Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Volcanic rocks hold clues to Earth's interior

25.11.2015

The journey for volcanic rocks found on many volcanic islands began deep within the Earth.

Brought to the Earth's surface in eruptions of deep volcanic material, these rocks hold clues as to what is going on deep beneath Earth's surface.


A group of former and current Arizona State University researchers say chemical differences found between rocks samples at volcanic hotspots around the world can be explained by a model of mantle dynamics that involves plumes, upwellings of abnormally hot rock within the Earth's mantle, that originate in the lower mantle and physically interact with chemically distinct piles of material.

Credit: NASA/Jeff Schmaltz/LANCE/EOSDIS MODIS Rapid Response Team/GSFC

Studies of rocks found on certain volcanic islands, known as ocean island basalts, revealed that although these erupted rocks originate from Earth's interior, they are not the same chemically.

According to a group of current and former researchers at Arizona State University, the key to unlocking this complex, geochemical puzzle rests in a model of mantle dynamics consisting of plumes - upwelling's of abnormally hot rock within the Earth's mantle - that originate in the lower mantle and physically interact with chemically distinct piles of material.

... more about:
»Arizona »Earth »helium-4 »volcanism

The team revealed that this theoretical model of material transport can easily produce the chemical variability observed at hotspot volcanoes (such as Hawaii) around the world.

"This model provides a platform for understanding links between the physics and chemistry that formed our modern world as well as habitable planets elsewhere," says Curtis Williams, lead author of the study whose results are published in the Nov. 24 issue of the journal Nature Communications.

Basalts collected from ocean islands such as Hawaii and those collected from mid-ocean ridges (that erupt at spreading centers deep below oceans) may look similar to the naked eye; however, in detail their trace elements and isotopic compositions can be quite distinct. These differences provide valuable insight into the chemical structure and temporal evolution of Earth's interior.

"In particular, it means that the Earth's mantle - the hot rock below Earth's crust but above the planet's iron core - is compositionally heterogeneous. Understanding when and where these heterogeneities are formed and how they are transported through the mantle directly relates to the initial composition of the Earth and how it has evolved to its current, habitable state," said Williams, a postdoc at UC Davis.

While a graduate student in ASU's School of Earth and Space Exploration, Williams and faculty members Allen McNamara and Ed Garnero conceived a study to further understand how chemical complexities that exist deep inside the Earth are transported to the surface and erupt as intraplate volcanism (such as that which formed the Hawaiian islands). Along with fellow graduate student Mingming Li and Professional Research Associate Matthijs van Soest, the researchers depict a model Earth, where in its interior resides distinct reservoirs of mantle material that may have formed during the earliest stages of Earth's evolution.

Employing such reservoirs into their models is supported by geophysical observations of two, continent-sized regions - one below the Pacific Ocean and one below parts of the Atlantic Ocean and Africa - sitting atop the core-mantle boundary.

"In the last several years, we have witnessed a sharpening of the focus knob on seismic imaging of Earth's deep interior.  We have learned that the two large anomalous structures at the base of the mantle behave as if they are compositionally distinct. That is, we are talking about different stuff compared to the surrounding mantle. These represent the largest internal anomalies in Earth of unknown chemistry and origin," said Garnero.

These chemically distinct regions also underlie a majority of hotspot volcanism, via hot mantle plumes from the top of the piles to Earth's surface, suggesting a potential link between these ancient, chemically distinct regions and the chemistry of hotspot volcanism.

To test the validity of their model, Williams and coauthors compare their predictions of the variability of the ratios of helium isotopes (helium-3 and helium-4) in plumes to that observed in ocean island basalts.

3He is a so-called primordial isotope found in the Earth's mantle. It was created before the Earth was formed and is thought to have become entrapped within the Earth during planetary formation. Today, it is not being added to Earth's inventory at a significant rate, unlike 4He, which accumulates over time.

Williams explained: "The ratio of helium-3 to helium-4 in mid-ocean ridge basalts are globally characterized by a narrow range of small values and are thought to sample a relatively homogenous upper mantle. On the other hand, ocean island basalts display a much wider range, from small to very large, providing evidence that they are derived from different source regions and are thought to sample the lower mantle either partially or in its entirety."

The variability of 3He to 4He in ocean island basalts is not only observed between different hotspots, but temporally within the different-aged lavas of a single hotspot track.

"The reservoirs and dynamics associated with this variability had remained unclear and was the primary motivation behind the study presented here," said Williams.

###

Williams continues to combine noble gas measurements with dynamic models of Earth evolution working with Sujoy Mukhopadhyay (Professor and Director of the Noble Gas Laboratory) at the University of California at Davis.

The School of Earth and Space Exploration is a unit of ASU's College of Liberal Arts and Sciences.

Media Contact

Karin Valentine
karin.valentine@asu.edu
480-695-7340

 @ASU

http://asunews.asu.edu/ 

Karin Valentine | EurekAlert!

Further reports about: Arizona Earth helium-4 volcanism

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>