硫黄
basin
blue
boardwalk
boil
bubbling
crust
earth
erupt
eruption
explode
firehole lake
firehole lake drive
firehole spring
geology
geothermal
geyser
great fountain geyser
heat
hill
hot
hot spring
landscape
national park
natural
nature
pond
pool
sign
steam
sulfur
sunlight
temperature
thermal
tourism
travel
united states
volcanic
volcano
warm
water
wyoming
yellowstone
yellowstone national park