Running the latest version of DF. I did try to record the video using the DF movie recorder, but for some reason I could not get it to work. I'm probably doing something wrong, but in the meantime here is a .avi of my erupting volcano, compressed into a .rar.

Not the best quality video, and my computer stuttered a LOT capturing it, so there are some long pauses. I'm not running any mods. Anyone know if this is a built-in but rare feature of DF volcanoes, or is my game bugged? It LOOKS intentional, but given the reaction on the forums I don't know what to think.

If you watch the video, you'll see when I travel up the caldera to where the magma is pouring through, that there are plumes of magma bubbling from the top surface, and its pouring through gaps where the previously empty caldera eroded.