Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Simulations and Ancient Magnetism Suggest Mantle Plumes May Bend Deep Beneath Earth's Crust

Computer simulations, paleomagnetism and plate motion histories described in today's issue of Science reveal how hotspots, centers of erupting magma that sit atop columns of hot mantle that were once thought to remain firmly fixed in place, in fact move beneath Earth's crust.

Scientists believe mantle plumes are responsible for some of the Earth's most dramatic geological features, such as the Hawaiian islands and Yellowstone National Park. Some plumes may have shallow sources, but a few, such as the one beneath Hawaii, appear to be rooted in the deepest mantle, near Earth's core.

Such deep plumes have long been thought to be so immobile that the motions of continental and oceanic plates were measured against them, but University of Rochester geophysicist John Tarduno and his colleagues at Ludwig-Maximilians, Münster, and Stanford universities have combined magnetic evidence from the Pacific sea floor with computer modeling to show how the plume beneath Hawaii likely bent—its root barely moving while its top moved nearly 1,000 miles across the underside of the Pacific Ocean.

"In 2003, we showed that the hotspot—the plume—that created the Hawaiian chain of islands must have moved. We suggested that mantle motion was involved, but the cause of the change in motion remained a mystery," says Tarduno.

Tarduno cites five possible mechanisms in Science, but one in particular, he says, stands out as a likely explanation for the way the Hawaiian chain of islands and seamounts formed. "We know from theory and from models, including work by Ulrich Hansen and Norm Sleep, that a plume can move slightly near its base, potentially contributing to motion of the Hawaiian hotspot and hotspots elsewhere," says Tarduno. "But a key observation came from a numerical simulation resulting from Hans-Peter Bunge's models, which show how the upper end of the plume, starting at 1500 depth, can drift like a candle flame drawn toward a draft."

The draft in this case, he says, is an ancient oceanic ridge in the Pacific where the seafloor spreads, allowing magma to bubble up through the ocean crust. The ancient ridge is now lost to subduction, but its past presence is recorded by a few magnetic lineations in oceanic crust south of the Bering Sea. The ridge was active around 80 million years ago but extinguished completely by 47 million years ago. Those dates correspond very closely with the motion history Tarduno detected in the Hawaiian hotspot.

In 2001, Tarduno and an international team spent two months aboard the ocean drilling ship JOIDES Resolution, retrieving samples of rock from the Emperor-Hawaiian seamount chain miles beneath the sea's surface. The team started at the northern end of the chain, near Japan, braving cold, foggy days and dodging the occasional typhoon to pull up several long cores of rock as they worked their way south. Using a highly sensitive magnetic device called a SQUID (Superconducting Quantum Interference Device), Tarduno's team discovered that the magnetism of the cores did not fit with the conventional wisdom of fixed hotspots.

The magnetization of the lavas recovered from the northern end of the Emperor-Hawaiian chain suggested these rocks were formed much farther north than the current hotspot, which is forming Hawaii today. As magma forms, magnetite, a magnetically sensitive mineral, records the Earth's magnetic field just like a compass. As the magma cools and becomes solid rock, the "compass" orientation is locked in place, preserving a precise record of the latitude of origin.

If the Hawaiian hot spot had always been fixed at its current location of 19 degrees north, then all the rocks of the entire chain should have formed and cooled there, preserving the magnetic signature of 19 degrees even as the Pacific plate dragged the new stones north-westward. Tarduno's team, however, found that the more northern their samples, the higher the samples' latitude. The northern-most lavas they recovered were formed at over 30 degrees north about 80 million years ago, nearly a thousand miles from where the hot spot currently lies.

"The only way to account for these findings is if the hotspot itself was moving south," says Tarduno. His magnetic readings leveled off at a latitude of nearly 19 degrees, suggesting that the magma plume ceased moving in the area it resides in today.

In addition to the "draft" created by the upwelling of magma into the paleo-ridge, Tarduno says that theory and computer simulations suggest that the most a plume can bend under such conditions would result in about 1,000 miles of movement across the crust—matching what he sees as the distance between the start and stop points of the Hawaiian hotspot. He points out that the bending of a mantle plume helps reconcile the evidence of mobile hotspots on the Earth's crust with the theories that suggest plumes originate in the deepest mantle where high viscosity limits rapid motion. He points out that the plume-ridge capture mechanism may also help explain seemingly anomalous volcanic features on the seafloor, and help geoscientists to use ancient volcanic tracks to understand the past flow of Earth mantle.

This research was funded by the National Science Foundation.

About the University of Rochester
The University of Rochester ( is one of the nation's leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College of Arts, Sciences, and Engineering is complemented by the Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, Schools of Medicine and Nursing, and the Memorial Art Gallery.

Jonathan Sherwood | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>