That's not deep lava, that's dark/shadow lava; the stuff you see around the cliffs -> lava transition. There is no tile for that though because the shadows weren't meant to stretch out from the shorelines.
They're meant to be used like this:
It wasn't until 2001 when pics1 got revamped that stand-alone water shadow tiles got added, however these transitions were never made for lava because it's a neglected(for good reason) portion of the tileset.