Question

which occurs just before a volcanic eruption?
lava flows onto the sides of the volcano.
the expanding gases push magma through the pipe.
a pocket of magma forms beneath the volcano.
new rocks are formed as lava hardens.

Explanation:

• Lava flowing and new rocks forming happen during/after an eruption, not just before.
• Magma forming beneath a volcano is an early, pre-eruption stage, not the immediate pre-eruption event.
• Expanding gases pushing magma through the volcano's pipe is the immediate event that triggers the eruption, occurring just before it begins.

Answer:

The expanding gases push magma through the pipe.