Its intervals range from 20 to 80 minutes. Given Echinus Geyser's great show and its relatively short interval, it is worth waiting for even if you don't know the next prediction. Echinus is the largest frequently active acid geyser in the world. Unlike most geysers in Yellowstone and around the world which tend to be alkaline in nature, Echinus, along with most of the other thermal features at Norris Geyser Basin, is acidic in nature. The water in Echinus is reportedly about as acidic as lemon juice.
Acid affects the formation of sinter deposits around the geyser.
Because acid water can carry more dissolved silica than alkaline water, the sinter deposited from acidic water forms faster than sinter deposited from alkaline water. Also, the sinter deposited by acid water tends to look spiny. This spiny character is the reason for Echinus' name. Early explorers thought the tiny spiny formations found on pebbles around Echinus looked like sea urchins or echinoderms. Hence, the name.