Monday, 12 December 2011

Subduction of undersea mountains

Amazing new images from the depths of the Pacific Ocean reveal one of Earth's most violent processes: the destruction of massive underwater mountains. They expose how tectonic action is dragging giant volcanoes into the ocean trench. The volcanoes are strung across several thousand kilometres of ocean floor and are moving westward on the Pacific tectonic plate at up to 6cm per year.
The extraordinary scene was captured along the Tonga Trench during a research expedition last summer. The trench is a highly active fault line running north from New Zealand towards Tonga and Samoa.

1 comment:

Richard said...

Re the BBC seamount video, the seamount nearest the Tonga Trench is called Osborne Seamount, according to Google Earth's bathymetry. The seamounts' flat tops due to having been peneplaned when they were at sea level but now in a descending sequence, have been mapped well,
Its worth 'flying' along the Tonga trench in GE, and noting some interesting linear features nearby. One straight line on the resisting plate edge looks like it has volcanics extruding along it. In the trench's subducting side, many parallel fractures may be extensional faulting where the ocean floor is flexing to go downwards. Another thing is there are thin strips of much finer mapping embedded in more blurred areas.
The seamounts might get welded on to the resisting plate to form an interesting terrane. or, they might partly get subducted so would spend c.200 million years doing a circuit within the mantle convection system along with the host oceanic crust. As they passed the depth of melting, they might add a signature to the type of volcanism found on the island-arc on the resisting plate.