Plate tectonic rifting

(Image credited to NERC/University of Leeds/Barbara Hofmann/Tim Wright)

Where continents rift apart, new crust is formed from upwelling magma. Eventually, a new ocean basin forms. In this web focus we present opinion pieces, along with research and overview articles that explore the dynamic processes that occur during plate rifting. Case studies include both rifting on land, in east Africa and Iceland, and at the mid-ocean ridges that divide the oceanic crust.



What lies beneath p229


The mid-ocean ridges mark the lines along which the Earth is turning itself inside out through the process of plate tectonics. Advances in technology are helping to reveal the intricate details of the magma systems that feed the rifting process.


News and Views

Plate tectonics: Piecing together rifts pp235-236

Douglas R. Toomey


Earth's crust is formed where tectonic plates rift apart and upwelling magma solidifies. Disparate observations from rifts beneath the oceans and on land provide insights into the dynamics of rifting and opportunities for synthesis.



Geophysical constraints on the dynamics of spreading centres from rifting episodes on land pp242-250

Tim J. Wright, Freysteinn Sigmundsson, Carolina Pagli, Manahloh Belachew, Ian J. Hamling, Bryndís Brandsdóttir, Derek Keir, Rikke Pedersen, Atalay Ayele, Cindy Ebinger, Páll Einarsson, Elias Lewi & Eric Calais

Most of Earth's crust is created at mid-ocean ridges that are submerged deep beneath the oceans. Analyses of geodetic and seismic data from rare sections of ridges that are exposed on land in Iceland and the Afar region in east Africa demonstrate that rifting episodes at these sites operate with remarkably similar mechanisms.


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Protracted timescales of lower crustal growth at the fast-spreading East Pacific Rise pp275-278

Matthew Rioux, C. Johan Lissenberg, Noah M. McLean, Samuel A. Bowring, Christopher J. MacLeod, Eric Hellebrand & Nobumichi Shimizu


Rates of crust formation at mid-ocean ridges are expected to vary with rates of plate spreading. U-Pb dating of zircon minerals from the fast-spreading East Pacific Rise reveals protracted formation of gabbroic rocks over timescales comparable with slow-spreading mid-ocean ridges, suggesting similar timescales of magmatic processes at slow- and fast-spreading ridges.

Network of off-axis melt bodies at the East Pacific Rise pp279-283

J. P. Canales, H. Carton, S. M. Carbotte, J. C. Mutter, M. R. Nedimović, M. Xu, O. Aghaei, M. Marjanović & K. Newman


At faster-spreading mid-ocean ridges, the creation of new oceanic crust through magmatism usually occurs within a narrow zone on the ridge axis. Three-dimensional seismic images of the fast-spreading East Pacific Rise reveal a network of magmatic bodies 4–8 km away from the ridge axis that seem to be connected to the axial magma chamber.

Shallow axial magma chamber at the slow-spreading Erta Ale Ridge pp284-288

Carolina Pagli, Tim J. Wright, Cynthia J. Ebinger, Sang-Ho Yun, Johnson R. Cann, Talfan Barnie & Atalay Ayele


Thermal models predict that spreading velocity at mid-ocean rifts should influence the geometry of the underlying magma chamber. InSAR data from the slow-spreading Ethiopian Rift identify a shallow, elongated magma chamber — a feature usually associated with fast-spreading rifts — beneath the Erta Ale segment, implying that spreading velocity may not be so important after all.



Initiation of the western branch of the East African Rift coeval with the eastern branch p289-294

E. M. Roberts, N. J. Stevens, P. M. O'Connor, P. H. G. M. Dirks, M. D. Gottfried, W. C. Clyde, R. A. Armstrong, A. I. S. Kemp & S. Hemming


Rifting of the eastern part of the East African Rift System was thought to have begun several million years before its western counterpart. Reconstructions of drainage development, combined with dating of rift-related volcanic activity, suggest that rifting in the western branch may instead have begun at the same time as in the eastern branch.


From the archives


News and Views

Mid-ocean ridges: Widening the goal-posts

John Maclennan


Oceanic crust forms through the addition of volcanic rock to mid-ocean ridges. Widely dispersed, young lavas observed at an ultraslow-spreading ridge provide impetus for the redevelopment of models of oceanic magmatism.

Volcanology: Carbon below the sea floor

David Goldberg


Magma from the mantle meets the ocean at seafloor spreading centres. At young rifts, basalt sills may heat overlying sediments and induce natural carbon release; basalt flows elsewhere may offer secure reservoirs for sequestration of anthropogenic carbon.


In the press

Volcano mix-up

Axel Bojanowski


Deep sea vent diversity

Alexandra Witze




The role of magma injection in localizing black-smoker activity

William S. D. Wilcock, Emilie E. E. Hooft, Douglas R. Toomey, Paul R. McGill, Andrew H. Barclay, Debra S. Stakes & Tony M. Ramirez


The mechanisms for localization of black-smoker systems at mid-ocean ridges remain to be fully understood. Seismic data for a segment of the Juan de Fuca ridge with long-lived black-smoker vents reveal ongoing magma recharge into the crustal magma chamber, thereby providing an explanation for the localization.

Stress transfer between thirteen successive dyke intrusions in Ethiopia

Ian J. Hamling, Tim J. Wright, Eric Calais, Laura Bennati & Elias Lewi


Large earthquakes are known to trigger subsequent earthquakes in nearby regions, but similar triggering has not been confirmed for volcanic hazards. Analysis of the progressive deformation associated with 13 volcanic dykes intruded in Ethiopia between 2005 and 2009 indicates that magmatic intrusions can help to trigger subsequent intrusions.

Carbon release by off-axis magmatism in a young sedimented spreading centre

Daniel Lizarralde, S. Adam Soule, Jeff S. Seewald & Giora Proskurowski


Continental rifting creates narrow ocean basins, where coastal ocean upwelling and enhanced silicate weathering remove carbon dioxide from the atmosphere. Evidence from seismic data, sonar backscatter and seafloor images, and geochemical water analyses suggest that in young sedimented rifts, active magmatism occurs in a broader region than appreciated and releases carbon from the sediments.

The protracted development of the continent-ocean transition in Afar

Ian D. Bastow & Derek Keir


The timing and style of magmatism and extension during the final stages of continental breakup are uncertain. Analysis of ongoing rifting processes in Ethiopia reveals that after a protracted period of extension by magma intrusion, late-stage breakup is characterized by a final phase of plate stretching and voluminous basalt extrusion.



Young off-axis volcanism along the ultraslow-spreading Southwest Indian Ridge

Jared J. Standish & Kenneth W. W. Sims


Mid-ocean ridges grow through tectonic and volcanic processes. Uranium-series dating of volcanic rocks at the ultraslow-spreading Southwest Indian Ridge reveals widely dispersed, young, off-axis volcanism that is spatially coincident with fault surfaces. Faults may therefore provide a mechanism for the wide dispersal of magma at ultraslow-spreading ridges.

Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

John S. Pallister, Wendy A. McCausland, Sigurjón Jónsson, Zhong Lu, Hani M. Zahran, Salah El Hadidy, Abdallah Aburukbah, Ian C. F. Stewart, Paul R. Lundgren, Randal A. White & Mohammed R. H. Moufti


Volcanic fields at the eastern margin of the Red Sea rift were regarded as seismically quiet until a swarm of 30,000 earthquakes struck in 2009. Geological analyses reveal the intrusion of a volcanic dyke and indicate that rift-related extension is spread over a broad region far from the rift axis.

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