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Fidel Costa publishes in Nature
EOS Principal Investigator Fidel Costa along with Professor Timothy Druitt and their colleagues published “Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano” in Nature. This important paper was picked up by news agencies around the world due to its relevance to future prediction of explosive volcanic eruptions. Below is a brief write-up on the scientific contribution of this work by Dr. Fidel Costa.
Volcanic crystals provide clues to anticipate large explosive eruptions
The largest explosive eruptions on Earth are produced by caldera-type volcanoes, a remarkable example of which is Toba, only about 550 km north-west of Singapore. Some 73,000 years ago, more than 2000 km3 (cubic kilometres) of volcanic material was injected into the atmosphere. The eruption covered large parts of Asia with ash and had such an effect on climate that may have dramatically reduced the global human population at the time. Fortunately, such large explosive eruptions have not happened in our modern times. But this also means that we have very limited information to answer the question: how long in advance can we know that a caldera volcano is getting ready for a large explosive eruption, and what are the signs?
Druitt, Costa et al. (2012) recently addressed this question in a study of the Minoan eruption that occurred in the bronze age (1660 BCE) from Santorini caldera volcano in Greece (Fig. 1). The eruption spread about 60 km3 of volcanic material over the Mediterranean. The related caldera collapse has been linked to the myth of Atlantis in Plato’ s writings, and is propopsed to have cause large tsunamis. The authors collected volcanic samples and investigated the chemical zoning patterns of the volcanic crystals using a variety of micro-analytical techniques including the electron- and ion-microprobes. Much like we can examine tree rings to learn about past climate, we can use the information contained in the growth zoning in volcanic crystals (plagioclase in this case; Fig. 2) to interpret the processes that occurred below the volcano. The authors treated the crystal data with the method of geospeedometry, using numerical modeling based on chemical kinetics to obtain the time scales of the process that occurred below the volcano.
The authors show that before the Minoan eruption, the volcano system experienced two distinct processes. First, a few decades before the eruption, different volcanic melts mixed at great depths several kilometres below the volcano. Second, just a few months before the eruption, several cubic kilometres of these volcanic high-temperature fluids moved towards the surface. This probably caused many earthquakes to happen, large fumaroles, and the surface of the volcano to bulge. Thus, there were obvious signs of activity on the volcano's surface a few months in advance of the Minoan eruption. Archeological evidence also suggests that Minoans evacuated Santorini Island well in advance of the eruption. The implications this study are that large explosive eruptions at volcanoes worldwide could happen after just a few months of volcanic unrest, much faster than previously thought. This is very relevant for living with the hazard of large caldera volcanoes such as Yellowstone, (USA) and Campi Flegrei (Italy), and many others. The results were widely reported in the international news (see also Blundy and Rust, 2012; Witze, 2012a, 2012b).