It can harden into igneous rock (4)
I believe the answer is:
lava
(Other definitions for lava that I've seen before include "Volcanic outflow" , "What volcano ejects" , "Molten volcanic rock" , "Hot molten rock" , "Flowing volcanic matter" .)
I believe the answer is:
lava
(Other definitions for lava that I've seen before include "Volcanic outflow" , "What volcano ejects" , "Molten volcanic rock" , "Hot molten rock" , "Flowing volcanic matter" .)