Rock Information
Yellowstone Caldera contains the following rocks:
"Rhyolite is a light-colored, fine-grained, extrusive igneous rock that typically contains quartz and feldspar minerals."
Tuff is a sedimentary rock formed by the accumulation of volcanic ash.
Basalt is dark-colored igneous rock mainly composed of minerals.
The volcanic rhyolites and tuffs are rich in quarts and potassium feldspar, which forms poor-nutrient soils. The soil is usually moist but occasionally dry;the soil is fertile.