Underground explosions occur in front of lava flowing over burning vegetation. Plants burn without oxygen as they are covered by lava, creating methane gas. The gas fills underground lava tubes.
When the methane ignites, the ground explodes up to 100 yards/meters in front of the advancing lava flow. Rocks and debris blast in all directions.
Stay more than 50 ft away from lava flowing through vegetation.
Blue burning flame indicates methane at the lava front - John Seach
Don't try this!
Seconds after this person moved away, there was a large methane explosion right where he was standing.