Volcanic rock volcanic rock they are selling. The sub-family of rocks that form from volcanic lava are called igneous volcanic rocks (to differentiate them from igneous rocks that form from magma below the surface, called igneous plutonic rocks). The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition. If a rhyolite lava-stream cools quickly, it can quickly freeze into a black glassy substance called obsidian. When filled with bubbles of gas, the same lava may form the spongy appearing pumice. Allowed to cool slowly, it forms a light-colored, uniformly solid rock called rhyolite. The lavas, having
Potrillo volcanic field are five maars in the Potrillo volcanic field. A cinder cone also known as scoria cone, is a steep, conical hill formed on top of a vent. The cinder cones often occur in groups usually on the sides and around the shield volcanoes and the strato volcanoes. They are formed form lava fragments called cinders, it is magma that is glassy and has hundreds of gas bubbles that are frozen, it cools quickly after it is ejected into the air. The lava is expelled from the vent and formed around the vent when they fall back after it is ejected.