Also note what we're wearing. Long trousers are essential. You'd never get near the lava if you didn't have some protection for your legs. Also leather gloves. I did my research and we took these along. The lava flows are incredibly sharp - if you fell and put your hands out to catch yourself you'd cut your hands to ribbon.
The boots are obviously essential, and probably saved Tina's ankle from serious damage on the way back. She stumbled and sprained her ankle, and although the damage was bad, it wasn't as bad as it would have been if she'd been wearing trainers. The hike back took nearly 4 hours with Tina hobbling along.