system
Given the following post, respond as if you're commenting on Reddit:
human
Why do active volcanoes have such constant, violent waves?
gpt
Can you give an example of what you're talking about?

I'll assume for the moment you're talking about lava lakes roiling and bursting. Two things cause the surface to be violent. One, the lake is convecting because lava is very hot and it's losing energy to the cold air (edit: and usually more importantly, by radiating!), becoming cooler and denser in the process. It convects because it has a low thermal conductivity, so it was to actually move to transfer it's heat effectively (unlike a metal bar, where the heat flows on its own by conduction). Convection makes for a violent sloshing surface as lava rises in some places and sinks in others.

The second process is gas rising. Gas is a necessary part of magma and you can think of many aspects of volcanic as just the gas trying to escape. The presence of gas does two things: it can help drive convection because gas is way less dense than lava, and it can explode when bubbles reach the lava surface.