The Black Sand Basin is named from black volcanic glass (small fragments of obsidian) and is the home of some beautiful hot springs. Located a very short drive from the main road, the basin features geysers and hot pools. Iron Spring Creek flows through the middle of the basin providing a unique division among the various geothermal features. Emerald Pool is the most notable due to the clear water of the pool reflecting the blues of the color spectrum, with yellow and brown bacteria and algae surrounding the periphery. Like Morning Glory Pool, park visitors have thrown objects into the pool over the years leading to a lessening of the vibrant emerald blue color core and an encroachment of the yellow and brown periphery toward the center of the pool. The first feature when entering the wheelchair accessible boardwalk is Cliff Geyser, and when it erupts it does so in rhythmic fashion accompanied by burping sounds that seem to originate from deep within the earth. The parking lot at the basin has only 25 vehicle slots.