On February 15, 2022, the research of ESA pointed out that although the amazing power of Tonga volcano eruption shocked the whole world, the earth scientists who used satellite data to study the temperature changes in the depth of the surface were not surprised by the fact that this submarine volcano erupted.

It is reported that the catastrophic eruption of Hongjiatonga volcano in the Tonga Sea from June 5438 to October 2022/KLOC-0 was the largest volcanic eruption in the world in the past 30 years. The volcanic eruption enveloped the island nation of Tonga in volcanic ash, and the sonic boom could be heard as far away as Alaska, and the tsunami waves crossed the Pacific Ocean. Although Tonga volcano erupted violently, it was short-lived. In 20021year, the cambria volcano on the Spanish island of La Palma Canary erupted less violently, but it lasted for nearly three months. Although they are different, these two recent volcanic eruptions remind people that it is possible to accurately predict volcanic eruptions only by better understanding the natural processes in the deep part of the earth.

An advanced global lithosphere model has been jointly developed by an international team of ESA geoscientists. The model combines different satellite data, such as gravity data of ESA GOCE and field observation data, mainly seismic tomography data. In the model showing the temperature or thermal structure difference of the earth's upper mantle, researchers can see that these volcanoes will erupt at some time. However, it is more difficult to accurately predict when this will happen.

Researchers at the University of Cambridge in the United Kingdom pointed out that in these models and seismic tomography, they saw structures rising from the depths of the Canary Islands. These anomalies reflect that hot matter rises to the earth's surface, which is called hot spot or mantle plume, and is the continuous source of surface volcanoes.

The origin of Tonga volcano is different. It is a part of the Tongkemadek island arc, and the edge of the Pacific tectonic plate dives under the Australian plate. The image shows the water-bearing and partially melted rock layers above the inclined Pacific plate, which provide water for the volcanoes on the island arc. It is found that these thermal anomalies come from a deeper place with a depth of about 2800 kilometers, which is related to the structure of the core-mantle boundary: low shear wave velocity block (LLSVPs). These prominent continental-sized structures seem to have a great influence on the behavior of the surface.

Norwegian scientists say that there is a connection between the mantle flow driven by convection circle and the main position of mantle plume. The flow along the mantle boundary of the core pushes the columnar material to LLSVPs, forming columnar material. In the model, this flow is driven by downhill plates around two LLSVPs. For example, the Canary Islands are located on the edge of LLSVP in Africa.

However, the exact origin and formation of LLSVPs is still unclear. At the recent 4D Earth Science Conference, alternative concepts and ideas were discussed using satellite data and earthquake models, which is expected to lead to more detailed research on the earth's interior in the near future.

Scientists at Delft University of Technology have come to the conclusion that a multidisciplinary approach is needed to combine different types of satellite data and seismic data to study the exact structure of the deep earth in a * * * way.

Please indicate the source and author of this article: Wang Liwei, Lanzhou Literature and Information Center, China Academy of Sciences, compiled the Earth Science Dynamic Monitoring Express, No.4, 2022.