Thursday, July 7

The analysis of the wash “opens a window” into the La Palma volcano

Image from the air of the lava flow of the La Palma volcano.

Image from the air of the lava flow of the La Palma volcano.

To understand the behavior of the Cumbre Vieja volcano and help the teams operating on the ground, a group of scientists led by the researcher from the Department of Mineralogy and Petrology of the University of Granada Jane H. Scarrow analyzes lavas and pyroclasts, as well as the minerals they contain. These studies help to understand how the eruption evolves and to interpret the conditions and processes that occur in the deep magmatic reservoir. “Analyzing the lava is like opening a window inside the volcano and allows you to know what is happening under the ground,” explains Scarrow.

The researcher traveled to La Palma between September 21 and 25 to sample the initial eruptions and collaborate with the Volcanological Institute of the Canary Islands (Involcan) in setting up a petrological laboratory. “The collection of samples is very important, because we want to preserve the high temperature conditions to be able to get as close as possible to the conditions that occur in depth”, details Scarrow. As the lava flow progresses, an incandescent sample is taken, at 800 or 900 degrees, and cooled by placing it in a bucket of water to “freeze” its conditions, which allows the processes to be analyzed at high temperature. The researcher points out that new material is collected every day to observe the evolution of the magmatic system, through the examination of samples from the most recent eruptive stages.

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Scarrow studies in Granada the global composition of lava and that of the minerals it contains. With this research “the processes of the magmatic system can be seen, which gives us information that makes it easier for us to understand what has happened and gives us clues about its evolution and origin”, the researcher emphasizes. However, it clarifies that these data do not allow a estimation of the possible duration of the volcanic eruption, since it focuses on detecting the processes that are taking place or will take place inside the volcano, such as, for example, the crystallization of minerals or the mixture of magmas.

Magma viscosity

The specialist in Mineralogy and Petrology has already carried out an X-ray diffraction, to find out the minerals that the samples contain, and has extracted thin 30-micron plates, which allow the study of rocks and minerals under a microscope and an electronic microwave. “The sample is exposed to the light of the microscope and the characteristics of the minerals that make up the magma can be observed,” he emphasizes. Scarrow also uses X-ray fluorescence to measure the composition of major elements in rocks, the ionization source mass spectrometer to measure the composition of trace elements in rocks, and the electron microprobe to measure the composition of the minerals in the samples.

The viscosity of magma and lava is largely dependent on temperature. In the first stage of the eruption the material was more viscous and now the volcano expels a more fluid runoff. “In the early days, when the lava reached Todoque, it was very viscous, due to the cooling, and it slowed down,” recalls Scarrow.

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The preliminary conclusions of this study are in the hands of the scientific teams of the Canary Islands Volcanic Emergency Plan (Pevolca) and will be published in the coming days. This research is carried out thanks to the collaboration of researchers from Involcan, the University of La Laguna, the University of Exeter (United Kingdom) and Michigan Technological University (United States).

This study is added to the work that seismologists from the University of Granada, belonging to the Andalusian Institute of Geophysics and Seismic Disaster Prevention (Iagpds), have recently carried out in La Palma to analyze and understand the characteristics of the volcanic phenomenon of this Spanish island. These experts have also been instrumental in the study of the seismic swarm that began at the end of 2020 in the Granada metropolitan area.

The laboratory of the Mineralogy and Petrology department of the Faculty of Geological Sciences of the Complutense University of Madrid also analyzes lava samples from La Palma. One of his first conclusions is that the magmatic material comes from the upper mantle of the Earth. Also, lhe composition of these stones explains the reasons why the eruption was not explosive and the laundry has shifted as it has. According to this study, the molten rock has not interacted with the Earth’s crust on which the island building rests, a circumstance that would have generated large amounts of gases. In addition, he points out that the magma rose a few years ago, a fact that could explain the earthquakes detected on the island since 2017, until it accumulated enough pressure for the volcano to emerge.

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