Like a Walk into our Planets Prehistoric Past

My wife and I went to Yellowstone last month to see its wilderness; but we also made time in our schedule to visit its world-renown geyser, Old Faithful.

Before planning the trip, I assumed that Old Faithful was the one and only geyser in Yellowstone. While planning, I found out that Yellowstone has many more (there is more geothermal activity - over 10,000 features - in Yellowstone than the rest of the world combined). However, I still wasn't quite prepared for the abundance of geysers and other geothermal activity that we would encounter. I was really blown away.

While waiting for Old Faithful, we noted that a ranger walk was scheduled for about 20 minutes after the next eruption, so we decided to attend it. Walking to the starting point, we were thrilled with the geothermal activity that we passed. The basin surrounding Old Faithful has dozens, maybe hundreds of geysers, fumaroles, and hot springs. Being in the middle of the sound and sight of all this activity took my breath away.

During our Ranger Walk we were introduced to some fascinating geologic wonders. Hot springs a beautiful blue or green (from heat-loving micro-organisms living in them), fumaroles sending a steady stream of steam into the air, and of course, the geysers.

Many of the geysers had intriguing characteristics. Take Grotto Geyser. It's very odd shape (see middle image) has caused much speculation as to its origin. It is thought that Grotto Geyser formed between some old tree stumps; as time went on the tree stumps were covered with geyserite (geyser water contains dissolved rock. The topography that gets covered with geyser water eventually accumulates layers of this solidified rock, known as geyserite).

It seemed that each geyser we came to had its own unique and fascinating characteristics. I soon began to wonder why Old Faithful alone was so well known. It seemed rather ordinary. I immediately realized the answer to my own question: Because it can be predicted. People want to see a geyser erupt, and they can count on Old Faithful.

But what cause the geysers to erupt as they do? The following is taken word for word from Yellowstone National Parks official website (link below):

"Expanding steam bubbles generated from the rising hot water build up behind these constrictions [in the geysers "plumbing" on the way to the surface], ultimately squeezing through the narrow passageways and forcing the water above to overflow from the geyser. The release of water at the surface prompts a sudden decline in pressure of the hotter waters at great depth, triggering a violent chain reaction of tremendous steam explosions in which the volume of rising, now boiling, water expands 1,500 times or more. This expanding body of boiling superheated water bursts into the sky as one of Yellowstone’s many famous geysers."

There is so much more to be said. What about the fumaroles, mudpots and hot springs? Why is all of this activity in the Yellowstone area? When I started this post I intended to delve into these areas, in fact, the title was going to be What Causes Yellowstones Geothermal Activity? But this post is already longer than I like. Follow this link to the National Park website that has links to all of these answers. It is fascinating reading, and is only the beginning.

Above are pictures, from top to bottom, of Old Faithful, Grotto Geyser, and fumaroles alongside the river.