Rifts

Oceanic spreading centres are sites of extensive tectonic, magmatic and hydrothermal activity that provide nutrients to the ocean and multifaceted habitats for life. This Review explores processes governing variations in hydrothermal vents, microbial ecosystems and global fluxes from ocean ridges.

Continental margins record the last stages of rifting before a new ocean basin is formed, with their variety reflecting interactions between tectonic, magmatic, sedimentary and hydrothermal processes. This Review provides a process-based understanding of rifted margin formation, gaining insights into their resource potential for the energy transition.

Continental rift zones are regions of crustal extension that manifest through seismic and magmatic activity. This Review explores the variety and development of rifts by assessing their geodynamic drivers, resisting factors and weakening processes.

New observations of volcanic and magmatic activity in Africa are changing our views of continental rifting and raising awareness of the associated hazards. However, despite a shift from crisis response to reducing disaster risks, limited capacity means mitigating geohazards remains challenging.

Feedbacks between chemical, physical, and biological processes at rift zones evolve through various time (seconds to 10⁷ yrs) and spatial (microns to 10⁶ m) scales. Consideration of these scales is needed to tap rift energy, water, and mineral resources safely and equitably while preserving biodiversity in these changing settings.

International researchers flock to study the East African Rift, but local researchers and monitoring facilities are often overlooked. Nature Reviews Earth & Environment speaks to Atalay Ayele, Head of the seismology unit at the Institute of Geophysics, Space Science and Astronomy at Addis Ababa University, Ethiopia, about the challenges and potential of local seismic monitoring at the East African Rift.

Drilling into the uppermost mantle through a complete section of intact ocean crust, formed at a fast-spreading mid-ocean ridge, would liberate fundamental knowledge into Earth processes. The activities and achievement will also inspire future generations of geoscientists, who are essential to adapt to climate change and deliver the energy transition.

Numerical model experiments show that deep valleys cutting across the East African Rift System dry out East Africa by channelling water vapour towards Central Africa, leading to elevated rainfall in the Congo Basin rainforest.

Initial seawater influx into South Atlantic rift basins entered from the south across the Rio Grande Rise-Walvis Ridge as the South Atlantic began to open in the Early Cretaceous, according to sedimentary hydrocarbon biomarker records in two drill cores from offshore West Africa.

A reduction in olivine grain size can cause weakening of mantle lithosphere, facilitating continental rifting, according to coupled grain-size-evolution thermo-mechanical modelling of a mantle dynamics.

Carbon dioxide and helium data support lateral advection of carbon-rich cratonic mantle below the East African Rift System, which concentrates deep carbon and causes active carbonatite magmatism near the craton edge.

The mantle lithosphere has thinned more than the crust beneath the Malawi Rift despite being melt-poor, according to seismic wave imaging; this suggests early melting of fusible mantle material.

A link between post-thickening lithospheric extension and the differentiation of continental crust is implied by granulite conditions beneath the Rio Grande Rift, inferred from analysis of lower-crustal xenoliths and thermobarometric modelling.

The transition from wide continental rift to continental break-up remains enigmatic. Here, the authors show that northern margin of the South China Sea records the transition between wide continental rift to a highly extended continental margin, with strikingly similar structures and metamorphic core complexes to those described from the North American Cordillera and the Aegean.

One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions.

The location of orogenic belts has a strong influence on the rifting of supercontinents after mantle plumes trigger the initial break-up and contribute to lithospheric weakening, according to numerical simulations of the break-up of Pangea.

An article in Journal of Volcanology and Geothermal Research explores the stratigraphy of eruptive deposits from Corbetti Caldera, Ethiopia, to gain insights into the eruption frequency and hazard.

The development of offset normal faults in the conjugate Flemish Cap and Galicia magma-poor rifted margins is explored. The authors propose alternating opposite dipping detachments to be the underlying cause.

Distal edges of volcanic passive margins contain exhumed continental crust that suggests continental material in oceans may be more common than previously thought, according to high-quality multichannel seismic data collected off Namibia

Westward drifting and southward tapering of the South American continent have modulated the asymmetry and non-uniformity in South Atlantic opening, according to analytical modelling informed by geological and geophysical data

The seismic reflection Moho at the Mid-Norwegian continental rifted margin can be imaged in the context of the lower crust and upper mantle across the whole margin using high resolution seismic reflection data.

The evolution of rifts and rifted margins is controlled by the rheology of the lithosphere. Thus, pre-existing lateral rheological variations can dominate the rifting process and lead to margin segmentation, with along-strike changes in crustal structure and nature and timing of continental breakup.

Magmatic productivity at passive margins is controlled by mantle temperature and rifting style. The authors reveal that melt volume at rifted margins is linearly correlated with margin width and that volcanic margins may result from depth dependent extension without high temperature mantle plumes.

An article in Tectonics identified asymmetric rifting during the break-up of Gondwana from variations in a thermal lithosphere–asthenosphere boundary model for the South American and African passive margins.

An uncultivated, aerobic chemolithotrophic Sulfurimonas species with a reduced genome is abundant across diverse, hydrogen-rich hydrothermal plumes in the deep ocean.

Oceanic detachment faults play a central role in accommodating the plate divergence at mid-oceanic ridges. Here, the authors show micro-seismicity of a nearly-amagmatic flip-flop detachment fault system at the ultraslow spreading Southwest Indian Ridge.

Deep hydration of the upper mantle at transform plate boundaries due to seawater infiltration leads to hydrous melting and lithospheric thinning, according to seismic surveys and thermal modelling of the Romanche transform fault.

The lower oceanic crust forms through the accretion of injected melt that cools and crystallizes in situ over hundreds of thousands of years, according to seismic data from the slow-spreading equatorial Mid-Atlantic Ridge.

The Aurora hydrothermal field (Arctic Ocean) is hosted in volcanic rocks but also shows evidence of mantle rock influence in the shallow sub-surface. Our discovery is pertinent to disciplines from marine mining to the search for life beyond Earth.

Uniform magmatic crust formed at the Mid-Atlantic Ridge in the equatorial Atlantic Ocean reveals a two-dimensional mantle upwelling facilitated by the large transform faults and the high concentration of volatiles in the primitive melt in the mantle.

The oceanic plateau of the Rio Grande Rise, South Atlantic, was formed by mantle plume- and rift-related volcanism and shows no evidence of a continental crustal component, according to petrological and geochemical analyses of dredged volcanic rocks.

Testing feedbacks between climatic and geological processes are challenging. Here, the authors show that geomorphological features of the southern Red Sea margin are best interpreted by a feedback cycle between orographic precipitation, mid-ocean spreading and coastal magmatism, and that the feedback is enhanced by the trade wind.

Oceanic transform faults are systemically deeper than their associated fracture zones, owing to the plate boundary experiencing increasingly oblique shear at increasing depths below the seafloor.

The lower oceanic crust beneath Iceland is flowing and internally deforming, according to constraints on seismic anisotropy in the Icelandic crust from an analysis of seismic surface waves.

Here, based on earthquake data, vertical gravity gradient data and high-resolution bathymetry, the authors show that the Red Sea is not in transition from rifting to spreading as previously proposed. They instead suggest it to be a mature ocean basin in which continuous seafloor spreading began quasi-instantaneously along its entire length around 13 Ma ago.

Magmatic and tectonic activity at mid-oceanic ridges can give detailed insights into high-temperature hydrothermal circulation of fluids. The authors here present geochemical and geophysical datasets that suggest a hydrothermal system penetrating the upper lithospheric mantle at an ultra-slow spreading mid-oceanic ridge.

Plate tectonics necessitates mantle recycling throughout Earth’s history, yet direct geochemical evidence for mantle reprocessing remains elusive. Here, the authors present evidence of recycled supra-subduction zone mantle wedge peridotite dredged from the Mid-Atlantic Ridge near 16°30′N.

Characterization of hydrothermal plumes in terms of redox, rather than distance from the vent, illuminates the dominant transport processes and fate of metals, focusing on iron and manganese.

Bottom water renewal on the western flank of the mid-Atlantic Ridge is driven by rapid intrusion of cold, dense water enabled by gradual warming due to geothermal heat flux and diapycnal mixing, as revealed by six-year observational records.

An article in Molecular Ecology describes the factors shaping microbial eukaryotic populations and their role in the carbon cycle at deep-sea hydrothermal vents.