The Volcanic Activity at The Yellowstone National Park

Yellowstone, The Slumbering Giant

Yellowstone National Park is not exactly a volcano, nor does it visibly have a specific mountain out of which lava or ash erupts, but it is a highly volcanic area. Only a few eruptions have taken place in Yellowstone over the past millennia, yet they were powerful and destructive. No big eruptions have occurred that humans were around to remember, but that doesn’t mean that another will not occur in the near future.

Yellowstone Park currently sits in a giant caldera from a previous eruption that occurred around 640,000 years ago. The park is a hot spot, or an area of high volcanic activity. Yellowstone, along with most of the continent, is on a plate of Earth that, along with other adjacent plates, rests on the planet’s flowing mantle core. The section of flowing mantle is called the asthenosphere, and the collection of plates is called the lithosphere. In the asthenosphere, a thermal plume pushes magma up against the lithospheric plate. How the thermal plume is created is a long process that is difficult to explain, but basically the asthenosphere (mantle core) is stationary, while the plate is not (Hendrix, 8). There were more areas of volcanic eruption before Yellowstone, such as the Picabo and Twin Falls volcanic fields, and they all follow a path. From a first impression, this path would look like a trail made by the thermal plume, but since the plume is not moving, the trail actually reflects the opposite path of the moving North American Plate (Breining, 27; Hendrix, 6, 7, 130). It can be comparable to stitches on clothing made by a sewing machine: the stitches are made by the needle (thermal plume) but the needle doesn’t move; the clothing does (lithospheric plate). Yellowstone just happened to be the next section of the plate that the thermal plume could easily break through, and cause great eruptions three times (Hendrix, 130).

The area of Yellowstone is still active today. If it was not active, there would be no Old Faithful, no geysers and springs smelling of sulfur, and no hot mud pools. (Breining, 17; Hendrix, 1). The thermal plume makes up the current volcano under Yellowstone: one so immense that it’s known as a supervolcano. A common misconception of a volcano is that of a tall, ominous mountain that spews out both ash clouds and lava, but in reality, a volcano can either spew lots of lava or lots of ash. The type of volcano depends on the viscosity, or thickness, of lava and magma. If the mountain’s magma has a high viscosity, it will harden easily on the outside, building up the mountain to a great height, and harden on the inside, where it will plug up the volcanic tubes and build up pressure until pyroclastic clouds explode, making it a composite volcano. If the magma has a low viscosity, it will not harden easily, and will flow and spread, making a shield volcano. The lava won’t build the mountain to a great height, and it will not plug up pressure channels either, but it will cover a great distance on the ground (Cain, 1). Yellowstone is neither one of these anymore. It was originally a composite volcano that had already erupted and had most of the mountain stripped away. The viscosity of lava depends on the amount of silica it has; if there is lots of silica, it is felsic, and if not, the lava is mafic. Throughout Yellowstone, rhyolite, which is a felsic rock, is abundant. There are also traces of basalt, which is a mafic rock, but the amount pales in comparison to the amount of felsic rock (Hendrix, 157). Basically, Yellowstone is sitting in the remnants of a giant composite volcano that erupted previously, with great amounts of rock with high silica content. The park is sitting within a caldera (Allen, 148).

The amount of eruptions in the area can only add up to three. The largest eruptions were the oldest and the most recent. The second eruption had only slightly changed the landscape compared to the effects of the other two. The first eruption took place 2.1 million years ago, the second 1.3 million years, and the last one 640,000 years. The recurrence interval for these eruptions would be a mean of 700,000 years. The biggest precursor for these eruptions, and for future eruptions, would be earthquakes, because of the movement of magma and the pressure it causes (Klemetti, 1). The first eruption itself was mostly a seemingly endless series of explosions of ash and gaseous clouds. These massive bursts of pyroclastic debris went on for days, and covered a great percentage of the continent. The climate was changed dramatically for near decades because the volcanic gases were able to encircle the planet and block the sun’s heat, making the world cold (Breining, 16-17). The most recent eruption only finished forming the caldera the national park sits in today (Hendrix, 143).

The effects of the future eruption, however far away it may be, will be hazardous and affect humanity on a gigantic scale, because humanity will be around to be affected. America has now become one of the most market-supported and economically-important countries around the globe, and as a result the next eruption could be close to being the end of the world. Humanity would only be able to predict it a year before it happens (Martin, 1). Its power would be hundred-fold that of common eruptions, and would have the same effects as a meteor impact. The land and animal population would be gone and, unless a great amount of people left on an early exodus, thousands of humans would die too (Breining, 228-235). If a certain percentage of people died from the eruption itself, than a greater percentage would die post-eruption. The gigantic ash clouds would be a major difficulty for transportation services, on the ground or aerial, and communication technology would be down, so people would be isolated, assuming they survived the initial eruption. Famine would be a consequence because the abundance of crops and farm grown foods in the center of the United States would be destroyed. Other countries will be affected by the influx of people trying to escape the eruption’s destructive influence, or the lack of America’s ability to market anything that is not destroyed. The volcanic ash and gas clouds would block the light and heat of the sun, once again changing the climate, and people would have trouble adjusting to it, even down to breathing. The only difference between past eruptions and the future one is that humans will be around to witness and be affected by it (Breining, 16-17, 228-235).

Yellowstone National Park today is still one of nature’s beautiful, yet terrifying phenomenons because it is a fossil of the colossal power it once was. The rhyolite-littered caldera still mesmerizes people with its small eruptions of geysers and wildlife. As long as there’s always the thermal plume underneath, however, the Yellowstone hot spot will have potential to take out a huge percentage of humanity in the future. The volcano will have great destructive effects in the aftermath of the eruption more than during the eruption itself. Until then, human beings will have to figure out how to deal with the now slumbering giant.