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It would be logical to hear the term “volcanic bomb” and assume that such an object tends to explode. But a particular type of volcanic bomb rarely lives up to the second half of its name: These objects pop up into the air, fall to the ground, and do not explode disappointingly.
These volcanic bombs — bubbles of plastic, partially molten magma no smaller than a peach — are launched from a volcano that has been submerged by a shallow body of water, such as a lake or a near-shore sea. In this process, bombs get plenty of water. This trapped water encounters the scorching hot interior of the bomb and is boiled violently, turning into steam.
The sudden accumulation of vapor in the bullet should detonate the bomb in mid-air. The rocks cannot survive in the face of this pressure,” he said. Mark McGuinness, a mathematician at Victoria University Wellington, New Zealand. And yet many of these bombs smash into the ground with an anticlimatic rumble and become duds.
Solving this riddle does more than scratch a long-standing scientific itch. Volcanic bombs, an essential part of many explosive eruptions, also a mortal danger. If more of them blow up mid-flight, it’s preferable to hitting someone in the head.
Hoping to break the case, Ian SchipperA volcanologist in Victoria, Dr. He joined forces with McGuinness and Emma Greenbank, also a mathematician in college. They created a mathematical model that simulates the launch of a bomb from a virtual volcano and replicates the varying pressures and temperatures of the interior of the sphere.
Results this Wednesday Proceedings of the Royal Society AThe team concludes that water both produces and defuses these paste-like volcanic bombs.
Volcanic bombs are a common feature of a series of explosive eruptions. This includes the Surtseyan explosions. SurtseyA volcano off the coast of Iceland that erupted above the waves until it formed a new island in the 1960s.
During this type of eruption, magma clumps are pushed out of a shallow body of water. At the same time, volcanic eruptions splashed into the sky and splashed back into the same water. This creates an ashy slurry dense enough to pierce and moisten the gloopy igneous clumps that will turn into bombs.
It has long been surprising that these wet bombs rarely explode. But scientists can’t really study these fast projectiles in detail, as they were launched from a volcano.
“You don’t want to try to catch them,” he said. Rebecca Williams, a volcanologist at the University of Hull in England who was not involved in the study.
Volcanologists studied volcanic blocks, which are completely solid pieces of ballistic volcanic material. firing them from a bespoke cannon. But they haven’t yet launched clumps of molten magma from a gun; this is an activity that will never pass a security review.
This new mathematical model, powered by data from real-life Surtseyan bombs that descended and cooled, seems to have come to the rescue.
As magma rises through a volcano and towards the surface, its pressure drops and the water trapped inside escapes as steam and forms bubbles. This foamy magma mound is then launched into the water and becomes a bomb. Lake or sea water seeping into the bomb boils violently. But the team’s mathematical simulations show that the already foamy nature of the bomb means that there are numerous ways steam can flow through it and thus stop a pressure build-up and ultimately an explosion.
A few bombs without a sparkling network of holes created by the magma’s own water will succumb to the pressure of the newly produced steam and self-destruct. Most, however, are foamy enough and allow steam to be evacuated without incident.
“His solutions are really elegant; I think it works really well,” said Dr. Williams, referring to the model.
Dr. For McGuinness, the research achieved another purpose: As a striking example of how mathematics can solve non-abstract problems, she hopes it will help change public perception of this field of study.
“It is much more inspiring to say that you are working on exploding bombs and volcanic bombs,” he said.
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