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Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck

The eastern part of Juan Fernandez ridge, located on the Nazca tectonic plate, opposite to the city of Valparaiso, has recently been mapped and sampled during an expedition under the patronage of SERNAGEOMIN, with funding provided by CONICYT between November 20 and December 13, 2015.

 Location of the Juan Fernandez ridge, south of the Nazca plate - Doc. Andean geology / Scielo.cl

Location of the Juan Fernandez ridge, south of the Nazca plate - Doc. Andean geology / Scielo.cl

The research focused on underwater volcanoes, Monte O'Higgins and O'Higgins Guyot.

The Monte O'Higgins base to almost 3,000 meters below sea level, and its highest point is at 360 meters depth. It features volcanic forms with a relatively new aspect, which leaves suggest a subsequent volcanic activity to the main construction phase ... in association with the hypothesis of a stationary mantle plume above which the Nazca plate moving move eastward at an average speed of 6 to 7 cm per year. This is supported by the age of Monte O'Higgins, more aged than Robinson Crusoe Island, older that Alexander Selkirk Island.

Location of the submarines volcanoes recently visited - Doc. SERNAGEOMIN

Location of the submarines volcanoes recently visited - Doc. SERNAGEOMIN

  Bathymetry of Guyot O'Higgins, left and Monte O'Higgins, right - Doc.Sernageomin

Bathymetry of Guyot O'Higgins, left and Monte O'Higgins, right - Doc.Sernageomin

Near the Monte O'Higgins, the Guyot of the same name, is a distinct volcanic center, apparently contemporary but with a different evolution. A guyot is a flat-roofed building, interpreted as a form of typical marine erosion of a submarine volcano growing up to reach, or even exceed, the sea level.

As these volcanic structures belong to a long chain of several kilometers in length, called Juan Fernandez ridge, whose islands are younger going towards the west, the most recent episodes of volcanism at the old structures ask another explanation that association with a fixed mantle plume.

Samples of volcanic rock extracted on the summit of Monte O'Higgins will help to understand the origin and evolution of this submarine volcanoes and the Nazca plate islands.

Rock samples collected on the summit of Monte O'Higgins - photo SERNAGEOMIN
Rock samples collected on the summit of Monte O'Higgins - photo SERNAGEOMIN

Rock samples collected on the summit of Monte O'Higgins - photo SERNAGEOMIN

The results of the study and interpretation of geologists / volcanologists is eagerly awaited.

 

Sources :

- Sernageomin busca desentrañar secretos de volcanes submarinos de la placa de Nazca - link

- A plate model for Jurassic to recent intraplate volcanism in the Pacific Ocean basin - Alan D.Smith & al. - link

- Plate tectonics and the origin of the Juan Fernández Ridge: analysis of bathymetry and magnetic - link

 

To follow : the islands of the Juan Fernandez ridge.

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