Genned a world with quite a lot good of good spots for volcanoe lovers.
Throughout the map, I've found a few volcanoes with limestone plus sand plus streams. Also, there are at least two embarks with crossing rivers plus volcanoe plus sand plus flux. Most are in temperate or cold biomes, also mirthful or joyous.
Parameters (31.16):
[WORLD_GEN]
[TITLE:Greater Sparrownia]
[CUSTOM_NAME:Greater Sparrownia]
[SEED:2782789474]
[HISTORY_SEED:3573619702]
[NAME_SEED:410307676]
[CREATURE_SEED:3335891272]
[DIM:257:257]
[EMBARK_POINTS:10000]
[END_YEAR:1050]
[BEAST_END_YEAR:300:80]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:0]
[ELEVATION:50:400:2400:2400]
[RAINFALL:10:100:800:800]
[TEMPERATURE:25:45:800:800]
[DRAINAGE:25:100:800:800]
[VOLCANISM:20:100:1600:1600]
[SAVAGERY:0:100:800:800]
[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]
[MEGABEAST_CAP:75]
[SEMIMEGABEAST_CAP:150]
[TITAN_NUMBER:30]
[TITAN_ATTACK_TRIGGER:80:0:100000]
[DEMON_NUMBER:52]
[GOOD_SQ_COUNTS:800:8000:32000]
[EVIL_SQ_COUNTS:0:0:0]
[PEAK_NUMBER_MIN:50]
[PARTIAL_OCEAN_EDGE_MIN:0]
[COMPLETE_OCEAN_EDGE_MIN:4]
[VOLCANO_MIN:200]
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:12000:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:300]
[RIVER_MINS:800:800]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:20]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:5]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:100]
[CAVERN_LAYER_WATER_MIN:5]
[CAVERN_LAYER_WATER_MAX:100]
[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:80]
[NON_MOUNTAIN_CAVE_MIN:160]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:60]
[TOTAL_CIV_POPULATION:100000]
[SITE_CAP:1400]
[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:0:0:1000]
If requested, I'll post a screenshot showing some embarks I've found.