Even during a quiet period of dormancy, a volcano can quickly become active, and its eruptions can pose unknown threats to the surrounding area. Researchers studied the Theomadur volcano to understand how the long-dormant volcano suddenly erupted. Their results on the chemical and mineralogical composition of magma provide valuable insights into volcanic reactivation and eruption forecasting, highlighting the potential dangers of inactive volcanoes.
Do volcanoes erupt after being dormant for tens of thousands of years? If so, how to explain it? What makes a volcanic eruption more dangerous, i.e. explosive? These are key questions in volcanic hazard assessment and can also draw attention to seemingly inactive volcanoes. Even during periods of quiet dormancy, volcanoes can quickly become active, and their eruptions can pose previously unknown threats to the surrounding area. New research by Hungarian scientists helps reveal the signs that precede such a volcanic eruption.
A team from Hungary's Institute of Geography and Earth Sciences and HUN-REN-ELTE's Volcanology Research Group, in collaboration with other European scientists, studied Ciomadul, the youngest volcano in the Carpathian-Pannonian region.
They used high-resolution comprehensive data on mineral texture and chemical composition to quantify the conditions of magma evolution, reconstruct the structure of the magma chamber under the volcano, determine the characteristics of the resident mud and replenishing magma that triggered the volcanic eruption, and explain why the last active period of volcanic activity was dominated by explosions.
Theomadur: a typical long-term dormant volcano
The team previously used U-Th-Pb-He geochronology of a tiny crystal, zircon, to reveal the eruptive history of Theomadur volcano. Professor Szabolcs Harangi, the leader of the research project, emphasized: "In the nearly million-year life of this volcano, there have been several long periods of dormancy, but even after tens of thousands of years of dormancy, sometimes even more than 100,000 years, volcanic eruptions started again!"
The most important volcanic activity occurred as recently as 160,000 years ago, with lava dome extrusion occurring from 160,000 to 95,000 years ago, and then after more than 30,000 years of dormancy, volcanic eruptions resumed 56,000 years ago.
Barbara Cserép, a doctoral student at Eötvös Eötvös Eötvös, is studying the products of the youngest eruptions: "They were formed by more dangerous and explosive eruptions compared to previous active periods. It is therefore important to understand the reasons for this change in eruption patterns!" The last eruption occurred 30,000 years ago, and since then the volcano has gone dormant again. "
The causes of volcanic eruptions and the processes that control how they erupt are hidden in the rocks formed during volcanic activity. These causes can be revealed through detailed study of the minerals from which rocks are formed. The team determined the chemical composition of all mineral phases in pumice formed during volcanic eruptions between 56 and 30,000 years ago, typically at high resolution from the core to the edge of the crystal.
They then critically evaluated the results of various methods of calculating crystallization temperature, pressure, redox state, melt composition, and melt moisture content to quantify magma conditions and determine how these crystals were incorporated into the erupting magma. This helps reveal the structure of magma reservoir systems, the processes that lead to eruptions, and the causes of explosive eruptions.
The key to explosive eruptions
The key figure in this oil detective study is a mineral called amphibole. Barbara Cserép explains: "Many elements can enter the crystal lattice of amphibole, but the replacement of elements is strongly controlled by magmatic conditions. The chemical composition of amphibole in Ciomadul pumice varies greatly even within a single sample. Some amphibole represents a low-temperature, highly crystalline magma reservoir at depths of 8-12 kilometers, but most of the amphibole was transported to this shallow magma reservoir by high-temperature feed magma from deeper depths."
"Compared with the last eruption period that formed the lava dome, these fresh recharge magmas carry amphibole with a unique composition, that is, these magmas are slightly different, which may be an important reason why the eruption became an explosive volcano." Cserép added: "We found several amphibole whose chemical composition has not been reported in volcanic rocks from other volcanoes. They interpreted this amphibole as an early crystallization stage of superhydrous magma. These water-rich recharge magmas may have played a key role in triggering explosive eruptions."
The outermost edge of the crystal and the composition of the iron-titanium oxides provide information about the conditions of the magma before the eruption. "When magma conditions change, the composition of the iron-titanium oxides reaches equilibrium within a few days; they show that the erupting magma was 800-830 degrees Celsius and was oxidized," said postdoctoral researcher Máté Szemerédi, another lead author of the study.
Currently, the Theomadur volcano shows no signs of waking up. However, the study also notes that reactivation could occur rapidly, within weeks or months, if fed by hot, watery magma. Quantitative volcanic petrology studies are very important for reconstructing the structure of magma reservoirs and magma storage conditions under volcanoes, which also helps us predict volcanic eruptions and better understand the signals before volcanic eruptions.
Szabolcs Harangi noted: "The novelty of this study is that it was conducted on a long-dormant volcano, which is therefore receiving increasing international attention. This helps to highlight that, in addition to the 1,500 or so potentially active volcanoes on Earth, long-dormant volcanoes can also pose previously unrecognized dangers, especially if there is still molten magma beneath the volcano."
Compiled from: ScitechDaily