Lightning During A Hawaiian Volcano Eruption
In July 2008, the ocean entry plume at Kalapana, Hawaii erupted with a spectacular display of lava, ash, and dark-clouded fury.
But within those eruption clouds was something else entirely: Lightning.
This is a fairly common phenomenon, though it’s rare in Hawaii. In this case, it occurred due to “unusually dry conditions.”
“ As the hot plume rises, it draws up cooler air and moisture from the sea, forming a vortex (similar to a waterspout). Location is Kilauea volcano, near Kalapana.“

The lightning is clearly visible, especially during the night shots, in the above video (beginning at about the 2:00 mark). The footage is courtesy the Center for the Study of Active Volcanoes, or CSAV.
You can read more about lightning in volcano eruption clouds — and the 2008 Kalapana area eruption in particular — at the official CSAV website.