Question

What would happen if all the volcanoes in the world erupted at once?

Answer 1

If all active volcanoes on Earth went off at the same time, there would be a lot of explosions. Explosive eruptions would churn out wall of rocks, ash and gas, wiping out the nearby areas. ... They would travel for thousands of kilometers, and cover the Earth with the thick blanket of ash.

Answer 2

Answer:

If all of these supervolcanoes erupted at once, they'd likely pour thousands of tons of volcanic ash and toxic gases into the atmosphere. The gas would likely fall back to Earth as acid rain, devastating agriculture and leading to global famine.