All geysers have constrictions in their plumbing but they erupt in two different fashions. Some geysers erupt in a column of water; others spray water all around. The temperature of the underground water is responsible for the difference in the eruption. When water is heated to 350° F (180° C) it dissolves the silica in underground rock depositing sinter and forming a cone-like nozzle at the surface of the geyser. These geysers are called cone geysers and they erupt in a steady stream of water. When water is heated to a slightly lower temperature it doesn't dissolve silica and nozzles don't form. Geysers without a cone are called fountain geysers. They erupt from open craters spraying water in all directions. Old Faithful is an example of a cone geyser. Grand Geyser is an example of a fountain geyser.