Search | Encyclopedia MDPI

You're using an outdated browser. Please upgrade to a modern browser for the best experience.

Subject:

Sort:

Most Viewed Latest Alphabetical (A-Z) Alphabetical (Z-A)

Filter:

All Topic Review Biography Peer Reviewed Entry Video Entry

Topic Review

Mercury's Magnetic Field

Mercury's magnetic field is approximately a magnetic dipole (meaning the field has only two magnetic poles) apparently global, on planet Mercury. Data from Mariner 10 led to its discovery in 1974; the spacecraft measured the field's strength as 1.1% that of Earth's magnetic field. The origin of the magnetic field can be explained by dynamo theory. The magnetic field is strong enough near the bow shock to slow the solar wind, which induces a magnetosphere.

3.7K
15 Nov 2022

Topic Review

Climate Change Adaptation in Greenland

Climate change adaptation is a pressing issue in Greenland. The term climate change describes long-term changes to the climate system. Since the 1950s a stark rise in global temperatures has been observed. As climate change, whether natural or anthropogenic, impacts the livelihoods of people across the globe, responses i.e. ways to prepare and adjust under changing vulnerabilities become important. Such responses are commonly discussed under the term adaptation, "the process of adjustment to actual or expected climate and its effects", as defined by the IPCC. Geographically Greenland is situated between the Arctic and the Atlantic Ocean, with one third of the island being north of the Arctic Circle. Since the middle of the 20th century, the Arctic has been warming at about twice the global rate. Rising temperatures put increasing pressure on certain plant and tree species and contribute to Greenland's melting ice sheet. This affects and changes the livelihood of the Greenlandic population, particularly the Inuit people, which make up to 80 percent of the total population. Besides the decline of fish stocks, the country's landscape is changing: the melting ice reveals minerals, oil and gas. This has attracted interest from local and foreign investors for potential resource extraction. As new industries are accompanied by new job opportunities and potential wealth, lifestyles are changing. Greenland is in transition, in terms of biophysical as well as cultural and social conditions.

3.7K
20 Nov 2022

Topic Review

Stone Mountain is a quartz monzonite dome monadnock and the site of Stone Mountain Park near Stone Mountain, Georgia. At its summit, the elevation is 1,686 feet (514 m) above sea level and 825 feet (251 m) above the surrounding area. Stone Mountain is well known for not only its geology, but also the enormous rock relief on its north face, the largest bas-relief in the world. The carving depicts three Confederate figures, Jefferson Davis, Robert E. Lee and Stonewall Jackson, and has been the subject of widespread controversy. Stone Mountain was once owned by the Venable Brothers. It was purchased by the State of Georgia in 1958 "as a memorial to the Confederacy." Stone Mountain Park officially opened on April 14, 1965 – 100 years to the day after Lincoln's assassination, although the park had been in use for a few years. It is the most visited destination in the state of Georgia. Stone Mountain is more than 5 miles (8 km) in circumference at its base. The summit of the mountain can be reached by a walk-up trail on the west side of the mountain or by the Skyride aerial tram.

3.5K
04 Nov 2022

Topic Review

Intermarium (Polish: Międzymorze, Polish pronunciation: [mʲɛnd͡zɨˈmɔʐɛ]) was a geopolitical project conceived by politicians in successor states of the former Polish–Lithuanian Commonwealth in several iterations, some of which anticipated the inclusion as well of other, neighboring states. The proposed multinational polity would have extended across territories lying between the Baltic, Black and Adriatic Seas, hence the name meaning "Between-Seas". Prospectively a federation of Central and Eastern European countries, the post-World War I Intermarium plan pursued by Polish leader and former political prisoner of the Russian Empire, Józef Piłsudski (1867–1935), sought to recruit to the proposed federation the Baltic states (Lithuania, Latvia, Estonia), Finland , Belarus, Ukraine, Hungary, Romania, Yugoslavia and Czechoslovakia. The Polish name Międzymorze (from między, "between"; and morze, "sea"), meaning "Between-Seas", was rendered into Latin as "Intermarium." The proposed federation was meant to emulate the Polish–Lithuanian Commonwealth, stretching from the Baltic Sea to the Black Sea, that, from the end of the 16th century to the end of the 18th, had united the Kingdom of Poland and the Grand Duchy of Lithuania. Intermarium complemented Piłsudski's other geopolitical vision, Prometheism, whose goal was the dismemberment of the Russian Empire and that Empire's divestment of its territorial acquisitions. Intermarium was, however, perceived by some Lithuanians as a threat to their newly established independence, and by some Ukrainians as a threat to their aspirations for independence, and while France backed the proposal, it was opposed by Russia and by most other Western powers. Within two decades of the failure of Piłsudski's grand scheme, all the countries that he had viewed as candidates for membership in the Intermarium federation had fallen to the Soviet Union or Nazi Germany, except for Finland (which suffered some territorial losses in the 1939–40 Winter War with the Soviet Union).

3.5K
19 Oct 2022

Topic Review

Mercator 1569 World Map

The Mercator world map of 1569 is titled Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata (Renaissance Latin for "New and more complete representation of the terrestrial globe properly adapted for use in navigation"). The title shows that Gerardus Mercator aimed to present contemporary knowledge of the geography of the world and at the same time 'correct' the chart to be more useful to sailors. This 'correction', whereby constant bearing sailing courses on the sphere (rhumb lines) are mapped to straight lines on the plane map, characterizes the Mercator projection. While the map's geography has been superseded by modern knowledge, its projection proved to be one of the most significant advances in the history of cartography, inspiring map historian Nordenskiöld to write "The master of Rupelmonde stands unsurpassed in the history of cartography since the time of Ptolemy." The projection heralded a new era in the evolution of navigation maps and charts and it is still their basis. The map is inscribed with a great deal of text. The framed map legends (or cartouches) cover a wide variety of topics: a dedication to his patron and a copyright statement; discussions of rhumb lines, great circles and distances; comments on some of the major rivers; accounts of fictitious geography of the north pole and the southern continent. The full Latin texts and English translations of all the legends are given below. Other minor texts are sprinkled about the map. They cover such topics as the magnetic poles, the prime meridian, navigational features, minor geographical details, the voyages of discovery and myths of giants and cannibals. These minor texts are also given below. A comparison with world maps before 1569 shows how closely Mercator drew on the work of other cartographers and his own previous works, but he declares (Legend 3) that he was also greatly indebted to many new charts prepared by Portuguese and Spanish sailors in the portolan tradition. Earlier cartographers of world maps had largely ignored the more accurate practical charts of sailors, and vice versa, but the age of discovery, from the closing decade of the fifteenth century, stimulated the integration of these two mapping traditions: Mercator's world map is one of the earliest fruits of this merger.

3.4K
22 Nov 2022

Topic Review

List of Selected Stars for Navigation

Fifty-eight selected navigational stars are given a special status in the field of celestial navigation. Of the approximately 6,000 stars visible to the naked eye under optimal conditions, the selected stars are among the brightest and span 38 constellations of the celestial sphere from the declination of −70° to +89°. Many of the selected stars were named in antiquity by the Babylonians, Greeks, Romans, and Arabs. The star Polaris, often called the "North Star", is treated specially due to its proximity to the north celestial pole. When navigating in the Northern Hemisphere, special techniques can be used with Polaris to determine latitude or gyrocompass error. The other 57 selected stars have daily positions given in nautical almanacs, aiding the navigator in efficiently performing observations on them. A second group of 115 "tabulated stars" can also be used for celestial navigation, but are often less familiar to the navigator and require extra calculations. For purposes of identification, the positions of navigational stars — expressed as declination and sidereal hour angle — are often rounded to the nearest degree. In addition to tables, star charts provide an aid to the navigator in identifying the navigational stars, showing constellations, relative positions, and brightness.

3.4K
26 Oct 2022

Topic Review

The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 6,300,000 km2 (2,400,000 sq mi), or about 35.5 percent that of the South American continent. It is located in the countries of Bolivia, Brazil , Colombia, Ecuador, Guyana, Peru, Suriname and Venezuela. Most of the basin is covered by the Amazon Rainforest, also known as Amazonia. With a 5.5 million km2 (2.1 million sq mi) area of dense tropical forest, this is the largest rainforest in the world.

3.4K
03 Nov 2022

Topic Review

Platinum Group Minerals

Russia and South Africa are the world’s leading producers of platinum group elements (PGEs). This places them in a unique position regarding the supply of these two key industrial commodities. The purpose of this paper is to provide a comparative high-level overview of aspects of the geological occurrence, mineralogy, and processing by flotation of the platinum group minerals (PGMs) found in each country. A summary of some of the major challenges faced in each country in terms of the concentration of the ores by flotation is presented alongside the opportunities that exist to increase the production of the respective metals. These include the more efficient recovery of minerals such as arsenides and tellurides, the management of siliceous gangue and chromite in the processing of these ores, and, especially in Russia, the development of novel processing routes to recover PGEs from relatively low grade ores occurring in dunites, black shale ores and in vanadium-iron-titanium-sulphide oxide formations.

3.3K
26 Jan 2021

Topic Review

New Guinea Highlands

The New Guinea Highlands, also known as the Central Range or Central Cordillera, is a long chain of mountain ranges on the island of New Guinea, including the island's tallest peak, Puncak Jaya 16,024 ft (4,884 m), the highest mountain in Oceania. The range is home to many intermountain river valleys, many of which support thriving agricultural communities. The highlands run generally east-west the length of the island, which is divided politically between Indonesia in the west and Papua New Guinea in the east.

3.3K
09 Nov 2022

Topic Review

A sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.

3.2K
11 Oct 2022

Topic Review

List of Minerals (Complete)

Mineralogy is an active science in which minerals are discovered or recognised on a regular basis. Use of old mineral names is also discontinued, for example when a name is no longer considered valid. Therefore, a list of recognised mineral species is never complete. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species. Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety. The International Mineralogical Association (IMA) is the international group that recognises new minerals and new mineral names. However, minerals discovered before 1959 did not go through the official naming procedure. Some minerals published previously have been either confirmed or discredited since that date. This list contains a mixture of mineral names that have been approved since 1959 and those mineral names believed to still refer to valid mineral species (these are called "grandfathered" species). Presently, each year about 90-110 new mineral species (the sum of all mutations c. 120/year) are officially approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association. The IMA/CNMNC administrates c. 6,500 names, and (As of January 2018), the Handbook of Mineralogy lists 4,507 species. (As of March 2018), the IMA Database of Mineral Properties/ Rruff Project lists 5,312 valid species (IMA/CNMNC) of a total of 5,525 minerals. There are 1,289 Pre-IMA minerals. (As of April 2011), the Webmineral.com website lists 2,722 published and approved (IMA/CNMNC) minerals, 81 discredited minerals (IMA/CNMNC status; Michael Fleischer discredited around thousand species in his lifetime), 2,691 synonyms and 123 "not approved" names. (As of November 2018), the IMA - CNMNC Master List of Minerals lists 5,413 valid minerals, including c. 1,166 pre-IMA minerals (grandfathered), c. 272 approved minerals but without a published description yet and c. 99 questionable minerals. Due to the length of this list, it is divided into alphabetical groups. The minerals are sorted by name.

3.1K
02 Nov 2022

Topic Review

Jet is a type of lignite, the lowest rank of coal, and is a gemstone. Unlike many gemstones, jet is not a mineral, but is rather a mineraloid. It is derived from wood that has changed under extreme pressure. The English noun jet derives from the French word for the same material, jaiet (modern French jais), ultimately referring to the ancient town of Gagae. Jet is either black or dark brown, but may contain pyrite inclusions which are of brassy colour and metallic lustre. The adjective "jet-black", meaning as dark a black as possible, derives from this material.

3.1K
27 Oct 2022

Topic Review

Dome C, also known as Dome Circe, Dome Charlie or Dome Concordia, located at Antarctica at an elevation of 3,233 metres (10,607 ft) above sea level, is one of several summits or "domes" of the Antarctic Ice Sheet. Dome C is located on the Antarctic Plateau, 1,100 kilometres (680 mi) inland from the French research station at Dumont D'Urville, 1,100 kilometres (680 mi) inland from the Australian Casey Station and 1,200 kilometres (750 mi) inland from the Italian Zucchelli station at Terra Nova Bay. Russia's Vostok Station is 560 kilometres (350 mi) away. Dome C is the site of the Concordia Research Station, jointly operated by France and Italy.

3.1K
04 Nov 2022

Topic Review

The Bruun Rule is a formula for estimating the magnitude of the retreat of the shoreline of a sandy shore in response to changes in sea level. Originally published in 1962 by Per Bruun, the Bruun Rule was the first to give a relationship between sea level rise and shoreline recession. The rule is a simple, two dimensional mass conversion, and remains in common use to estimate shoreline recession in response to sea level rise, despite criticism and modification, and the availability more complex alternate models.

3.1K
28 Oct 2022

Topic Review

Evolutionary History of Life

The evolutionary history of life on Earth traces the processes by which living and fossil organisms evolved, from the earliest emergence of life to the present. Earth formed about 4.5 billion years (Ga) ago and evidence suggests life emerged prior to 3.7 Ga. (Although there is some evidence of life as early as 4.1 to 4.28 Ga, it remains controversial due to the possible non-biological formation of the purported fossils.) The similarities among all known present-day species indicate that they have diverged through the process of evolution from a common ancestor. Approximately 1 trillion species currently live on Earth of which only 1.75–1.8 million have been named and 1.6 million documented in a central database. These currently living species represent less than one percent of all species that have ever lived on earth. The earliest evidence of life comes from biogenic carbon signatures and stromatolite fossils discovered in 3.7 billion-year-old metasedimentary rocks from western Greenland. In 2015, possible "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. In March 2017, putative evidence of possibly the oldest forms of life on Earth was reported in the form of fossilized microorganisms discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec, Canada, that may have lived as early as 4.28 billion years ago, not long after the oceans formed 4.4 billion years ago, and not long after the formation of the Earth 4.54 billion years ago. Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean Epoch and many of the major steps in early evolution are thought to have taken place in this environment. The evolution of photosynthesis, around 3.5 Ga, eventually led to a buildup of its waste product, oxygen, in the atmosphere, leading to the great oxygenation event, beginning around 2.4 Ga. The earliest evidence of eukaryotes (complex cells with organelles) dates from 1.85 Ga, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. Later, around 1.7 Ga, multicellular organisms began to appear, with differentiated cells performing specialised functions. Sexual reproduction, which involves the fusion of male and female reproductive cells (gametes) to create a zygote in a process called fertilization is, in contrast to asexual reproduction, the primary method of reproduction for the vast majority of macroscopic organisms, including almost all eukaryotes (which includes animals and plants). However the origin and evolution of sexual reproduction remain a puzzle for biologists though it did evolve from a common ancestor that was a single celled eukaryotic species. Bilateria, animals having a left and a right side that are mirror images of each other, appeared by 555 Ma (million years ago). The earliest complex land plants date back to around 850 Ma, from carbon isotopes in Precambrian rocks, while algae-like multicellular land plants are dated back even to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2.7 Ga. Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event. (The long causal chain implied seems to involve the success of early tree archaeopteris (1) drew down CO2 levels, leading to global cooling and lowered sea levels, (2) roots of archeopteris fostered soil development which increased rock weathering, and the subsequent nutrient run-off may have triggered algal blooms resulting in anoxic events which caused marine-life die-offs. Marine species were the primary victims of the Late Devonian extinction.) Ediacara biota appear during the Ediacaran period, while vertebrates, along with most other modern phyla originated about 525 Ma during the Cambrian explosion. During the Permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the Permian–Triassic extinction event 252 Ma. During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates; one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After the Cretaceous–Paleogene extinction event 66 Ma killed off the non-avian dinosaurs, mammals increased rapidly in size and diversity. Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify.

3.0K
24 Nov 2022

Topic Review

Wolf Distribution

Wolf distribution is the species distribution of the wolf (Canis lupus). Originally, wolves occurred in Eurasia above the 12th parallel north and in North America above the 15th parallel north. However, deliberate human persecution has reduced the species' range to about one-third, because of livestock predation and fear of wolf attacks on humans. The species is now extirpated (made locally extinct) in much of Western Europe, Mexico, and the contiguous United States , and completely from the British Isles and the Japanese archipelago. In modern history, the gray wolf occurs mostly in wilderness and remote areas, particularly in Canada , Alaska, the Northern United States, Europe and Asia from about the 75th parallel north to the 12th parallel north. Wolf population declines have been arrested since the 1970s, and have fostered recolonization and reintroduction in parts of its former range, due to legal protection, changes in land-use and rural human population shifts to cities. Competition with humans for livestock and game species, concerns over the danger posed by wolves to people, and habitat fragmentation pose a continued threat to the species. Despite these threats, because of the gray wolf's relatively widespread range and stable population, it is classified as Least Concern on the IUCN Red List. In Africa the population of wolves is limited to the northern regions with the African golden wolf (Canis lupaster) north of the Sahara and the Ethiopian wolf (Canis simensis) in Ethiopia.

3.0K
25 Oct 2022

Topic Review

List of Minerals N (Complete)

This list includes those recognised minerals beginning with the letter N. The International Mineralogical Association is the international group that recognises new minerals and new mineral names, however minerals discovered before 1959 did not go through the official naming procedure, although some minerals published previously have been either confirmed or discredited since that date. This list contains a mixture of mineral names that have been approved since 1959 and those mineral names believed to still refer to valid mineral species (these are called "grandfathered" species). The list is divided into groups: The data was exported from mindat.org on 29 April 2005; updated up to 'IMA2018'. The minerals are sorted by name, followed by the structural group (rruff.info/ima and ima-cnmnc by mineralienatlas.de, mainly) or chemical class (mindat.org and basics), the year of publication (if it's before of an IMA approval procedure), the IMA approval and the Nickel–Strunz code.

2.9K
10 Oct 2022

Topic Review

The Earth's inner core is the Earth's innermost part. It is primarily a solid ball with a radius of about 1,220 kilometres (760 miles), which is about 70% of the Moon's radius. It is composed of an iron–nickel alloy and some other elements. The temperature at the inner core's surface is approximately 5,700 K (5,430 °C) or 9806 °F, which is about the temperature at the surface of the Sun.

2.8K
10 Nov 2022

Topic Review

Rodrigues (French: Île Rodrigues [il ʁɔdʁiɡ]; Creole: Rodrig) is a 108 km2 (42 sq mi) autonomous outer island of the Republic of Mauritius in the Indian Ocean, about 560 km (350 mi) east of Mauritius. It is part of the Mascarene Islands, which include Mauritius and Réunion. Rodrigues is of volcanic origin and is surrounded by coral reef, and some tiny uninhabited islands lie just off its coast. The island used to be the tenth District of Mauritius; it gained autonomous status on 10 December 2002, and it is governed by the Rodrigues Regional Assembly. The capital of the island is Port Mathurin. Its inhabitants are Mauritian citizens. (As of 2014), the island's population was about 41,669, according to Statistics Mauritius. Most of the inhabitants are of African descent. Its economy is based mainly on fishing, farming, handicraft and a developing tourism sector. The island (together with Agaléga and Saint Brandon) forms part of the larger territory of the Republic of Mauritius with the President as head of state and the Chief Commissioner as head of government.

2.8K
11 Nov 2022

Topic Review

One Tree Hill (New Zealand)

Maungakiekie / One Tree Hill is a 182-metre (597 ft) volcanic peak in Auckland, New Zealand. It is an important memorial place for both Māori and other New Zealanders. The suburb around the base of the hill is also called One Tree Hill. It is surrounded by the suburbs of Royal Oak to the west, and clockwise, Epsom, Greenlane, Oranga, and Onehunga. The summit provides views across the Auckland area, and allows visitors to see both of Auckland's harbours. The hill's scoria cones were erupted from three craters – one is intact and two have been breached by lava flows that rafted away part of the side of the scoria cone. Lava flows went in all directions, many towards Onehunga, covering an area of 20 square kilometres (7.7 sq mi), making it the second largest (in area covered) of the Auckland volcanic field, behind Rangitoto Island. The volcano erupted approximately 60,000 years ago.

2.8K
10 Nov 2022

Page
of
16

Featured Entry Collections

>>

Featured Books

>>

Encyclopedia of Engineering

Encyclopedia of Social Sciences

Encyclopedia of Social Sciences
Chief Editor:
Kum Fai Yuen

Encyclopedia of COVID-19

Encyclopedia of COVID-19
Chief Editor:
Stephen Bustin

Encyclopedia of Digital Society, Industry 5.0 and Smart City

Encyclopedia of Digital Society, Industry 5.0 and Smart City
Chief Editor:
Sandro Serpa

Academic Video Service

Feedback

Top

<<	2020-2029					>>
201920202021202220232024202520262027202820292030
Today

<<	2020-2029					>>
201920202021202220232024202520262027202820292030
Today