A study published in Gondwana Research reveals that the Lord Howe and Tasmantid seamount chains were formed by a single mantle plume split by an obstacle.
Key facts
- •Lord Howe Island is the only part of the Lord Howe seamount chain currently above sea level.
- •The Tasmantid and Lord Howe chains have tracked the northward drift of the Australian plate for 40 million years.
- •Computer models indicate that plumes within 1,000 kilometers of each other typically merge, making the persistence of these two separate chains unusual.
- •Lead isotopes in the lava from both chains share a unique 'fingerprint' that suggests a common deep-mantle origin.
- •The study suggests the Tasmantid chain will likely become the primary conduit as the Lord Howe chain stops growing.
New research published in Gondwana Research explains the origin of the Lord Howe and Tasmantid seamount chains off the coast of Australia. While most volcanic chains are formed by individual mantle plumes, scientists found that these two side-by-side chains were created by a single plume of hot rock rising from deep within the Earth. The plume was obstructed by a slab of old ocean floor, forcing it to split into two branches that reached the surface.
By the numbers
Mechanism of the Plume Split
The study suggests that a single plume rising from near the Earth's core encountered a slab of old ocean floor that had sunk at a subduction zone and stalled approximately 500 kilometers deep. Unable to pass through the stiffer mantle material, the plume diverted around the slab, escaping through gaps on either side. This process created two distinct branches that formed the nearly identical, parallel volcanic chains.
Evidence and Future Predictions
Researchers supported this theory using three lines of evidence: a computer simulation of Earth's interior, a reconstruction of plate motion over the last 200 million years, and chemical analysis of lead isotopes. The simulation showed that as the obstructing slab sinks deeper, one branch of the plume eventually becomes dominant while the other shuts down. Observations of eruption volumes suggest this transition is already occurring, with the Lord Howe chain showing a decline over the past 23 million years while the Tasmantid chain remains active.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by Phys.org.
