[Rockhounds] A Massive Subterranean ‘Tree’ Is Moving Magma to Earth’s Surface

[Kreigh Tomaszewski]

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
<https://www.quantamagazine.org/the-new-historian-of-the-smash-that-made-the-himalayas-20210414/>
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
<https://www.nytimes.com/2019/12/18/science/volcano-3d-reunion-island.html> or
“peak of the furnace,” is one of the most hyperactive volcanoes on the
planet.

But the plume’s modern-day punch is nothing compared to its past.

Around 65 million years ago, when the plume was under what is now India, a
series of lava floods named the Deccan Traps smothered 1.5 million square
kilometers of land <https://www.pnas.org/content/110/7/2435> — enough to
bury Texas, California and Montana — in a mere 700,000 years, a geologic
heartbeat. A giant asteroid strike
<https://www.quantamagazine.org/a-rapid-end-strikes-the-dinosaur-extinction-debate-20200325/>
would
be the coup de grâce for the dinosaurs, but the Deccan Traps have long
muddled the picture of the climatic conditions the dinosaurs
<https://www.science.org/news/2019/02/did-volcanic-eruptions-help-kill-dinosaurs>
had
to contend with
<https://www.nationalgeographic.com/science/article/volcanoes-helped-life-bounce-back-afterdinosaur-killing-asteroid>
.

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* <https://www.nature.com/articles/s41561-021-00762-9> 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
<https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JB019929>, 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.

https://www.quantamagazine.org/a-massive-subterranean-tree-is-moving-magma-to-earths-surface-20210915/