2021-05-16

Scientists have recognized the causes and conditions that trigger large-scale volcanic eruptions

By yqqlm yqqlm

Scientists have recognized the causes and conditions that trigger large-scale volcanic eruptions

However, Kilauea’s 2018 eruption was Especially large-scale. In fact, this is the largest eruption of the volcano in more than 200 years. Scientists at NASA’s Jet Propulsion Laboratory in Southern California used the massive data collected from this rare event to reveal the reasons for such large-scale eruptions, and perhaps more importantly, what mechanism triggered them.

Scientists have recognized the causes and conditions that trigger large-scale volcanic eruptions(1)

JPL’s Alberto Roman is recently published The lead author of the new study in the journal Nature, he said: “In the end, the cause of this eruption much larger than normal was the collapse of the crater-a large crater-like depression on the top of the volcano. During the collapse of the crater, the huge rock near the top of the volcano slipped into the volcano. When it slides, it is caught by the surrounding jagged walls, and then slides again. This rock squeezes out more magma than usual. .”

Scientists have recognized the causes and conditions that trigger large-scale volcanic eruptions(2)

But the science team really wants What we know is what caused the caldera to collapse in the first place-they found the answer. What is the possible culprit? The crater – the opening through which lava flows – is located far away from the volcano’s apex, and its elevation is much lower than the volcano’s apex. The co-author of the study, Paul Lundgren of JPL, said: “Sometimes, volcanoes erupt at the top of the mountain, but they also erupt when lava bursts from the vents below the volcano. Eruptions through these low-altitude vents may cause the caldera Collapse.”

During an eruption, the surface of a volcano can deform or change shape. The ribbon in the animation box in the lower right corner shows these changes from Kilauea before the eruption in 2018 to the middle of the eruption. The closer the color bands are to each other, the more severe the deformation of the area – just like the contour lines on a topographic map indicate rapidly changing heights.

Lundgren likens this type of vent to a faucet on a collapsible water bottle that you carry on a camping trip. When the water level drops to the position of the tap, the water flow will slow down or stop. Similarly, the lower the crater (or “spout”) is, the longer the lava may flow before it reaches the stopping point.

A large amount of magma can be quickly discharged from the chamber (or cavity) below the volcano through these vents, so that the rocky ground and walls of the caldera above the chamber do not have enough support force, and finally the rocks in the caldera Can collapse into the magma chamber. As the rock falls, it pressurizes the magma chamber. For Kilauea, the research team identified two of the magma chambers, which increase the total volume of magma flowing to distant vents and eruptions. Pressurization is similar to squeezing a kettle to force out the last bit of water.

After establishing the models of these eruptions, using Kilauea’s large amount of data, they also compared the predictions of the model with the observations of similar eruptions caused by the collapse of the caldera of other volcanoes. Compare. The results are consistent. Even if the model cannot predict when a volcano will erupt, it can provide critical data to understand the severity of the eruption once it begins. If we see an eruption in a low-altitude vent, this is a warning that the caldera may collapse; similarly, if we detect an earthquake that coincides with the fall of rocks in the caldera, the eruption may be much larger than usual. .