Back to the Yellowstone series, after a long break.
This shot is of the margins of the well-known Grand Prismatic Spring, probably the park's most well-known feature after the Old Faithful geyser. The familiar view is an aerial shot but we didn't have a helicopter handy.
The main part of the spring is shrouded in steam, since the water is at about 70°C and, although this was taken in late June, that's only really spring at an altitude of a mile and a half! The colours are caused by mats of bacteria that thrive in the hot water. Zones of different temperatures support different mixes of bacteria, causing the banded effect — greener bacteria like hotter water so orange turns to yellow and green closer to the centre. This area is the run-off down towards the Firehole River.
#2 is a closer view of the bacterial mat, taken nearby. I was originally going to upload it on its own but decided it wasn't interesting enough.