Boulders serve the purpose of slowing or preventing access to an area. They are classified into two categories: Volcano Boulders and Snow Cave Boulders.
Volcano Boulders spawn within the Boulder Cave and roll downward once the Volcano's obstacle course has been triggered. They are grey, spherical rocks that are twice the size of a player. If a boulder hits a player, it will not damage him/her, but are capable to push vehicles and reflect against loose items. The boulders will stop spawning once all players that entered the Volcano exit the obstacle.
Snow Cave Boulders
Snow Cave Boulders spawn within the Snow Cave, both when servers initialize and whenever the game detects that a majority of them have been missing for a short period of time. These boulders tend to be at least 6 units wide on all sides; when they spawn, they slide out of the cave and into the passage separating the Taiga from the Main Biome, preventing vehicles and large objects (but usually not players and small items) from passing through. Blockages caused by Snow Cave Boulders can be removed by detonation of Dynamite --- when affected by the resulting explosion, the boulders will move out of the way, then fade away after a short time.Snow Cave Boulders, like Volcano Boulders, can be pushed using loose items, potentially allowing players to move them out of the way without the use of Dynamite.
Volcano Boulders: The boulders may occasionally fail to be destroyed upon hitting the lava at the bottom of the Volcano, causing them to pile up at the volcano's entrance and hinder entry for a time.
Snow Cave Boulders: The boulders may occasionally fail to respawn correctly, preventing them from re-blocking the passage separating the Taiga from the Main Biome after it has been unblocked once with Dynamite. Also, boulders flung away from the passage by Dynamite may fail to disappear if they collide with a tree shortly after detonation.