Science Current Events | Science News | Brightsurf.com
 

Earth's Moving Crust May Occasionally Stop

January 10, 2008

The motion, formation, and recycling of Earth's crust-commonly known as plate tectonics-have long been thought to be continuous processes. But new research by geophysicists suggests that plate tectonic motions have occasionally stopped in Earth's geologic history, and may do so again. The findings could reshape our understanding of the history and evolution of the Earth's crust and continents.

Synthesizing a wide range of observations and constructing a new theoretical model, researchers Paul Silver of the Carnegie Institution of Washington and Mark Behn of the Woods Hole Oceanographic Institution (WHOI) have found evidence that the process of subduction has effectively stopped at least once in Earth's past. Subduction occurs where two pieces of Earth's crust (tectonic plates) collide, and one dives beneath the other back into the interior of the planet.

Most of the major geologic processes on Earth-the formation of continents, the birth of volcanic island arcs, the opening and closing of ocean basins-are driven by tectonic plate motions and intimately linked to subduction and to seafloor spreading. If those processes were shut down, there would likely be a global decrease in earthquakes and volcanism.

Today, the vast majority of subduction occurs around the edges of the Pacific Ocean, which is slowly closing as the Atlantic Ocean opens. In roughly 350 million years, researchers estimate that the Pacific basin will be effectively closed and a new supercontinent will be formed.

Closure of the Pacific basin could shut down most of the Earth's capacity for subduction, unless the process begins somewhere else on the planet. However, there is no evidence that subduction is currently expanding or initiating anywhere else on the planet.

Though such a shutdown defies the prevailing wisdom about plate tectonics, Silver and Behn read the geologic evidence to suggest that just such a dramatic decrease in subduction happened about one billion years ago, after the formation of the supercontinent Rodinia.

Their findings-captured in a paper entitled "Intermittent Plate Tectonics?"-were published in the January 4 issue of the journal Science.

"The scientific community has typically assumed that plate tectonics is an active and continuous process, that new crust is constantly being formed while old crust is recycled," said Behn, an assistant scientist in the WHOI Department of Geology and Geophysics. "But the evidence suggests that plate tectonics may not be continuous. Plates may move actively at times, then stop or slow down, and then start up again."

Behn and Silver started their investigation by considering how the Earth releases heat from its interior over time, also known as "thermal evolution." If you take the rate at which the Earth is releasing heat from its interior today and project that rate backwards in time, you arrive at impossibly high and unsustainable numbers for the heat and energy contained in the early Earth. Specifically, if the planet has been releasing heat at the modern rate for all of its history, then it would have been covered with a magma ocean as recently as one billion years ago.

But we know this is not true, Behn said, because there is geological evidence for past continents and supercontinents, not to mention rocks (ophiolites) on the edges of old plate boundaries that are more than one billion years old.

The Earth cools more quickly during periods of rapid plate motions, as warm material is pulled upward from deep in the Earth's interior and cools beneath spreading ridges.

"If you stir a cup of coffee, it cools faster," said Behn. "That's why people blow on their coffee to get the surface moving."

"It is a similar process within the Earth," Behn added. "If the tectonic plates are moving, the Earth releases more heat and cools down faster. If you don't have those cracked and moving plates, then heat has to get out by diffusing through the solid rock, which is much slower."

Periods of slow or no subduction would help explain how the Earth still has so much heat to release today, since some of it would have been capped beneath the crust.

Silver and Behn conclude their paper by suggesting that there is a cycle to plate tectonics, with periods when the shifting and sliding of the crust is more active and times when it is less so. Rather than being continuous, plate tectonics may work intermittently through Earth history, turning on and off as the planet remakes itself.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment.

The Carnegie Institution of Washington has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.

Woods Hole Oceanographic Institution


Related Subduction Current Events and Subduction News Articles


New research estimates probability of mega-earthquake in the Aleutians
A team of researchers from the University of Hawai'i at Mānoa (UHM) published a study this week that estimated the probability of a Magnitude 9+ earthquake in the Aleutian Islands--an event with sufficient power to create a mega-tsunami especially threatening to Hawai'i.

Microbes make tubular microtunnels on earth and perhaps on mars
Tubular microtunnels believed to be the trace fossils formed by microbes inhabiting volcanic rock interiors have only been reported in oceanic and subglacial settings.

Experimental study of the electrical conductivity of hydrous minerals under high P-T conditions
A newly published paper "Experimental study of the electrical conductivity of hydrous minerals in the crust and the mantle under high pressure and high temperature" on SCIENCE CHINA Earth Sciences overviews the studies of electrical conductivity measurement of hydrous minerals in recent years.

Revealing potential tsunami inundation on California coast
sunami hazard maps exist for California coastlines, but recent geological studies indicated some faults may be capable of unleashing more powerful quakes than previously thought.

Diamonds used to 'probe' ancient Earth
Diamonds dug up from ancient rock formations in the Johannesburg area, between 1890 and 1930 - before the industrialisation of gold mining - have revealed secrets of how the Earth worked more than 3.5 billion years ago.

Reptile fossils offer clues about elevation history of Andes Mountains
On an arid plateau in the Andes Mountains of southern Bolivia, a Case Western Reserve University researcher flagged what turned out to be the fossil remains of a tortoise nearly five feet long -- a find indicating this highland was likely less than a kilometer above sea level 13 million years ago.

Age of blueschist is not an indicator of the date of emergence of plate tectonics
One of the big mysteries in the history of the Earth is the emergence of plate tectonics. When exactly did the processes of plate tectonics begin that today involve the subduction of oceanic plates? Scientific opinion varies widely as to this.

Minerals from Papua New Guinea hold secret for recycling of noble gases
With every breath we take, we inhale not only oxygen, but also a mix of gases. This mixture includes carbon dioxide and nitrogen, but also a gas called argon. Neon, the gas that illuminates the signs of all-night diners, is also in the mix.

How the Earth's Pacific plates collapsed
Scientists drilling into the ocean floor have for the first time found out what happens when one tectonic plate first gets pushed under another.

When did the Andes mountains form?
The Andes have been a mountain chain for much longer than previously thought, new research from the University of Bristol, UK suggests.
More Subduction Current Events and Subduction News Articles

Streetcar to Subduction and Other Plate Tectonic Trips by Public Transport in San Francisco (Special Publications)

Streetcar to Subduction and Other Plate Tectonic Trips by Public Transport in San Francisco (Special Publications)
by Clyde Wahrhaftig (Author)


Published by the American Geophysical Union as part of the Special Publications Series. It is hard to be unaware of the earth in San Francisco. Built on rocky hills, the city is surrounded on three sides by bay and ocean that can be seen from nearly everywhere within it. Precipitous cliffs face the city from across the Golden Gate, and the skyline to the north, east, and south is dominated by mountains. Occasional tremors from the San Andreas and related faults nearby remind us that the earth here is active. Until recently the rocks so abundantly exposed in San Francisco baffled geologists. Jumbled together without apparent order and lacking visible fossils, they defied explanation. The theory of plate tectonics has changed all that. We now have an explanation for the origin of the rocks...

The Big One: What To Do Before, During, After the Imminent Cascadia Subduction Zone Earthquake

The Big One: What To Do Before, During, After the Imminent Cascadia Subduction Zone Earthquake
by Vernelle J. Judy (Author)


This manual is the guidance needed to prepare for the largest natural disaster to hit the West Coast of America in more than 300 years: The Cascadia Subduction Zone earthquake. On these pages you will find specific, practical and easy steps to prepare your home, your family, yourself to remain safe, stay healthy and survive well.

Subduction Zone

Subduction Zone
by Colin Setterfield


The Pacific Northwest region of the North American continent is a prolific seismic area. The Cascadia Subduction Zone stretches from Vancouver Island down to Cape Mendocino, California, separating the Juan de Fuca and North American plates. It holds a great potential for spawning the ‘Big One’, a megathrust earthquake that could have devastating consequences for the region.
Paul Brinkworth, a seismologist with the Geoscience Center in Victoria, a city of Vancouver Island and capital of British Columbia, has a dilemma. Due to recent seismic tremors, emanating from the neighboring subduction zone, he is convinced that a megathrust quake is about to take place. Does he go public with a theory and risk his career or does he remain silent, allowing nature to take its course? The...

Subduction

Subduction
by Todd Shimoda (Author), L.J.C. Shimoda (Illustrator)


"Shimoda is a consummate storyteller" — Booklist

"Shimoda skillfully weaves (these) tales into the narrative, revealing how past events "continue to affect the island, like aftershocks." Earthquakes are an apt metaphor for the social disruptions on the island, and Shimoda links modern earthquake science, ancient Japanese myths on the origin of earthquakes, and an unforgettable cast of characters to create a suspenseful, richly illustrated novel." — Publishers Weekly

"Husband and wife team Todd and Linda Shimoda’s skills blend seamlessly together to make Subduction a hauntingly beautiful and highly unique novel. The author’s prose and illustrator’s talent give the book a tone and quality that is both rare and memorable." — ForeWord

"Subduction heaves with a...

The Sierra Nevada Foothills:: Anatomy of a Subduction Zone Complex

The Sierra Nevada Foothills:: Anatomy of a Subduction Zone Complex
by Mr. William A. Szary (Author)


The contents presents an overview of Sierra Nevada Mountain regional geologic history; regional geologic setting of the Sierra Foothills Terrane; theoretical overview of subduction zone tectonics; a summary of Foothills Terrane field evidence obtained from the Hogan Reservoir recreational area including geological analyses of lilthology, presentation of a preliminary geologic map and cross section including plate tectonic models offering discussions of ophiolite tectonism and accretion models for the Foothills. Intended audiences are undergraduate and graduate level geology students.

Subduction Zone

Subduction Zone


Set it the near future, this book describes what might happen to an isolated section of the Oregon coast before, during, and after a large earthquake and Tsunami along the Cascadia Subduction zone. This story is speculative fiction and the events described within may never be a reality. The regional and National implications of this earthquake as depicted in this story go far beyond the small area covered here. This may not be a worst case scenario.

Subduction Dynamics: From Mantle Flow to Mega Disasters (Geophysical Monograph Series)

Subduction Dynamics: From Mantle Flow to Mega Disasters (Geophysical Monograph Series)
by American Geophysical Union


Subduction dynamics has been actively studied through seismology, mineral physics, and laboratory and numerical experiments. Understanding the dynamics of the subducting slab is critical to a better understanding of the primary societally relevant natural hazards emerging from our planetary interior, the megathrust earthquakes and consequent tsunamis. Subduction Dynamics is the result of a meeting that was held between August 19 and 22, 2012 on Jeju island, South Korea, where about fifty researchers from East Asia, North America and Europe met. Chapters treat diverse topics ranging from the response of the ionosphere to earthquake and tsunamis, to the origin of mid-continental volcanism thousands kilometers distant from the subduction zone, from the mysterious deep earthquakes triggered...

Subduction Zone Metamorphism (Benchmark papers in geology ; v. 19)

Subduction Zone Metamorphism (Benchmark papers in geology ; v. 19)
by W. G. Ernst (Author)


Book by Ernst, W. G.

Subduction Top to Bottom (Geophysical Monograph Series)

Subduction Top to Bottom (Geophysical Monograph Series)
by Gray E. Bebout (Editor), David W. Scholl (Editor), Stephen H. Kirby (Editor), John P. Platt (Editor)


Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 96.

Perhaps no other plate tectonic setting has attracted as diverse multidisciplinary attention as convergent margins. This has in part been spurred by the extremely tangible hazards imposed by subduction, particularly in the form of earthquakes and tsunamis and arc volcanism. Concern regarding these hazards is heightened by the tendency of convergent margins to be heavily populated coastal regions. There has also been great interest in convergent margin settings for their potential (and demonstrated capability) of producing economically important oil and gas reservoirs and ore deposits. The cycling of materials (e.g., CO2 at convergent margins has been recognized as potentially...

Deep-Sea Turbidites as Guides to Holocene Earthquake History at the Cascadia Subduction Zone-Alternative Views for a Seismic-Hazard Workshop: Open-File Report 2012-1043 - Scholar's Choice Edition

Deep-Sea Turbidites as Guides to Holocene Earthquake History at the Cascadia Subduction Zone-Alternative Views for a Seismic-Hazard Workshop: Open-File Report 2012-1043 - Scholar's Choice Edition
by Brian F. Atwater (Author), Gary B. Griggs (Author), United U.S. Department of the Interior (Creator)



This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work.

This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.

As a reproduction of a historical artifact, this work may contain missing or...

© 2017 BrightSurf.com