A Sacrificial Ledge                                    -      -      - 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      S      -

You are standing on the rim of a gigantic crater that leads downward
into the depths of the volcano.  From here, you can go back down the outside
volcano, or dive into the depths of this smoldering mountain of fire.  Fiery
heat rushes upward, heating the stones here till the water around them to
steam.