Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Twin volcanic chains above a single hotspot with distinct roots

28.07.2015

Scientists from Kiel find explanation for geochemically distinct parallel tracks of volcanoes formed by the same volcanic hotspot

Located in the South Atlantic, thousands of kilometers away from the nearest populated country, Tristan da Cunha is one of the remotest inhabited islands on earth. Together with the uninhabited neighboring island of Gough about 400 kilometers away, it is part of the British Overseas Territories. Both islands are active volcanoes, derived from the same volcanic hotspot.


Die Lage der Vulkaninseln Tristan da Cunha und Gough im Südatlantik. Image reproduced from the GEBCO world map 2014, www.gebco.net

A team of marine scientists and volcanologists from the GEOMAR Helmholtz Centre for Ocean Research Kiel, from the University of Kiel and the University of London discovered that about 70 million years ago, the composition of the material from the Tristan-Gough hotspot deposited on the seafloor changed.

In the international scientific journal Nature Communications, the team provides an explanation for this compositional change that could help explain similar findings in other hotspots worldwide.

Volcanic hotspots can be found in all oceans. "Pipe-like structures, so-called 'Mantle Plumes', transport hot material from the earth's interior to the base of the earth's lithospheric plates. As the mantle material rises beneath the plate, pressure release melting takes places and these melts rise to the surface forming volcanoes on the seafloor," explains Professor Kaj Hoernle from GEOMAR, lead author of the current study.

As the earth's plates move over the hotspots, the volcanoes are moved away from their sources but new volcanoes form above the hotspots. "As a result long chains of extinct volcanoes extend from the active volcano located above the hotspot for over thousands of kilometers in the direction of plate motion", adds the volcanologist.

Unlike most other hotspots, scientists can trace the history of the Tristan-Gough hotspot back to its initiation. Huge outpourings of flood basalts in Etendeka and Brazil at the initiation of the hotspot 132 million years ago most likely contributed to the breaking apart of the Gondwana supercontinent into new continents including Africa and South America.

The rifting apart of Africa and South America has led to the formation of the South Atlantic Ocean basin. As the Atlantic widened, two underwater mountain ranges (the Walvis Ridge and Guyot Province on the African Plate and the Rio Grande Rise on the South American Plate) formed above the hotspot. The active volcanic islands of Tristan da Cuhna and Gough lie at the end of the track on the African Plate.

Several expeditions, including two with the German research vessel SONNE (I) led by Kiel researchers, recovered samples from these submarine mountains. Geochemical analyzes show that the oldest parts of the Walvis Ridge, as well as the intial volcanic outpourings on the continents, have compositions similar to the presently active Gough volcano.

The northwestern part of the Walvis Ridge and Guyot Province younger than 70 million years, however, is divided into two geographically distinct geochemical domains: "The southern part also shows the geochemically enriched Gough signature, while the northern part is geochemically less enriched, similar to the present Tristan da Cunha Volcano", says co-author Joana Rohde.

A very likely explanation is hidden more than 2,500 kilometers deep in the Earth's lower mantle. At the base of the lower mantle beneath southern Africa, seismic surveys have shown a huge lens of material, which has different physical properties than the surrounding mantle material. This lens is called a "Large Low Shear Velocity Province" (LLSVP).

The Tristan-Gough hotspot is located above the margin of this LLSVP. "In its early stages, the plume only appears to have sucked in material from the LLSVP," explains Professor Hoernle, "but over the course of time the LLSVP material at the NW side of the margin was exhausted and material from outside the LLSVP was drawn into the base of the plume."

Since then, the plume has contained two types of compositionally distinct mantle, leading to the formation of parallel but compositionally distinct plume subtracks. "At some point in the future, the plume might be completely cut off from the LLSVP lens, again erupting only one type of composition, but now Tristan rather than Gough type of material." says the volcanologist.

This model is also applicable to other hotspot tracks such as Hawaii. There, too, is evidence that parallel chains of volcanoes emit geochemically distinct material with one or the other composition dominating at different times in the history of the hotspot. A second LLSVP exists beneath the Pacific. "Thanks to the investigations at the Tristan-Gough-Hotspot, we now understand better the mysterious processes taking place in the interior of our planet," says Professor Hoernle.

Jan Steffen | EurekAlert!

Further reports about: Atlantic GEOMAR Ocean Ocean Research Tristan da Cunha hotspots mantle volcanic volcanoes

More articles from Earth Sciences:

nachricht Colorado River's connection with the ocean was a punctuated affair
16.11.2017 | University of Oregon

nachricht Researchers create largest, longest multiphysics earthquake simulation to date
14.11.2017 | Gauss Centre for Supercomputing

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>