Related Clues:

• Soap containing volcanic pumice
• Rock that runs
• Source of basalt
• Magma, after surfacing
• Soap brand containing ground pumice
• Etna outflow
• Etna ejection
• 56-Across's output
• Red river?
• Magma on the surface
• Source of pumice
• 58-Down output
• 9-Down output
• Volcanic threat
• Steamy flow