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( Tuff)
Tuff (from the Italian "tufo") is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff should not be confused with tufa, another type of rock. The products of a volcanic eruption are volcanic gases, lava, steam, and tephra. Magma is blown apart when it interacts violently with volcanic gases and steam. Solid material produced and thrown into the air by such volcanic eruptions is called tephra, regardless of composition or fragment size. If the resulting pieces of ejecta are small enough, the material is called volcanic ash, defined as such particles less than 2 mm in diameter, sand-sized or smaller. These particles are small, slaggy pieces of magma and rock that have been tossed into the air by outbursts of steam and other gases; magma may have been torn apart as it became vesicular by the expansion of the gases within it. Among the loose beds of ash that cover the slopes of many volcanoes, three classes of materials are represented. In addition to true ashes of the kind described above, there are lumps of the old lavas and tuffs forming the walls of the crater, etc., which have been torn away by the violent outbursts of steam, and pieces of sedimentary rocks from the deeper parts of the volcano that were dislodged by the rising lava and are often intensely baked and recrystallized by the heat to which they have been subjected. In some great volcanic explosions nothing but materials of the second kind were emitted, as at Mount Bandaisan in Japan in 1888. There have been many eruptions also in which the quantity of broken sedimentary rocks that mingled with the ash is very great; as instances we may cite the volcanoes of the Eifel and the Devonian tuffs, known as "Schalsteins," in Germany. In the Scottish coalfields some old volcanoes are plugged with masses consisting entirely of sedimentary debris in such a case we must suppose that no lava was ejected, but the cause of the eruption was the sudden liberation and expansion of a large quantity of steam. These accessory or adventitious materials, however, as distinguished from the true ashes, tend to occur in angular fragments; and when they form a large part of the mass the rock is more properly a "volcanic breccia" than a tuff. The ashes vary in size from large blocks twenty feet or more in diameter to the minutest impalpable dust. The large masses are called "volcanic bombs"; they have mostly a rounded, elliptical or pear-shaped form owing to rotation in the air before they solidified. Many of them have ribbed or nodular surfaces, and sometimes they have a crust intersected by many cracks like the surface of a loaf of bread. Any ash in which they are very abundant is called an agglomerate.
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Tuff Subcategories
Tuff Articles
Weight Loss: More Preferable by Fat Free Food Stuffs by Francis Adam
Dietetic fiber is one of your finest foods to obstruct both the amalgamation of fat & to blaze up additional calories. It works similar to slimming capsules such as Lida DaiDaihua. Echoes almost too excellent to be factual; however, it actually works...
Alkaline and Acidic nature of food - Deep drill by Rachel Broune
A surprising number and variety of physical problems and diseases can be caused by the problem of foods that are acid-producing after digestion. Today the vast majority of the populace in industrialized nations suffers from problems caused by the str...
Important Minerals - Iron and Zinc by Rachel Broune
Zinc is one fat-soluble mineral that can cause harm if an overdose is taken. Zinc can rob the body of copper, mentioned above as a key nutrient in hair growth and health, not to mention in other functions of the body. Zinc supplements should be taken...
Vitamin A - Roles and benefits of Vitamin A in body functioning by Rachel Broune
Vitamin A is a generic term for a large number of related compounds. Retinol (an alcohol) and retinal (an aldehyde) are often referred to as preformed vitamin A. Vitamin A that is found in colorful fruits and vegetables is called provitamin A caroten...
Vitamins C as the key ingredient for Healthy life by Rachel Broune
Vitamins are required by the body in tiny amounts (hundredths of a gram in many cases) as the key ingredient for Healthy life. We get vitamins from three sources viz. Foods, Beverages and Our own bodies - vitamin K comes from bacteria within our inte...
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