 Taking place 0.3 mya, the second eruption was the most extensive. It was probably between 250 cubic kilometres (60 cu mi) and 300 cubic kilometres (72 cu mi) in volume and extended past the reaches of the caldera, down the adjacent foothills. Beyond the caldera, the eruptive products are poor in phenocrysts (unlike those of the first eruption). They are instead rich in lithic material, which makes up as much as 10 percent of the rock in parts (50 percent at the base of the caldera). As the first of the ash was deposited, it accumulated in layers that formed quickly and resisted erosion, but only partially melded together. However, except for these basal layers and thin zones where the ash was devitrified (loses the properties of a glass and becomes brittle), the entire sheet is melded together. Inside Calabozos, the ash resisted welding and contains more phenocrysts. Instead, erosion ate away at it, in the form of acid leaching, and broke down much of its pumice content. Still, the rock layer here contains five to 30 percent phenocrysts, and has high levels of devitrification and lithic content.
