There is a new study on the topic: “In August 2014, USGS scientists Larry Mastin and Jacob Lowenstern, and National Science Foundation researcher Alexa Van Eaton published research on where volcanic ash would fall if a Yellowstone supereruption were to occur today….” The researchers were particularly interested in the amount and location of the ash fallout.
If you live at the foot of Mt. Saint Helen’s volcano, you might worry about the lava flow from an eruption. Lava flows are usually rather slow. But it’s probably inadvisable to shovel it or poke it with a stick. Another issue with ordinary eruptions is the falling large chunks of rock or lava. But only the immediate area around the volcano is at risk.
The ash from a volcano is what makes any volcanic eruption harmful to faraway places. The ash cloud interferes with airline flights, causing them to be cancelled or rerouted. For a large enough eruption, the ash can reach the upper atmosphere, remain there for months (or years) and reduce the amount of sunlight reaching the earth. The cooling effect can be remarkable.
The year without a summer (1816) is believed to have been caused by:
“the eruption of the Tambora volcano on the island of Soembawa in Indonesia on April 15th 1815. The eruption lasted one week and rumbled for 3 months. The mountain elevation dropped from 14,000 feet to 9000 feet, killed close to 10,000 people on the island and another 80,000 people would eventually die from starvation and diseases related to the eruption. Tambora was one of the largest recorded eruptions with estimates of 1.7 million tons of dust put into the air equaling 6 million atomic bombs. The theory is that the dust reached the Northern Hemisphere during 1816 reducing solar output.” [NOAA article]
The Tambora volcano is similar to the Yellowstone volcano in that each is a caldera — a volcano hidden deep underground, rather than a volcanic mountain. However, the Yellowstone caldera is much larger, and therefore its eruption would have much more severe effects on the weather.
The cooling of the year without a summer caused an estimated 200,000 deaths in Europe, mostly from starvation. It was the worst famine of the 19th century. Crop failures occurred worldwide, especially in the northern latitudes, where the cooling effect is greater. If the same cooling occurred today, with our much higher world population, deaths might be in the millions. You can propose that perhaps food would be transported from lower latitudes, where the cooling effect is minimal, to people in higher latitudes. But the world only makes so much food each year. The sudden loss of spring, summer, and fall crops for even a single year, even if only in northern latitudes, would result in an insufficient amount of food for 7 billion persons.
The Yellowstone caldera is much larger than Tambora, and so the cooling effects from the ash would be much greater. Crop failures would be more extensive, even in latitudes closer to the equator. And the cooling would last for several years, perhaps longer. The study authors note that “the 1991 Pinatubo eruption produced global cooling by an average of 1° C for a few years”. If Yellowstone erupted, global cooling would be severe, and a worldwide severe famine would be inevitable.
The study considered different eruption scenarios: a 3-day eruption, a one week eruption, and a month-long eruption. $#@*!!!! I had no idea a month-long eruption was even a possibility! In any case, the falling ash would blanket most of the continental U.S. In some scenarios, parts of Texas and Florida would be spared, but that’s about it.
The depth of the ash would vary from over 3 feet (sorry, Billings Montana) — to 1 to 3 feet (Salt Lake City) to 4 to 12 inches (Denver) to an inch or so, to a fraction of an inch. Most of the nation would have inches or less of ash. But that should not be reassuring.
“North America’s highest population density lies along its coastlines. Deposit thicknesses on the coasts from nearly all simulations is millimeters to a few centimeters. Thicknesses of this magnitude seem small but their effects are far from negligible. A few millimeters of ash can reduce traction on roads and runways [Guffanti et al., 2009], short out electrical transformers [Wilson et al., 2012] and cause respiratory problems [Horwell and Baxter, 2006]. Ash fall thicknesses of centimeters throughout the American Midwest would disrupt livestock and crop production, especially during critical times in the growing season. Thick deposits could threaten building integrity and obstruct sewer and water lines [Wilson et al., 2012]. Electronic communications and air transportation would likely be shut down throughout North America. There would also be major climate effects.”
So electronic communications would be shut down: no internet, no cell phones, and in many places no electrical power. There would be no way to get these services back up in the short term, as might happen after a snowstorm power outage. If a large number of electrical transformers short out, there is not enough equipment in warehouses to replace the parts. And the ash would continue to blow around, shorting out new transformers. The USGS says that volcanic ash is “mildly corrosive and potentially conductive.” The ash is also coated with “sulphuric and hydrochloric acid.”
The result would be no electronic communication and no electrical power for most of the nation. And the situation would last for many years. The lack of power would mean that factories which ordinarily could make electrical equipment would be shut down. It’s a catch-22. You can’t rebuild the electrical power and communications infrastructure without electrical power. And since the effects of the eruption would be global, other nations might not be willing to make and send replacement parts.
Unlike snow, the ash does not melt, and it cannot really blow away. So the ash would be a continuing problem. The ash in one location could be blown away by the wind, but since most of the nation would be blanketed in ash, more ash would be carried in by the same wind. Eventually, the areas with only an inch or less of ash would see much larger amounts carried in by the wind. Instead of snow drifts, there would be “ash drifts”. The continued presence of ash would prevent the rebuilding of the power grid for a long time.
The ash would also make breathing difficult. Filtering the air would be futile, since filters would quickly become clogged and replacements would be unavailable. Many people would die from respiratory problems. In winter, many persons would die from the freezing temperatures, since the power would be out and the distribution of fossil fuels would cease. The cooling effect of the ash in the upper atmosphere would result in New England-style winters in the deep South, and constant winter in the northern States. Agriculture would be shut down. Livestock would quickly die from inhalation of the ash, even in places where the ash fallout is very limited. The U.S. would be unable to produce a substantial amount of food. Famine would grip the nation.
Ash would fall into rivers and lakes, killing the fish. Ash in the ocean would have a similar effect, killing much of the fish near the coastlines. Fishing would not be an option for obtaining food. Wildlife would be effected just as livestock, so hunting would also not provide food. The acid coating of the ash would make the fresh waters of most of the nation undrinkable, and the effects on plant life would be severe.
A large portion of the greenery in the nation — trees, bushes, grasses, other plants — would be killed by the acid, the reduced sunlight, the sudden freezing temperatures, and the abrasion of the ash. Volcanic ash is glass-like, with many tiny sharp edges. A strong wind blowing a large quantity of ash would be highly abrasive, and in a matter of hours could strip trees and other plants of their leaves. “Volcanic ash is hard, does not dissolve in water, is extremely abrasive and mildly corrosive, and conducts electricity when wet.” [USGS]
The ash in oceans would kill plankton, resulting in a reduction in the production of oxygen. About 70% of the planet’s oxygen is produced by marine plant life, especially plankton. Much of the land plant life in North America would be killed by the acid from the ash, the abrasion of ash and wind, the freezing temperatures, and the reduced sunlight. Oxygen levels might actually fall, worldwide, though how much is very uncertain.
The whole world would also experience a severe cooling effect, resulting in crop failures worldwide. A worldwide famine would quickly follow the famine in the U.S. Help would not be available from other nations. The vast majority of the U.S. population would simply die. The worldwide famine would next kill a large portion of the rest of the world, with a continuing die-off in successive years, since the cooling effect would severely reduce agricultural output for many years.
But the cooling effect would not be the only cause of reduced crop production. Modern agriculture depends on machinery to plant and harvest crops. Modern agriculture depends on modern commerce to provide seed, fertilizer, and the distribution of the harvested food. The ash would shut down machinery, and fossil fuels would no longer be available to power those machines. A farmer would have no way to harvest a crop in the field, no way to plant the next crop, no way to transport any food that his land might eke out. But then again, the acid and abrasion from the ash would probably kill any crop he could plant. A farmer with a thousand acres of fertile land would not be able to feed his own family, let alone feed a nearby town or the rest of the nation.
Best chance of survival? Immediate rapid bug-out to another continent. South America would be better than Europe, since the ash in the upper atmosphere would take a year or more to affect the weather in the southern hemisphere. The weather systems of the northern and southern hemispheres are not closely connected.
The only ray of hope in this dire analysis: an eruption is very unlikely. Remember in my previous post on this topic, there was a reference to a 1 in 1000 chance of a Yellowstone eruption this century? The study authors propose “a confidence of at least 99.9% that 21st-century society will not experience a Yellowstone supereruption.” So that’s where the 1 in 1000 figure comes from. However, a 99.9% confidence level is not the same as one chance in a thousand; the figure only expresses the certitude of the data, not the absolute risk. There have only been 3 major Yellowstone eruptions in the last 2.1 million years. So a major eruption is unlikely.