Yeah I think the volcano is only around the observation deck/drop slide platform height and I think once the rock work is on that opening you mention wont look as big. Reason I believe this is because of the following:
So below I found the best angle recent photo I could to match the concept art and it is pretty close, so I overlaid the photo with the concept art and the openings that can now be spotted in the steel work also reasonably matched up the openings showing day light through on the concept art. I then took both separate photos and highlighted in red the main features on the concept art and then over laid them onto the real construction photo. Again matching up quite well. Hopefully this will give some a good idea where the volcano is at in terms of height and features. This also gives a good idea of which slides are coming out of which openings. The photo is not the clearest but it was the only recent one at the best angle so if anyone struggles to spot the openings I have highlighted study some other pictures and you should start to see them n relation to the concept art.