The eruption of Alaska’s Pavlof Volcano has sent ash spewing 37,000 feet into the atmosphere, and Earth Science Professor Jeffrey Karson says, it’s not over yet. Karson is a geologist, and works in collaboration with Assistant Art Professor Robert Wysocki on the Lava Project. The pair use lava for research involving science and art, and as such have formed a keen understanding of one of the byproducts of a volcanic eruption. Karson offered his thoughts on this natural disaster.
Considering the news attention and public interest, how unique is a volcanic eruption?
Jeffrey Karson
This is not unique at all. Volcanic island chains like the Aleutians, lie above places where the seafloor is being shoved back down into the Earth’s mantle (subduction). This is happening all around the Pacific (Ring of Fire). Volcanic eruption ebb and flow on a time scale that is typically longer than human lifetimes, so when a volcano like Pavlof erupts, it seems somewhat unusual. Pavlof has a long history of eruptions over the past century or so. We can expect many more eruptions in the future. Other similar active volcanoes include Mt. Fuji in Japan, White Island in New Zealand, Mt. Pinatubo in the Phillippines, Tungurahua in Ecuador, Popocatepl in Mexico, and Mt. St. Helens in Washington State. All are dangerous, potentially explosive volcanoes. It is not a question of IF they will erupt again, it is more about WHEN and how violently.
Is ash the only problem with an eruption like this, and in fact if we did have lava flowing, would ash still be a bigger issue/potential problem?
Lava cannot flow very far. It cools, becomes viscous and slows down as it crosses the surface of the Earth. The very longest lava flows are about 100 km long. Lavas from places like Pavlof (called andesites) have a higher viscosity and tend not to flow very far, thereby building up steep mountains typical of subduction zones. Despite being highly visible, lava is far down the list of potential hazards for volcanoes like Pavlof. Others include the emission of poisonous gases, suffocating density of ash, rain of large blocks and “bombs” blown out of a volcano—fast-moving (200 mph) mixtures of super-heated gases and ash (think Mt. Vesuvius and Pompeii), and mud flows from mixtures of ash and water. Ash in the atmosphere is a nuisance at small eruptions, a regional airline hazard in medium-sized eruptions (ash and airline engines do not mix!) and a global-scale event that can affect the Earth’s atmospheric temperature and chemistry for the very largest eruptions.
Why would a volcano suddenly begin to spew ash like this?
Volcanic eruptions are not predictable in part because of the vastly complex processes happening in the Earth’s crust beneath them. Magma chambers beneath volcanoes evolve chemically as they cool, separating out crystals, liquids and gases. The release of gases from the top of a magma chamber can result in the violent ejection of liquid rock material (magma) as well as fragments of rock above the magma chamber. Changes in the gas pressure can be caused by may different processes. Faulting above expanding and contracting magma chambers can permit the sudden, violent release of gases and ash.
Is this something that catches your attention, considering the lava project?
The SU Lava Project intentionally avoids potentially explosive activity. Our experiments focus on basalt, the most common, black lava found on Earth—the entire bottom of the oceans, Iceland, Hawaii, etc. It tends to have a relatively low viscosity and have a very low concentration of volatiles, so it typically flows fairly smoothly, as seen in the effusive eruptions in Iceland or Hawaii. We hope to do some experiments on lavas that are more typical of subduction zone volcanoes (like Pavlof) called andesite (for their abundance in the Andes). Andesites should melt at a lower temperature (<1000°C) and have a much higher viscosity than the basalt that with which we usually work.
