Regarding lighting and volcanoes...
The earth’s atmosphere has a voltage gradient. (the higher you go, the higher the voltage)
Volcanoes emit ionized gases (among other things), which are conductive.
So when you have a large conductive column stretching up into to the sky (think huge capacitor and path of least resistance), you’ll get a few sparks.
FYI.
Thanks for that explanation brings backs my rusty physics.