The geology of Yellowstone’s geyser basin is fascinating. This whole area lies in the caldera (or depression) from an ancient volcano that had erupted at least 3 times that be determined. The most recent eruption was 640,000 years ago, and ash from that eruption covered an area of the US as far south as Louisiana. The molten lava core of this volcano is responsible for the geysers, hot springs, fumaroles and boiling mud pots which occur throughout the geyser basins. The hot core, being so close to the surface, heats the underground water. Cracks in the earth leading to the surface allow the water or steam to escape, forming hot springs if there is enough water, or fumaroles if there is only steam. When there is an obstruction or narrowing of the passage, the water flow is restricted. When sufficient pressure builds up, the water is pushed up past the obstruction and erupts as a geyser. All of this creates a VERY strange looking landscape of steaming earth, mineral deposit formations, and pools of hot water and sometimes mud.
What struck me most about Yellowstone were the colors. There are bacteria and other organisms called thermophiles (organisms that love heat) or extreme-ophiles (organisms that live in places deemed too extreme to support life – you gotta love that!). These bacteria form mats and create the colors that you see in the water and along the rocks and edges and bottoms of the pools. They are responsible for the blue, orange and yellows that you see. The white is calcium or other mineral deposits that build up due to the overflowing, heated water.
In this hot spring, you can see the funnel shaped opening through which water is coming from deep in the earth. The bacterial mat lining this spring is mustard yellow.
The water looked the most amazing shade of blue.
Note the mineral deposits along the edges of this hot spring.
This is the edge of a bacterial mat.
This is a geyser that is currently dry, leaving a funnel shaped opening and a build up of minerals.
This is a boiling mud pot. The sulfuric acid in this spring dissolved the surrounding rock into mud. Then, the gases that are released bubble to the surface.
The geyser basin was fascinating, but there is more to Yellowstone than just the geysers………………