Mega Volcano uses nine colors! The board is expanded to 6x6 using five nests of seven colors and one nest of a eighth 'wild' color which count as any of the other seven colors. (published in Hypothermia #15)
Another way to do MegaVolcano is to use four nests of nine colors, and a tenth color of smalls for caps. This eliminates the wild color, and makes the game longer by increasing the number of colors needed to trigger the endgame.
Mini Volcano uses five nests of four colors. Some prefer to shrink the board down to 4x4; others use a sparsely populated 5x5 board.
In Compass Volcano a direction die (N, NE, E, SE, S, SW, W, and NW) (or a d8 where 1=North, 2=Northeast, 3=East, 4=Southeast, 5=South, 6=Southwest, 7=West and 8=Northwest) is used to restrict the movement of caps to a random direction.
In Melting Volcano the matching-sized piece that is landed on, rather than the erupting piece, is captured.
In Single Cap Move Volcano players can only move one cap one space.
Coastercano uses Martian Coasters instead of a fixed board.
Iceland Volcano uses 5HOUSE and puts the black drones and queens on the board as immovable anchors.
Caldera is a redevelopment of Volcano that uses SIX nests of four colors (and one empty square in the center of the 5x5 board), and greatly changes the endgame trigger and victory conditions.
Scrambled Volcano is a variation of Volcano where the nests are built in random pattern layer by layer (pawn-drone-queen).
Plain Earth Volcano is a variation of Volcano that is played just like regular Volcano except that when the cap lands on an empty square, it is removed from the game. Once the last cap is removed from the game, the game ends and it is scored like regular Volcano.
Speed Volcano is a variation of Volcano where a chess or G8 game timer is used to limit the time a player has to make a move. Optionally, an overall time limit can be set for the entire game. When time runs out, the game ends and it is scored like regular Volcano.
Abiegnus uses Volcano eruptions on a 4x5 board, where caps of different colors are activated by rolling an IceDice color die.