question: Why does sand turn into glass when exposed to extremely high temperatures?
comment: Melting is magic. Hundreds of ice cubes when exposed to sufficient heat will melt. Take the melted ice (water) and expose it to cold again and you will have a continuous sheet of ice. Sand is like ice cubes. Get a bunch of them hot enough and it will melt. Make the melty stuff cold again and you have one giant sand (glass).
passages: Electron charge differences of ions within the structure form the basis of its bonding. Both viscosity and transition temperature are related to the availability of oxygen bonds in the glass's composition. Modifying agents tend to lower the melting point of the silica. Higher contents of SiO increase acidity of the glass. Higher contents of CaO, NaO, and KO increase basicity.
   Vitrified sand
  
  Vitrified sand is sand that has been heated to a high enough temperature as to partly or fully melt the silicon dioxide or quartz that is the main ingredient of common sand. When sand is used to make glass, soda ash or potash are added to lower the melting point. Pure quartz melts at . There are several natural processes that produce more or less melted sand and one man-made form:
  
  BULLET::::- fulgurite is sand fused by a lightning bolt hitting sand.
   Diffusion's exponential dependence upon temperature makes precipitation strengthening, like all heat treatments, a fairly delicate process. Too little diffusion ("under ageing"), and the particles will be too small to impede dislocations effectively; too much ("over ageing"), and they will be too large and dispersed to interact with the majority of dislocations.
  
  Section::::Alloy design.
   Glass shards are cleaned and milled to a powder before a foaming agent, active carbon, is added in either liquid or solid form. The material is passed through a continuous tunnel furnace and heated to a temperature of 800–900 °C. Optimum temperatures produce maximum quantities of the foamed product. The foamed molten glass breaks into gravel on cooling.
  
  Section::::Uses.
   Glass ceramics may also occur naturally when lightning strikes the crystalline (e.g. quartz) grains found in most beach sand. In this case, the extreme and immediate heat of the lightning (~2500 °C) creates hollow, branching rootlike structures called fulgurite via fusion.
  
  Section::::Classes of solids.:Organic solids.
   As part of a collaborative research effort with the U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC), the U.S. Navy Naval Air Systems Command (NAVAIR) and the National Aeronautics and Space Administration (NASA), ARL modified the HPIR so that it can model how sand particles adhere, melt, and glassify on thermal barrier coatings.
   Temperature does alter the Sandman. At 3,400 degrees Fahrenheit his body turns into glass, also a form he can control. Unlike Sandman's fast transformation from sand to glass, his transformation from glass to sand takes time.
   The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide, or SiO), usually in the form of quartz, which, because of its chemical inertness and considerable hardness, is the most common mineral resistant to weathering.
   The sand was turned into black glass near the craters, and pellets of the glass are scattered all over the area, decreasing in size with distance from the craters due to wind-sorting. The glass is about 90% local sand and 10% meteoritic iron and nickel.
   BULLET::::3. The first heating process during which no fillers are added. The heating process eradicates impurities inside the fractures. Although this can be done at temperatures up to 1400 °C (2500 °F) it most likely occurs at a temperature of around 900 °C (1600 °F) since the rutile silk is still intact.
   BULLET::::- The second barrier is due to the precipitation, when the surficial pH gets below 10, of a layer of alumina gel (AH3 in cement chemistry notation). AH3 is a stable compound down to a pH of 4 and it will form an acid-resistant barrier as long as the surface pH is not lowered below 3-4 by the bacterial activity.
   Section::::Transition temperature "T".
  
  Refer to the figure on the upper right plotting the heat capacity as a function of temperature. In this context, "T" is the temperature corresponding to point A on the curve. The linear sections below and above "T" are colored green. "T" is the temperature at the intersection of the red regression lines.
   The process of tempering float glass can cause a NiS to change from its normal state (known as a low-temperature structure) to a different high-temperature, crystalline structure. When the glass is cooled quickly (as part of the process) the NiS particle is unable to change back to its original form. 
  
  Over a certain period of time NiS will slowly convert to the original low temperature structure. This means the NiS increases in size, and the mechanical stresses caused by this cause the tempered pane to shatter, for no apparent reason (hence spontaneous glass breakage).
   These reactions are slightly more favorable at low temperatures. This process occurs naturally over geologic time frames and is responsible for much of the Earth's surface limestone. The reaction rate can be made faster however, by reacting at higher temperatures and/or pressures, although this method requires some additional energy. Alternatively, the mineral could be milled to increase its surface area, and exposed to water and constant abrasion to remove the inert Silica as could be achieved naturally by dumping Olivine in the high energy surf of beaches. Experiments suggest the weathering process is reasonably quick (one year) given porous basaltic rocks.
   The likelihood of degradation due to glass disease depends on the amount and proportion of alkaline compounds mixed with silica, and on surrounding conditions.
   Section::::Governing equations.
  
  There are two main types of equations to describe the two mechanisms for precipitation hardening:
  
  Dislocation cutting through particles:
   This technique was modified for use as a "passive sand migration analysis tool".(Figure 2). The research shows direct consequences resulting from the improper replenishment of starving beaches using fine sands. Beach nourishment is a problem worldwide and receives large amounts of attention due to the millions of dollars spent yearly in order to keep beaches beautified for tourists, e.g., in Waikiki, Hawaii. Sands with sizes 90-150 μm (very fine sand) were found to migrate from the swash zone 67% faster than sand grains of 150-212 μm (fine sand; Figure 3). Furthermore, the technique was shown to provide a passive method of policing sand replenishment and a passive method of observing riverine or other sand inputs along shorelines (Figure 4).
   Glass containers can be sensitive to sudden changes in temperature. One method of testing involves rapid movement from cold to hot water baths, and back.
  
  Section::::Examples of thermal shock failure.
  
  BULLET::::- Hard rocks containing ore veins such as quartzite were formerly broken down using fire-setting, which involved heating the rock face with a wood fire, then quenching with water to induce crack growth. It is described by Diodorus Siculus in Egyptian gold mines, Pliny the Elder, and Georg Agricola.
   The temperature differential that borosilicate glass can withstand before fracturing is about . This compares well with soda lime glass, which can withstand only a change in temperature and is why typical kitchenware made from traditional soda-lime glass will shatter if a vessel containing boiling water is placed on ice, but Pyrex or other borosilicate laboratory glass will not.
  
  Optically, borosilicate glasses are crown glasses with low dispersion (Abbe numbers around 65) and relatively low refractive indices (1.51–1.54 across the visible range).
  
  Section::::Physical characteristics.:Glass families.
   In 2004, NIST researchers presented evidence that an isotropic non-crystalline metallic phase (dubbed "q-glass") could be grown from the melt. This phase is the first phase, or "primary phase", to form in the Al-Fe-Si system during rapid cooling. Experimental evidence indicates that this phase forms by a "first-order transition". Transmission electron microscopy (TEM) images show that the q-glass nucleates from the melt as discrete particles, which grow spherically with a uniform growth rate in all directions. The diffraction pattern shows it to be an isotropic glassy phase. Yet there is a nucleation barrier, which implies an interfacial discontinuity (or internal surface) between the glass and the melt.
   Spectral analysis of the dunes of the circumpolar ergs, including Siton Undae, using the OMEGA instrument on board the European Mars Express orbiter, indicates that 80 to 90 percent of these sands are composed of volcanic glass produced by eruptions of volcanoes situated in Martian glaciers. These ratios of glass and crystalline material are similar to those obtained in Iceland from eruptions of volcanoes below the ice. It is also theorised that significant amounts of granular glass may have been transferred to Vastitas Borealis, and Siton Undae, by catastrophic floods originating from Chryse Planitia, Valles Marineris, Juventae Chasma, and the southern Acidalia region of Mars.
   John and Dick join an aeroplane excursion: in Russia, they find only a flat glass surface; Greece is in classical times. They later realize that the glass surface they found was the world long after all life was extinct.
   It is worth noting that depending on the crystal structure, this behavior can be different. For example, face-centered cubic (FCC) metals remain ductile even at low temperatures, so a plastic zone is always present.
  
  Section::::Effect of grains and inclusions on crack propagation.:Presence of inclusions.
   Rapid cooling of molten glass generates an uneven temperature distribution in the body of the glass, which results in mechanical stress sufficient to cause cracking before the object has reached ambient temperature, or to result in susceptibility to cracking in later use, often triggered by thermal shock. To prevent this, objects manufactured from molten glass are annealed by cooling gradually in a lehr from a temperature just below the solidification point of the glass. Anneal cooling rate depends on the thickness of the glass and can range from several tens of degrees Celsius per hour for thin sections to a fraction of a degree Celsius per hour for thick slabs or castings.
   Glass chemistry has a huge impact on the process since it controls the melting, forming and annealing temperatures, liquidus temperature (point where various chemicals that make up the glass start to crystallize out of the glass) and rates of change of characteristics of the glass itself.
  