The beautiful Fly Geyser
The Fly Geyser is one of only about 80 manmade geysers in the world. That's not what it was supposed to be, though. It was supposed to be a simple artesian well for watering crops and animals. But things don't always go according to plan.
The old geyser
About 100 years ago, a farmer named Fly settled in Nevada's Black Rock Desert. His land was vast and not near any rivers or creeks, so he decided to drill a well to get water for farming and cattle. But unknown to him at the time, there is dormant volcanic activity deep down underneath the Black Rock Desert. When he struck water, it was around 200 degrees fahrenheit (93 degrees celsius) and heavily laden with minerals. It could never be good for growing crops or providing water for farm animals. So he abandoned the well with the pipes just left open and the almost boiling water spewing out.
Volcanic activity being what it is, the water kept boiling out and the minerals kept building a mound. So a geyser cone - a mound of deposited rock with a water bearing tube in the middle of it (shown directly above) - was formed.
The cone for that geyser stands about 12 feet (3.7 meters) high. In the picture directly above, you can see that the water around the cone was starting to build its first pond wall - a natural artifact of geysers (explanation below). The cone and its pond wall would have kept growing if it hadn't been for another event that came about 50 years later....
In 1964 a geothermic energy company drilled a fairly large test well a few hundred feet from the first well hole. They wanted to use the heat to generate large amounts of electricity for the state. They thought that the larger hole would let the water get to the surface while it was still steam. But it didn't. The water they struck was that same 200 degrees, and not hot enough for their purposes. They supposedly capped the well before leaving, but if so, the seal did not hold. A new geyser formed. Having a larger vent, it robbed the first geyser of its water pressure and the older cone now sits dry and will not continue to grow.
The newer geyser has multiple vents.
Each geyser has had about 50 years to grow (as of 2014). Since the hole that makes the new geyser is larger than the hole for the old geyser was, it carries more mineral-laden water. So it has grown much faster than the original one did. In its faster growth, it has developed several "vents". The old geyser had only one vent, so it grew straight upward, but the new one, with its multiple vents, has grown outward as well.
The fly geyser has another distinction: almost all natual geysers have a surge of water, then a long period of quiet before another surge. Since the Fly Geyser is the only place in hundreds of miles for the water to escape, this geyser rarely ever stops spewing hot water.
And that causes those surrounding pools...
The surrounding pools
Minerals that are disolved in very hot water will "precipitate" (turn solid and fall out) when the water cools to a certain temperature. The fact that the spewing is almost continuous means that the water nearest the cone is continually being pushed out and away, where it cools and deposits its minerals farther away from the cone. Over time, the minerals make walls at that distance. As the walls grow higher, the pools behind them grow deeper and hold the heat better, making the water hotter as it spills over the walls. The now hotter water is pushed farther away, dropping its minerals and forming more walls at a greater distance. That process has repeated over the years, and a stair-stepped system of walls and ponds has grown up around Fly Geyser, forming a beautiful mosaic of clear-water pools, each at a different temperature.
The cones, themselves, form at the center because some of the water that spews out is in the form of a fine spray, rather than a thick stream. It cools while still above the cone and its minerals fall straight back down to deposit directly onto the cone. Also, some of the water coming from the vent simply runs down the sides, depositing even more to build the cone both outwards and upwards.
Why all the colors?
So, you're probably wondering what makes all the colors. The colors are not a natural part of the cone nor the minerals that go to make it up. There is a class of algae called, "thermophilic (heat loving) algae". The near-boiling water is exactly what this type of algae needs for growth. There are several different kinds of thermophilic algae, each with its own color, and each favoring a different temperature of water. So the various colors that you see basically act as a natural "mood ring" and tell you the temperature of the water at each point on the cone or wall.
Note: This is on private property, but the owners do conduct tours seasonally for $25-$50/day (head to Bruno's Restaurant in Gerlach and they've been known to put tourists in contact with the owners). Or contact these guys: http://blackrockdesert.org/friends/2008-1004-fly-geyser-tour
If you got impressions for which this feedback is insufficient, more information,
pictures and videos can be found at the following web sites:
Google photos (many more than shown above)
Fly Geyser tour arrangers
Wikipedia entry for Fly Geyser
Atlas Oscura web site