A steam plume in Hawaii Volcanos National Park. This plume is from lava entering the Pacific Ocean. The sign in the foreground says something like "WARNING: Steam plume is hazardous to your health". Personally, since the plume is a good four miles away, I don't think people really have to worry until they get good and close.
This lava field is from Kilauea eruptions in the late '80s and early '90s, and was the one that wiped through Kalapana. Some houses were missed by the lava, though, but they've all been evacuated. There was a heiau (temple) out there as well, but a more recent (August '97) flow overwhelmed it.