Add "Volcano" option (instead of the desert hex)
Create the game board in the same manner as a normal game but replace the Desert tile with the special Volcano tile (see image).
Randomly assign a number token (in addition to the number tokens already placed on the island) whose value can be any number except "7". Show this number token on the Volcano hex. The number will determine how active the Volcano is.
The Robber begins the game on the Volcano hex.
During the initial construction turns, no player may place either of their two starting settlements on an intersection that borders the Volcano.
During the game, the volcano may erupt! When it does, settlers who are unfortunate enough to be in the path of the lava will be swept away! When the number on the token that was placed on the Volcano is rolled, the Volcano erupts!
When the Volcano erupts, roll a die to determine the direction the lava will flow. One of the six intersections on the Volcano tile will be affected. [See full description online].