Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Looking deep in Earth, researchers see upwellings that could be root of volcanic islands

02.06.2005


Deep within Earth, researchers are finding hints of exotic materials and behaviors unrivaled anywhere else on the planet. Now a team of researchers is making connections between the dynamic activities deep inside Earth and geologic features at its surface.



The researchers, which include two seismologists from Arizona State University, have detected a relatively small and isolated patch of exotic material, called an ultra low velocity zone (ULVZ), that may in fact be a "root" for mantle plumes that connect Earth’s hot and tumultuous core and its surface. Specifically, the researchers have found a spot at Earth’s core-mantle boundary, 3,000 km (1,900 miles) deep inside Earth that could play a pivotal role in the formation and existence of volcanic islands and island chains like Hawaii.

"This is a small and very isolated region of possibly molten mantle material that is sitting at Earth’s core mantle boundary," said Sebastian Rost, an ASU faculty research associate. Rost and fellow researchers -- seismologist Edward Garnero of ASU, Quentin Williams of the University of California-Santa Cruz, and Michael Manga of University of California Berkeley -- recently detected an ultra low velocity zone, a region where seismic waves propagate extremely slowly, under the southwest Pacific Ocean. They report their findings in the June 2 issue of Nature.


In "Seismological Constraints on a Possible Plume Root at the Core Mantle Boundary," the researchers describe a small and highly active region of inner Earth that is peculiar on several levels.

"We have identified a little bubble of partially molten rock at the bottom of Earth’s solid mantle, which we relate to a plume of hot material," said Garnero. "Such plumes may give rise to surface volcanoes, like Hawaii or Iceland. Now we might know what feeds such plumes."

The size of the "bubble" is about 50 km (30 miles) across, smaller than the metropolitan Phoenix area, and only about 8 km (5 miles) deep. The density of the material in the bubble is significantly higher than the density of the area that surrounds it.

"It might be that every plume might have one of these at its source," Rost explained. "Geodynamic modeling shows that these dense blobs of material don’t move around a lot in the mantle. So while the mantle is convecting, and material is moving around, these dense piles of material do not get pushed around that much. They may actually give a stable root to long lived mantle plumes and that might be the reason why we have island chains like Hawaii."

The team studied a portion of Earth’s core-mantle boundary layer (CMB) -- where Earth’s molten iron core meets the silicate mantle rock, east of Australia and slightly to the south of New Caledonia. Traditional thought of this area inside Earth had been of a fairly well defined and predictable region. Researchers now are finding that the core mantle boundary is a complex and dynamic area that churns and chugs as the liquid iron core roils at the bottom of the rock-like mantle, Garnero said.

Within this environment lies the peculiar bubble of ULVZ material.

"It is very isolated, very dense and it is partially molten," said Garnero. "There in lies the enigma."

The existence of dense and partially molten material poses a dynamical problem for keeping the material in a neat pile. It would be expected that the material spread out along the CMB, something that is not observed in the seismic data, Rost said.

The researchers propose a model that resembles a sponge, where the molten material fills the holes of the sponge and is kept in place by surrounding crystals of the Earth’s mantle. The material’s high density might also indicate the existence of core material in this region, although leaking of the molten iron of the core in the mantle is not expected from current geophysical Earth models. The recent finding might change this view by allowing material to flow through the core-mantle boundary.

The new findings were made possible by clever use of a seismic array, an instrument consisting of several distributed seismic monitoring stations in Australia. The array allowed high enough resolution to detect the relatively small bubble using seismic waves that are reflected from the CMB. The monitoring stations were first installed in the 1960s to detect nuclear detonations and can be used like a sensitive antenna to look deep inside Earth.

In this study, the team sampled a 100 x 250 km region using newly assembled data sets of 305 Tonga-Fiji earthquakes recorded at the small-scale (20 km diameter) Warramunga seismic array. The team basically used the array data as a way to perform ultrasound scans of Earth’s interior.

Rost said one of the tasks of the team in follow up studies is to determine "if this is just a tiny bubble or a paradigm for what is down there."

The work, according to Garnero, is helping seismologists see the inner workings of Earth in a new light and will help fill out their view of the relationship between Earth’s interior and its surface.

"Other researchers have suggested that by using seismic tomography they can see where mantle plumes appear to be connected from Earth’s surface down to the core mantle boundary," Garnero said. "This work enables us to go to those areas, and study them in great detail, to see if the hot spots at the surface are connected at the core mantle boundary. It gives us a chance to connect the dots between the surface and the core."

Skip Derra | EurekAlert!
Further information:
http://www.asu.edu

More articles from Earth Sciences:

nachricht NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center

nachricht The melting ice makes the sea around Greenland less saline
16.10.2017 | Aarhus University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Ocean atmosphere rife with microbes

17.10.2017 | Life Sciences

Neutrons observe vitamin B6-dependent enzyme activity useful for drug development

17.10.2017 | Life Sciences

NASA finds newly formed tropical storm lan over open waters

17.10.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>