Figure 4.40. Movie of a model magma chamber filled with an H2O–KCl solution that was boiling at 110°C and allowed to cool to room temperature (20°C). The movie shows five-second clips beginning at 5, 20, 45, 80, 125, 180, 245, 320, and 405 seconds after the solution was poured into the box. The “chamber” is a rectangular glass box made of 26-mm-wide microscope slides glued together. Rectangular rock chips were placed inside the box on two sides to provide nucleation sites. Sylvite crystals nucleate homogeneouslyat first, then heterogeneously on the surface, sides, and other crystals as the solution cools. Many crystals sink, although some are carried upward by thermal convection currents. Sylvite crystals that nucleate on the surface are held there by surface tension, growing as a crust until it is large enough to break free and sink. (Source: Brady, 2009)