Mantle Plumes & Extinctions

AAAS: “Surveys capture the pulsing of mantle plumes — a potential cause of mass extinctions.” New research published in March in Geochemistry, Geophysics, Geosystems, combines seismic imaging and offshore drilling data collected over the past 5 years, perhaps a “smoking gun.” The textbook view of mantle plumes — the long-lived columns of hot rock that rise from deep in the planet — makes them seem like giant blowtorches, steadily searing the crust from below.

“But new studies of the sea floor around Iceland are pointing to a long-debated alternative: that plumes are actually more like blobs rising in a lava lamp, delivering intermittent pulses of heat.” This may help explain an abiding puzzle. “Mantle plumes are thought to have caused several of the planet’s mass extinctions by driving massive volcanic eruptions that belched carbon dioxide and other greenhouse gases, disrupting the climate.” But such eruptions can last for millions of years, whereas the climate shocks tied to extinctions can unfold within thousands, an obvious chronological mismatch.

“Pulsing plumes could drive bursts of volcanic activity better matched to the climatic upheavals.” These massive volcanic bursts fed by mantle plumes, sometimes called “large igneous provinces,” can release climate-altering amounts of carbon quickly enough to trigger extinctions. “A blob of hot mantle hitting an area where the crust is thin — such as the Rockall Trough northwest of the United Kingdom — might do the trick.”

This new picture “could also help explain the Paleocene-Eocene thermal maximum (PETM), an event some 56 million years ago in which global temperatures shot up by at least 5°C over several thousand years.”

“But whether most large igneous provinces dance to the same beat…that’s not easy to resolve.” Sometimes I love to curl up on the couch + read a cozy mystery. But lava lamps — I remember them, I go back that far, but I never succumbed to their allure.