This Holder is designed for Palo Santo and Incense. You can also use it for white sage. When burning the palo santo or incense, small amount of smoke will be generated. The designer was thinking any natural phenomenon also generating smoke spontaneously. When volcanos were erupted, lava expelled, the smoke was generated along.
Putting the burned palo santo under the ceramic volcano mountain, it will looks like smoke billowing out of a volcano.
