Why two underwater volcano chains run side by side off Australia
A mantle plume bent around dense seafloor creates two parallel underwater volcano chains off eastern Australia.
Lord Howe Island sits about 600 kilometres off the NSW coast. It is the weathered remains of a volcano.
Roughly 650 kilometres west runs an almost identical chain of submerged volcanoes called the Tasmantid seamounts. Scientists puzzled over why two separate chains would form side by side in the middle of a tectonic plate.
A new study published in Gondwana Research found both chains trace back to a single mantle plume rising from Earth's deep interior. The plume hits a slab of old ocean floor sinking down from the surface.
It cannot break through. Instead it splits.
It flows around gaps on either side to reach the surface as two separate volcanic chains. The theory is backed by three lines of evidence.
Computer models reproduce the exact spacing. Mapping shows where ancient seafloor sank.
Chemical fingerprints in lava from both chains match.
- 600 kilometres
- Lord Howe distance from NSW coast
- 650 kilometres
- Tasmantid seamounts distance west
- 500 kilometres
- Depth where mantle stiffens
- 40 million years
- Plate drift duration
Why it mattersThis explains how Australia's underwater geology took shape and shows how Earth's deep interior can create paired features in unexpected ways.
