Hi,
Without full context, I would wonder to what "which" refers. The comma doesn't tell me enough in this case, but it may be sufficient in other cases. In this sentence, the "which" could be an intro to a clause referring to the whole of the three things together (bulge, north side, mountain), e.g, "... which hid the potential problem from the people living in the valley to the south."
When the "which" does refer to one of the specific items (bulge, north side, mountain), it makes sense to pair the "which" closely to the item, but I think, again, it depends on the context. In this case, if the phrase was "... a tremendous bulge on the north side of the mountain, which changed the shape of the ridge," it would be fairly clear that "which" refers to the bulge.
Hope that helps rather than confuses. :-)