Grand Prismatic Spring
First on the list of geyser marvels, after Old Faithful, is the Grand Prismatic Spring, a wonder of colour that is part of the Midway basin. Several hotsprings are linked by a broad walking path. It was rather windy and some people had lost their hats and they lay now out of reach on the hot and treacherous ashen ground.
Most of the springs here have light blue water, bubbling and producing a light sulfuric mist. The highlight is the Prismatic Spring of turquoise colour, with mist rising from its surface and surrounded by an multicoloured area, brown, yellow, red, white, green, grey...
The colour spots are in fact innumerable microorganisms that only thrive in these extreme conditions of heat, acidity or alkalinity. These bacteria are in fact pointillist painters... The colours vary from dark green to orange and red, according to the balance between chlorophyll (green) and carotenoids (red), and depend on temperature and the pH of the water they live in.
