Sombrero-Shaped Uplift Found in Earth’s Crust

Geophysics professor Yuri Fialko and Alberta Geological Survey Remote Sensing Specialist Jill Pearse have spent the last few months pouring over 20 years’ worth of satellite data, provided by the European Satellite Agency, from the Altiplano-Puna Plateau in the central Andes region of South America. They discovered an ongoing deformation inside earth’s crust that is 100 kilometers wide. The sombrero-shaped geological formation is a broad uplift that sits in the middle of a magma body. Their study was published on Oct. 11 in Science magazine.

“If our interpretation is correct, that would mean that this is the first ever observation of a buoyant magnetic diapir anywhere on earth,” Fialko said.

A large blob of magma is ballooning like a sphere and rising through the middle of the crust, causing the sombrero-like shape.  

“[The profile] has this kind of central dome and there are side lobes where areas of subsidence are on the boundary of the central uplift and that very much looks like the profile of a sombrero,” Fialko said.

Fialko said it is likely that this uplift has been occurring for over 20 years, but they have no way knowing how long the formation has actually been occurring before the satellite observations were taken.

“Given the steadiness of this process, it’s very likely that this continued for a longer time,” Fialko said.

The discovery of this active diapir means this process could be happening anywhere on earth. The diapir is on the Altiplano-Puna Plateau, which is a large seismic body of magma at a depth of 20 kilometers.  There has been debate about the transport mechanism for magmas from the deepest region of the crust to the shallower depths in the upper crust. There are different competing theories about the process of diapirs, but they have not been observed in real time until now.

“[Diapirs] are kind of ghosts from the past, we can only observe what happened a long time ago,” Fialko said. “What we observed was an indication of a bunch of processes occurring in the present. We made that connection between geologic evidence in other places and the active ongoing diapiric growth right now in South America.”

According to researchers, there were super-volcanoes in the Altiplano-Puna Plateau millions of years ago that threw thousands of cubic kilometers of ash into the atmosphere. The process occurring now may be the very initial stages of large eruptive systems. The information from the diapirs could potentially explain how magma moves from deeper parts of the earth to the shallower crust. Diapirs could also be the same mechanism that created super-volcanoes.

The discovery gives scientists information about layering ages, rates and the overall dynamics of diapirs. Fialko said one use of the data is to learn more about the transportation of magma through the earth.

There is evidence of a diapir in central New Mexico, and it is estimated to be about 100 years old. But it moves five times slower than the diapir in South America. The New Mexico diapir is being tracked but it is not as significant as the diapir in South America.

“It was really exciting to see that this process is occurring at a much greater rate and therefore the imprints would be that the magma diapir depths are much larger,” Fialko said. “Both finding this unusual shape of uplift and linking this surface of duration to process of depth is precisely what we tried to do at the beginning.”

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