Question

what causes supersonic shock fronts in a volcano?
the lava expanding as it heats up.
the lava cooling when it hits the air.
the magma turning to lava when it reaches the surface and flows down the sides of a volcano.
the erupting particles moving faster than the speed of sound.
rewatch

Explanation:

To determine the cause of supersonic shock fronts in a volcano, we analyze each option:

• "The lava expanding as it heats up" does not relate to supersonic speeds.
• "The lava cooling when it hits the air" is about cooling, not supersonic motion.
• "The magma turning to lava...flows down" describes lava flow, not supersonic events.
• "The erupting particles moving faster than the speed of sound" matches the definition of supersonic (faster than sound), so this causes shock fronts.

Answer:

The erupting particles moving faster than the speed of sound.