It sounds like you might be having the same problem I am also having.
My issue is linked to a desperate need for a volcano in each embark I choose.
Behold...Volcano World:
[WORLD_GEN]
[TITLE:Flat volcano region]
[SEED:1237524024]
[HISTORY_SEED:4252085152]
[NAME_SEED:3787295952]
[CREATURE_SEED:508840976]
[DIM:129:129]
[EMBARK_POINTS:1274]
[END_YEAR:100]
[BEAST_END_YEAR:200:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:1:400:1600:1600]
[RAINFALL:0:100:200:200]
[TEMPERATURE:25:75:200:200]
[DRAINAGE:0:100:200:200]
[VOLCANISM:0:100:600:600]
[SAVAGERY:0:100:200:200]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[MINERAL_SCARCITY:100]
[MEGABEAST_CAP:5]
[SEMIMEGABEAST_CAP:30]
[TITAN_NUMBER:9]
[TITAN_ATTACK_TRIGGER:100:0:200000]
[DEMON_NUMBER:10]
[GOOD_SQ_COUNTS:25:251:503]
[EVIL_SQ_COUNTS:25:251:503]
[PEAK_NUMBER_MIN:4]
[PARTIAL_OCEAN_EDGE_MIN:1]
[COMPLETE_OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:150]
[REGION_COUNTS:SWAMP:260:1:1]
[REGION_COUNTS:DESERT:260:1:1]
[REGION_COUNTS:FOREST:1040:3:3]
[REGION_COUNTS:MOUNTAINS:2080:2:2]
[REGION_COUNTS:OCEAN:2080:1:1]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:2080:3:3]
[REGION_COUNTS:HILLS:2080:3:3]
[EROSION_CYCLE_COUNT:250]
[RIVER_MINS:100:100]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:0]
[CAVERN_LAYER_OPENNESS_MAX:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:0]
[CAVERN_LAYER_WATER_MIN:30]
[CAVERN_LAYER_WATER_MAX:70]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:15]
[LEVELS_ABOVE_LAYER_1:5]
[LEVELS_ABOVE_LAYER_2:1]
[LEVELS_ABOVE_LAYER_3:1]
[LEVELS_ABOVE_LAYER_4:1]
[LEVELS_ABOVE_LAYER_5:2]
[LEVELS_AT_BOTTOM:1]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:15]
[NON_MOUNTAIN_CAVE_MIN:25]
[ALL_CAVES_VISIBLE:0]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:40]
[TOTAL_CIV_POPULATION:15000]
[SITE_CAP:1040]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:0:0:0]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]
I got this from a post here in the forums. It has volcanos pretty much all over, so I almost always have an embark with flux somewhere. Also, DFusion's Embark Anywhere is an awesome tool to open up more options.