Hotspot volcanoes

Collapsing volcanoes erupt longer and harder


Scientists have discovered what triggers large-scale volcanic eruptions and the conditions that can lead to them.

Hawaii’s Kilauea is one of the most active volcanoes in the world. For this reason and its relative ease of access, it is also one of the most equipped with monitoring equipment, instruments that measure and record everything from earthquakes and ground movements to the volume and progress of lava.

The eruption of Kilauea in 2018, however, was particularly massive and accompanied by summit collapse. In fact, it was the volcano’s largest eruption in over 200 years. Scientists at NASA’s Jet Propulsion Laboratory in Southern California used the abundance of data collected from this rare event to shed light on the cause of large-scale eruptions like this and, perhaps more importantly, what mechanisms trigger them.

“Ultimately what made this eruption much larger than normal was the collapse of the volcano’s caldera – the large, crater-shaped depression at the top of the volcano,” said Alberto Roman of JPL. , lead author of the new study recently published in Nature. “When a caldera collapses, a massive block of rock near the top of the volcano slides into the volcano. As it slides, gets stuck on the jagged walls surrounding it and slips a bit. plus, the block of rock expels more magma than would normally be expelled.

But what the science team really wanted to know was what caused the caldera to collapse in the first place – and they found their answer.

The probable culprit? Vents – openings through which lava flows – located at a distance and at an altitude much lower than the top of the volcano.

“Sometimes volcanoes erupt at the top, but an eruption can also occur when lava passes through vents much lower in the volcano,” said Paul Lundgren of JPL, co-author of the study. “The eruption through these low-level vents likely led to the collapse of the caldera.”

A large amount of magma can be expelled quickly from the chamber (or chambers) below the volcano through these vents, leaving the rocky soil and caldera walls above the chamber without sufficient support. The rock in the caldera can then collapse into the magma chamber.

As the rock falls, it pressurizes the magma chambers – for Kilauea, the research team has identified two – increasing the flow of magma to distant vents as well as the total volume of the eruption. . Pressurizing is like squeezing a bag of water to squeeze out the last bit of water.

The following video shows how the surface of a volcano deforms during an eruption leading to the collapse of the caldera at the top. The colored bands in the lower right animation area show these changes from before the midpoint of the Kilauea eruption in 2018. The closer the colored bands are to each other, the greater the distortion. in this area

After developing their model of these eruption processes, taking advantage of available data from Kilauea, they also compared the model’s predictions to observations of similar eruptions caused by the caldera collapse of other volcanoes. The results were consistent.

Even though the model doesn’t predict when a volcano will erupt, it can provide crucial information about the likely severity of an eruption once it has started.

“If we see an eruption at a low-level vent, that’s a red flag or a warning that caldera collapse is possible,” Roman said. “Likewise, if we detect earthquakes consistent with the sliding of the caldera boulder, we now know that the eruption will likely be much larger than usual.”