Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Towards a better understanding of hot spot volcanism

01.02.2008
Most of the Earth’s listed active volcanoes are located at the borders between two tectonic plates, where upsurge of magma from the mantle is facilitated.

When these magmatic uprisings occur at a subduction zone, where one tectonic plate plunges under another, they give rise to volcanic massifs such as the Andes cordillera. Other volcanic chains are formed along oceanic ridges, submarine regions of ocean-floor extension.

However, some volcanoes are governed by a completely different mechanism: intraplate volcanism. As their name suggests, these volcanic constructions appear in the very centre of tectonic plates. Scientists now know that some of them, such as the Hawaii-Emperor archipelago or Reunion Island, result from magmatic upsurges generated at the boundary between the Earth’s core and mantle situated 2 900 km deep. Others, such as those of the central Pacific, display different characteristics. They are anomalous, in their simultaneously high number, unusually high concentration and short life-span and prompt scientists to look for hypotheses other than a deep-mantle plume to explain the causes of intraplate volcanism.

Researchers from the IRD and the University of Chile focused on a group of islands and archipelagos in the central Pacific Ocean (Samoa, Cook, Rurutu, Austral, Tahiti, Marquis, Pitcairn), each listed as resulting from hot-spot activity. These scientists aimed to find out if movements of the Pacific plate where these seven hot spots are located could be involved in their formation. They used numerical mechanical simulation models of the effect of the westward displacement of the Pacific plate on internal deformations during the past 10 million years. This model incorporates a differential tension regime which acts on the Pacific plate, the northern part moving with greater velocity than the southern part, which undergoes a kind of braking effect exerted by the bloc of the Australian plate (see the 3D diagram). The model shows the region to be the site of an East-West shear band which superimposes on the geographical zone where the seven hot spots investigated in the study are grouped.

Another model was subsequently built up that takes into account the cooling of the tectonic plate with increased distance from the oceanic ridge that generated it. This second model also brought evidence of a shearing band, but this zone appeared more diffuse towards the east than in the first simulation. Moreover, this more diffuse shearing zone was superimposed on an anomaly of the Earth’s surface classically attributed to an upswelling of the oceanic lithosphere. This anomaly, caused by the upward pressure of the underlying mantle, appears along with an unexplained variation in the ocean floor. This second numerical model therefore indirectly allows the geographical location of the hot spots on an East/West line of weakened lithosphere to be matched with a variation in its thickness.

The existence of a hot spot is usually considered to be linked to the occurrence of a mantle plume, a sort of giant bubble of magma generated by the thermal convection currents circulating in the mantle. This magmatic bubble exerts an upward pressure pushing on the base of the oceanic lithosphere. Then, once broken through, the latter allows the magma to erupt through the Earth’s crust. Although this process effectively explains the origin of deep-seated hot spots, it does not provide satisfactory explanations for other forms of intraplate volcanism such as that which occurs in the African rift or certain more recent hot spots situated in the central part of the Pacific Ocean.

The results of this study suggest an alternative scenario which envisages the involvement of shearing strain within the tectonic plates during the formation of a certain type of hot spot volcanism. In the central Pacific, such deformation could therefore be a step towards the break-up of the Earth’s largest tectonic plate into two in a timescale of around ten million years. Furthermore, if the movements of a tectonic plate were effectively to play a role in the formation of a hot spot, that would signify that such spots would not be so static as hitherto believed. The characteristic time-scale for heat-transfer processes in the mantle is in the order of more than 100 million years whereas the movement of the plates occurs over shorter geological time-scales of around ten million years. Certain hot spots could thus change and develop in space relatively rapidly, in line with displacements undergone by the tectonic plates.

Grégory Fléchet - DIC

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/us/actualites/fiches/2007/fas285.pdf

More articles from Earth Sciences:

nachricht Impacts of mass coral die-off on Indian Ocean reefs revealed
21.02.2017 | University of Exeter

nachricht How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Microhotplates for a smart gas sensor

22.02.2017 | Power and Electrical Engineering

Scientists unlock ability to generate new sensory hair cells

22.02.2017 | Life Sciences

Prediction: More gas-giants will be found orbiting Sun-like stars

22.02.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>