Here’s a guy running up a lava flow — and here’s why he still has legs
We strongly recommend that you do not use this method to get in touch, as it were, with the Earth. But as this video shows, it is technically possible to run over eight or 10 feet of red-hot lava and emerge with your limbs intact. Someone tell those kids pretending the floor is lava that it’s safe to get off the couch!
At Wired’s Eruptions blog, geoscientist Erik Klemetti explains why this stunt, while dumb, is not the dumbest possible thing.
Taking a look at the video, the lava flow in question is moving pretty slow and has a dark crust on it. This means it is likely pretty cool — in fact, it looks like it is a`a lava, which is even more viscous than the pahoehoe many people associate with lava flows. Crust forms quickly on lava flows because there is a high temperature gradient between the lava (at ~1000°C) and the air (~25ºC), so the lava hardens into a semi-flexible crust. Based on where the guys are standing, the lava flow isn’t likely very large because the guy who doesn’t run up the flow doesn’t seem concerned to be standing only a few feet away. The flow itself looks confined to a small channel surrounded by solidified lava. My guess is that this little flow is fairly far from the vent (source).
Now, I’m not sure why he chose this route to get up the ridge (well, beyond showing off), but if that flow has a decent crust (which it does) and is moving fairly slow (which it is), and if you move quickly, your weight isn’t going to be enough to cause you to sink into the flow.
But you could still trip and put your hand in the flow, or tread on an area with a thinner crust and go in up to your ankles. It’s a stupid, horrible idea. But it might make you a YouTube star for five minutes, and isn’t that worth it? (Spoiler: no.)