Volcanologists’ ability to estimate the risk of an eruption relies heavily on knowing where the magma pools deep in the Earth’s crust are stored. But what if you can’t find the magma?
Shane Luyackers, a postdoctoral fellow at GNS Science in New Zealand, grew up behind Mount Taranaki on New Zealand’s North Island and hiked many volcanoes on the island. Today, his research reveals hidden dangers that may have been at his feet all the time.
A new study published yesterday GeologyInvestigate the threats recently discovered by volcanologists. A surprisingly shallow magma pool that is too small for a typical volcano monitor to detect. Such a magmatic body was discovered in Iceland in 2009. When scientists from the Iceland Deep Drilling Project accidentally drilled directly into molten rock 2 km shallower than previously detected magma. The magma began to crawl up the drill hole, reaching several meters before stopping with cold drilling fluid. This study adds important information to the puzzle by linking hidden magma to eruptions centuries ago.
Rooyakkers, the lead author of the study, who completed his work while attending McGill University, compared the composition of quenching magma, which formed smooth volcanic glass, with rocks from an eruption from the same volcano, Krafla, in 1724. Studies show that scientists believed that the shallow magma they dug into was installed after a series of eruptions in the 1980s. Rooyakkers was surprised to find the hidden magma, as no one expected it to be associated with the 1724 eruption.
“When we examined the composition in 1724, we found that it was almost exactly the same as what was sampled during drilling,” says Rooyakkers. “It actually suggests that this magmatic body has been there since 1724 and was previously involved in the eruption at Krafla. So,” Why didn’t geophysics pick it up? ” Raise a question.
The answer is size. Most magma detection relies on seismic imaging, as oil companies use to detect deep seafloor reserves. When an earthquake occurs, the instrument detects the time it takes for the sound waves to pass through the crust. Depending on the density of the rock, the sound waves will return at different times. Therefore, if water, oil, or magma is stored underground, the sound waves should reflect it. However, these hidden magma chambers are too small for these devices and other detection tools to find.
“Traditional approaches to volcanic monitoring focus a lot on knowing where the magma is and which magma body is active,” says Rooyakkers. “Krafla is one of the most closely monitored and instrumented volcanoes in the world. From a geophysical point of view, everything except the kitchen sink is thrown in. Still, this rhyolite magma body We didn’t know that we were just sitting. A depth of 2 kilometers that could cause a dangerous eruption. “
Studies such as Rooyakkers suggest that smaller, more widely distributed magma chambers may be more common than previously thought, and most eruptions are larger and more reliably detectable. It disagrees with the traditional view that it is sourced from deep magma chambers.
In addition to the inability to monitor magmatic activity, eruption planning and risk estimation become more difficult if scientists suspect that hidden magmatic bodies may exist. For example, Krafla volcano is usually dominated by basalt, a type of basalt (like the recent eruption at Fagradallsfjall in Iceland), which tends to erupt passively rather than explode. However, Krafla’s hidden magma body is made of rhyolite. Rhyolite is a magma type that often causes a violent explosion when it erupts.
“Therefore, the concern in this case is that you have shallow rhyolitic magma that you do not know, which is not considered in the risk plan,” Rooyakkers explains. “If a new magma is hit by a rise, a much more explosive eruption than expected can occur.”
Volcanologists are aware of the dangers associated with these shallow distributed magma systems and can work to improve surveillance in an attempt to capture these hidden magma pools. Covering volcanic areas with more detectors can be costly, but by improving the resolution of magma imaging, scientists may save far more communities and companies than the cost of research. not. Risks vary from volcano to volcano, but in general, familiarity with these magma systems will allow scientists interested in estimating danger to realize the potential for hidden magma.
Do Rooyakkers still live around the volcano, despite the risks he reveals?
“Yes, sure,” he says with a laugh. “In other words, there is a risk in something.”
Hidden magma pools pose a risk of eruptions that we have not yet detected-ScienceDaily
https://www.sciencedaily.com/releases/2021/04/210416143037.htm Hidden magma pools pose a risk of eruptions that we have not yet detected-ScienceDaily