Deltas are sheets of constrained lava found among the terrain of basalt deltas biomes. These lava terraces have just enough magma blocks that they don't entirely look like the lava sections of bastion remnants (which do not generate in the basalt deltas biome). Tending to be narrower than wide, they sometimes allow passage amongst their lava.
Often diagonal more than straight, they are more visible dangers than lava and magma blocks within basalt piles. Being relatively smooth in elevation, they also do not conceal drops within. They are as likely to be adjacent to such piles of ("eruptive") basalt as to flatter "cooled lava flows," of basalt and blackstone.
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|Upcoming Java Edition|
|1.17||20w45a||Due to a bug, deltas no longer generate.|
|20w46a||Deltas now generate again in the nether.|
|1.16.0||beta 18.104.22.168||Added deltas.|