Runion is a French island located in the western Indian Ocean. It looks like a marshmallow hovering over the blowtorch's business end. It is situated above one of Earth's mantle plumps, a tower of superheated rocks that rises from the deep mantle. This flambes the base of tectonic plates that are the jigsaw pieces of the changing face of the planet. The plumes effects can be hard to miss: One of the island's two large volcanoes, Piton de la Fournaise (or Peak of the Furnace), is one of the planet's most active volcanoes.
However, modern-day plumes are nothing in comparison to the past.
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A series of lava floods called the Deccan Traps, which occurred 65 million years ago when the plume was located under what is now India, covered 1.5 million kilometers of land. Enough to submerge Texas, California, and Montana in just 700,000 years. The Deccan Traps would have been the coup de grace for the dinosaurs. However, they have long obscured the reality of the climatic conditions that the dinosaurs had to deal with.
Geophysicists and seismologists began mapping the plume in 2012 by deploying large networks of seismometers to the Indian Ocean seafloor. Nearly a decade later the team has discovered that the mantle is more complex than they expected. In June, Nature Geoscience reported that the plume wasn't just a column. A titanic mantle plume tree emerges from the planet's molten core, and superheated branchlike structures appear to grow diagonally. These branches appear to grow smaller, more vertically-oriented branches as they approach the crust. This is the result of superhot plumes, which are known to be underlie volcanic hot spots on the surface.
This discovery of a massive structure under Runion coincides almost with another discovery that was made in November and found additional structures within the plumes below Africa. These two discoveries are a major scientific breakthrough. They show that plumes can be more complex and can have elaborate backstories than conventional models assumed.