0. All regular Diplomacy rules apply except when they don't.

1. Each move each player may:
(a) cause one geophysical event; and
(b) "stabilize" any one given space or boundary on the board for each s.c. that player controls.

2. A Geophysical move may be:
(a) MARINE PLATFORM UPLIFT : converts a sea space to a land space;
(b) EROSION : converts a mountain space to a land space or a land space to a sea space (or a lake space if inland);
(c) OROGENISIS : converts a land space to a mountain space (impassable);
(d) EARTHQUAKE : along a specified border between two spaces separates them. Earthquake along a ravine closes the gap. Splits with land on one side and sea on the other, or between two sea spaces have no effect until both spaces are land.
(e) ICE ADVANCE; ICE RETREAT : the top of the board is permanently frozen. Ice Advance can only be ordered in a space bordering on a frozen space. Ice Retreat can be ordered on any iced up space not completely surrounded by ice.

3. A space or a boundary stabilized cancels out any geophysical attack on that space / boundary. However, a player may use his geophysical move to support another player's geophysical move. Players may also stabilize a space or boundary more than once.
Eg.
TURKEY : Erode Mos; AUSTRIA : Support TURKISH Erode Mos;
RUSSIA : 2 Stabilize Mos. The result is a stand off, no change.

4. Geophysical changes are adjudicated before movement. Any units remaining in illegal positions are destroyed.

5. Mountain spaces are impassable. At the beginning of the game Switzerland is the only mountain space.

6. If an unstabilized space is subjected to two different geophysical attacks, the result is the combined effect. Eg. Erosion and Orogenisis equals no change.

7. Supply centres are downgraded to normal spaces if they are under water or they become mountains. However, on any Spring move a player may elect to create a new s.c. in any space instead of a geophysical attack, whether he/she controls that space or not.

8. An army can cross a frozen space provided it keeps moving. If it remains in the same ice space for two consecutive seasons it is destroyed. Fleets cannot move through ice fields. If ice engulfs a fleet it is unable to move until the ice retreats and continues to need a s.c.

9. Spaces retain their names, but go to capital letters when seas, Eg. F(BUR) C A(Bel)-Mar. Extra usable spaces are Switzerland (Swi), Iceland (Ice) and Caspian Sea (CAS). When changes in geography result in a space having multiple coasts they must be specified if ambiguous. A lake has all the characteristics of a sea space, fleets can be built in s.c.'s on its coast, but would be destroyed if the lake was filled in. Remember to specify coasts when ordering builds. The players may vote to play the build season separately to avoid confusion.