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Topic Review
100,000-Year Problem
The 100,000-year problem ("100 ky problem", "100 ka problem") of the Milankovitch theory of orbital forcing refers to a discrepancy between the reconstructed geologic temperature record and the reconstructed amount of incoming solar radiation, or insolation over the past 800,000 years. Due to variations in the Earth's orbit, the amount of insolation varies with periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of incident solar energy drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of glaciations. While there is a Milankovitch cycle in the range of 100,000 years, related to Earth's orbital eccentricity, its contribution to variation in insolation is much smaller than those of precession and obliquity. The 100,000-year-problem refers to the lack of an obvious explanation for the periodicity of ice ages at roughly 100,000 years for the past million years, but not before, when the dominant periodicity corresponded to 41,000 years. The unexplained transition between the two periodicity regimes is known as the Mid-Pleistocene Transition, dated to some 800,000 years ago. The related "400,000-year-problem" refers to the absence of a 400,000-year periodicity due to orbital eccentricity in the geological temperature record over the past 1.2 million years. The transition in periodicity from 41,000 years to 100,000 years can now be reproduced in numerical simulations that include a decreasing trend in carbon dioxide and glacially induced removal of regolith, as explained in more detail in the article Mid-Pleistocene Transition.
  • 920
  • 08 Oct 2022
Topic Review
Antarctic Circumpolar Current
File:Thermohaline Circulation using Improved Flow Field.ogv The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise (as seen from the South Pole) from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and has a mean transport estimated at 100-150 Sverdrups (Sv, million m³/s), or possibly even higher, making it the largest ocean current. The current is circumpolar due to the lack of any landmass connecting with Antarctica and this keeps warm ocean waters away from Antarctica, enabling that continent to maintain its huge ice sheet. Associated with the Circumpolar Current is the Antarctic Convergence, where the cold Antarctic waters meet the warmer waters of the subantarctic, creating a zone of upwelling nutrients. These nurture high levels of phytoplankton with associated copepods and krill, and resultant foodchains supporting fish, whales, seals, penguins, albatrosses, and a wealth of other species. The ACC has been known to sailors for centuries; it greatly speeds up any travel from west to east, but makes sailing extremely difficult from east to west, although this is mostly due to the prevailing westerly winds. Jack London's story "Make Westing" and the circumstances preceding the mutiny on the Bounty poignantly illustrate the difficulty it caused for mariners seeking to round Cape Horn westbound on the clipper ship route from New York to California. The eastbound clipper route, which is the fastest sailing route around the world, follows the ACC around three continental capes – Cape Agulhas (Africa), South East Cape (Australia), and Cape Horn (South America). The current creates the Ross and Weddell gyres.
  • 658
  • 08 Oct 2022
Topic Review
Ocean-bottom Seismometer
An ocean-bottom seismometer (OBS) is a seismometer that is designed to record the earth motion under oceans and lakes from man-made sources and natural sources. Sensors at the sea floor are used to observe acoustic and seismic events. Seismic and acoustic signals may be caused by different sources, by earthquakes and tremors as well as by artificial sources. Computing and analyzing the data yields information about the kind of source and, in case of natural seismic events, the geophysics and geology of the sea floor and the deeper crust. The deployment of OBS along a profile will give information about the deep structure of the Earth's crust and upper mantle in offshore areas. OBS may be equipped with a maximum of a three-component geophone in addition to a hydrophone, and thus it needs a capacity of more than 144 Mbytes, which would be the minimum for an adequate MCS profiling. In a typical survey, the instruments should be operational for several days (deployments can exceed 12 months), which requires a data storage capacity of more than 500 Mbyte. Other experiments, such as tomographic investigations within a 3D-survey or seismological monitoring, demand even larger capacities.
  • 555
  • 08 Oct 2022
Topic Review
Phanerozoic
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present and began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons. The time span of the Phanerozoic starts with the sudden appearance of fossilized evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.
  • 6.7K
  • 08 Oct 2022
Topic Review
Atmospheric Models
Static atmospheric models describe how the ideal gas properties (namely: pressure, temperature, density, and molecular weight) of an atmosphere change, primarily as a function of altitude. The World Meteorological Organization defines a standard atmosphere as "a hypothetical vertical distribution of atmospheric temperature, pressure and density which, by international agreement, is roughly representative of year-round, midlatitude conditions. Typical usages are as a basis for pressure altimeter calibrations, aircraft performance calculations, aircraft and rocket design, ballistic tables, and meteorological diagrams." For example, the U.S. Standard Atmosphere derives the values for air temperature, pressure, and mass density, as a function of altitude above sea level. Other static atmospheric models may have other outputs, or depend on inputs besides altitude.
  • 683
  • 08 Oct 2022
Topic Review
Waste Tire Management Practice
Montenegro faces serious challenges in terms of waste tire management. The financial and economic justification of the implementation of the first phase of the project of collection, takeover and transport, sorting, and storage of waste tires from the three municipalities in Montenegro.
  • 953
  • 08 Oct 2022
Topic Review
Source of Water Pollution
Water pollution is a severe health concern. Several studies have recently demonstrated the efficacy of various approaches for treating wastewater from anthropogenic activities. Wastewater treatment is an artificial procedure that removes contaminants and impurities from wastewater or sewage before discharging the effluent back into the environment. It can also be recycled by being further treated or polished to provide safe quality water for use, such as potable water.
  • 528
  • 08 Oct 2022
Topic Review
Flower Strips
Wildflower strips, a semi-natural manmade habitat comprising mixtures of native herbaceous species, can be sown on arable field margins to provide multiple ecological, agricultural and conservation benefits. The main aim of creating flower strips is to enrich the fauna of farmland with the species that are beneficial in terms of the agricultural economy: animals that limit the population density of pests (e.g., parasitic insects, including parasitoids, predatory insects and spiders and birds) and pollinators (insects that feed on pollen or nectar), including those with economic significance. For this reason, flower strips should be included in agri-environmental programs to enhance sustainable plant production and the biodiversity of pollinators on farmland or natural aphid enemies. Flower strips are thus increasingly frequently promoted in environmental programmes, and financial support is being implemented as an additional business incentive.
  • 1.1K
  • 08 Oct 2022
Topic Review
List of Minerals U–V (Complete)
This list includes those recognised minerals beginning with the letters U and V. 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. The first link is to mindat.org, the second link is to webmineral.com, and the third is to the Handbook of Mineralogy (Mineralogical Society of America).
  • 933
  • 07 Oct 2022
Topic Review
Cartography of Jerusalem
The cartography of Jerusalem is the creation, editing, processing and printing of maps of Jerusalem from ancient times until the rise of modern surveying techniques. Almost all extant maps known to scholars from the pre-modern era were prepared by Christian mapmakers for a Christian European audience. Maps of Jerusalem can be categorized between original factual maps, copied maps and imaginary maps, the latter being based on religious books. The maps were produced in a variety of materials, including parchment, vellum, mosaic, wall paintings and paper. All maps marking milestones in the cartography of Jerusalem are listed here following the cartographic histories of the city, from Titus Tobler and Reinhold Röhricht's studies in the 19th century to those of Hebrew University of Jerusalem academics Rehav Rubin and Milka Levy-Rubin in recent decades. The article lists maps that progressed the cartography of Jerusalem before the rise of modern surveying techniques, showing how mapmaking and surveying improved and helped outsiders to better understand the geography of the city. Imaginary maps of the ancient city and copies of existing maps are excluded. The Madaba Map is the oldest known map of Jerusalem, in the form of a mosaic in a Greek Orthodox Church. At least 12 maps survive from the Catholic mapmakers of the Crusades; they were drawn on vellum and mostly show the city as a circle. The first printed map of the city was drawn by Erhard Reuwich and published in 1486 by Bernhard von Breydenbach in his Peregrinatio in Terram Sanctam, based on his pilgrimage of 1483. Approximately 500 maps are known between the late-1400s and the mid-1800s; the significant increase in number is due to the advent of the printing press. Few of the mapmakers had travelled to Jerusalem – most of the maps were either copies of others' maps or were imaginary (i.e. based on reading of religious texts) in nature. The first map based on actual field measurements was published in 1818 by the Czech mapmaker Franz Wilhelm Sieber. The first map based on modern surveying techniques was published by Charles Wilson of the Palestine Exploration Fund in 1864–65, who produced two maps for the British Ordnance Survey.
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  • 07 Oct 2022
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