A Very Hot Tunnel                                      -      N      - 
(-------------------------------------------------)     - <---(M)---> E
                                                        -      -      -

The temperature in this section of the tunnel is much higher than in the
rest of the area.  You can hear an incredible roaring sound to the north,
and the ground here is glowing red-hot so you decide not to try touching it
again.  A haze of heat obscures what lies to the north, but to the east you
can find a cooler section of the caverns.