The constancy of temperature at the normal freezing point is due to the equilibrium of exchange existing between the liquid and solid. Unless both solid and liquid are present, there is no condition of equilibrium, and the temperature is indeterminate. It has been shown by H. A. Miers (Jour. Chem. Soc., 1906, 89, p. 413) that for a supersaturated solution in metastable equilibrium there is an inferior limit of temperature, at which it passes into the “labile” state, i.e. spontaneous crystallization occurs throughout the mass in a fine shower. This seems to be analogous to the fine misty condensation which occurs in a supersaturated vapour in the absence of nuclei (see Vaporization) when the supersaturation exceeds a certain limit. 4. Effect of Pressure on the F.P.—The effect of pressure on the fusing-point depends on the change of volume during fusion. Substances which expand on freezing, like ice, have their freezing points lowered by increase of pressure; substances which expand on fusing, like wax, have their melting points raised by pressure. In each case the effect of pressure is to retard increase of volume.

Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath A glacier (US: ; UK: or ) is a persistent body of natural ice, a form of rock, that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It slowly flows and deforms under stresses induced by gravity, undergoing both ductile and brittle deformation, and acquiring distinguishing surface features, such as A glacier (US: ; UK: or ) is a persistent body of natural ice, a form of rock, that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It slowly flows and deforms under stresses induced by gravity, undergoing both ductile and brittle deformation, and acquiring distinguishing surface features, such as crevasses and seracs. As a glacier moves,… τD = ρgh sin α where τD is the driving stress, and α the ice surface slope in radians. τB is the basal shear stress, a function of bed temperature and softness. τF, the shear stress, is the lower of τB and τD. It controls the rate of plastic flow. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have a lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly, the increased pressure can facilitate melting. Most importantly, τD is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to a kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again.

to the pressure of expanding water when it freezes. Because ice is less dense than liquid water, it floats, and this prevents bottom-up freezing of the Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 °C, 32 °F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. Depending on the presence of impurities such as particles of soil or Ic…