Volcanoes

This mod adds land and underwater volcanoes to the game, with their own eruption cycles

All volcanoes start as dormant and have a chance to erupt throughout the game. Once a volcano has erupted, it will not erupt again. Volcanoes provide no base yield, but the Public School will give +10 Science to the tile

The land volcano is very destructive, with the ability to completely destroy cities, caution must be taken when settling near these. However, if the volcano has no adjacent mountain tiles, after it’s finished eruption the city will gain a total of +12 food from volcanic soil tiles, plus an obsidian resource

Phase 1 Eruption
Lasts 1 Turn
Doesn’t do any damage

Phase 2 Eruption
Lasts 5 Turns
Pillages all improvements within 2 tiles
Causes all cities within 2 tiles to go into resistance for 5 turns (production ceases)

Every turn:
Instantly kills all adjacent units and deals 50 damage to units 2 tiles away
Any adjacent city will lose 1 population, if the city is at 1 population, then the city will be destroyed (excluding original capitals)
All food stored is destroyed in cities up to 2 tiles away
Damages all adjacent cities by 30% and all cities 2 tiles away by 15%, walls and other defensive buildings do not protect against this damage. By the end of Phase 2, all adjacent cities will be at 0 HP

Phase 3 Eruption
Last 4 turns
All adjacent improvements are removed, forest/jungle/marsh is removed
1 Obsidian resource is placed randomly on an adjacent tile

Every turn:
All adjacent cities take 10% damage, and all adjacent units take 50 damage

Phase 4 Extinct
All adjacent non-mountain tiles will gain the Volcanic Soil feature

Underwater volcanoes are only dangerous to naval units and have a simpler eruption cycle. Underwater volcanoes are fully passable but take 1 more movement point (like forest)

Active
Lasts 10 turns
Removes all adjacent improvements

Every turn:
Instantly kills all units on top of the tile
Deals 50 damage to all adjacent units

Extinct
The volcano tile turns into a Volcanic Island
1 Coral resource is placed randomly on an adjacent tile (prioritising plots next to land)

Terrain feature that provides a base +2 food to the tile, doesn’t have any other effects

Impassible feature, same yield as atoll (+1 food, +1 production). I have also changed Japan’s ability to make Volcanic Islands have +2 Culture, like Atolls

Unique luxury resource, same yields as Gems but improved with a Quarry

Unique luxury resource, base yield +2 food, but fishing boats will provide +1 gold instead of +1 production

Volcanoes are placed randomly, spread out evenly across the map. I have stopped underwater volcanoes from generating near ice

Only one volcano (of the same type) can be active at a time, thus on larger maps or quick game speed, the game may finish before some of the volcanoes have even erupted. Conversely, on small maps or slow game speeds, the volcanoes may all erupt too early

To solve this, I have made eruption chance scale depending on map size and game speed, such that all volcanoes should have erupted by the time the atomic era starts. Eruptions are still entirely randomised

Works with "More luxuries" – the coral resource will be replaced with this version. Volcanoes will also allow you to build a Bathhouse and Geothermal Plant if using my other mod: Hot Springs