Janice Shiu - 2020 - 12.307
History of the Yellowstone Caldera
The Yellowstone Caldera has erupted multiple times in its existence, with each eruption covering great portions of North America with ash (Figure 1) (USGS, 2014). Given that it has been nearly 640,000 years since the last major Yellowstone eruption, which occurs at a 600,000 - 800,000 year cycle, There is a possibility that Yellowstone will erupt soon in geologic time (USGS, 2014).
Figure 1: Known ashbed cover from major Yelowstone eruptions shaded in brown with white dashed borders (USGS, 2014).
Significant Impacts of a Yellowstone Supereruption
For humans, a Yellowstone supereruption can be catastrophic, from displacement of people throughout the North America to global changes in climate. From Yellowstone's geologic history and composition, one significant impact of a Yellowstone Supereruption may be ash deposition across the United States (Figure 2) (USGS, 2014). Initially, the fine-grained particles may cause disruptions in aviation. However, as the particles disperse and fall, there may be far more effects. Ash may damage human infrastructures such as buildings, transportation, water supply, agriculture, and energy supply. Additionally, even a few millimeters of ash may cause issues, as there may be health impacts to ash when ingested or inhaled (USGS, 2016) . Consequently, should a Yellowstone supereruption occur, populations in the United States, Mexico, and Canada may have to evacuate and relocate.
Figure 2: Modeled ash deposition from a month-long Yellowstone eruption using historical wind data from January 2001 (USGS, 2014).
Another potential impact of a Yellowstone eruption is global cooling and the spread of harmful gasses and sulfate aerosols. In volcanic eruptions, many gases are released from rising magma. Gasses such as sulfur dioxide, hydrogen sulfide, and hydrogen halides may cause acid rain or health problems in humans (USGS, 2016). If sulfur dioxide reaches the stratosphere, the substance becomes a sulfate aerosol, which, in significant amounts, can significantly cool the climate and reduce Earth's radiation budget, or sunlight received (USGS, 2018). Using the eruptions of Krakatau and Tambora in 1883 and 1815, respectively, as causes of significant disturbances in Earth's recent climatological past, global temperatures may cool suddenly by several degrees, causing significant disruptions in agriculture and climate across the world (USGS, 2018).
Modeling the Spread of Materials
This experiment models the spread of material over 10 days if the Yellowstone erupted on February 21, 2017. The purpose is to visualize how material will travel at different altitudes, which may imply the distribution of an eruption's impacts across the globe.
This experiment modifies Professor Glenn Flierl's program for tracing and interpolating atmospheric particle positions using six-hour tracks of wind data from the National Centers for Environmental Prediction's Global Forecast System. The model interpolates the wind speed and direction at the location of each particle. Using these values, the model predicts each particle's location in three hours. Then, the model repeats its processes using the new particle locations, producing a predicted trajectory of a lightweight particle at a certain level of the atmosphere.
To create visualizations of the predicted trajectories, 11 particles were released in a diagonal transect spanning 43-45oN and 111-113oW of Yellowstone National Park at varying atmospheric pressure levels (Figure 3). The trajectories are plotted on an Eckert IV projection. The transect represents material ejected all across the park, as it is difficult to predict the exact location of the next eruption as well as the initial distribution of material in the initial plume of ejecta.
Figure 3: Particles released in a transect from 43-45oN and 111-113oW with approximately 0.2o resolution in both latitude and longitude.
Results and Implications of the Model
Each set of particles is released and tracked between 1000-100 hPa with 100 hPa resolution for 10 days at 3 hour time steps (Figures 4a-j). In the lower levels of the atmosphere from 1000-800 hPa (Figures 4a-c), the particles have a relatively localized travel distance across North America, suggesting a localized impact for particles released at this level. This relates to the travel distances of ejecta such as ash, which is modeled to spread across North America. As particles are released at higher levels of the atmosphere, particles travel farther from North America in more distinct paths (Figures 4d-j). In particular, the 200 and 100 hPa trials demonstrate fairly uniform trajectories that follow the Northern Hemisphere's jet stream. Such particles are likely to be gases, which are lighter than ash, potentially are sulfate aerosols, and could possibly cause global changes in temperature due to their properties and spread.
a. 1000 hPa  | b. 900 hPa |
c. 800 hPa | d. 700 hPa |
e. 600 hPa | f. 500 hPa |
g. 400 hPa | h. 300 hPa |
i. 200 hPa | j. 100 hPa |
Figures 4a-i: Predicted trajectory of 11 particles released at 1000-100 hPa (100 hPa resolution) in Yellowstone eruption over 10 days after February 21, 2017 with 3 hour time steps.
Future Exploration:
There are many ways to expand this project to greatly improve its predicting power. Some necessary investigations for the future include eruption materials, plume dynamics, material residence time, and the relevant effects of a supereruption to human activity. This model is still very limited, as it assumes the use of lightweight particles with no change in altitude. Particle size, particle density, and weather phenomena (such as rain) should be factored into models that observe the deposition and travel distance of released materials. Consequently, different materials will experience different travel times and initial spread from the eruption, which, as seen in Figures 2a-i, can greatly affect how and where material will travel.
References:
Ashfall is the Most Widespread and Frequent Volcanic Hazard (2016). (2016, February 2), Retrieved from
https://volcanoes.usgs.gov/vhp/tephra.html
Modeling the Ash Distribution of a Yellowstone Supereruption (2014). (2014, August 27). Retrieved from
https://volcanoes.usgs.gov/volcanoes/yellowstone/yellowstone_sub_page_91.html
Volcanoes Can Affect the Earth's Climate (2018), (2018, January 1) Retrieved from
https://volcanoes.usgs.gov/vhp/gas_climate.html