Yellowstone - The Deep Blue Hole (Morning Glory Pool)
Located in the Upper Geyser Basin of Yellowstone National Park (Wyoming, US), the Morning Glory Pool is one of the most beautiful hot springs in the park. The shades of deep blue emerge from the centre, then turn light blue and green, and then finally a yellow border encloses the spring. Such colors are due to the presence of thermophilic cyanobacteria.
Photo credit: ©Kevin McNeal