This is a friendly reminder from your favorite VolcanOSHA Representative.
Lava and magma are two different things.
While fundamentally the same, both being molten rock from the earth. They are also fundamentally different and should not be interchangeably used to describe molten rock.
For clarification.
Lava is molten rock that has reached the surface through volcanic activity.
Magma is molten rock that is still trapped underground.
Please reach out if you would like more clarification.
Why do you stop people from walking on the forbidden pavement?
I will try to keep things brief, as this is a topic I am passionate about, but this will still likely be a long post.
But it is mostly because there is no way for you to be sure that you are stepping on solid or stable ground.
Lava crust can be incredibly deceptive as to how thick it actually is, especially if it is fresh.
You could step or fall into lava or fall into a lava tube. Not to mention the dangerous gasses that come from eruptions may affect your judgement or even harm you.
Please stick to the marked out trails for your safety.
We really do want you to visit the volcanoes, but we want you to be safe while you are here.
If you go out on the lava, and you are hurt or anything happens.
Our rescue will not help you.
They will not go onto the lava to help you. They will not take that risk.
Do not be one of these people and stay on the marked trails.
This is the TLDR of answering this question.
To prevent an unfortunately long post on the dash I will continue under the cut if anyone does want to learn more about this in more depth.
While it is not impossible to walk on lava that is fresh and has a crust.
As seen in Hawaii with pahoehoe (or helluhraun as we call it in Icelandic) lava. It can support a human's weight after 5 to 10 minutes once it has stopped flowing and a crust has formed.
It becomes safe enough for you to step on, but you would not want to stand on it, as it is still boilingly hot and will melt or burn through your footwear and if you are on it for long enough, you will burn as well.
I have heard it is a very uncomfortable experience and not one someone should do for the fun of it.
Though some daredevils have been known to stand on it for a while. (This photo is staged, but it is a good visual.)
There are also just the people who do it for fun.
This image (as the video is no longer available) is of a man in Italy walking on an a'a lava flow (apalhraun in Icelandic). The lava he is walking on is still moving (though slow and likely much cooler as it is likely far from the vent it came from).
You can see the bottom of his boot has combust and there is now a small flame from the heat of walking on the flow.
It is not staged. And the man was unharmed.
You should only ever walk on fresh lava if you absolutely must. Which should never be the case at the current eruption here in Iceland.
If you get cut off by lava and are stranded on an island, the rescue team will call in a helicopter. (Though this should not happen as they usually mark off routes that will be cut off soon.)
There is also the risk of lava tubes or pockets of air in cooled lava.
Sky lights are beautiful, they give us a peek underground. But we would not want to see one form because someone fell through thin crust.
Lava in these tubes are often very liquid and move a little faster than on the surface due to the surrounding lava acting like an insulator and keeping it incredibly hot.
And finally, an honourable mention, and the reason I refer to lava as forbidden pavement.
Crustal Foundering.
This is when very hot, liquid lava forces the dense crust under and then replaces it.
All volcanoes in the my home universe have or have had a physical 'human' body.
And, bonus treat.
A volcanos hair is physically lava. And the amount of hair that's glowing rather than cooled, will always represent the level of activity at that volcano at the time of the ask being answered. Here's an example for me!
