Temperature shifts in the depths of the Earth lead to volcanic eruptions

Hot and cold under Tonga volcano. Credit: © Planetary Visions (ESA / Planetary Visions)

The amazing power of the eruption of Tonga volcano shocked the world, but the fact that this underwater volcano did erupt was less of a surprise to geologists, who used satellite data to study changes in temperature deep below the Earth’s surface.

The Tonga-Hung Haapai volcano cataclysm in January was reported to be the largest eruption on the planet in 30 years. It sent a plume of ash into the sky, left the island nation of Tonga with suffocated ashes, sound of thunder was heard all the way to Alaska, and tsunami waves swept across the Pacific Ocean.

While Tonga’s eruption was powerful but brief, last year’s eruption of Cumbre Vieja volcano on the Spanish Canary Island of La Palma was less explosive but lasted nearly three months.

Despite the differences, both of these recent eruptions remind us all of how destructive nature can be. A better understanding of the natural processes that take place deep beneath our feet can bring closer the possibility of predicting eruptions.

This is one of the goals 3D project of the Earth ESA “Science for Society”. where an international team of geologists has joined forces to develop a modern global model of the lithosphere, which is a term to describe the fragile crust, upper mantle and sublithospheric upper mantle to a depth of 400 km. The model combines various satellite data, such as gravitational data from GOCE ESA, with field observations, primarily seismic tomography.

Rising heat under the volcano La Palma

Rising heat under the volcano La Palma. Credit: © Planetary Visions (ESA / Planetary Visions)

In their model, which shows the difference in temperature or thermal structure of the Earth’s upper mantle, the researchers were able to see that these volcanoes would erupt at some point. However, it is more difficult to predict when this will happen.

Javier Fulea of ​​the Complutense University of Madrid said: “Ours WINTERC-G model, which uses tomographic data and gravitational data from the GOCE satellite, shows a branch of the Azores plume. It is visible from the surface down to a depth of 400 km, at the base of the upper mantle. The plume flows southeast toward Madeira and the Canary Islands, surrounding a cold mantle beneath the African edge of the North Atlantic.

“Around the globe, we see that the Tonga volcano is located in the basin of the back arc created by the subduction of the Tonga plate. The volcanoes of the rear arc are due to the fact that the cold plate melts in the mantle when the plate slides into the mantle ”.

Sergei Lebedev from the University of Cambridge in the UK adds: “From such models and seismic tomography we see structures rising from great depths under the Canary Islands. These anomalies reflect hot material that rises to the Earth’s surface, and is called hotspots or plumes and is a constant source for volcanoes on the surface.

“The origin of the Tonga-Hung Haapai volcano is different. It is part of the Tonga-Kermadec Arc, where the edge of the Pacific Tectonic Plate sinks beneath the Australian Plate. Here, our image shows a layer of hydrated, partially molten rock over a deepening Pacific plate that feeds the arc volcanoes. ”

But where do these thermal anomalies come from?

The answer lies even deeper, at a depth of about 2,800 km, and is related to structures at the core-mantle border: the provinces of high and low seismic velocity (LLSVP). These prominent structures the size of a continent seem to have a big impact on how the surface behaves.

Clint Conrad of the Norwegian Center for the Dynamics of Earth Evolution said: “There is a link between the flow in the mantle, where convection cells move plate tectonics, and the main places of the plume. The flow along the core-mantle boundary pushes the plume material against the LLSVP, forming plumes. In the models, this flow is due to the immersion plates surrounding the two LLSVPs. The Canary Islands, for example, are over the edge of the African LLSVP ”.

ESA Gravitational Field and Sustainable Ocean Circulation Researcher (GOCE)

Launched on March 17, 2009, the ESA Gravity field mission and the Ocean Circulation Explorer stationary mission (GOCE) became the first Earth Explorer mission in orbit. This new mission has provided a wealth of data to reach a new level of understanding of one of the most fundamental forces of Earth’s nature – the field of gravity. This sleek, high-tech gravitational satellite has embodied many of the first in its design and use of new technologies in space to map the Earth’s gravitational field in unprecedented detail. Credit: ESA-AOES-Medialab

However, the exact origin and build-up of LLSVP remains unclear. A recent 4D Earth Science meeting discussed alternative concepts and ideas using satellite data and seismological models that will hopefully lead to more detailed studies of the Earth’s inner space in the near future.

Bart Ruth of TU Delft, one of the organizers, sums up: “Obviously, an interdisciplinary approach is needed when different types of satellite data are combined with seismological data in a common way to address the exact structure of the Earth’s depths.”

Diego Fernandez of ESA said: “I am delighted to see that the ESA FutureEO Science for Society project is delivering results that will further improve our understanding of the deep sources of events such as those we have just seen in La Palma and Tonga.

“It should be noted that data from the GOCE satellite were key in this study. GOCE, which reflected the changes in the Earth’s gravitational field with extreme detail and accuracy, completed its mission in orbit back in 2013 – and scientists are still counting on this data. This is another example of the benefits that our satellite missions bring beyond their lives in orbit. ” Temperature shifts in the depths of the Earth lead to volcanic eruptions

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