Color theory primary colors work at all is that the imperfect pigments being used have sloped absorption curves, and thus change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and
Paired metamorphic belts of plate tectonics in the late 1960s, led to a better understanding of regional metamorphism and permitted the association between paired metamorphic belts and subduction zones. The asymmetric deformation of earth's lithosphere along subduction zones produces two distinct thermal environments. These two distinct thermal conditions are parallel to the trend of the subduction zone. Low temperature, high pressure conditions are generated in the areas along the oceanic trench, whereas high temperature, low pressure conditions are generated beneath the arc region. A positive thermal gradient is visualized, extending from the colder oceanic trench to the warmer arc region. The thermal and