We walked out onto lava that was only a few months old on the Big Island of Hawaii....You could still feel heat coming out of vents, if you grabbed some long grass and stuffed it down a crack, it would start smoldering, the one night we saw a new vent open with lava coming out, we were a long way from the fresh lava and I thought that was plenty close enough....
1) Taken at dusk.
2) Same location taken at night.