Amazing stuff!
"... Rather than study common precursors such as earthquakes or gas, a team decided to take a peek inside of Earth at tiny crystals that grow within magma.
Magma contains many kinds of crystal minerals depending on how deep it is stored beneath a volcano. Researchers turned to a mineral called plagioclase—one of the most common in the chain of volcanoes known as the Pacific Ring of Fire—that has different appearances and compositions depending on the conditions of the surrounding magma. Plagioclase can therefore provide clues as to what magma was doing before an eruption.
Researchers collected volcanic rocks from the Andean Mountains, one of the most active regions in the Ring of Fire, then analyzed the structures and compositions of the rocks’ plagioclase.
Across seven volcanoes, the team found that the tiniest crystals—only the width of a human hair—form just before a volcano erupts, when hot magma fills in where cold magma used to sit and destabilizes the system. Similar tiny crystals appeared in existing datasets of eruptions. ..."
"... researchers have shown tiny crystals are a window to activity inside volcanoes and could provide clues to when they might erupt. ...
examined a common white crystal called ‘plagioclase’, found in rocks.
The smallest crystals from Andean volcanoes of different ages, eruptive styles and activity levels had the same chemical signature.
“Plagioclase grows in magma only a few kilometres below the surface, reacting to changes in temperature, water content and magma composition,” ...
"Analysing the chemistry of individual crystals rather than whole rocks allows us to reconstruct different stages of a volcano's history and identify the processes that occurred immediately before eruption.
“The smallest, newest crystals – just the width of a human hair – were formed during the final stages of an eruption. ..."
From the abstract (unfortunately, a very technical):
"Arc andesites are hybrids generated by mixing of mafic and silicic magmas. The silicic endmember can contribute to crustal growth or trigger explosive eruptions, yet remains difficult to constrain due to limited representation in the erupted record.
Here, we show that textural, elemental and isotopic records preserved in plagioclase can distinguish between trapped and erupted crystal mush, thus constraining conditions of magma storage vs. eruption in arc systems.
We define the plagioclase eruptibility field, a narrow and recurrent anorthite range (An~61) that represents erupted melt across Central Andes volcanoes upon mafic recharge.
The recycled plagioclase cargo is dominantly An~43, recording prolonged crystallisation and assimilation within silicic mushes. This pattern repeats in continental and composite arcs globally, indicating strong eruptive filtering of arc magmas and widespread occurrence of dormant felsic and mafic mushes that, in most cases, contribute to crustal growth; yet exceptionally, felsic mushes can rapidly remobilise to generate super-eruptions."
ScienceAdviser
Fig. 1: Back-scattered electron (BSE) and transmitted-light images (PPL, plane-polarised light; XPL, cross-polarised light) illustrating the plagioclase textural classification.
