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67-808: Dust storms from the Bodélé Depression occur on average about 100 days per year, one typical example being the massive dust storms that swept over West Africa and the Cape Verde Islands in February 2004. As the wind sweeps between the Tibesti and the Ennedi Mountains in Northern Chad , it is channeled across the depression. The dry bowl that forms the depression is marked by a series of ephemeral lakes , many of which were last filled during wetter periods of

134-495: A gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another. The arid regions of North Africa , the Middle East , Central Asia and China are the main terrestrial sources of airborne dust. It has been argued that poor management of Earth's drylands , such as neglecting

201-504: A catalyst's surface area and activity . For example, nickel can be supported on the material—the combination is called Ni–Kieselguhr—to improve its activity as a hydrogenation catalyst. Natural freshwater diatomaceous earth is used in agriculture for grain storage as an anticaking agent , as well as an insecticide. It is approved by the Food and Drug Administration as a feed additive to prevent caking . Some believe it may be used as

268-431: A considerable amount of larger sand particles are blown closer to the surface. The term dust storm is more likely to be used when finer particles are blown long distances, especially when the dust storm affects urban areas . As the force of dust passing over loosely held particles increases, particles of sand first start to vibrate, then to move across the surface in a process called saltation . As they repeatedly strike

335-452: A deposit has not been proven to affect their functionality when it comes to the adsorption of lipids; however, certain applications, such as that for slugs and snails, do work best when a particularly shaped diatom is used, suggesting that lipid adsorption is not the only factor involved. For example, in the case of slugs and snails, large, spiny diatoms work best to lacerate the epithelium of the mollusk. Diatom shells will work to some degree on

402-569: A feature now called the Bodélé Low Level Jet. In the reanalysis data sets such as ERA-40 , the wind shows up as a clear wind speed maximum at about 900 hPa (or roughly 1 km above the surface) near 18 N and 19 E. This jet maximum coincides with the exit gap of the North-easterlies between the Tibesti mountains and the Ennedi massif, which lie 2600 m and 1000 m above the flat terrain in

469-519: A fine white to off-white powder. It has a particle size ranging from more than 3  mm to less than 1  μm , but typically 10 to 200 μm. Depending on the granularity , this powder can have an abrasive feel, similar to pumice powder, and has a low density as a result of its high porosity . The typical chemical composition of oven-dried diatomaceous earth is 80–90% silica , with 2–4% alumina (attributed mostly to clay minerals ), and 0.5–2% iron oxide . Diatomaceous earth consists of

536-505: A major health hazard. Drought and wind contribute to the emergence of dust storms, as do poor farming and grazing practices by exposing the dust and sand to the wind. Wildfires can lead to dust storms as well. One poor farming practice which contributes to dust storms is dryland farming . Particularly poor dryland farming techniques are intensive tillage or not having established crops or cover crops when storms strike at particularly vulnerable times prior to revegetation . In

603-560: A marked seasonal cycle. It is active in the October–March period and relatively inactive from June–August. This timing closely matches the seasonality of dust emission from the Bodélé. Individual dust storms in the Bodélé were also shown in this research to coincide with a major strengthening of the Bodélé Low Level Jet which, in turn, is associated with the ridging of the Libyan High, a feature of

670-589: A mean particle size below about 12 μm (i.e., food grade— see below ). Although considered to be relatively low-risk, pesticides containing diatomaceous earth are not exempt from regulation in the United States under the Federal Insecticide, Fungicide, and Rodenticide Act and must be registered with the Environmental Protection Agency . Its thermal properties enable it to be used as

737-464: A natural anthelmintic (dewormer), although studies have not shown it to be effective. Some farmers add it to their livestock and poultry feed to prevent the caking of feed. "Food-Grade Diatomaceous Earth" is widely available in agricultural feed supply stores. Freshwater diatomite can be used as a growing medium in hydroponic gardens. It is also used as a growing medium in potted plants, particularly as bonsai soil. Bonsai enthusiasts use it as

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804-411: A negative charge relative to the ground which in turn loosens more sand particles which then begin saltating. This process has been found to double the number of particles predicted by previous theories. Particles become loosely held mainly due to a prolonged drought or arid conditions, and high wind speeds. Gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm . Or,

871-422: A semi-arid climate, these practices increase susceptibility to dust storms. However, soil conservation practices may be implemented to control wind erosion . A sandstorm can transport and carry large volumes of sand unexpectedly. Dust storms can carry large amounts of dust, with the leading edge being composed of a wall of thick dust as much as 1.6 km (5,200 ft) high. Dust and sand storms which come off

938-422: A soil additive, or pot a bonsai tree in 100% diatomaceous earth. In vegetable gardening it is sometimes used as a soil conditioner , because like perlite , vermiculite , and expanded clay , it retains water and nutrients, while draining fast and freely, allowing high oxygen circulation within the growing medium. Natural dried, not calcinated diatomaceous earth is regularly used in livestock nutrition research as

1005-457: A source of acid-insoluble ash (AIA), which is used as an indigestible marker. By measuring the content of AIA relative to nutrients in test diets and feces or digesta sampled from the terminal ileum (last third of the small intestine) the percentage of that nutrient digested can be calculated using the following equation: where: Natural freshwater diatomaceous earth is preferred by many researchers over chromic oxide, which has been widely used for

1072-442: A stabilizing component of dynamite , a thermal insulator , and a soil for potted plants and trees as in the art of bonsai . It is also used in gas chromatography packed columns made with glass or metal as stationary phase. Diatomaceous earth consists of the fossilized remains of diatoms that accumulated over millions of years. It usually comprises 80% to 90% silica, 2% to 4% alumina minerals, and 0.5% to 2% iron oxide, although

1139-464: A system of processes operating over paleo timescales. The largest town associated with the Bodélé dust source is Faya-Largeau ( 17°55′00″N 19°7′00″E  /  17.91667°N 19.11667°E  / 17.91667; 19.11667 ), located just to the northeast of the depression. Dust storm A dust storm , also called a sandstorm , is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when

1206-416: A wide area. The vertical extent of the dust or sand that is raised is largely determined by the stability of the atmosphere above the ground as well as by the weight of the particulates . In some cases, dust and sand may be confined to a relatively-shallow layer by a low-lying temperature inversion . In other instances, dust (but not sand) may be lifted as high as 6,000 m (20,000 ft). Dust storms are

1273-442: A wide variety of other rock types but lacustrine diatomites are almost always associated with volcanic rock. Diatomaceous chert consists of diatomite that has been cemented with silica. Diatoms are able to extract silica from water that is less than 1% saturated in amorphous silica (saturation index (SI): -2). Their frustules remain undissolved because they are surrounded by an organic matrix. Clay minerals may also precipitate on

1340-525: A year since 2007, according to English geographer Andrew Goudie , professor at the University of Oxford . Levels of Saharan dust coming off the east coast of Africa in June 2007 were five times those observed in June 2006, and were the highest observed since at least 1999, which may have cooled Atlantic waters enough to slightly reduce hurricane activity in late 2007. Dust storms have also been shown to increase

1407-418: Is as a very mild abrasive and has been used in toothpaste , metal polishes , and some facial scrubs. Diatomite is of value as an insecticide because of its abrasive and physico- sorptive properties. The fine powder adsorbs lipids from the waxy outer layer of the exoskeletons of many species of insects; this layer acts as a barrier that resists the loss of water vapour from the insect's body. Damaging

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1474-502: Is available commercially in several formats: In 1866, Alfred Nobel discovered that nitroglycerin could be made much more stable if absorbed in diatomite ( kieselguhr in German). This allowed much safer transport and handling than pure nitroglycerin in liquid form. Nobel patented this mixture as dynamite in 1867; the mixture is also called guhr dynamite in reference to the kieselguhr. The Celle engineer, Wilhelm Berkefeld, recognized

1541-510: Is commonly used in lieu of boric acid and can be used to help control and possibly eliminate bed bugs , house dust mite , cockroach , ant , and flea infestations. Diatomaceous earth is widely applied for insect control in grain storage. It is used to control cannibalistic behaviors in confused flour beetles , which infest flour storages. In order to be effective as an insecticide, diatomaceous earth must be uncalcinated (i.e., it must not be heat-treated prior to application) and have

1608-489: Is dependent upon the age and paleoecology of the deposit. In turn, the shape of a diatom is determined by its species. Many deposits throughout British Columbia , such as Red Lake Earth, are from the Miocene epoch and contain a species of diatom known as Melosira granulata . These diatoms have a small globular shape. A deposit containing diatoms from this epoch can provide certain benefits over others. For example, diatoms from

1675-524: Is frequently emitted into the Mediterranean atmosphere and transported by the winds sometimes as far north as central Europe and Great Britain. Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing topsoil loss in Niger , Chad , northern Nigeria , and Burkina Faso . In Mauritania there were just two dust storms a year in the early 1960s; there are about 80

1742-493: Is increased when there are great temperature variations like those seen at the equator during the Martian summer. Diatomite Diatomaceous earth ( / ˌ d aɪ . ə t ə ˈ m eɪ ʃ ə s / DY -ə-tə- MAY -shəs ), also known as diatomite ( / d aɪ ˈ æ t ə m aɪ t / dy- AT -ə-myte ), celite , or kieselguhr , is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into

1809-453: Is used in chemistry as a filtration aid, to increase flow rate, and filter very fine particles that would otherwise pass through or clog filter paper . It is also used to filter water, particularly in the drinking water treatment process and in fish tanks , and other liquids, such as beer and wine. It can also filter syrups, sugar, and honey without removing or altering their color, taste, or nutritional properties. The oldest use of diatomite

1876-502: Is used in some home products where dryness or the ability to wick away moisture is critical. In particular there are bath mats made of DE which absorb water from the bather and allow it to spread the material and rapidly evaporate away. There are also spoons made of DE for scooping sugar and other hydroscopic kitchen ingredients. Certain species of bacteria in oceans and lakes can accelerate the rate of dissolution of silica in dead and living diatoms by using hydrolytic enzymes to break down

1943-537: The Eocene epoch are not as effective in their ability to absorb fluids because as older diatoms recrystallize, their small pores become filled with silica. Diatomite forms by the accumulation of the amorphous silica ( opal , SiO 2 · n H 2 O ) remains of dead diatoms (microscopic single-celled algae ) in lake sediment or marine sediments . The fossil remains consist of a pair of symmetrical shells or frustules . Marine diatomites are found in association with

2010-632: The Holocene . Diatoms from these fresh water lakes, once part of the prehistoric Mega-Lake Chad, now make up the surface of the depression and are the source material for the dust, which, carried across the Atlantic Ocean, is an important source of nutrient minerals for the Amazon rainforest . As the Sahara dried out over the last few thousand years , Mega-Lake Chad receded to the current position of Lake Chad in

2077-514: The Sahara Desert are locally known as a simoom or simoon (sîmūm, sîmūn). The haboob (həbūb) is a sandstorm prevalent in the region of Sudan around Khartoum , with occurrences being most common in the summer. The Sahara desert is a key source of dust storms, particularly the Bodélé Depression and an area covering the confluence of Mauritania , Mali , and Algeria . Sahara dust

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2144-769: The Southern California coast . This is the world's largest deposit of diatomite. Additional marine deposits have been worked in Maryland , Virginia , Algeria and the MoClay of Denmark. Freshwater lake deposits occur in Nevada, Oregon , Washington and California . Lake deposits also occur in interglacial lakes in the eastern United States, in Canada and in Europe in Germany, France, Denmark and

2211-425: The fallow system, are increasing the size and frequency of dust storms from desert margins and changing both the local and global climate, as well as impacting local economies. The term sandstorm is used most often in the context of desert dust storms, especially in the Sahara Desert , or places where sand is a more prevalent soil type than dirt or rock, when, in addition to fine particles obscuring visibility,

2278-465: The fossilized remains of diatoms , a type of hard-shelled microalgae , that have accumulated over millions of years. It is used as a filtration aid, mild abrasive in products including metal polishes and toothpaste , mechanical insecticide , absorbent for liquids, matting agent for coatings, reinforcing filler in plastics and rubber, anti-block in plastic films, porous support for chemical catalysts, cat litter , activator in coagulation studies,

2345-473: The Bodélé Low Level Jet flows over a near-surface inversion, but quickly mixes down to the surface a few hours after sunrise once the intense surface heating induces turbulence in the lowest layers. Dust from the Bodélé may be seen as a simple coincidence of two key requirements for deflation: strong surface winds and erodible sediment. But recent research has argued that long-term links exist between topography, wind, deflation and dust, and that topography acts as

2412-555: The Czech Republic. The worldwide association of diatomite deposits and volcanic deposits suggests that the availability of silica from volcanic ash may be necessary for thick diatomite deposits. Diatomaceous earth is sometimes found on desert surfaces. Research has shown that the erosion of diatomaceous earth in such areas (such as the Bodélé Depression in the Sahara ) is one of the most important sources of climate-affecting dust in

2479-553: The Djourab Desert of Chad, respectively. The effect of the Tibesti massif is clearly evident in creating a split in the low-level easterly flow north and south of these mountains. While the jet feature is pronounced over the Bodélé, it is absent from other longitudes over west Africa along 18 N. It is therefore a feature which uniquely overlies the greater Bodélé region, downwind of the mountains of Chad. The Bodélé Low Level Jet undergoes

2546-610: The Sahara; iron-poor ocean regions get iron; and dust in Hawaii increases plantain growth. In northern China as well as the mid-western U.S., ancient dust storm deposits known as loess are highly fertile soils, but they are also a significant source of contemporary dust storms when soil-securing vegetation is disturbed. Iranian cities existence are challenged by dust storms. Dust storms are not limited to Earth and have also been known to form on Mars . These dust storms can extend over larger areas than those on Earth, sometimes encircling

2613-555: The ability of the diatomaceous earth to filter and developed tubular filters (known as filter candles) fired from diatomaceous earth. During the cholera epidemic in Hamburg in 1892, these Berkefeld filters were used successfully. One form of diatomaceous earth is used as a filter medium, especially for swimming pools. It has a high porosity because it is composed of microscopically small, hollow particles. Diatomaceous earth (sometimes referred to by trademarked brand names such as Celite)

2680-546: The atmosphere. The siliceous frustules of diatoms accumulate in fresh and brackish wetlands and lakes. Some peats and mucks contain a sufficient abundance of frustules such that they can be mined. Most of Florida's diatomaceous earths have been found in the muck of wetlands or lakes. The American Diatomite Corporation, from 1935 to 1946, refined a maximum of 145 tons per year from their processing plant near Clermont, Florida . Muck from several locations in Lake County, Florida

2747-408: The barrier material in some fire-resistant safes. It is also used in evacuated powder insulation for use with cryogenics. Diatomaceous earth powder is inserted into the vacuum space to aid in the effectiveness of vacuum insulation. It was used in the classical AGA cookers as a thermal heat barrier. Diatomaceous earth also finds some use as a support for catalysts , generally serving to maximize

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2814-614: The calcined form had developed pneumoconiosis . Today's standard diatomaceous earth formulations are safer to use, as they are predominantly made up of amorphous silica and contain little or no crystalline silica. The crystalline silica content of diatomaceous earth is regulated in the United States by the Occupational Safety and Health Administration (OSHA). There are guidelines from the National Institute for Occupational Safety and Health that set maximum amounts allowable in

2881-526: The circulatory system. Dust pneumonia is the result of large amounts of dust being inhaled. Prolonged and unprotected exposure of the respiratory system in a dust storm can also cause silicosis , which, if left untreated, will lead to asphyxiation ; silicosis is an incurable condition that may also lead to lung cancer . There is also the danger of keratoconjunctivitis sicca ("dry eyes") which, in severe cases without immediate and proper treatment, can lead to blindness . Dust storms cause soil loss from

2948-439: The controlling agent ensuring the long term maintenance of this source. The spatial co-location of strong winds and dust is not simply fortuitous, but results from a set of processes. Specifically: Wind conditions which deflate the erodible sediment now may have created the depression necessary for generating the erodible diatomite in the past. Instead of a simple coincidence of nature, the world's largest dust source results from

3015-594: The depression produces an average of 700,000 tonnes of dust each day (Todd et al., 2007). Research published in the 25 March 2004 edition of Geophysical Research Letters , which used images taken by the Moderate Resolution Imaging Spectroradiometer (MODIS), aboard NASA 's Terra and Aqua satellites, indicated that storms move across the Bodélé Depression at about 47 km/h (29 mi/h)—two times faster than previously believed. The research also found that winds have to whip across

3082-450: The drylands, and worse, they preferentially remove organic matter and the nutrient-rich lightest particles, thereby reducing agricultural productivity. Also, the abrasive effect of the storm damages young crop plants. Dust storms also reduce visibility, affecting aircraft and road transportation. Dust can also have beneficial effects where it deposits: Central and South American rainforests get significant quantities of mineral nutrients from

3149-532: The entire worldwide production of diatomaceous earth was from this region. In Poland diatomaceous earth deposits are found in Jawornik, and are composed mostly of diatomaceous skeletons (frustules). In Germany, diatomaceous earth was also extracted at Altenschlirf on the Vogelsberg ( Upper Hesse ) and at Klieken ( Saxony-Anhalt ). There is a layer of diatomaceous earth more than 6 meters (20 ft) thick in

3216-399: The frustules and protect them from dissolution in sea water. When the diatom dies, the frustule is stripped of its organic layer and exposed to sea water. As a result, only 1% to 10% of frustules survive long enough to be buried under sediments and some of this is dissolved within the sediments. Only an estimated 0.05% to 0.15% of the original amount of silica produced by diatoms is preserved in

3283-420: The ground, they loosen and break off smaller particles of dust which then begin to travel in suspension. At wind speeds above that which causes the smallest to suspend, there will be a population of dust grains moving by a range of mechanisms: suspension, saltation and creep . A study from 2008 finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires

3350-417: The layer increases the evaporation of water from their bodies, so that they dehydrate, often fatally. This also works against gastropods and is commonly employed in gardening to defeat slugs . However, since slugs inhabit humid environments, efficacy is very low. Diatomaceous earth is sometimes mixed with an attractant or other additives to increase its effectiveness. The shape of the diatoms contained in

3417-409: The lungs, causing silicosis . Amorphous silica is considered to have low toxicity, but prolonged inhalation causes lung changes. Diatomaceous earth is mainly amorphous silica but contains some crystalline silica, especially in the saltwater forms. In a 1978 study of workers, those exposed to natural diatomaceous earth for over five years had no significant lung changes while 40% of those exposed to

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3484-621: The nature reserve of Soos in the Czech Republic. Deposits on the Isle of Skye , off the west coast of Scotland, were mined until 1960. In Colorado and in Clark County, Nevada , United States, there are deposits that are up to several hundred meters thick in places. Marine deposits have been worked in the Sisquoc Formation in Santa Barbara County, California near Lompoc and along

3551-521: The organic algal material. The Earth's climate is affected by dust in the atmosphere , so locating major sources of atmospheric dust is important for climatology . Recent research indicates that surface deposits of diatomaceous earth play an important role. Research shows that significant dust comes from the Bodélé Depression in Chad , where storms push diatomite gravel over dunes , generating dust by abrasion . Inhalation of crystalline silica harms

3618-403: The planet, with wind speeds as high as 25 m/s (60 mph). However, given Mars' much lower atmospheric pressure (roughly 1% that of Earth's), the intensity of Mars storms could never reach the hurricane-force winds experienced on Earth. Martian dust storms are formed when solar heating warms the Martian atmosphere and causes the air to move, lifting dust off the ground. The chance for storms

3685-400: The precise composition of every deposit is different. Deposits may contain different amounts of silica depending on the sedimentation conditions , the presence of other sediments (clay, sand, volcanic ashes), and the age of the deposit ( diagenesis , silica (SiO 2 ) dissolution/precipitation, diatoms tests ageing). The species of diatom may also differ among deposits. The species of diatom

3752-411: The product (1%) and in the air near the breathing zone of workers, with a recommended exposure limit at 6 mg/m over an 8-hour workday. OSHA has set a permissible exposure limit for diatomaceous earth as 20 mppcf (80 mg/m /%SiO 2 ). At levels of 3,000 mg/m , diatomaceous earth is immediately dangerous to life and health. In the 1930s, long-term occupational exposure among workers in

3819-412: The radiation budget in the Bodélé Depression for the first time. This work coincided with a major dust emission event during which the Bodélé Low Level Jet sustained surface wind speeds of around 16 m/s. The core of the Bodélé Low Level Jet was also mapped for the first time from the wind data, and was shown to undergo a very marked diurnal cycle with peak winds occurring mid morning. During night time,

3886-546: The region at a minimum of 36 km/h (22 mi/h), to kick up a dust storm . The pattern of air flow is so common that the winds have scoured a straight path in the ground, marking their southwesterly flow. Complementary research published in Geophysical Research Letters by Richard Washington from the University of Oxford and Martin Todd from the University of Sussex has shown that these strong winds are part of

3953-505: The same purpose, the latter being a known carcinogen and, therefore, a potential hazard to research personnel. Spent diatomaceous earth from the brewing process can be added to ceramic mass for the production of red bricks with higher open porosity. Diatomaceous earth is considered a very prominent inorganic non-metallic material that can be used for the production of various ceramics, including production of porous ceramics under low temperature hydrothermal technology. Diatomaceous earth

4020-572: The sedimentary record. In 1836 or 1837, German peasant Peter Kasten discovered diatomaceous earth (German: Kieselgur ) when sinking a well on the northern slopes of the Haußelberg hill, on Lüneburg Heath in North Germany . The extraction site on Lüneburg Heath was 1863–1994 Neuohe, while the storage sites were: The deposits are up to 28 meters (92 ft) thick and are all of freshwater diatomaceous earth. Until World War I , almost

4087-427: The south-west corner of Chad. As the waters receded, the silts and sediments resting on the lakebed, which included fossilized diatoms , were left to dry in the scorching sun, forming a layer of fine dust. These small grains of sediment are swept up by the strong wind gusts that occasionally blow over the region. Once heaved aloft, the Bodélé dust can be carried for hundreds or even thousands of kilometers. In winter,

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4154-532: The spread of disease across the globe. Bacteria and fungus spores in the ground are blown into the atmosphere by the storms with the minute particles and interact with urban air pollution. Short-term effects of exposure to desert dust include immediate increased symptoms and worsening of the lung function in individuals with asthma , increased mortality and morbidity from long-transported dust from both Saharan and Asian dust storms suggesting that long-transported dust storm particles adversely affects

4221-520: The subtropical High Pressure belt. The same researchers who in 2004 more accurately determined the speed of wind through the depression also published in 2006 work showing that more than half of the dust needed for fertilizing the Amazon Rainforest is provided by the Bodélé depression, which deposits up to 50 million tonnes in South America per year. The research also shows that, contrary to what

4288-416: The vast majority of animals that undergo ecdysis in shedding cuticle , such as arthropods or nematodes . It also may have other effects on lophotrochozoans , such as mollusks or annelids . Medical-grade diatomite has been studied for its efficacy as a deworming agent in cattle; in both studies cited the groups being treated with diatomaceous earth did not fare any better than control groups. It

4355-626: The wind gusts may be produced by a dry cold front : that is, a cold front that is moving into a dry air mass and is producing no precipitation —the type of dust storm which was common during the Dust Bowl years in the U.S. Following the passage of a dry cold front, convective instability resulting from cooler air riding over heated ground can maintain the dust storm initiated at the front. In desert areas, dust and sand storms are most commonly caused by either thunderstorm outflows, or by strong pressure gradients which cause an increase in wind velocity over

4422-747: Was dried and burned ( calcined ) to produce the diatomaceous earth. It was formerly extracted from Lake Mývatn in Iceland. The commercial deposits of diatomite are restricted to Tertiary or Quaternary periods. Older deposits from as early as the Cretaceous Period are known, but are of low quality. Diatomite deposits rich in fossils have been located in New Zealand, but mining of the Foulden Maar deposits on an industrial scale, for conversion to animal feed, has drawn strong opposition. Diatomaceous earth

4489-522: Was previously thought, most of the Saharan dust that reaches the east coast of the United States originates from a single source—the Bodélé depression. In February 2005 the first field experiment, the Bodélé Dust Experiment or BoDEx 2005, was carried out in the Bodélé Depression. The experiment measured the surface winds and near surface winds, dust concentrations, and the influence of dust on

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