Understanding Ash Sedimentation to Predict Volcanic Outcomes

Mar 7, 2021 | Daily Space, Earth

Understanding Ash Sedimentation to Predict Volcanic Outcomes
IMAGE: Volcanic plume associated with the April-May 2010 eruption of Eyjafjallajökull volcano (Iceland) and Scanning Electron Microscope image of a typical ash cluster made of micrometric volcanic particles collected on an adhesive paper during fallout. CREDIT: UNIGE, Costanza Bonadonna

Some of you may remember that back in 2010, an Icelandic volcano beyond my ability to either pronounce or spell [Ed. note: Eyjafjallajökull], erupted with a mighty and ongoing plume of ash that disrupted air travel between North America and Europe and made chaos of European travel. While horrifying for commerce, that particular eruption also demonstrated how little we knew about how ash would move through the atmosphere. Since then, volcanologists have been using other eruptions to try and fix this knowledge gap before another big volcano goes off.

The way they did some of this research was super simple. In one instance, volcanologists studying Japan’s Sakurajima volcano put out adhesive strips to capture falling ash so they could see how it was structured — something that can’t be done once ash falls to the ground and gets mixed in with other materials. It was discovered that ash particles will clump up, and in general, these clumped particles will fall closer to the volcano.

In general, however, isn’t the same thing as always. Back in the 1993, it was theorized that if particles clumped together just right, they could form ash rafts capable of floating in the air for great distances. This theory was promptly squashed by other scientists and declared impossible. Well, it turns out, the theory was absolutely correct, as demonstrated by ash clumps that rafted themselves from Iceland to the United Kingdom back in 2010.

In the mix, teams also realized, and here I quote Eduardo Rossi: During a volcanic explosive eruption, fragments ranging from a few microns to more than two meters are ejected from the volcanic vent. 

These particles are essentially knife-sharp bits of glass and rock capable of scouring airplane engines and windshields until the engines fail and the glass can no longer be seen through. Rossi goes on to explain: This is why the new strategies have integrated concentration thresholds better defining the dangerousness for aircraft engines. From two milligrams per cubic meter, airlines must have an approved safety case to operate.

This work appears in the journal Nature Communications.

More Information

University of Geneva press release

The fate of volcanic ash: premature or delayed sedimentation?“, Eduardo Rossi et al., 2021 February 26, Nature Communications

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