Still, it's funny you should mention continuity, because one of the things in the games that irked me was the pretty generous disregard for the Mushroom Kingdom's geography. What I mean is, let's look at all the Mario games that have taken place in the Mushroom Kingdom with an honest-to-goodness "map":
--SMRPG
--Paper Mario
--PiT
--BiS
Actually, I was quite fond of how accurate the PiT map was to the Paper Mario map, just done in SS style.
You've got the Mushroom Castle in the center with Toad Toad directly below it, a star-falling region behind the castle, some vegetation areas to the west, the dry/desert areas on the east, and the snow areas on the northeast. But I don't think these maps are ever meant to be a comprehensive layout on the whole Mushroom Kingdom--they're more like outlines of the main areas you explore in each specific game. Just because Thwomp Volcano doesn't appear on the BIS map doesn't mean it doesn't exist; it's just not a place you visit in that game. Imagine if the developers put it in the map for the sake of making a comprehensive map--I think people would have been disappointed to discover that you actually don't visit that area.
On a side note, this may be a bit of fanonizing, but seeing as how Blubble Lake appears to be off the mainland of Mushroom Castle and around the area where Kero Sewers would be on the SMRPG map, I like to think that Blubble Lake is actually connected to or on the same mainland where Midus River and Tadpole Pond intertwine.
