Privileged Planet: current magma movements (Introduction)

by David Turell , Wednesday, September 15, 2021, 22:45 (1166 days ago) @ David Turell

The process of Earth evolution is alive and well:

https://www.quantamagazine.org/a-massive-subterranean-tree-is-moving-magma-to-earths-su...

"Réunion, a French island in the western Indian Ocean, is like a marshmallow hovering above the business end of a blowtorch. It sits above one of Earth’s mantle plumes — a tower of superheated rock that ascends from the deep mantle and flambés the bases of tectonic plates, the jigsaw pieces that make up the ever-changing face of the world. The plume’s effects are hard to miss: One of the island’s two massive volcanoes, the aptly named Piton de la Fournaise or “peak of the furnace,” is one of the most hyperactive volcanoes on the planet.

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"In 2012, a team of geophysicists and seismologists set out to map the plume, deploying a giant network of seismometers across the vast depths of the Indian Ocean seafloor. Nearly a decade later, the team has revealed that the mantle is stranger than expected. The team reported in June in Nature Geoscience that the plume isn’t a simple column. Instead, a titanic mantle plume “tree” rises from the fringes of the planet’s molten heart, with superheated branchlike structures appearing to grow diagonally out of it. As these branches approach the crust, they seem to sprout smaller, vertically rising branches — super hot plumes that underlie known volcanic hot spots at the surface.

"The discovery of this massive structure beneath Réunion nearly coincides with another recent discovery, reported in November, that found additional structures in the plumes under Africa. Taken together, the two findings represent a significant scientific advance: They suggest that plumes can be more idiosyncratic, and can have more elaborate backstories, than traditional models presumed.

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"Over the following decades, geophysicists concluded that plumes are around 200 degrees Celsius hotter than the ambient mantle. When plumes reach the base of tectonic plates, their heat melts their surroundings, making plenty of magma. The plumes also carry mantle material up from Earth’s depths. This material melts at the lower pressures found away from the core, feeding additional magma into the crust. The combined supply of hot magma neatly explains a great number of Earth’s intraplate volcanoes.

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"If the team’s theoretical model is correct, it bolsters two long-held trains of thought. The first, said Goes, is that Earth’s plumes are “not as simple as just making an upwelling in a box of syrup in a laboratory.” Nature is complex, and in oft-surprising ways.

"The second is that these giant blobs have played, and will continue to play, a pivotal role in the planet’s tumultuous history.

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"And yet, for all the chaos they cause, they are a key part of the unceasing cycle of plate tectonics, one that erratically buries and erupts carbon and water and has, miraculously, resulted in a habitable planet with a breathable atmosphere and expansive oceans — a paradise made by abyssal behemoths. “Knowing how a planet manages to do this for billions of years to basically allow human existence is important,” said Rychert."

Comment: The last paragraph is the key point. The fine tuning is not just confined to the universe's attributes but also the active processes on Earth which allow the Earth to host us.