Note from [~GoldenHelmet]
Earlier comments on this report and many of the linked "duplicate" reports have conflated this with some other issues such as MCPE-7284, MCPE-43990, and MCPE-21038. This focuses on the following unexpected behavior:
Water and lava placed or updated by the player may touch and not form cobblestone.
Three cases are presented:
Water next to fully-horizontally-spread lava: no interaction.
[media]
Water next to down-flowing lava: no interaction.
[media]
Water next to down-flowing lava with a supporting block below: lava flows into the water and replaces it.
In Java Edition these behaviors do not occur. With (1) and (2) the lava changes to cobblestone, and as a result it is impossible to test (3).
Note that the demonstration of (3) includes the issue raised by MCPE-21038 (lava can appear to flow faster than water and break cobblestone generators), but we should keep that distinct. None of the cases above is related to (apparent) flow speed.
Cases (1) and (2) seem to occur for the same reason: cobblestone formation depends on lava's ability to spread horizontally. Fully-horizontally-spread lava (liquid_depth 3) and down-flowing lava (liquid_depth 8) cannot spread horizontally, so they don't transform. I would guess that the formation of cobblestone occurs when lava gets ticked as a result of an adjacent block update. When it gets ticked it checks for adjacent water along with scheduling an attempt to spread and set fire. If it has liquid_depth 3 or 8 it skips the water check. (It is impossible to determine in-game whether it is skipping the water check along with or instead of skipping the spread check.)
Case (3) occurs because lava is able to flow into and replace water, but water is not able to flow into lava. Water sees lava as a block it could flow into when calculating a path to spread, but it is not able to actually flow into it. Lava does not have that limitation. I am not sure exactly why this difference exists, but it may have some importance to the mechanics of their interaction. However, since case (3) requires case (2) to set up, if (1) and (2) are fixed then (3) will no longer occur.
This bug has been around for a longgg time, and it's kind of a nasty one. Not sure of the root cause, but basically due to the rate at which lava and water flow, they can touch each other, and have no reaction. No stone, no cobble, no obsidian created.
This isn't due to a lack of updates, as you can place/break blocks all around them and nothing will change. My best guess is that its due to liquids being affected by random ticks, but that doesn't really explain the no reaction.
Even just by placing water/lava on the ground, you can still get them to touch. No tricky business, so this is likely a combination of bugs.
By being slightly tricky, i was also able to get water completely surrounded by lava 😝
In this video i show how to reproduce this bug, and several others having to do with liquids!
https://youtu.be/axIXQLdgpEg
Linked issues
is duplicated by 37
relates to 3
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Comments 11
This happens with me a lot. When in caves, I try to put water near lava to make some cobblestone/safe way to walk on. Instead, they don't interact in any way. Water just stands on smaller lava falls as it they're a separate block and do not interact as they should whatsoever. Next time I reproduce this bug I will make sure I take screenshots to share.
Affects 1.17.30.20
Encountered a 1x1 lava column in a very large cave containing a deep aquifer. The lava column had the "flowing" appearance but ended on a single 1x1x1 cobblestone block where it hit the aquifer's surface. After I broke this block the lava began behaving in a more typical manner, spreading out and generating a cobblestone plate.
I guess this is related to it. The downflow of lavaedge get watersource_block stuck next to it.
this is still happening in 1.18.31 and is making it hard to descend to the bottom of the end to make a farm.
thanks, updated the post to include that information🙂