The FDW Well - Rather Shallow & Not As Cold

Is it me or did the well in Across the Sea seem a little shallow? A ladder was apparently used to get down there for MIB and possibly mother, and light could be seen coming from above. The cave also wasn't frozen over. All later views of the well or the room with the wheel made it much deeper. When Locke was climbing down the rope we couldn't even see the bottom of the well. He had climbed down rather far and still fell far enough for a compound fracture to the leg. The trip down the elevator in the Orchid was also rather long. I think Ben made some comment as to how deep. This is also evident when the Orchid is being excavated. It seems like hundreds of feet farther down than in ATS. This leaves us with what would cause the room to suddenly freeze over. Ben even knew to expect the temperature even though it was hidden since before his time. What could cause this temperature change and addition of earth. The only thing I can think of is a Volcano, but this doesn't fix the temperature, but it does the depth. Any thoughts? I would like to think that the discrepancy wasn't just to make the ladder scene easier. Doubt we'll see an answer, at least until maybe the dvd.