One of the many geyser pools near Lake Yellowstone at the area known as West Thumb. This one is known as Blue Funnel Spring. By the color of alage growing in or the lack of algae in the geyser one is able to tell roughly how hot the water is. This water is quite hot, hence the blueness or lack of algae. if it was brown,black ,yellow or rust the temperture would still be hot but cooler than this pool. ( I have seen that on some monitors if the color is not set right, the teal blue of the pool does not show up as well as on other monitors)