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Rift zone

A rift zone is a linear region of the Earth's crust subjected to extensional tectonic forces, resulting in the stretching and thinning of the lithosphere, the development of normal faults, grabens, and rift valleys, and frequently associated with significant volcanic and seismic activity as magma rises from the mantle.^[1] Continental and oceanic rift zones form at divergent plate boundaries, where tectonic plates move apart, facilitating the upwelling of asthenospheric material and the creation of new crustal material, while volcanic rift zones develop in intraplate settings such as hotspots.^[2] Rift zones are classified into three main types based on their tectonic setting: continental, oceanic, and volcanic. Continental rift zones occur within the interiors of tectonic plates, where the thick continental lithosphere is extended, leading to the formation of elongated basins flanked by fault-block mountains and filled with sediments and volcanic deposits; notable examples include the East African Rift System, which stretches over 3,000 kilometers from the Afar Triple Junction to Mozambique, and the Rio Grande Rift in North America, active since approximately 35 million years ago.^[3]^[4] Oceanic rift zones, often manifested as mid-ocean ridges, represent the global system of seafloor spreading centers where new oceanic crust is continuously generated; the Mid-Atlantic Ridge, for instance, bisects the Atlantic Ocean and accounts for a substantial portion of Earth's volcanic output, with spreading rates varying from 2 to 10 centimeters per year.^[1]^[2] Volcanic rift zones, a specialized subtype, develop on intraplate volcanoes such as those in hotspot settings, where radial dike intrusions propagate outward from a central magma reservoir, creating zones of weakness prone to fissure eruptions; on Kīlauea volcano in Hawaii, the East Rift Zone extends about 50 kilometers onshore and is responsible for many historical lava flows, including the 2018 eruption that destroyed over 700 homes.^[5] These zones play a critical role in plate tectonics by driving continental breakup—potentially leading to the formation of new ocean basins, as seen in the ongoing divergence of the African and Arabian plates—and influencing global heat flow, magmatism, and resource distribution, including hydrocarbons in rift basins.^[1]^[3]

Definition and Characteristics

Definition

A rift zone is an extensive linear deformational belt characterized by crustal extension, where the lithosphere undergoes tensile stresses leading to normal faulting, crustal thinning, and frequently associated magmatism.^[6] These zones represent regions of divergent tectonics, often spanning hundreds to thousands of kilometers, and serve as precursors to either continental breakup or oceanic spreading centers.^[3] Key surface expressions of rift zones include fault scarps, wide grabens forming elongated troughs, and alignments of volcanic vents or ridges, particularly on oceanic islands or continental margins.^[6] Subsurface features encompass dyke swarms intruding the crust, upwelling of asthenospheric material, and the development of low-angle detachment faults or magma chambers that facilitate further extension.^[5] These characteristics arise from the mechanical weakening of the lithosphere under extensional forces, promoting both brittle fracturing in the upper crust and ductile deformation deeper within.^[7] The concept of rift zones was first articulated in the late 19th century through explorations of continental features, notably by John Walter Gregory, who described the East African continental rift system in 1896 based on geological observations of faulted valleys and volcanic activity.^[8] Oceanic counterparts, such as mid-ocean ridges, were identified in the mid-20th century through bathymetric surveys, but the unifying framework emerged in the 1960s with the development of plate tectonics theory, which explained rift zones as sites of lithospheric divergence driven by mantle convection.^[2] Rift zones are distinguished from individual rifts or rift valleys, as they denote broader tectonic provinces that integrate multiple aligned segments of extension, whereas rift valleys refer specifically to the topographic depressions or grabens resulting from localized faulting within these zones.^[1] This broader scope highlights rift zones' role in encompassing interconnected fault systems and magmatic pathways, rather than isolated surface landforms.^[3]

Types of Rift Zones

Rift zones are primarily categorized into three main types—oceanic, continental, and volcanic—based on their tectonic environment and location within the lithosphere. Oceanic rift zones form at divergent plate boundaries in oceanic settings, such as mid-ocean ridges, where lithospheric plates pull apart, enabling the upwelling of asthenospheric mantle and the creation of new oceanic crust through seafloor spreading.^[9]^[2] In contrast, continental rift zones develop intracontinentally due to extensional tectonics that stretch and thin the thicker continental lithosphere, often preceding the formation of new ocean basins if rifting progresses.^[3]^[10] Volcanic rift zones represent a specialized type that develops on intraplate volcanoes, particularly shield volcanoes in hotspot settings, where radial dike intrusions propagate outward from a central magma reservoir, creating zones of weakness prone to fissure eruptions and flank instability. Unlike oceanic and continental types, which occur at or near plate boundaries, volcanic rift zones are not driven by large-scale plate divergence but by localized magmatic pressures; notable examples include the East and Southwest Rift Zones of Kīlauea volcano in Hawaii, which have facilitated numerous historical eruptions.^[5] Subtypes of rift zones further distinguish their driving mechanisms and deformation styles. Active rifts are primarily driven by buoyancy forces from mantle plumes or upwelling, which initiate and sustain extension through thermal weakening of the lithosphere.^[11]^[12] Passive rifts, however, result from far-field plate boundary stresses that impose lithospheric stretching without dominant mantle-driven forces.^[11]^[12] Additionally, rifts are classified as narrow or wide based on strain distribution: narrow rifts exhibit localized deformation concentrated along faults within a limited zone (typically tens of kilometers wide), while wide rifts involve distributed strain across broader regions (hundreds of kilometers), influenced by lithospheric rheology and extension rate.^[13]^[14] Key differences between oceanic and continental rift zones are summarized in the following table, highlighting variations in crustal properties, magmatic activity, and long-term evolution:

Aspect	Oceanic Rift Zones	Continental Rift Zones
Crustal Thickness	Typically 6-7 km, basaltic composition	Initially 30-40 km, granitic; thins to 20 km or less during extension^[15]^[16]
Magmatism Intensity	High, with continuous mafic (basaltic) volcanism from decompression melting^[10]	Variable and often lower; includes bimodal mafic-felsic magmatism, with intensity depending on mantle temperature and extension rate^[10]^[16]
Evolution Potential	Progresses to steady seafloor spreading, widening ocean basins at consistent rates^[2]^[9]	May stall or evolve into passive margins and new ocean basins if extension persists; many become inactive^[3]^[10]

Modern classifications of rift zones increasingly rely on geodetic and geophysical data to refine these categories. GPS measurements and seismic imaging reveal varying extension rates across rift zones, typically ranging from 1 to 10 cm/year, with faster rates (e.g., >4 cm/year) associated with more localized, narrow rifting and higher magmatic productivity, while slower rates (e.g., 0.5-2 cm/year) often characterize wider or passive systems.^[17]^[18]^[19] These data help distinguish rift dynamics, such as how strain localizes in narrow zones during early extension phases.^[20]^[21]

Formation Processes

Tectonic Mechanisms

Rift zones primarily form through lithospheric extension driven by divergent plate motions at tectonic boundaries, where plates move apart, leading to the upwelling of asthenospheric material and thinning of the overlying lithosphere.^[22] This extension is propelled by key forces including slab pull, where subducting slabs generate traction on the overlying plate, and ridge push, arising from gravitational sliding of elevated oceanic crust away from mid-ocean ridges.^[23] Mantle convection contributes by facilitating broad-scale upwelling beneath divergent zones, while hotspots—localized plumes of hot mantle material—can enhance extension in intraplate settings, as seen in the East African Rift.^[24] The stress regime during rifting involves extensional forces that deform the lithosphere, modeled primarily through pure shear and simple shear mechanisms. In the pure shear model, extension occurs symmetrically across a broad zone, with uniform thinning of the crust and mantle lithosphere, resulting in balanced subsidence and uplift patterns.^[25] Conversely, the simple shear model describes asymmetric extension along a detachment fault, leading to one-sided tilting of fault blocks and deeper lithospheric roots on the non-extended side, which better explains observed asymmetries in many rift basins.^[26] The degree of extension is quantified by the stretching factor \beta, defined as \beta = \frac{T_{\text{initial}}}{T_{\text{final}}}, where T_{\text{initial}} and T_{\text{final}} represent the initial and final crustal thicknesses, respectively; values of \beta > 1 indicate significant thinning.^[27] Geophysical evidence supports these mechanisms through imaging of subsurface structures. Seismic tomography reveals low-velocity zones in the upper mantle beneath active rifts, interpreted as hot, upwelling asthenosphere that reduces density and promotes extension, with anomalies as low as 4-5% beneath the East African Rift.^[28] Gravity anomalies, particularly negative Bouguer anomalies, arise from crustal thinning and isostatic compensation, as observed in the Baikal Rift where Moho uplift correlates with reduced crustal thickness of about 10 km.^[29] Rifting often initiates at zones of pre-existing lithospheric weakness, which localize deformation and lower the threshold for extension. Ancient sutures from prior continental collisions or inherited shear zones act as mechanical heterogeneities, guiding fault propagation and rift axis alignment, as evidenced in numerical models of oblique rifting where such features control strain distribution.^[30] These weaknesses facilitate the onset of extension by reducing frictional resistance, enabling divergent motions to exploit them preferentially over intact lithosphere.^[31]

Evolutionary Stages

Rift zones evolve through a series of distinct temporal stages driven by lithospheric extension, beginning with initial deformation and potentially culminating in continental breakup or failure. The primary phases include the syn-rift stage, characterized by active tectonic extension; the post-rift stage, marked by thermal relaxation; and, in successful cases, the breakup stage leading to oceanic basin formation. These stages typically unfold over timescales of 10 to 50 million years for continental rifts, influenced by factors such as mantle plume activity, crustal inheritance, and regional stress fields. During the syn-rift stage, distributed extension gives way to localized faulting and basin formation, accompanied by sedimentation in developing grabens and half-grabens. This phase involves mechanical thinning of the lithosphere, with normal fault networks accommodating strain at rates often ranging from 1 to 10 mm per year, though variability depends on the tectonic setting. Magmatic activity begins modestly with minor intrusions and dike swarms but can escalate to voluminous flood basalts in volcanic rifts, where upwelling asthenosphere contributes to crustal weakening and basin subsidence. Sedimentary sequences in this stage reflect tectonic control, with coarse alluvial fans and lacustrine deposits dominating proximal areas. The post-rift stage follows cessation of active extension, dominated by thermal subsidence as the lithosphere cools and contracts isostatically. This results in broad sagging of the rift basin, fostering widespread marine or continental sedimentation under reduced tectonic influence. Subsidence rates slow to less than 1 mm per year, persisting for tens of millions of years and creating thick passive margin sequences in aborted or successful rifts alike. Magmatism diminishes, though residual effects from prior underplating may influence basin architecture. The transition is often marked by a breakup unconformity, an erosional surface separating syn-rift faulted strata from the overlying post-rift conformable layers, serving as a key stratigraphic indicator of rift maturity.^[32] In successful rifts, the breakup stage involves final crustal separation, exhumation of mantle peridotites in magma-poor settings or hyper-extension with oceanic crust initiation in magma-rich ones, ultimately forming a new ocean basin. This phase is brief relative to prior stages, often lasting 1 to 10 million years, with plate divergence rates accelerating to 20 mm per year or more as seafloor spreading commences. Only a subset of rifts achieve this outcome, as evidenced by numerous preserved failed structures.^[33] Many rifts fail before breakup, arresting during the syn-rift or early post-rift phases to form aulacogens—embayed, aborted arms of ancient triple junctions preserved as linear sedimentary basins. These structures, often intersecting cratonic margins at high angles, record incomplete extension with inherited faulting and subsidence, later subject to inversion under compressional regimes. Factors like changes in far-field stress or insufficient mantle upwelling contribute to failure, leaving behind economically significant hydrocarbon reservoirs in their infilled depocenters.^[34]

Geological Structure

Morphological Features

Rift zones exhibit distinctive morphological features shaped by extensional tectonics, including grabens and half-grabens as primary basin structures. A graben forms a down-dropped block bounded by two parallel normal faults, while a half-graben is an asymmetric depression bounded by a single major border fault on one side and a flexure or minor faults on the other, resulting in a wedge-shaped geometry that thickens toward the border fault.^[35] These structures often alternate in polarity across accommodation zones, which are complex transfer regions linking adjacent half-grabens with opposing fault dips, characterized by oblique faults, horsts, and grabens that accommodate strain between segments.^[36] Rift shoulders, elevated margins adjacent to border faults, arise from footwall uplift and define the outer boundaries of these basins.^[35] Fault patterns in rift zones typically involve arrays of listric normal faults that curve concave-upward and dip toward the rift axis, flattening at depth into detachment surfaces to facilitate extension.^[37] These faults exhibit maximum displacement near segment centers, decreasing toward tips, and propagate to widen and lengthen the rift over time.^[35] Topographic expressions vary between continental and oceanic settings. In continental rifts, asymmetric valleys dominate, with structural relief reaching depths of 5-10 km in basins like the central Baikal rift, where sediment and water fill create pronounced depressions flanked by uplifted shoulders.^[38] In oceanic rift zones, particularly at fast-spreading mid-ocean ridges, axial highs form elongate topographic elevations along the spreading center, contrasting with the deeper valleys of slower-spreading ridges.^[39] Sedimentary infill in rift zones consists of syn-rift deposits that record basin evolution, including basal alluvial fans and fluvial sands near fault scarps, transitioning to lacustrine shales and evaporites in deepening sub-basins as subsidence outpaces sediment supply. Uplift of rift shoulders drives erosion, producing angular unconformities at the rift base and contributing coarse detritus to adjacent basins.^[35] Remote sensing techniques, such as analysis of Shuttle Radar Topography Mission (SRTM) digital elevation models, enable mapping of rift features at scales of 10-100 km, revealing fault scarps, basin geometries, and accommodation zones through shaded relief and structural interpretations.^[40]

Lithospheric Components

In rift zones, the crust undergoes significant thinning due to extensional tectonics, typically reducing from a normal continental thickness of 30–40 km to 10–20 km in highly extended domains.^[41] This thinning is often accompanied by uplift of the Mohorovičić discontinuity (Moho), which marks the crust-mantle boundary, as the lithosphere responds to gravitational forces and thermal weakening.^[41] However, the expected isostatic uplift of the Moho is frequently compensated by magmatic underplating, where mafic intrusions from the mantle accumulate at the base of the crust, forming high-velocity lower crustal layers with seismic velocities exceeding 7.0 km/s.^[42] Such underplating helps maintain crustal stability during extension, as observed in seismic refraction profiles from the East African Rift, where velocity anomalies indicate intrusive bodies offsetting thinning-induced subsidence.^[41] The mantle lithosphere in rift zones experiences parallel modifications, with overall thinning to depths of 50–100 km, compared to the typical 100–200 km in stable cratons.^[43] This process involves the upward migration of the asthenosphere-lithosphere boundary, driven by convective upwelling and thermal erosion, which weakens the mechanical lithosphere and facilitates further extension.^[43] Seismic profiles reveal low-velocity zones in the upper mantle, indicative of elevated temperatures and partial melting near this boundary. Geophysical models of rift zones incorporate seismic refraction and wide-angle reflection data to map these changes, showing sharp velocity gradients from crustal velocities of 6.0–6.5 km/s to mantle values of 8.0 km/s, often with reflective lower crustal layers signaling intrusions.^[41] Isostatic compensation in these settings adapts the Airy model, where variations in crustal thickness are balanced by root adjustments, but rifted margins require modifications to account for dynamic support from asthenospheric flow and magmatic loading. In the Airy framework for rifted systems, the compensation depth z_c relates to topographic height h and crustal density \rho_c versus mantle density \rho_m via:

h = z_c \left(1 - \frac{\rho_c}{\rho_m}\right)

This equation, adjusted for underplating densities (e.g., \rho_c \approx 2.9 g/cm³ for mafic layers), explains the subdued subsidence in magma-influenced rifts compared to pure extensional models.^[44] Asymmetry characterizes many rift systems, particularly in continental settings versus more symmetric oceanic rifts. In magma-poor continental rifts, hyper-extended domains develop where crust thins to less than 10 km over widths exceeding 100 km, leading to conjugate margin asymmetries as observed in the Iberia-Newfoundland system.^[45] Oceanic rifts, by contrast, exhibit bilateral symmetry due to uniform asthenospheric upwelling, with less pronounced hyper-extension and more consistent magmatic addition along spreading centers.^[45] These variations arise from inherited crustal heterogeneities and differential extension rates, resulting in narrower, more focused lithospheric modification on one flank.^[46]

Global Examples

Oceanic Examples

Oceanic rift zones, primarily manifested as mid-ocean ridges, represent the most extensive divergent boundaries on Earth, where new oceanic crust forms through seafloor spreading. These submarine features dominate the global ridge system, which totals approximately 65,000 kilometers in length, facilitating the continuous creation of lithosphere at rates varying from ultraslow to fast spreading.^[47] The Mid-Atlantic Ridge exemplifies a slow-spreading oceanic rift zone, extending about 16,000 kilometers from the Arctic Ocean to the southern Atlantic, with a typical spreading rate of 2 to 4 centimeters per year.^[48]^[2] This ridge is characterized by prominent transform offsets that segment its length into discrete spreading centers, often tens of kilometers long, and deep axial valleys up to several kilometers wide that serve as sites of crustal construction.^[49]^[50] These morphological elements reflect the limited magma supply at slow rates, leading to more pronounced faulting and tectonic exposure of mantle rocks in places.^[51] In contrast, the East Pacific Rise illustrates a fast-spreading rift zone, with rates ranging from 6 to 16 centimeters per year, resulting in broader axial zones and reduced faulting compared to slower counterparts.^[47] Here, abundant magma supply sustains continuous volcanism, forming smoother topographic highs rather than deep valleys, and supports effusive eruptions that pave the seafloor with extensive lava flows.^[52] This dynamic fosters a narrower, more focused plate boundary, often less than a kilometer wide, where volcanic activity predominates over tectonic deformation.^[52] The historical development of these oceanic rift zones traces back to the breakup of the supercontinent Pangea around 180 million years ago, initiating the formation of the modern mid-ocean ridge system as continents drifted apart.^[53] Over time, spreading rates have varied, giving rise to subtypes such as ultraslow-spreading ridges like the Gakkel Ridge in the Arctic (less than 2 centimeters per year), which exhibit amagmatic segments and widespread mantle exposure, versus fast-spreading ones like the East Pacific Rise that maintain robust magmatic budgets.^[51] This evolution has progressively widened ocean basins, with the Atlantic expanding steadily since the Jurassic period.^[53] Modern observations of oceanic rift zones have been advanced through submersible dives, such as those by the Alvin, which have documented hydrothermal features like black smokers—high-temperature vents emitting mineral-rich fluids—and expansive fields of pillow lavas formed by underwater eruptions.^[54] These expeditions, particularly along the Mid-Atlantic Ridge and East Pacific Rise, reveal active seafloor processes, including recent volcanic flows and associated ecosystems, providing direct evidence of ongoing crustal accretion.^[55]^[56]

Continental Examples

The East African Rift (EAR) represents one of the most prominent active continental rift systems, extending approximately 3,000 km from the Afar triple junction in the north to the southern end of the Malawi Rift.^[57] Current extension rates across the rift vary but average 6-7 mm/year in the northern segments, driven by the divergence of the Nubian and Somalian plates.^[58] This rifting is associated with extensive volcanic provinces, including the Afar Depression, where Quaternary basaltic volcanism and shield volcanoes reflect ongoing magma intrusion and crustal thinning.^[59] A November 2025 study has provided the first empirical evidence that climate-driven changes in lake levels are accelerating fault activity and rifting rates in the region.^[60] In North America, the Rio Grande Rift serves as a key example of intra-continental extension, stretching over 1,000 km from central Colorado southward into Mexico along the Rio Grande River valley.^[61] Characterized by a series of north-south trending basins with widths averaging 50 km, the rift features alkaline mafic volcanism, including potassic basalts and trachytes erupted since the Miocene, linked to asthenospheric upwelling.^[62] This extension integrates with the broader Basin and Range Province, where late Cenozoic faulting and thinning of the lithosphere have produced half-graben structures and elevated heat flow.^[63] Ancient continental rifts provide insights into aborted breakup processes that preceded ocean basin formation, such as the precursors to the Iapetus Ocean around 500 Ma, when rifting between Laurentia and Gondwana fragments initiated continental separation in the Appalachian-Caledonian region.^[64] These Paleozoic rifts involved hyperextension and magmatism that ultimately led to seafloor spreading but left relict structures preserved in suture zones.^[65] Similarly, the Baikal Rift System in Siberia exemplifies a modern potentially failed rift, extending about 1,500 km with low extension rates of 2-4 mm/year, where intracontinental stresses have not progressed to full oceanic rifting despite active faulting and sedimentation in Lake Baikal.^[66] This system highlights stalled divergence within the Eurasian plate, with limited volcanism confined to alkali basalts.^[67] Aborted continental rifts often host significant hydrocarbon resources due to their syn-rift sedimentary basins, which trap organic-rich deposits during extension phases. For instance, the North Sea Basin preserves pre-rift and syn-rift sequences from a Late Paleozoic to Mesozoic aborted rift system, where fault-block structures and source rocks have accumulated vast petroleum reserves estimated at over 50 billion barrels of oil equivalent.^[68] These features underscore the economic legacy of failed rifting, where preserved basins contrast with successful oceanic rifts by retaining continental crust and hydrocarbons.^[68]

Geological Significance

Associated Volcanism

Rift zone volcanism arises primarily from partial melting of the upwelling asthenosphere, triggered by decompression as the overlying lithosphere thins during extension.^[69] This process generates basaltic magmas through low-degree partial melting, with melt fractions typically ranging from 1% to 5%, depending on mantle composition and extension rate.^[70] Magma compositions span tholeiitic basalts, characteristic of higher-degree melts in mature rifts, to alkali basaltic series in less extended settings, reflecting variations in source fertility and depth.^[71] In continental rifts like the Rio Grande, asthenospheric sources dominate later-stage magmatism, while earlier melts often incorporate subduction-modified lithospheric components.^[71] Eruptive activity in rift zones manifests through fissure eruptions, where magma ascends along extensional fractures, forming linear vent systems and extensive lava flows.^[72] Shield volcanoes develop from repeated low-viscosity basaltic eruptions, building broad, gently sloping edifices, while calderas form from collapse following large-volume evacuations of magma chambers.^[73] In early rift stages, voluminous flood basalt provinces emerge, as seen in precursors to large igneous provinces like the Deccan Traps, where rift-related extension facilitated massive outpourings along multiple fault zones.^[74] Magmatism in rift zones exhibits distinct temporal patterns, with syn-rift phases characterized by high-volume, tholeiitic eruptions tied to active extension and asthenospheric upwelling, contrasting with post-rift stages featuring lower-volume, more alkaline magmas from lithospheric sources.^[75] Large igneous provinces associated with rifts can involve magma volumes up to 10^6 km³, significantly influencing crustal architecture and regional uplift.^[76] Recent examples include the 2024 eruption in Kīlauea's Southwest Rift Zone, which began on June 3 and marked significant activity in that area since 1974.^[77] Monitoring of rift zone volcanism relies on satellite-based thermal infrared data to detect active vents and lava flows, enabling real-time assessment of eruptive activity, as demonstrated in ongoing observations of the Kīlauea East Rift Zone.^[78] Geochemical tracers, such as strontium-neodymium (Sr-Nd) isotopes, provide insights into mantle sources, distinguishing asthenospheric melts (high εNd, low ⁸⁷Sr/⁸⁶Sr) from enriched lithospheric contributions in systems like the Rio Grande Rift.^[71]

Seismicity and Hazards

Rift zones are characterized by frequent shallow earthquakes associated with normal faulting, typically ranging in magnitude from 4 to 7, which reflect the extensional tectonic regime driving continental breakup.^[79] These events are predominantly shallow crustal, typically at depths less than 20 km, where normal-faulting focal mechanisms dominate, accommodating east-west extension in regions like the Red Sea Rift.^[79] In the Baikal Rift Zone, seismicity patterns show spatial clustering along active faults, with focal mechanisms consistently indicating tensile stress, underscoring the role of brittle deformation in the upper crust.^[80] Recent seismic activity includes the 2024–2025 dyke intrusions in the Fentale volcanic chain, Afar, Ethiopia, where successive intrusions from September 2024 to March 2025 were accompanied by seismic swarms.^[81] Hazard assessment in rift zones highlights distinct risks depending on whether the setting is oceanic or continental. In oceanic rifts, such as segments of the Mid-Atlantic Ridge, submarine earthquakes can trigger landslides that generate tsunamis, posing threats to coastal populations despite the remote locations.^[82] Continental rifts, like the East African Rift, face amplified hazards from earthquake-induced landslides and potential triggers for volcanic unrest, as seen in the 2005 Dabbahu rifting episode in Afar, Ethiopia, where a Mw 5.2 event initiated a sequence that deformed the surface over 60 km and heightened local instability.^[83] Seismic monitoring in rift zones relies heavily on the Global Seismographic Network (GSN), a worldwide array of over 150 broadband stations that captures high-fidelity data on ground motions from rift-related events, enabling detailed analysis of source mechanisms and wave propagation.^[84] In specific regions like Ethiopia's Southern Main Ethiopian Rift, supplementary local networks enhance resolution, integrating GSN data to track swarm activity and fault interactions.^[85] Probabilistic models for earthquake recurrence adapt the Gutenberg-Richter law, with b-values typically ranging from 0.8 to 1.0 in rift settings, indicating a relatively higher proportion of moderate-to-large events compared to other tectonic regimes; these models inform hazard maps by estimating event frequencies based on cataloged seismicity.^[86] Human impacts from rift zone seismicity are pronounced in densely populated areas of East Africa, where earthquakes cause population displacement and significant economic disruption. For instance, events in the Rift Valley have led to thousands displaced due to structural collapses and ground fissuring, exacerbating vulnerabilities in informal settlements.^[87] Economic costs from infrastructure damage, such as roads, bridges, and power lines, have reached billions of dollars cumulatively; the 1989 Malawi earthquake alone inflicted $28 million in losses, while broader East African Rift activity contributes to ongoing development challenges through repeated disruptions.^[88]

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Oct 21, 2016 · The shallow upper mantle, down to ~100 km, reveals a broad low-velocity layer with the strongest anomalies following the rift morphology (4.5% ...
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[PDF] Significant Crustal Thinning beneath the Baikal Rift Zone
Oct 30, 2004 · Our observations are inconsistent with results from inversion of gravity anomalies or DSS studies in this area, which suggested a nearly flat.
[30]
[PDF] Geodynamics of continental rift initiation and evolution - EarthArXiv
Suture zones, remnants from previous plate collision events, often constitute a zone of weakness that may get reactivated [G] during eventual extensional ...<|control11|><|separator|>
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Syn‐Rift Magmatism and Oceanic Spreading Initiation Controlled by ...
During divergent plate motions, if the orientation of these pre‐existing weak zones is not perpendicular to the direction of extension, oblique rifting occurs.
[32]
Evolution of Rift Systems and Their Fault Networks in Response to ...
Feb 13, 2022 · We find that regardless of the rift type, rifts evolve according to five phases that can be assessed through the evolution of the fault network ...Missing: aulacogens | Show results with:aulacogens
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New Insights into North America's Midcontinent Rift - Eos.org
Aug 4, 2016 · When a rift succeeds, the continent splits, and a new ocean basin forms between the two parts of the continent. Some rifts, however, fail to ...This Newsletter Rocks · How Did This Hybrid Evolve? · Surprises From Seismic...<|separator|>
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Rift Basin Architecture & Evolution - Columbia University
Rift basins are found on all passive (Atlantic-type) continental margins and provide a record of the early stages of (super)continental breakup.<|control11|><|separator|>
[36]
Internal structure and deformation of an accommodation zone in the ...
These two sets of rift-parallel faults form several horsts and grabens in the accommodation zone. Areas dipping parallel to the northern or southern half ...
[37]
Listric Fault - an overview | ScienceDirect Topics
Listric faults are defined as curved normal faults where the fault surface is vertically concave, and the dip decreases with depth.
[38]
Structure and evolution of the Baikal rift: A synthesis - AGU Journals
Nov 21, 2006 · In this paper, we use forward and inverse models of gravity data to map the Moho and lithosphere-asthenosphere boundary in three dimensions.<|control11|><|separator|>
[39]
The axial topographic high at intermediate and fast spreading ridges
An axial topographic high is commonly observed at both fast spreading ridges and some segments of intermediate spreading ridges.
[40]
Fault growth and propagation during incipient continental rifting ...
Jun 28, 2008 · Visual interpretations of SRTM DEM are shown in the form of structural maps illustrating the strike, dip direction, and spatial distribution of ...3. Data Acquisition And... · 3.1. Shuttle Radar... · 5.2. Fault Growth And...
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Magma-compensated crustal thinning in continental rift zones - Nature
Feb 1, 2009 · We suggest that the expected Moho uplift was compensated by magmatic intrusion into the lower crust, producing the observed high-velocity zone.
[42]
Moho and magmatic underplating in continental lithosphere
Dec 8, 2013 · The presence of a deep rift graben above a flat Moho may be explained by compensation of crustal thinning by magmatic intrusions (underplating) ...
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Seismic Evidence for Lithospheric Thinning and Heat in the northern ...
Apr 15, 2019 · Seismic images resolve very thin lithosphere beneath the northern Canadian Cordillera (~50 km) and a dipping structure at upper mantle depth ...
[44]
Seismic evidence for lithospheric boudinage and its implications for ...
May 12, 2022 · We propose that during the Triassic-Jurassic rifting event, the lithosphere was first deformed under pure shear and experienced initial ...
[45]
On isostasy at Atlantic‐type continental margins - AGU Journals
Apr 10, 1982 · The model suggests that a low-rigidity plate (or Airy-type model) is most applicable early in rifting history, while a high-rigidity plate is ...
[46]
Rift migration explains continental margin asymmetry and crustal ...
Jun 6, 2014 · When continents break apart, continental crust and lithosphere are thinned until break-up is achieved and an oceanic basin is formed.
[47]
Influence of the architecture of magma-poor hyperextended rifted ...
Apr 1, 2017 · Based on recent seismic and petrologic data, we synthesize the structure and lithology of magma-poor hyperextended rifted margins and oceans, ...
[48]
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Jul 8, 2014 · The mid-ocean ridge system is the most extensive chain of mountains on Earth, stretching nearly 65,000 kilometers (40,390 miles) and with more ...
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[PDF] EX-22-05, Voyage to the Ridge 2 (ROV and Mapping)
Jan 17, 2023 · Spanning the north-south length of the Atlantic Ocean and stretching an impressive 16,000 km, the Mid-Atlantic Ridge (MAR) is part of the ...
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Mid-Atlantic Ridge Volcanic Processes
Mar 1, 1998 · The Mid-Atlantic Ridge is composed of discrete spreading segments that are tens of kilometers long, and offset by transform faults and nontransform offsets.
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[PDF] Mid-Atlantic Ridge Volcanic Processes
The central valley floor is the primary site of ocean crust con- struction, and most segments contain an axial vol- canic ridge that runs down the center of the ...
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[PDF] An ultraslow-spreading class of ocean ridge
The SWIR and the Knipovitch ridge are examples of ultraslow- to slow-spreading transitional ridges while the intermediate-rate Southeast Indian ridge is an ...
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[PDF] On origin of near-axis volcanism and faulting at fast spreading mid ...
At fast and superfast spreading mid-ocean ridges, such as the East Pacific Rise, a plate boundary is defined by a narrow (tens to hundreds of meters wide) ...
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Pangaea to the Present Lesson #2 - Volcano World
About 180 million years ago the supercontinent Pangea began to break up. ... The Atlantic Ocean will be much larger 50 million years from now and the Pacific ...
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Volcanic and hydrothermal processes - NOAA/PMEL
Several field seasons of investigations using sidescan sonar, a deep-tow camera system, and the submersible Alvin reveal that about 30 km of the ridge crest is ...
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Exploring The Global Mid-Ocean Ridge
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feb4
Feb 4, 2025 · The right photo is of a pile of pillow lavas associated with fissures that develop as the oceanic crust spreads away from the axis. The ...
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Seismicity of the Earth 1900-2013 East African Rift - USGS.gov
The East African Rift system (EARS) is a 3,000-km-long Cenozoic age continental rift extending from the Afar triple junction, between the horn of Africa and ...
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Mar 20, 2014 · Our best fit model predicts extension rates across the EAR basins up to 5.2 ±0.9 mm/yr (95% confidence) at the Afar triple junction. This is ...
[60]
[PDF] The East African rift system
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The Rio Grande rift | Rocky Mountain Geology | GeoScienceWorld
Mar 3, 2017 · ... distance of more than 1,000 km (Fig. 1). Since being recognized as an important continental rift in the 1970s (e.g., Riecker, 1979), this ...
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[PDF] Studies of Geology and Hydrology in the Basin and Range Province ...
The timing of this change in stress orientation has not been established, but a similar change occurred in the northern Rio Grande rift and in the rest of the.
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[PDF] Rio Grande rift--Problems and perspectives
Even though volcanism and extension associated with the Rio Grande rift are relatively minor, the lithosphere beneath the rift is being per- manently altered.
[64]
[PDF] notice - NASA Technical Reports Server (NTRS)
In many if not all cases, oceanic rifts originate as continental rifts. ... continental break up and the opening of the Iapetus Ocean. Jour. Geophy. Res ...<|separator|>
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On the origins of the Iapetus Ocean - ResearchGate
Sep 16, 2025 · The first phase of continental breakup occurred between eastern Laurentia and western Amazonia at 750–700 Ma, leading to the opening of the ...
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Lake Baikal - A Touchstone for Global Change and Rift Studies
The Lake Baikal rift system is a modern analogue for formation of ancient Atlantic-type continental margins. It tells us the first chapter in the story of ...Missing: failed | Show results with:failed
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[PDF] Three Major Failed Rifts in Central North America: Similarities and ...
The Midcontinent Rift. (MCR) and Southern Oklahoma Aulacogen. (SOA) show prominent gravity anomalies due to large volumes of igneous rift-filling rock. The ...
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[PDF] Hot deep origin of petroleum: Deep basin evidence and application
Examples of the ninth point, the prolific nature of aborted rift or block fault basins, are the North Sea basin; Sirte basin; the West Siberian Lowland.
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Syn‐Rift Magmatism and Sequential Melting of Fertile Lithologies in ...
Aug 26, 2023 · Continental rifting often leads to decompression melting of the rising mantle and associated basaltic magmatism. Melting of dry lherzolite ...
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RESEARCH FOCUS: The geodynamics of mantle melting | Geology
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[PDF] Temporal and spatial magmatic evolution of the Rio Grande rift
Continental rifts produce magmas from a variety of source regions; upwelling asthenosphere, enriched lithospheric mantle, and upper and lower crust have been ...
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Eruptions of Hawaiian Volcanoes [USGS]
Rift zones radiate from the summit calderas of both Mauna Loa and Kilauea and extend down the volcanic flanks into the sea. They are elongate tapering ridges ...
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Shield Volcanoes (U.S. National Park Service)
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Jun 10, 1989 · In the second part of the paper we review volcanic continental margins and flood basalt provinces globally and show that they are always related ...
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[PDF] Frontiers in Large Igneous Province research
May 13, 2004 · Continental LIPs can often be subdivided into two distinct pulses, a prerift pulse and a postrift (or syn-rift) pulse (Campbell, 1998;.
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[PDF] The life cycle of large igneous provinces - University of Oregon
Large igneous provinces (LIPs) are among the most extensive magmatic events punctuating Earth's his- tory. They typically emplace 105–107 km3 of mainly.
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Operational thermal remote sensing and lava flow monitoring at the ...
Jan 1, 2016 · Satellite data have been extremely useful for monitoring the ongoing lava flow activity on Kīlauea's East Rift Zone at Pu'u 'Ō'ō over the past ...<|control11|><|separator|>
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Seismicity During Continental Breakup in the Red Sea Rift of ...
Mar 1, 2018 · Focal mechanisms show that this seismicity is accommodating E-W extension. We suggest that the seismic activity at the marginal graben is either ...
[79]
Insights into Extensional Tectonics from a Large Deep Learning ...
Aug 14, 2025 · We observe that normal‐faulting mechanisms dominate the seismic activity only over the depth range of 2–9 km.
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Seismicity and earthquake focal mechanisms in the Baikal rift zone
The seismicity of the Baikal rift zone is considered on the basis of instrumental and field observations. The spatial pattern of epicentres, the frequency ...
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[PDF] Marine geohazards - OceanRep
Tsunamis may be triggered by earthquakes, volcanic eruptions, submarine landslides, and by onshore landslides in which large volumes of debris fall into the ...Missing: Afar quakes
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[PDF] Fault growth at a nascent slow-spreading ridge: 2005 Dabbahu ...
Rifting between Africa and Arabia during the past ∼30 Myr pro- duced the ∼300-km-wide Afar depression at the triple junction be- tween the Red Sea, Gulf of Aden ...
[83]
GSN - Global Seismographic Network | U.S. Geological Survey
The Global Seismographic Network is a permanent digital network of state-of-the-art seismological and geophysical sensors connected by a telecommunications ...
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[PDF] Advancing Earthquake Monitoring in Ethiopia's Southern Rift with a ...
Nov 25, 2024 · A team of international researchers has achieved a breakthrough in earthquake monitoring in Ethiopia's Southern Main. Ethiopian Rift (SMER) ...
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Systematic survey of high‐resolution b value imaging along ...
Feb 26, 2014 · In this study, we improve the methodology of b value imaging for application to a high-resolution 3-D analysis of a complex fault network.
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Critical evaluation of seismic activities in Africa and curtailment ...
Dec 20, 2018 · The magnitudes and intensities of these seismic activities has resulted in devastations, including: loss of lives, building and civil structures ...
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Tackling the drivers of East Africa's surprising earthquake risk
Oct 2, 2018 · In 1989, a 6.2-magnitude earthquake that struck Malawi killed 10 people and caused $28 million in economic losses.