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Roger Weller, geology instructor

by Sean Mendoza
Physical Geology
Fall 2012


                                                Yellowstone’s Geyser Basins

            Yellowstone National Park in the Northwest corner of Wyoming is the geyser Mecca of the world.  Nowhere else in the world can you find geothermal activity like these.  Geysers erupt in excess of 200 times a year and some geysers such as “Old Faithful” erupt every 90 minutes.  Half of the world’s 700 geysers are found right here in Yellowstone.


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Old Faithful located in the Upper Geyser Basin, is probably the most famous of the geysers at Yellowstone. It is, however, not the biggest. That title goes to the Steamboat Geyser. This Geyser is in the basin next to Old Faithful, the Norris Geyser Basin. Within this basin are a multitude of geysers, mud pots and other geo-thermal activist. Steamboat Geyser is currently the largest erupting geyser, throwing water as high as 90-meters or 300 ft. for us non-metric savy people. The eruptions from Steamboat Geyser are so huge that it steal’s the water from nearby, Cistren Stream, where it takes up to a week for the stream to refill.



            The Norris Geyser Basin,  

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Photos courtesy Wikipedia

            There are many areas in Yellowstone that have Geysers and Geo-thermal active such as Mammoth and Midway, Monument and Back country basins. Half of the world’s 700 Geysers are found right here in Yellowstone. These activities are the reaction of an event that happened millions of years ago, the eruption of the Yellowstone Volcano, leaving Yellowstone as one of North America’s few active hot spots. A hot spot is basically an area that has molten rock close to the surface and/or volcanic activity. This is what feeds the Geysers with their hot steam and violent eruptions. (Here is a map of the caldera and the water sources feeding the
 geo-thermal activity in Yellowstone today).

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            Geysers are the result of the geo-thermal pressure that is built by Yellowstone’s magma chamber that is boiling the brine (salty water) some two or three thousand feet below the basalt and sediment rock, where it is super-heated. It then travels through the porous rock (Rhyolite) found in the Yellowstone plateau with the groundwater it has joined. It is here where these two fluids dissolve minerals like silica, and add to this process. The silica helps build a pressure-tight system and forms other minerals like geyserite or sinter. These minerals are what build’s the geyser cones that pock mark Yellowstone’s countryside. The cones are the conduit that funnels the eruptions.

            Geysers get their strength from the pressure build up by the weight of the rock and water. This pressure causes steam bubbles and they rise to the surface, but as they work their way to the top they get caught up with all the other bubbles causing a blockage at the water’s surface. This produces the water to lift and a geyser is born. The decrease in pressure builds up more steam, thus forcing an eruption through the geyser cone. The eruption can last as long as there is a water source available, but usually the eruption is done before the geyser can recharge.

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Mammoth Geyser courtesy of Wikipedia.


            Above is a picture of the landscape after years of eruptions and minerals. Note the steam and dead trees that are prevalent here. The minerals and heat cause this rough environment, too harsh for wildlife to flourish. Lodge pole pine trees seem to be the only tree that grows in this hostile soil. They find that the rich rhyolite and alkaline soil is what they like. Not many other plants can survive in the mineral rich soil that the geysers produce. So what’s in the soil that makes the water so blue and the ground yellow or orange?


            The geysers consist of rhyolite which is a hard rock that is able to handle the extreme temperatures and produce silica a mineral that helps form the cones formations found around the geysers. Sinter is the silica induced mineral that is seen around the geysers. The pools are formed by the build- up of geyserite and/or sinter. The Mammoth Geyser terraces are formed with travertine a calcium rich mineral, though not as hard and heat resistant as sinter it is what is found draping the edges of these colorful pools.  The silica also helps produce the minerals in the streams that feed these geysers. The streams are rich in acid and/or alkali. Some of the streams even have both of these running side by side. The minerals and bacteria’s that are in the water can produce colors like deep blues and yellows, even orange.

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Some scientist say, that Yellowstone is becoming more dangerous every year and on the verge of a very big catastrophic event. Their thinking is that the Yellowstone Caldera has had a little too many earthquakes. From Jan, 17th 2010 to Feb, 1st 2010 they recorded 1620 earthquakes the largest being 3.8 on the Richter scale. This activity is the second largest amount since 1923.


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            The map above shows the potential ash fall out that could occur if Yellowstone erupted, and the possible time table of eruptions. Note that it is substantially larger than Mt. St. Helen’s or anything that has been recorded before.

There are satellite and 3-D views that show the raise in heat and earthquake activity of the Yellowstone Caldera area, glaciers that have melted away and animals dying in the geyser areas. The normal period of time that has been noted for Yellowstone’s volcanic activity has lapsed and this is also a reason for concern.

Why isn’t anyone doing anything?  Because there is nothing we can do. Sure we can warn people and move everyone away, but that’s not going to happen, this is mother earth and she will do what she wants and has done for millions of years.

Yellowstone is a unique geological place. It’s full of wildlife and is one of the largest nature habitat reserves in the world. It is a place that is beautiful and magic, wild and dangerous. Hopefully the geysers will continue to blow and the park will stay in one piece for generations to come.

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This is an image of the uplift of the continental crust, showing tectonic activity at the Yellowstone Caldera.







                                                Work Cited Geysers, Yellowstone media, 2011-2012.

Brennan, David, Mary Diman, Yellowstone super volcano, 25 Jan, 2011.

United States. National Park Service, Yellowstone, web. 23 April 2012. Yellowstone_National_Park, Geology, Wikimedia foundation, inc. 23 April, 2012.