They may strike quickly, with little or no warning.
They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.
The average tornado moves Southwest to Northeast, but tornadoes have been known to move in any direction.
The average forward speed of a tornado is 30 MPH, but may vary from stationary to 70 MPH.
Tornadoes can accompany tropical storms and hurricanes as they move onto land.
Waterspouts are tornadoes that form over water.
Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.
Peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer.
Tornadoes are most likely to occur between 3 p.m. and 9 p.m., but can occur at any time.
What to do Before a Tornado
Be alert to changing weather conditions.
Listen to NOAA Weather Radio or to commercial radio or television newscasts for the latest information.
Look for approaching storms
Look for the following danger signs:
Dark, often greenish sky
Large hail
A large, dark, low-lying cloud (particularly if rotating)
Loud roar, similar to a freight train.
If you see approaching storms or any of the danger signs, be prepared to take shelter immediately.
What to Do During a Tornado
If you are under a tornado WARNING, seek shelter immediately!
If you are in a structure (e.g. residence, small building, school, nursing home, hospital, factory, shopping center, high-rise building): then go to a pre-designated shelter area such as a safe room, basement, storm cellar, or the lowest building level. If there is no basement, go to the center of an interior room on the lowest level (closet, interior hallway) away from corners, windows, doors, and outside walls. Put as many walls as possible between you and the outside. Get under a sturdy table and use your arms to protect your head and neck. Do not open windows.
If you are in a vehicle, trailer, or mobile home: then get out immediately and go to the lowest floor of a sturdy, nearby building or a storm shelter. Mobile homes, even if tied down, offer little protection from tornadoes.
If you are in the outside with no shelter: then lie flat in a nearby ditch or depression and cover your head with your hands. Be aware of the potential for flooding. Do not get under an overpass or bridge. You are safer in a low, flat location. Never try to outrun a tornado in urban or congested areas in a car or truck. Instead, leave the vehicle immediately for safe shelter. Watch out for flying debris. Flying debris from tornadoes causes most fatalities and injuries.
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According to Dr. Dougal Jerram, an earth scientist at the University of Durham, UK, "Eruptions which are charged with gas start to froth and expand as they reach the surface. This results in explosive eruptions and this fine ash being sent up into the atmosphere. If it is ejected high enough, the ash can reach the high winds and be dispersed around the globe, for example, from Iceland to Europe. These high winds are exactly where the aeroplanes cruise." Volcanic ash can harm a plane mainly in four ways:
1.Sandblasting effect. Ash can "blind" pilots by sandblasting the windscreen requiring an instrument landing, damage the fuselage, and coat the plane (KLM Flight 867 and BA Flight 9). In addition, the sandblasting effect can damage the landing lights, making their beams diffuse and unable to be projected in the forward direction (BA Flight 9). Propellor aircraft are also endangered.
2. Clogging of the plane's sensors. Accumulation of ash can also block an aircraft's pitot tubes. This can lead to failure of the aircraft's air speed indicators.
3. Electromagnetic wave insulation. Volcanic ash particles are charged and disturb communication by radio.
4. Combustion power failure. The effect on jet aircraft engines is particularly severe as large amounts of air are sucked in during combustion operation, posing a great danger to aircraft flying near ash clouds.
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions,[1] less than 2 millimetres (0.079 in) in diameter. Volcanic ash can lead to breathing problems, malfunctions in machinery, and from more severe eruptions, years of global cooling. Ash deposited on the ground after an eruption is known as ashfall deposit. Significant accumulations of ashfall can lead to the immediate destruction of most of the local ecosystem, as well the collapse of roofs on man-made structures.
The second eruption of Eyjafjallajökull volcano in Iceland on 14 April 2010 is causing extensive air travel disruption across large parts of Europe.[1] In response to fears that particles ejected by the volcano into standard flight corridors could damage aircraft engines,[2] the controlled airspace of many countries was closed to IFR traffic, stranding millions of travellers. It is the largest air traffic shut-down since World War II.[3]
The eruption occurred beneath glacial ice, with the cold water from melting ice chilling the lava quickly, causing it to fragment into very small particles of glass (silica) and ash which were carried into the eruption plume. Due to the extremely fine nature of the ash particles and the large volume of steam produced from the glacial melt water, the ash plume hazardous to aircraft was rapidly sent high into the upper atmosphere. [4] The presence and location of the plume depended upon the state of the eruption and the winds. Due to the way air-masses function and the large volume of steam produced by this eruption, the plume was injected into the jet stream.[5]
With large parts of European airspace closed to air traffic,[6][7][8] many more countries were affected as flights to and from Europe were cancelled.
As of 17 April 2010 (2010 -04-17)[update], the eruption was continuing, but less explosively; the plume was rising to 5 kilometres (3 mi) rather than 13 kilometres (8 mi) previously; not high enough to travel across Europe.[9] The forecast for 18 April at 06:00 showed a significant plume continuing over northern Europe.[10] At 20:00 UTC on 16 April the ash cloud reached Kazakhstan. Jet stream forecasts indicated the ash cloud plume would persist until at least 21 April, shifting to the south and affecting more southerly parts of France and Italy.[11]
A geologically young land, Iceland is located on both the Iceland hotspot and the Mid-Atlantic Ridge, which runs right through it. This location means that the island is highly geologically active with many volcanoes, notably Hekla, Eldgjá, Herðubreið and Eldfell. The volcanic eruption of Laki in 1783–1784 caused a famine that killed nearly a quarter of the island's population;[26] the eruption caused dust clouds and haze to appear over most of Europe and parts of Asia and Africa for several months afterward.[27]
Dettifoss, located in northeast Iceland. It is the largest waterfall in Europe in terms of volume discharge, with an average water flow of 200 m3/second.
There are also many geysers in Iceland, including Geysir, from which the English word is derived, as well as the famous Strokkur, which erupts every 5–10 minutes. After a phase of inactivity, Geysir started erupting again after a series of earthquakes in 2000.
Surtsey, one of the youngest islands in the world, is part of Iceland. Named after Surtr, it rose above the ocean in a series of volcanic eruptions between 8 November 1963 and 5 June 1968.[24] Only scientists researching the growth of new life are allowed to visit the island.[29]
On 21 March 2010, a volcano in Eyjafjallajökull in the south of Iceland erupted, for the first time since 1821, forcing 600 people to flee their homes.[30] Further eruptions on 14 April forced hundreds of people to abandon their homes.[31] The resultant cloud of volcanic ashmajor disruption to air travel across Northern Europe.[32]
Calcium is essential for living organisms, particularly in cell physiology, where movement of the calcium ion Ca2+ into and out of the cytoplasm functions as a signal for many cellular processes. Calcium is a major material used in mineralization of bones and shells. Calcium is the fifth most abundant element by mass in the human body, where it is a common cellular ionic messenger with many functions, and serves also as a structural element in bone. It is the relatively high atomic-numbered calcium in the skeleton which causes bone to be radio-opaque. Of the human body's solid components after drying (as for example, after cremation), about a third of the total mass is the approximately one kilogram of calcium which composes the average skeleton (the remainder being mostly phosphorus and oxygen).
Recommended Adequate Intake by the IOM for Calcium: Age Calcium (mg/day) 0–6 months 210, 7–12 months 270, 1–3 years 500, 4–8 years 800, 9–18 years 1300, 19–50 years 1000, 51+ years 1200.
Approximately ninety-nine percent of the body's calcium is stored in the bones and teeth. The rest of the calcium in the body has other important uses, such as some exocytosis, especially neurotransmitter release, and muscle contraction.
1. In the electrical conduction system of the heart, calcium replaces sodium as the mineral that depolarizes the cell, proliferating the action potential.
2. In cardiac muscle, sodium influx commences an action potential, but during potassium efflux, the cardiac myocyte experiences calcium influx, prolonging the action potential and creating a plateau phase of dynamic equilibrium.
3. Long-term calcium deficiency can lead to rickets and poor blood clotting
4. In case of a menopausal woman, long-term calcium deficiency can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures.
5. A lifelong deficit can affect bone and tooth formation.
6. Over-retention can cause hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals.
7. High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, a high calcium intake has been associated with a lower risk for kidney stones in more recent research. Vitamin D is needed to absorb calcium.
is added to some calcium supplements. Proper vitamin D status is important because vitamin D is converted to a hormone in the body which then induces the synthesis of intestinal proteins responsible for calcium absorption.
The absorption of calcium from most food and commonly-used dietary supplements is very similar. This is contrary to what many calcium supplement manufacturers claim in their promotional materials.
Milk is an excellent source of dietary calcium because it has a high concentration of calcium and the calcium in milk is excellently absorbed.
Calcium carbonate is the most common and least expensive calcium supplement. It should be taken with food. It depends on low pH levels for proper absorption in the intestine. Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk. While most people digest calcium carbonate very well, some might develop gastrointestinal discomfort or gas. Taking magnesium with it can help to avoid constipation. Calcium carbonate is 40% elemental calcium. 1000 mg will provide 400 mg of calcium. However, supplement labels will usually indicate how much calcium is present in each serving, not how much calcium carbonate is present.
Antacids, such as Tums, frequently contain calcium carbonate, and are a very commonly-used, inexpensive calcium supplement.
Coral Calcium is a salt of calcium derived from fossilized coral reefs. Coral calcium is composed of calcium carbonate and trace minerals.
Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or proton-pump inhibitors. It is more easily digested and absorbed than calcium carbonate if taken on empty stomach and less likely to cause constipation and gas than calcium carbonate. It also has a lower risk of contributing to the formation of kidney stones. Calcium citrate is about 21% elemental calcium. 1000 mg will provide 210 mg of calcium. It is more expensive than calcium carbonate and more of it must be taken to get the same amount of calcium.
Calcium phosphate costs more than calcium carbonate, but less than calcium citrate. It is easily absorbed and is less likely to cause constipation and gas than either.
Calcium lactate has similar absorption as calcium carbonate], but is more expensive. Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements.
Calcium chelates are synthetic calcium compounds, with calcium bound to an organic molecule, such as malate, aspartate, or fumarate. These forms of calcium may be better absorbed on an empty stomach. However, in general they are absorbed similarly to calcium carbonate and other common calcium supplements when taken with food. The 'chelate' mimics the action that natural food performs by keeping the calcium soluble in the intestine. Thus, on an empty stomach, in some individuals, chelates might theoretically be absorbed better.
Microcrystalline hydroxyapatite (MH) is marketed as a calcium supplement, and has in some randomized trials been found to be more effective than calcium carbonate.
Orange juice with calcium added is a good dietary source for persons who have lactose intolerance.
Exceeding the recommended daily calcium intake for an extended period of time can result in hypercalcemia and calcium metabolism disorder.
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal. Calcium, with a specific mass of 1.55 g/cm3, is the lightest of the alkali earth metals. Chemically calcium is reactive and soft for a metal (though harder than lead, it can be cut with a knife with difficulty). It is a silvery metallic element that must be extracted by electrolysis from a fused salt like calcium chloride. In powdered form, the reaction with water is extremely rapid, as the increased surface area of the powder accelerates the reaction with the water. Many calcium salts are not soluble in water. When in solution, the calcium ion to the human taste varies remarkably, being reported as mildly salty, sour, "mineral like" or even "soothing". In human nutrition, soluble calcium salts may be added to tart juices without much effect to the average palate. Calcium occurs most commonly in sedimentary rocks in the minerals calcite, dolomite and gypsum.
Calcium compounds
Calcium carbonate (CaCO3) used in manufacturing cement and mortar, lime, limestone (usually used in the steel industry); aids in production in the glass industry, also has chemical and optical uses as mineral specimens in toothpastes.
Calcium hydroxide solution (Ca(OH)2) (also known as limewater) is used to detect the presence of carbon dioxide by being bubbled through a solution. It turns cloudy where CO2 is present.
Calcium arsenate (Ca3(AsO4)2) is used in insecticides.
Calcium carbide (CaC2) is used: to make acetylene gas (for use in acetylene torches for welding) and in the manufacturing of plastics.
Calcium chloride (CaCl2) is used: in ice removal and dust control on dirt roads, in conditioner for concrete, as an additive in canned tomatoes, and to provide body for automobile tires.
Calcium cyclamate (Ca(C6H11NHSO3)2) was used as a sweetening agent but is no longer permitted for use because of suspected cancer-causing properties.
Calcium gluconate (Ca(C6H11O7)2) is used as a food additive and in vitamin pills.
Calcium hypochlorite (Ca(OCl)2) is used: as a swimming pool desinfectant, as a bleaching agent, as an ingredient in deodorant, and in algaecide and fungicide.
Calcium permanganate (Ca(MnO4)2) is used in liquid rocket propellant, textile production, as a water sterilizing agent and in dental procedures.
Calcium phosphate (Ca3(PO4)2) is used as a supplement for animal feed, fertilizer, in commercial production for dough and yeast products, in the manufacture of glass, and in dental products.
Calcium phosphide (Ca3P2) is used in fireworks, rodenticide, torpedoes and flares.
Calcium stearate (Ca(C18H35O2)2) is used in the manufacture of wax crayons, cements, certain kinds of plastics and cosmetics, as a food additive, in the production of water resistant materials and in the production of paints.
Calcium sulfate (CaSO4·2H2O) is used as common blackboard chalk, as well as, in its hemihydrate form being more well known as Plaster of Paris.
Calcium tungstate (CaWO4) is used in luminous paints, fluorescent lights and in X-ray studies.
Hydroxylapatite (Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2) makes up seventy percent of bone. Also carbonated-calcium deficient hydroxylapatite is the main mineral of which dental enamel and dentin are comprised.
