What does a red dot on a minecraft map mean?
Solution 1:
It's really anything that is the majority of the blocks in the chunk shown, and is considered red by the maps. Here is a video to help explain it:
It isn't red wool because that is considered white since it shares the same data value as all the other wools. Lava, Netherbrick and TNT are detected as red. Bricks might turn out red also. If it isn't an area you have interacted with yet, I would have to say lava.