Эрдэмтэд Италийн Этна галт уулын өөр өөр цаг үед тохиолдсон хоёр том дэлбэрэлтийн үйл явцыг харьцуулж, галт уулын гүний хоолойн систем хувьсан өөрчлөгддөгийг тогтоожээ.
Судлаачид “Geochemistry, Geophysics, Geosystems” сэтгүүлд нийтлүүлсэн судалгаандаа Раман спектроскопийн аргаар магма доторх талстуудад хадгалагдсан хүний үсний зузаанаас ч нимгэн бичил хийн бөмбөлгүүдийг шинжилжээ. Максим Гавриленко болон түүний баг эдгээр бөмбөлгүүдийн нягтыг хэмжих замаар магма ямар гүнд, ямар даралттай байсныг нарийвчлан тодорхойлсон байна. Энэхүү арга нь галт уулын дотоод системийн бүтцийг урьд өмнө байгаагүй өндөр нарийвчлалтайгаар сэргээн харах боломжийг олгосон юм.
Судалгаагаар МЭӨ 122 онд болсон томоохон дэлбэрэлт болон 4000 жилийн өмнөх дэлбэрэлтүүд нь магмын урсгалын хувьд эрс ялгаатай байсныг тогтоожээ. МЭӨ 122 оны дэлбэрэлтийн үед магма 22 км-ийн гүнээс гарч, гадаргуугаас 2-5 км-ийн гүнд хэдэн долоо хоногийн турш саатаж хийгээ ялгаруулсны дараа дэлбэрсэн байна. Харин 4000 жилийн өмнөх үйл явдлын үед магма 24-30 км-ийн гүнээс маш хурдтайгаар дээшлэн, хэдхэн цагийн дотор дэлбэрэлт үүсгэжээ.
Энэхүү ялгаа нь нүүрстөрөгчийн давхар исэл (CO₂) болон усны харьцаанаас шууд хамаардаг болохыг эрдэмтэн Эстебан Газел тайлбарлав. Усны агууламж өндөр үед галт уулын үйл ажиллагаа гадаргуугийн ойролцоох түвшинд хянагддаг бол нүүрстөрөгчийн давхар исэл зонхилох үед магма маш гүнээс хүчтэй, хурдан дэлбэрэлт үүсгэдэг байна. Судлаачид уг аргачлалыг дэлхийн бусад бүс нутгийн галт уулуудад ашиглаж, галт уулын эрсдэлийг үнэлэх физик загварчлалыг сайжруулахаар ажиллаж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Two of Mount Etna’s most powerful eruptions took dramatically different paths beneath the volcano, revealing that its underground plumbing can change over time, according to a new study. The findings suggest that even a single volcano may erupt through entirely different mechanisms.
Although volcanoes often appear unchanged on the surface, the movement of magma deep underground is far more complex. Before reaching the surface, molten rock travels through a maze of reservoirs and conduits that can shift from one eruption to another, making volcanic behavior difficult to predict.
To uncover how these hidden systems evolve, researchers compared two major eruptions of Mount Etna in Italy separated by nearly 4,000 years. Their analysis, published in Geochemistry, Geophysics, Geosystems, revealed striking differences in the way magma rose to the surface during each event.
Tiny Gas Bubbles Revealed What Happened Underground
The strength of a volcanic eruption depends on several factors, including the amount of gas trapped inside rising magma. As pressure drops on the way to the surface, those gases expand and can turn an eruption explosive. Scientists have traditionally focused on water as the main gas involved in that process. More recently, researchers have shown that carbon dioxide can also play a major role.
To understand what happened beneath Mount Etna, the team used Raman spectroscopy to examine microscopic bubbles trapped inside crystals that formed in the magma. According to Cornell University, those bubbles are incredibly small, just 1 to 10% as thick as a human hair, but they preserve information about the pressure and depth at which they formed.
“The technique gives us the density of CO₂, and using a state equation we can transform that density into pressure, and pressure can be transformed into depth,” said first author Maxim Gavrilenko. “Then we apply those techniques to these explosive eruptions, and we are able to reconstruct the plumbing system with an unprecedented precision.”
The Same Volcano Took Two Very Different Routes
One of the eruptions studied took place in 122 B.C. and is one of the largest known events in Mount Etna’s history. It was a mafic Plinian eruption, meaning it involved magma rich in magnesium and iron and produced an exceptionally explosive eruption.
The researchers found that the magma rose from around 22 kilometers below the surface before stopping at a depth of 2 to 5 kilometers. It remained there for several weeks, gradually releasing gas before finally erupting. The second eruption, known as the Fall Stratified event, happened nearly 4,000 years ago. It unfolded very differently.
Instead of slowing down near the surface, the magma shot upward from a depth of 24 to 30 kilometers and erupted within just a few hours.The new study noted that eruption contained much higher levels of carbon dioxide than the later event.
The Hidden Battle Beneath Mount Etna
The comparison revealed something unusual about Mount Etna. Unlike many volcanoes, where one volcanic gas tends to dominate, Etna is influenced by both water and carbon dioxide. As stated by the latest research, lead researcher Esteban Gazel explained that volcanoes on oceanic islands are often controlled by carbon dioxide, while volcanoes in subduction zones are usually driven by water-rich magma. Mount Etna is one of the few places where both gases compete.
“This shows that at a certain threshold of CO₂, the eruption will come from very deep and really fast, but when you have a higher threshold of water, then the process is controlled at shallow levels,” Gazel said.
The team is now applying the same method to volcanoes in Chile, Hawaii, and other parts of the world. Gazel noted that the goal is to gather the data needed to improve the physical models that scientists use for volcanic risk assessment.
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