Well I tried something to deal with the issue:
1) I created a new shipwrecked file (in the second grid of the game list) via the same Mac. Then I entered the volcano again, but this time it worked. It means that my Mac can create the volcano successfully and that what happened to my first game file is special.
2) I changed the name of my first file ("shipwrecked_1") to "shipwrecked_2" and disconnected the network. When I entered the game in the second grid of the game list, the game loaded my first file, which have problem in entering the volcano. And what I saw was that the character stood in front of the volcano. All the things were unchanged just like that I had never gone into the volcano. However, when I chose to enter the volcano, the game crashed again. So this problem is likely to be cause by something in my game file. And I'm not sure what trigger those problem.
My device is MacBook Pro. And I play the game in Steam.
Hope you can find some cues from my file, which I have attached in this page (see "shipwrecked_2"). And I wish that my finding can help other players to save their game files - play a game without the volcano rather than lose all their effort.