Tiny but Mighty! Nanosized Drivers of Explosive Volcanism

Paper: Can nanolites enhance eruption explosivity?

Authors: F. Cáceres, F. B. Wadsworth, B. Scheu, M. Colombier, C. Madonna, C. Cimarelli, K-U. Hess, M. Kaliwoda, B. Ruthensteiner, D. B. Dingwell

Explosive volcanic eruptions have punctuated our planet’s geological record for millions of years. The explosive nature of these eruptions can lead to thousands of cubic kilometers (that’s a billion Olympic swimming pools) of material travelling hundreds of miles across our landscapes and into our atmosphere. Approximately 630,000 years ago, the most recent eruption from the Yellowstone volcanic center sent ash and dust from Wyoming to southern Texas, USA. More recently, the 1815 eruption of Mt. Tambora, Indonesia, led to 1816 being historically known as the “Year Without a Summer”. The “Year without a summer” was started when volcanic materials entered the atmosphere and induced a volcanic winter, which led to extreme weather, agricultural stresses, and food shortages across the globe.

Whether or not a volcanic eruption will be explosive (e.g., like that of Tambora in 1815, or Mt. St Helens in 1980), or more effusive, gentle, in nature (e.g., Mt. Etna, Italy, or Kīlauea, Hawaii) is initially considered to be controlled by how fast bubbles grow in the magma beneath these volcanoes. When these bubbles, which contain gases such as water (H2O), form (or nucleate) and grow at depth they promote magma ascent through the volcanic conduit towards the surface. This ultimately influences a volcanoes eruption style: the more bubbles present, and the faster their growth, the more explosive the eruption.

But what influences the behavior of magmatic bubbles beneath Earth’s volcanoes? Inside our planet, what processes are occurring that can ultimately lead to the ejection of material across the Earth’s surface and up into our atmosphere?

A new study by Francisco Cáceres and co-authors just might have the answer, particularly for volcanic systems that are chemically enriched in silica (SiO2). While explosive volcanic eruptions are typically associated with more silica-rich magmas, Francisco Cáceres and co-authors show that there is more to their explosivity than just their chemical composition, and this is where nanolites (nano-lights) come into play. No, not ultra-light sleeping bags one might take camping, or to be confused with a nanolight aircraft (a hand glider). Nanolites are crystals, which as the name suggests, are nano in scale with 1 nanometer (nm) equivalent to 0.000001 millimeters (mm) or one billionth of a meter. Think very tiny!

As shown by Francisco Cáceres and co-authors, the presence of these nanoscale crystals in magmas stored at depth have the ability to generate abundant bubble nucleation sites, i.e. more places for bubbles to grow and increasing the likelihood that a bubble will form in the first place. The presence of nanolites can therefore increase the bubble density of a magma, increase bubble growth rates deep in the volcano, and lead to a more explosive volcanic eruption. Importantly, the authors show magmas with nanolites present are more likely to generate higher bubble densities than magmas which are nanolite free.

Although other factors associated with the magmatic system that exists beneath a volcano will also influence the likelihood and style of eruption, e.g., temperature, water content, depth of magma storage, the presence of nanoscale crystals boost the chances of a volcanic eruption being explosive in nature, rather than effusive. Nanolites, as tiny as they are, therefore have a mighty role to play in understanding the dynamics of volcanic eruptions in the past, present, and future.

Tiny but Mighty! Nanosized Drivers of Explosive Volcanism by Claire McLeod is licensed under a Creative Commons Attribution 4.0 International License.

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