SUMMARY / RELATED TOPICS

Aeolian processes

Aeolian processes spelled eolian or æolian, pertain to wind activity in the study of geology and weather and to the wind's ability to shape the surface of the Earth. Winds may erode and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture and a large supply of unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts; the term is derived from the name of the keeper of the winds. Wind erodes the Earth's surface by abrasion. Regions which experience intense and sustained erosion are called deflation zones. Most aeolian deflation zones are composed of desert pavement, a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. Half of Earth's desert surfaces are stony deflation zones; the rock mantle in desert pavements protects the underlying material from deflation. A dark, shiny stain, called desert varnish or rock varnish, is found on the surfaces of some desert rocks that have been exposed at the surface for a long period of time.

Manganese, iron oxides and clay minerals form most varnishes and provide the shine. Deflation basins, called blowouts, are hollows formed by the removal of particles by wind. Blowouts are small, but may be up to several kilometers in diameter. Wind-driven grains abrade landforms. In parts of Antarctica wind-blown snowflakes that are technically sediments have caused abrasion of exposed rocks. Grinding by particles carried in the wind creates grooves or small depressions. Ventifacts are rocks which have been cut, sometimes polished, by the abrasive action of wind. Sculpted landforms, called yardangs, are up to tens of meters high and kilometers long and are forms that have been streamlined by desert winds; the famous Great Sphinx of Giza in Egypt may be a modified yardang. Major global aeolian dust movements thought to influence and/or be influenced by weather and climate variation: From Sahara averaged 182 million tons of dust each year between 2007 and 2011, carried past the western edge of the Sahara at longitude 15W.

Variation: 86%. Destination: 132 mln tons cross the Atlantic, 27.7 mln tons fall in Amazon Basin, 43 mln make it to the Caribbean. Texas and Florida receive the dust. Events have become far more common in recent decades. Source: NASA's Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data. Harmattan winter dust storms in West Africa occur blowing dust to the ocean. Gobi Desert to Korea, Japan and Western USA. See Asian dust. Thar Desert pre-monsoon towards Delhi, Uttar Pradesh, Indo-Gangetic Plain. See 2018 Indian dust storms. Shamal June–July winds blowing dust in north to south in Saudi Arabia, Iraq, UAE, parts of Pakistan. Haboob dust storms in Sudan, Arizona associated with monsoon. Khamsin dust from Libya and Levant in Spring associated with extratropical cyclones. Dust Bowl event in USA, carried sand eastward. 5500 tons were deposited in Chicago area. Sirocco sandy winds from Africa/Sahara blowing north into South Europe. Kalahari Desert blowing east to southern Indian Ocean and Australia.

Particles are transported by winds through suspension and creeping along the ground. Small particles may be held in the atmosphere in suspension. Upward currents of air support the weight of suspended particles and hold them indefinitely in the surrounding air. Typical winds near Earth's surface suspend particles less than 0.2 millimeters in diameter and scatter them aloft as dust or haze. Saltation is downwind movement of particles in a series of skips. Saltation lifts sand-size particles no more than one centimeter above the ground and proceeds at one-half to one-third the speed of the wind. A saltating grain may hit other grains; the grain may hit larger grains that are too heavy to hop, but that creep forward as they are pushed by saltating grains. Surface creep accounts for as much as 25 percent of grain movement in a desert. Aeolian turbidity currents are better known as dust storms. Air over deserts is cooled when rain passes through it; this cooler and denser air sinks toward the desert surface.

When it reaches the ground, the air is deflected forward and sweeps up surface debris in its turbulence as a dust storm. Crops, people and even climates are affected by dust storms; some dust storms are intercontinental, a few may circle the globe, they may engulf entire planets. When the Mariner 9 spacecraft entered its orbit around Mars in 1971, a dust storm lasting one month covered the entire planet, thus delaying the task of photo-mapping the planet's surface. Most of the dust carried by dust storms is in the form of silt-size particles. Deposits of this windblown silt are known as loess; the thickest known deposit of loess, 335 meters, is on the Loess Plateau in China. This same Asian dust is blown for thousands of miles, forming deep beds in places as far away as Hawaii. In Europe and in the Americas, accumulations of loess are from 20 to 30 meters thick; the soils developed on loess are highly productive for agriculture. Aeolian transport from deserts plays an important role in ecosystems globally, e.g. by transport of minerals from the Sahara to the Amazon

Eion

Eion, ancient Chrysopolis, was an ancient Greek Eretrian colony in Thracian Macedonia in the region of Edonis. It sat at the mouth of the Strymon River, it is referred to in Thucydides' History of the Peloponnesian War as a place of considerable strategic importance to the Athenians during the Peloponnesian War. Athenians for the first time attempted to capture Eion in 497 BC during the Ionian Revolt, unsuccessful as the revolt ended with Persians re-establishing control over the Thrace, including Eion, a Persian fortress meant for permanent stay was built there in 492 BC. Eion functioned as one of the main Achaemenid cities in Thrace where food was stored for the Persian king Xerxes I his great armies. Herodotus and Diodorus speak of Persian garrisons, of which the one at Eion was amongst them, which meant that its senior commander was ethnically Persian. Xerxes had recalled most of the Persian troops from the area in the winter of 480/479 BC, it was captured by the Delian League in 475 BC under the leadership of the Athenian general Cimon, the son of Miltiades the Younger, who started a siege on the city.

Refusing Cimon's offer of an honorable withdrawal, the Persian commander Boges destroyed the treasure, killed his family, committed suicide as the food ran out. Cimon turned the course of the River Strymon so that it flowed against the city walls, causing the mud brick fortifications to dissolve; the inhabitants were enslaved. The capture of Eion was the beginning of a military campaign undertaken by the newly formed Delian League, whose objective was to clear the Aegean Sea of Persian fleets and pirates in order to facilitate Athenian access to the Hellespont; the nearby Athenian colony of Amphipolis was founded in 437 BC three miles up the Strymon River. The settlers, led by Hagnon, used Eion as their initial base of operations. In 424 BC, during the Peloponnesian War, Eion was the site where the Athenian commander Aristides intercepted a Persian messenger named Artaphernes; the message, on its way to Sparta, was a letter from the Persian king addressing previous requests made to him by the Spartans.

In the war, in the winter of 424/423 BC, the Spartan general Brasidas captured Amphipolis with his Thracian allies. When he moved against Eion, however, he was unable to overcome the Athenian defenders, who were led by Thucydides, who had come from Thasos with his squadron in time to save it. Although he held Eion, Thucydides was subsequently ostracized by the Athenians for his failure to defend the more pivotal city of Amphipolis. Eion was known in the early 19th century as Rendina, hence the earlier name Gulf of Rendina for the Strymonian Gulf. Whether its site was that of Byzantine Chrysopolis is disputed; the location has been recovered since at least the 19th century, as William Martin Leake reported finding there extensive ruins of thick walls, constructed of small stones and mortar, among which appear many squared blocks in the Hellenic style, on the left bank of the Strymon. However, those ruins belong to the Byzantine period, have been attributed to a town of the Lower Empire, which the Italians converted into Contessa, siting on the site of Eion.

This article incorporates text from a publication now in the public domain: Smith, William, ed.. "Eion". Dictionary of Greek and Roman Geography. London: John Murray

Brigitte Sarry

Brigitte Sarry was a German chemist and a professor at the Technical University of Berlin. Sarry grew up in Allenstein. After moving with her family to Göttingen, she finished her Abitur in Göttingen in 1939. Sarry studied chemistry at the University of Göttingen, interrupted by an interlude at the Ludwig Maximilian University of Munich, she wrote her diploma thesis as well as her dissertation in the working group of Günther Rienäcker on para-hydrogen conversions on solid solutions of copper and platinum. She started her dissertation in Göttingen and finished it at the University of Rostock. Brigitte Sarry received her doctorate in Rostock on the 14th of April in 1945. In 1954, she finished her habilitation in Inorganic Chemistry at the University of Rostock; this habilitation focused on the investigation of hydrogen compounds of transition metals. Sarry declined a professorship Technical University Leuna-Merseburg, did research at the University of Stuttgart, worked as a lecturer at the University of Halle.

In 1958, Brigitte Sarry fled to West Berlin, where she continued her scientific research under difficult external conditions at the today's TU Berlin. She started as a "wissenschaftliche Rätin" and worked as an extraordinary professor. In March 1969, Sarry was appointed full professor at the TU Berlin, she worked there at the Institute of Inorganic and Analytical Chemistry in the field of organometallic compounds of transition elements, she provided important impulses for the development of homoleptic metal organyls. In autumn 1982, Brigitte Sarry retired early for health reasons. One of her research topics were homoleptic metal organyls, she was able to isolate and characterize pyrophoric and thermically unstable solids such as Li4Ta6 ∙ 3.5 O2 and Li3Mo6 ∙ 3 O2. Sarry published the following textbook on general chemistry: Sarry, Brigitte. Eigenschaften und Bau der Atome. Urania, she updated and extended a German translation of a textbook on inorganic chemistry: Huheey, James E.. Anorganische Chemie: Prinzipien von Struktur und Reaktivität.

Berlin: De Gruyter. ISBN 978-3110081633. OCLC 46194314