FIGURE 2.25 Simulation of the distribution of melt (as measured by porosity) in a deforming, reacting matrix. The melt organizes itself into channels that vary in width, position, and melt content with time. SOURCE: Courtesy of Marc Spiegelman, Columbia University. Used with permission. See also Spiegelman et al. (2001).

the essential physics and chemistry of Earth materials arises from structures and processes that occur at the atomic level. The new tools allow these small scales to be studied directly as well as simulated, bridging the gap between quantum mechanics and microscopy and paving the way for a new level of understanding of planetary processes at longer length scales.

Earth materials present a challenge to understanding because of their complex chemical composition and the high pressures and temperatures of planetary interiors. The long timescales of geological processes also create difficulties because some of the critical processes that affect planetary evolution take place so slowly that they cannot be simulated in the laboratory and because they may be caused by mechanisms that are not important or even perceptible at laboratory timescales. The physics of large domains, long timescales, and multiple interacting scales remains a major challenge in Earth science and one that will advance only with interdisciplinary effort.