Can you float in Lava?

[KittenMagician]

So my players are about to fight an ancient red dragon in a volcano and a long time back i gave them Plate Armor of Inborn Immunity (requires attunement and turns any damage resistances they have naturally into immunities). a red dragonborn fighter has the armor now and i was thinking of throwing her into the lava. she wouldnt take any of the fire damage but im not sure if she would float, sink, or something in-between. Rule of cool, I want to let her swim out but from a real world physics stand point, could she?

[Greywander]

I don't know for sure, but I imagine rock, molten or not, is probably a lot denser than water. That means a person would likely be a lot more buoyant in lava than in water. If the lava is thick enough, you might even be able to walk across it, though you might start to sink if you stand still for too long.

[Sigreid]

Lava is still much denser than the human body. They won't sink into it at all and instead burn to death quickly on top.

Youtube has a video about it.

[Rynjin]

Lava is about 3-4 times denser than the human body, IIRC from the last time this topic came up. If you were fireproof, you could walk on it.

[Anymage]

Lava is about three times as dense as a human. Assuming dragonborn are roughly as dense as a human, they'll stay on top.

Plus, a muscular human and/or one who's weighed down will wind up more dense than water and will naturally sink. A strong swimmer can overcome this. Since your dragonborn is wearing plate, I think it's safe to assume that they're a strength character. I'd rule of cool it to say that they can swim through lava as quickly as water (having to lose a turn swimming back to the fight you just got thrown out of is painful enough), and let them make a not too hard Strength(Athletics) check to get back to the fight sooner rather than later.

[5eNeedsDarksun]

Yes they float, but lava is a lot thicker than water (though not thick enough to walk on). They'd be moving really slowly, unless there's some other magic helping them out... or you can be kind and just give them swimming speed.

[GooeyChewie]

If the heat wasn’t a problem, it’d be like walking on goo. I would probably rule it difficult terrain, but not completely disallow it.

[Segev]

Depending on the lava, if you run fast enough, you can shift your weight to your next foot before you even break through its surface tension.

[Mastikator]

You probably wouldn't be able to stand on lava if it's molten, but crawling on your 4 should be rather easy. I'd probably give the player an acrobatics check to treat it as difficult terrain if they want their hands free.

Sitting on it would probably be very comfy :smallcool:

[KittenMagician]

What if the red dragon is keeping it really really hot with magic. would it be more liquidy and less dense?

[JLandan]

You probably wouldn't be able to stand on lava if it's molten, but crawling on your 4 should be rather easy. I'd probably give the player an acrobatics check to treat it as difficult terrain if they want their hands free.

Sitting on it would probably be very comfy :smallcool:

And if they start to sink, make them do a swim check.

Also water breathing ain't gonna cut it.

[ImproperJustice]

Who cares about physics?

Your fighting a magic dragon in a lake of lava with magic armor.

Let the hero be a darn hero and run around and flip on the stuff and fight a dragon.

Guarantee your friend / player is gonna love that better than slowly swimming / crawling around on all fours like a fool in the name of some odd call to realism.

[Greywander]

Here's the reality of what's going to happen. (https://www.youtube.com/watch?v=LAPo1dgrHms)

The player will then awkwardly rise up out of the lava on their next turn.

[Witty Username]

As I understand it, it would be virtually impossible for a human to sink in liquid rock as the density of the rock is too high, but you might be able to walk on lava due to the high density. Recall that we are all floating on magma right now.

[LudicSavant]

Who cares about physics?

I mean, I get where you're coming from -- you're saying that it's fine to be unrealistic in the name of Rule of Cool / Rule of Fun / some other bit. And it is. But it can still often be useful for a creative writer to learn about physics and such even if you're throwing large swathes of reality out the window in your story.

[da newt]

This is not my area of expertise but I understand basic buoyancy.

A person is nearly the same density as water so a person in water floats with most of themselves submerged (depending on the person's make up / density). Assuming lava is a liquid (by definition it is) and that it is about 3x as dense as water (also true) a person would float in lava with about 1/3 of themselves submerged - so swimming should be easy (assuming the lava is just as liquid as water - free flowing, not sticky or gelatinous) but if you tried to stand on it you'd sink in until 1/3 of your mass was below the surface so walking/running on it would be impossible.

Then again, how well is a dragon born in full plate and all their other crap gonna do? (if your PCs are anything like mine - they are loaded to the gills with all sort of crap including heaps of gold with a density 7x lava or 20x more than water ...)

But yeah - I'd probably err on the side of rule of cool or whatever suits the narrative best.

[Xuc Xac]

This is not my area of expertise but I understand basic buoyancy.

A person is nearly the same density as water so a person in water floats with most of themselves submerged (depending on the person's make up / density). Assuming lava is a liquid (by definition it is) and that it is about 3x as dense as water (also true) a person would float in lava with about 1/3 of themselves submerged - so swimming should be easy (assuming the lava is just as liquid as water - free flowing, not sticky or gelatinous) but if you tried to stand on it you'd sink in until 1/3 of your mass was below the surface so walking/running on it would be impossible.

Right. You can't walk on it. If you step on it, you'll sink in it. A meaty broad-shouldered warrior would probably sink to the waist while a more bottom-heavy character would sink to at least the upper thighs. That isn't a stable position, so they'll probably fall horizontal very quickly and find themselves lying partially sunken on the surface. Swimming in it would be more like crawling on extremely soft mud: very slow and exhausting because it resists flowing around you and you can't get as much of your surface in contact with it to paddle. If I had my choice, I would just tie an iron chain around my waist as a lifeline so I can pull myself back out. Even if the heat doesn't bother you, you don't want to spend a lot of time just floating there like a cork because there are a lot of toxic fumes coming out of the lava. Being immune to heat doesn't help against poison gas.

[Kane0]

Thick and viscous, i'd treat it similar to a quicksand hazard. Something like difficult terrain and if you dont move on your turn you start sinking (with a save to avoid and/or a check to get unstuck again).

[ImproperJustice]

I mean, I get where you're coming from -- you're saying that it's fine to be unrealistic in the name of Rule of Cool / Rule of Fun / some other bit. And it is. But it can still often be useful for a creative writer to learn about physics and such even if you're throwing large swathes of reality out the window in your story.

Certainly.
And if your writing a story it can really enhance the experience.

I love the Expanse and it pays a lot of attention to detail regarding real life physics.
I would expect an RPG in that setting would do the same.

I guess I view D&D as something entirely different. I feel players generally sign up to enact what they see on the cover art: Heroes engaged in battle in fantastic environments against enormous creatures who in rea life would collapse under their own body weights and suffer fatal heart attacks at the age of 25 due to gigantism complications.

I have seen way too many games just ruined or players arbitrarily hamstrung by what physics suddenly seem important at the time while ignoring all others.

But I see your point. I don’t wanna come off necessarily as championing ignorance.
Just wanna make sure someone who has a resource (magic lava proof armor) isn’t backhanded over lava density while fighting a dragon who shouldn’t be able to fly under it’s own weight.

[Imbalance]

So my players are about to fight an ancient red dragon in a volcano and a long time back i gave them Plate Armor of Inborn Immunity (requires attunement and turns any damage resistances they have naturally into immunities). a red dragonborn fighter has the armor now and i was thinking of throwing her into the lava. she wouldnt take any of the fire damage but im not sure if she would float, sink, or something in-between. Rule of cool, I want to let her swim out but from a real world physics stand point, could she?

So, all the posts about the reality of the density, surface tension, viscosity, ec. of molten rock are great and you should definitely consider those facts and maybe even relay them to the party on a decent nature check. Yes. Also tell them, because this would be true, that without some kind of resistance they can't even get near the stuff without suffering damage, and if it's a closed chamber there'll be super-heated, suffocating air. A lot of this is well-represented by lair actions, if you want verisimilitude instead of video game logic, that is.

Throw? the character into the lava? In any case, that's going to be like landing on concrete. That's not going to be a dramatic splash. Unless...

What if the red dragon is keeping it really really hot with magic. would it be more liquidy and less dense?

Molten rock is one thing; boiling rock is a whole 'nother level. To the unprotected, you could rule that it's so hot as to be double the normal fire damage roll (isn't it like 6d10?) as well as destructive to non-magical gear (see rust monster). You may want to make sure the rest of the party discovers a ring of fire resistance or a scroll or potion or two.

Your fighter, though? That's god-tier in this fight. Throw her in and she rises on a stone slab as the magic of the armor actually cools the swirling magma around her, each step making a foothold on the roiling surface that begins to melt into the glowing mire again as soon as she moves away. Make that epic. Then, have the ancient red make an intelligence check to determine the effect, and if successful, gloat, grapple, and attempt to forcibly doff the plate, all with opposing checks. Have that eat up at least an entire round for the foe, and if all of it fails, good ol' swallow on its next turn. No, it's not on the ancient dragon stat block, but it should be, or at least a comparable spell or effect to impede the fighter for a round. The dragon needs to be that smart, or it's a lame fight. The fighter needs that opportunity to shine, though not at the expense of everyone else's time in the spotlight.

[Keravath]

If lava is about 3 times the density of water/humanoid then a dragonborn weighting 200lbs would be 1/3 the density of the lava and float. A dragonborn carrying 200lbs of gear would at most double their density (that assumes the volume of the gear is negligible compared to the humanoid which isn't accurate). They would be roughly 2/3 the density of lava and still float - they would just ride lower in the lava.

So, as long as the character is immune to the effects of the heat, they will float on the lava.

However, the consistency of lava varies a lot. In your case, it sounds like you want it to be very hot and liquid. In that case, I'd probably give the character a swim speed or make it difficult terrain if they don't have a swim speed already. The thicker/cooler the lava gets the more difficult it will be to move in but the longer it will take for the character to sink into it.

[Chronos]

Quoth 5eNeedsDarksun:
Yes they float, but lava is a lot thicker than water (though not thick enough to walk on). They'd be moving really slowly, unless there's some other magic helping them out... or you can be kind and just give them swimming speed.
Fun fact: Swimming speed is mostly independent of viscosity (this has actually been tested). It generates more resistance, but you're also able to exert more propulsive force, and the two effects balance out. You will get tired more quickly swimming in a thick liquid, but given that a reasonably-fit human can swim for hours in water, this probably won't matter on timescales of a single combat.

I've never seen anyone do experiments for liquids significantly denser than water, but I expect that, if anything, that would result in faster swimming speeds: Less of your body is submerged, hence less drag, but you can ensure that the parts that are submerged include the parts that you're using to propel yourself, so you'd still have most of your thrust.

[Sandeman]

It looked good in the movie when Gollum sank completely into the lava.
But it is not a very scientifically correct scene.

[JackPhoenix]

This (https://www.youtube.com/watch?v=9UlDFHOgbYI) may help.

[Zetakya]

Fundamentally, Science can take a hike.

However, the fun thing to do is to have a crust on the lava flow but have the enemy (and/or just standing still for too long) breaking it, so you have some time in there but if you take too long things get worse.

[Rynjin]

Who cares about physics?

Knowing the baseline assumptions of reality is important for knowing when to break those assumptions, and how. At least, that's always been my perspective on it.

The same goes for game rules, honestly. I think it's always important for GM and player alike to have a strong grasp of the rules, so when they houserule something they know exactly what's going to happen afterward.

[TyGuy]

At typical eruption temperature lava is non-newtonian. Treat it like oobleck.

[sithlordnergal]

Funnily enough (https://www.quora.com/Do-people-sink-in-lava-or-do-they-burn-on-the-surface) someone has asked this on Quora before, and they were given a pretty good, in-depth answer as to what would happen. The TL;DR version is "No, you won't sink, you can actually run across lava, but if you're thrown into lava then force of the drop will cause you to sink a ways"

[Demonslayer666]

To everyone flipping the bird to science, if a DM treats things in a very unrealistic way, it makes for a game that feels like a cartoon rather than playing in a world that actually exists.

I saw in the lifting thread many people say that the characters are not human, but rather super human. Not in my game, and not in any game I have ever played in. Max strength equated to a guy the size of Arnold/The Mountain.

Since the DM has to determine difficulties, it should be based on things we know. Fun is ok, as long as it doesn't venture into silly.

[Sigreid]

To everyone flipping the bird to science, if a DM treats things in a very unrealistic way, it makes for a game that feels like a cartoon rather than playing in a world that actually exists.

I saw in the lifting thread many people say that the characters are not human, but rather super human. Not in my game, and not in any game I have ever played in. Max strength equated to a guy the size of Arnold/The Mountain.

Since the DM has to determine difficulties, it should be based on things we know. Fun is ok, as long as it doesn't venture into silly.

Silly fun is great as long as that's what the table signed up for.

[Demonslayer666]

Silly fun is great as long as that's what the table signed up for.

I am specifically referring to going into the ridiculous where it's no longer fun.

We do get pretty silly at our table with puns, jokes, and Holy Grail references, but the DM never goes full cartoon. Never go full cartoon.

[Xervous]

I am specifically referring to going into the ridiculous where it's no longer fun.

We do get pretty silly at our table with puns, jokes, and Holy Grail references, but the DM never goes full cartoon. Never go full cartoon.

So that’s why people frequently ban Animate Dead.

[kore]

I am specifically referring to going into the ridiculous where it's no longer fun.

We do get pretty silly at our table with puns, jokes, and Holy Grail references, but the DM never goes full cartoon. Never go full cartoon.

What you're talking about is verisimilitude and I agree. As one familiarizes themselves with "the rules" of the world they are aware of the possibilities that exist outside of reality but it doesn't mean all of reality is nullified. Gravity still exists, there are rules for falling, but there are also magical means to work against it that don't necessarily follow real-world physics and we're okay with that. This lava question is basically asking if heat (and I suppose suffocating air) wasn't a concern then what would an person's interaction be like with lava. I think we've answered it.

Sure, there may be other minute details like what of their non-magical gear. If the DM isn't looking to punish the player but provide them a unique, fun experience then they are at liberty to explain away such concerns in favor of fun. Perhaps when tossed the player's backpack is flung to the ground where the party remains.