undercutting the hard caprock, which gave way in great chunks; this process repeated countless times carving out the falls.
Submerged in the river in the lower valley, hidden from view, is the Queenston Formation, composed of shales and fine sandstones. All three formations were laid down in an ancient sea, their differences of character deriving from changing conditions within that sea. About 10,900 years ago, the Niagara Falls was between present-day Queenston and Lewiston, New York, but erosion of their crest has caused the waterfalls to retreat 6.8 miles southward. The Horseshoe Falls, which are about 2,600 feet wide, have changed their shape through the process of erosion. Just upstream from the falls' current location, Goat Island splits the course of the Niagara River, resulting in the separation of the Canadian Horseshoe Falls to the west from the American and Bridal Veil Falls to the east. Engineering has slowed recession; the current rate of erosion is appr
South America is a continent in the Western Hemisphere in the Southern Hemisphere, with a small portion in the Northern Hemisphere. It may be considered a subcontinent of the Americas, how it is viewed in the Spanish and Portuguese-speaking regions of the Americas; the reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west on the north and east by the Atlantic Ocean, it includes twelve sovereign states, a part of France, a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands and Tobago, Panama may be considered part of South America. South America has an area of 17,840,000 square kilometers, its population as of 2016 has been estimated at more than 420 million. South America ranks fourth in fifth in population. Brazil is by far the most populous South American country, with more than half of the continent's population, followed by Colombia, Argentina and Peru. In recent decades Brazil has concentrated half of the region's GDP and has become a first regional power.
Most of the population lives near the continent's western or eastern coasts while the interior and the far south are sparsely populated. The geography of western South America is dominated by the Andes mountains. Most of the continent lies in the tropics; the continent's cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the overwhelming majority of South Americans speak Portuguese or Spanish, societies and states reflect Western traditions. South America occupies the southern portion of the Americas; the continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border, although some may consider the border instead to be the Panama Canal. Geopolitically and geographically all of Panama – including the segment east of the Panama Canal in the isthmus – is included in North America alone and among the countries of Central America.
All of mainland South America sits on the South American Plate. South America is home to Angel Falls in Venezuela. South America's major mineral resources are gold, copper, iron ore and petroleum; these resources found in South America have brought high income to its countries in times of war or of rapid economic growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity has hindered the development of diversified economies; the fluctuation in the price of commodities in the international markets has led to major highs and lows in the economies of South American states causing extreme political instability. This is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth. South America is home to many interesting and unique species of animals including the llama, piranha, vicuña, tapir; the Amazon rainforests possess high biodiversity, containing a major proportion of the Earth's species.
Brazil is the largest country in South America, encompassing around half of the continent's land area and population. The remaining countries and territories are divided among three regions: The Andean States, the Guianas and the Southern Cone. Traditionally, South America includes some of the nearby islands. Aruba, Curaçao, Trinidad and the federal dependencies of Venezuela sit on the northerly South American continental shelf and are considered part of the continent. Geo-politically, the island states and overseas territories of the Caribbean are grouped as a part or subregion of North America, since they are more distant on the Caribbean Plate though San Andres and Providencia are politically part of Colombia and Aves Island is controlled by Venezuela. Other islands that are included with South America are the Galápagos Islands that belong to Ecuador and Easter Island, Robinson Crusoe Island, Chiloé and Tierra del Fuego. In the Atlantic, Brazil owns Fernando de Noronha and Martim Vaz, the Saint Peter and Saint Paul Archipelago, while the Falkland Islands are governed by the United Kingdom, whose sovereignty over the islands is disputed by Argentina.
South Georgia and the South Sandwich Islands may be associate
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric
United Nations Framework Convention on Climate Change
The United Nations Framework Convention on Climate Change is an international environmental treaty adopted on 9 May 1992 and opened for signature at the Earth Summit in Rio de Janeiro from 3 to 14 June 1992. It entered into force on 21 March 1994, after a sufficient number of countries had ratified it; the UNFCCC objective is to "stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system". The framework sets non binding limits on greenhouse gas emissions for individual countries and contains no enforcement mechanisms. Instead, the framework outlines how specific international treaties may be negotiated to specify further action towards the objective of the UNFCCC Initially, an Intergovernmental Negotiating Committee produced the text of the Framework Convention during its meeting in New York from 30 April to 9 May 1992; the UNFCCC was adopted on 9 May 1992, opened for signature on 4 June 1992. The UNFCCC has 197 parties as of December 2015.
The convention enjoys broad legitimacy due to its nearly universal membership. The parties to the convention have met annually from 1995 in Conferences of the Parties to assess progress in dealing with climate change. In 1997, the Kyoto Protocol was concluded and established binding obligations for developed countries to reduce their greenhouse gas emissions in the period 2008–2012; the 2010 United Nations Climate Change Conference produced an agreement stating that future global warming should be limited to below 2.0 °C relative to the pre-industrial level. The Protocol was amended in 2012 to encompass the period 2013–2020 in the Doha Amendment, which as of December 2015 had not entered into force. In 2015 the Paris Agreement was adopted, governing emission reductions from 2020 on through commitments of countries in Nationally Determined Contributions, lowering the target to 1.5 °C. The Paris Agreement entered into force on 4 November 2016. One of the first tasks set by the UNFCCC was for signatory nations to establish national greenhouse gas inventories of greenhouse gas emissions and removals, which were used to create the 1990 benchmark levels for accession of Annex I countries to the Kyoto Protocol and for the commitment of those countries to GHG reductions.
Updated inventories must be submitted annually by Annex I countries. "UNFCCC" is the name of the United Nations Secretariat charged with supporting the operation of the Convention, with offices in Haus Carstanjen, the UN Campus in Bonn, Germany. From 2010 to 2016 the head of the secretariat was Christiana Figueres. In July 2016, Patricia Espinosa succeeded Figueres; the Secretariat, augmented through the parallel efforts of the Intergovernmental Panel on Climate Change, aims to gain consensus through meetings and the discussion of various strategies. The United Nations Framework Convention on Climate Change was opened for signature at the 1992 United Nations Conference on Environment and Development in Rio de Janeiro. On 12 June 1992, 154 nations signed the UNFCCC, which upon ratification committed signatories' governments to reduce atmospheric concentrations of greenhouse gases with the goal of "preventing dangerous anthropogenic interference with Earth's climate system"; this commitment would require substantial reductions in greenhouse gas emissions Article 3 of the Convention states that Parties should act to protect the climate system on the basis of "common but differentiated responsibilities", that developed country Parties should "take the lead" in addressing climate change.
Under Article 4, all Parties make general commitments to address climate change through, for example, climate change mitigation and adapting to the eventual impacts of climate change. Article 4 states: The extent to which developing country Parties will implement their commitments under the Convention will depend on the effective implementation by developed country Parties of their commitments under the Convention related to financial resources and transfer of technology and will take into account that economic and social development and poverty eradication are the first and overriding priorities of the developing country Parties; the Framework Convention specifies the aim of developed Parties stabilizing their greenhouse gas emissions at 1990 levels, by the year 2000. After the signing of the UNFCCC treaty, Parties to the UNFCCC have met at conferences to discuss how to achieve the treaty's aims. At the 1st Conference of the Parties, Parties decided that the aim of Annex I Parties stabilizing their emissions at 1990 levels by the year 2000 was "not adequate", further discussions at conferences led to the Kyoto Protocol.
The Kyoto Protocol sets emissions targets for developed countries which are binding under international law. The Kyoto Protocol has had two commitment periods, the first of which lasted from 2008-2012; the second one runs from 2013-2020 and is based on the Doha Amendment to the Protocol, which has not entered into force. The US has not ratified the Kyoto Protocol, while Canada denounced it in 2012; the Kyoto Protocol has been ratified by all the other Annex I Parties. All Annex I Parties, excluding the US, have participated in the 1st Kyoto commitment period. 37 Annex I countries and the EU have agreed to second-round Kyoto targets. These countries are Australia, all members of the European Union, Croatia, Kazakhstan, Norway, Sw