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Tachylite (/ ˈ t æ k ə l aɪ t / TAK-ə-lyte; also spelled tachylyte) is a form of basaltic volcanic glass. This glass is formed naturally by the rapid cooling of molten basalt. It is a type of mafic igneous rock that is decomposable by acids and readily fusible. [citation needed] The color is a black or dark-brown, and it has a greasy ...
Perlite boulders with fireweed in foreground. Perlite softens when it reaches temperatures of 850–900 °C (1,560–1,650 °F). Water trapped in the structure of the material vaporises and escapes, and this causes the expansion of the material to 7–16 times its original volume.
[1] [2] Rock that contains greater than 75% ash is considered tuff, while rock containing 25% to 75% ash is described as tuffaceous (for example, tuffaceous sandstone). [3] A pyroclastic rock containing 25–75% volcanic bombs and/or volcanic blocks is called tuff breccia. [4] Tuff composed of sandy volcanic material can be referred to as ...
[2] [3] [4] The difference in water content can be used to distinguish tektites from terrestrial volcanic glasses. When heated to their melting point, terrestrial volcanic glasses turn into a foamy glass because of their content of water and other volatiles.
This is a list of notable volcanic eruptions in the 16th to 20th centuries with a Volcanic explosivity index (VEI) of 4 or higher, and smaller eruptions that resulted in significant damage or fatalities. Note that there may be uncertainties to dates with historical eruptions, and there are likely to be many large eruptions that have not been ...
In earlier terminology, scoria was usually defined with a size range, e.g. 2 to 24 mm (0.079 to 0.945 in) in diameter, but neither color nor composition was typically a part of the definition. [ 5 ] [ 6 ] During the 1980s, the size range disappeared from the definition, and a requirement was added that scoria be black or reddish in color and/or ...