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Divergent boundary

A divergent boundary is a type of tectonic plate boundary where two or more lithospheric plates move away from each other, resulting in the upwelling of hot mantle material that generates new crust through magmatic processes.^[1] These boundaries are fundamental to plate tectonics, driving seafloor spreading and continental rifting.^[2] Divergent boundaries occur primarily in two settings: oceanic and continental. Oceanic divergent boundaries form extensive submarine ridge systems, such as the Mid-Atlantic Ridge, where plates separate at rates typically ranging from 1 to 10 cm per year, allowing basaltic magma to erupt and solidify into new oceanic lithosphere.^[3] The global network of mid-ocean ridges spans nearly 46,000 miles (74,000 km), representing the longest mountain range on Earth and accounting for a significant portion of the planet's volcanism.^[4]^[5] In contrast, continental divergent boundaries, exemplified by the East African Rift System, involve the extension and thinning of continental crust, often producing rift valleys, fault-block mountains, and alkali basalt volcanism as the lithosphere stretches and partially melts.^[6] These processes can eventually lead to the formation of new ocean basins if divergence persists over millions of years.^[7] At divergent boundaries, tectonic activity manifests as shallow-focus earthquakes along normal faults and frequent effusive eruptions of fluid basaltic lava, which solidify to form features like fissure vents and pillow lavas in oceanic settings.^[8] The separation creates zones of reduced pressure that facilitate mantle decompression melting, sustaining the continuous production of crust and influencing global heat transfer from Earth's interior.^[9] Notable examples include the East Pacific Rise, a fast-spreading oceanic boundary off the western Americas, and the slower-spreading Mid-Atlantic Ridge, which bisects the Atlantic Ocean.^[1]

Definition and Characteristics

Definition

A divergent boundary is a linear zone of tectonic activity where two lithospheric plates diverge, or move away from each other, resulting in the upwelling of mantle material that generates new oceanic or continental crust and lithosphere.^[1] This process accommodates the relative motion between plates by creating new lithosphere at rates typically ranging from 1 to 10 cm per year.^[10] The concept of divergent boundaries emerged within the framework of plate tectonics theory, which built upon Alfred Wegener's 1912 proposal of continental drift but gained acceptance in the 1960s through evidence of seafloor spreading and magnetic striping on the ocean floor.^[11] In this theory, Earth's lithosphere is divided into rigid plates that interact at boundaries, with divergence representing one of three primary types alongside convergence and transform motion.^[12] Divergence facilitates global plate circulation by balancing subduction at convergent margins through the continuous production of lithosphere.^[13] Divergent boundaries manifest in two principal types: oceanic, occurring beneath ocean basins where seafloor spreading produces new basaltic crust, and continental, situated within landmasses where rifting thins and fractures the continental lithosphere.^[6] Oceanic divergence predominates along submarine spreading centers, while continental divergence initiates the breakup of supercontinents.^[14] Representative examples include mid-ocean ridges for oceanic settings and the East African Rift for continental ones.^[15]^[16]

Key Characteristics

Divergent boundaries exhibit features shaped by extensional or tensional stress, including normal faulting, which results from the stretching and thinning of the lithosphere.^[16]^[17] Volcanic activity at these boundaries primarily involves the eruption of basaltic magma produced through partial melting of the upper mantle, leading to the formation of pillow lavas in oceanic environments or flood basalts in continental settings.^[18]^[19] Seismic activity is characterized by shallow-focus earthquakes concentrated along the axis of the boundary, with magnitudes generally below 6.0 due to the brittle fracturing of newly formed crust.^[20]^[21] The underlying magmatic processes are initiated by the passive upwelling of asthenospheric material beneath the diverging plates, which reduces pressure and triggers decompression melting to generate magma.^[9] A hallmark of oceanic divergent boundaries is the symmetric progression of crustal rock ages, with the youngest rocks at the boundary and progressively older rocks forming mirror-image patterns on either side, indicative of continuous seafloor spreading.^[22]

Formation Processes

Driving Mechanisms

The primary driving mechanism for divergent boundaries is the upwelling of mantle convection currents beneath tectonic plates. These currents, driven by heat from Earth's core and radioactive decay in the mantle, cause hot, less dense material to rise toward the lithosphere, where it diverges and exerts tensile forces that pull plates apart. This process facilitates seafloor spreading at oceanic ridges and rifting in continental settings.^[2]^[23]^[24] Secondary forces contributing to plate divergence include ridge-push and slab-pull. Ridge-push arises from the gravitational sliding of elevated mid-ocean ridges, where buoyant, newly formed crust descends away from the ridge axis due to its topographic height. Slab-pull, originating at distant subduction zones, exerts a stronger tractive force as dense, cold oceanic lithosphere sinks into the mantle, effectively dragging the entire plate and enabling continued divergence at the opposite boundary. Together, these gravity-driven mechanisms supplement mantle convection to sustain plate motion.^[25]^[26]^[27]^[28]^[29] Localized mantle plumes, associated with hotspots, can enhance divergence by providing additional heat and buoyancy that weaken the lithosphere and promote rifting, particularly during continental breakup. These plumes rise from deep mantle sources, increasing magmatic activity and extensional stress in regions like the East African Rift. Recent studies as of 2025 have identified evidence of a vast superplume beneath the East African Rift, contributing to the ongoing continental breakup.^[30]^[31]^[32] Paleomagnetic evidence, notably the Vine-Matthews hypothesis proposed in 1963, supports these mechanisms through the observation of symmetric magnetic stripes on the ocean floor, which record reversals in Earth's magnetic field as new crust forms via seafloor spreading. This pattern confirms the continuous divergence driven by upwelling and associated forces.^[33] Divergence rates typically range from 1 to 10 cm per year, varying based on plate size, boundary geometry, and underlying mantle flow patterns, with faster rates at Pacific ridges and slower ones in the Atlantic. This upwelling supplies magma essential for crustal development at divergent zones.^[1]^[34]^[35]^[36]^[37]

Crustal Development

At divergent boundaries in oceanic settings, seafloor spreading drives the formation of new crust as magma ascends from the mantle through weakened zones at mid-ocean ridges, erupts or intrudes, and solidifies into basaltic igneous rock.^[12] This process renews the oceanic lithosphere, with the newly formed crust exhibiting a layered structure: an upper layer of pillow basalts and sheeted dikes overlying a lower gabbroic layer, all derived from partial melting of the upper mantle.^[38] The resulting oceanic crust is typically 5-10 km thick and composed primarily of dense mafic rocks like basalt, with an average density of about 2.9 g/cm³, contrasting sharply with the thicker, more felsic continental crust.^[38] Hydrothermal circulation along the ridge axis facilitates rapid cooling of the magma, promoting mineral precipitation and contributing to the crust's initial porosity and alteration.^[38] In continental settings, crustal development begins with rifting stages characterized by lithospheric extension, leading to progressive thinning and eventual breakup. Initial thinning occurs through ductile deformation and heating of the lower crust and mantle, accompanied by broad uplift and the onset of normal faulting that forms rift basins.^[39] As extension intensifies, localized faulting dominates, creating tilted fault blocks, half-grabens, and increased sedimentation, while partial melting generates syn-rift volcanism.^[39] This culminates in continental breakup when the lithosphere ruptures, allowing asthenospheric upwelling and the inception of seafloor spreading to form a new ocean basin, as seen in the transition from supercontinent configurations.^[39] Central to these processes are axial magma chambers beneath the ridge axis, which act as reservoirs for melt derived from mantle decompression. These chambers, typically located 2-4 km below the seafloor, supply magma to a network of vertical dikes that propagate upward to feed eruptions and horizontal sills that contribute to lower crustal accretion.^[40] The formation and stability of these chambers depend on spreading rate; faster rates promote thinner initial sills that evolve into persistent chambers, while slower rates require thicker sills for sustenance, influencing the efficiency of crustal construction.^[40] The geochemical and isotopic signatures of magmas at divergent boundaries reflect derivation from a depleted upper mantle source. Mid-ocean ridge basalts (MORB) are characterized by depletion in highly incompatible elements relative to primitive mantle compositions, with normal (N)-MORB showing systematic isotopic variations such as low 87Sr/86Sr and high 143Nd/144Nd ratios indicative of prior melt extraction events in the mantle.^[41] These signatures arise from low-degree partial melting of a heterogeneous but overall depleted mantle, distinguishing MORB from more enriched ocean island basalts.^[41] Over geological timescales, crustal development at divergent boundaries evolves from active rifting to passive margins following full continental separation. During the rift phase, elevated heat flow and extension maintain dynamic faulting and magmatism; post-breakup, the margins cool, subside thermally, and accumulate thick sedimentary wedges on the thinned continental crust, transitioning to tectonically quiescent passive margins adjacent to maturing ocean basins.^[42] This evolution stabilizes the newly formed lithosphere, with the passive margin featuring a seaward-thickening sedimentary prism and minimal ongoing deformation.^[42]

Geological Features

Oceanic Features

Oceanic divergent boundaries are primarily manifested as mid-ocean ridges, which form elevated, sinuous submarine mountain chains along the seafloor where tectonic plates pull apart. These ridges feature a central rift valley, typically 1-2 km deep and 20-40 km wide, resulting from the fracturing and extension of the lithosphere as new oceanic crust is generated through seafloor spreading. Collectively, the global mid-ocean ridge system spans approximately 65,000 kilometers, encircling the planet like a continuous seam and representing the longest mountain range on Earth.^[43]^[15]^[4] Hydrothermal vents, often termed black smokers, emerge prominently along these ridges, where seawater percolates into the fractured crust, is heated by underlying magma to temperatures exceeding 350°C, and rises to discharge mineral-rich fluids through chimney-like structures. These vents precipitate sulfides and metals, forming towering chimneys up to 15 meters high that emit dark plumes of iron and sulfide particles, creating unique deep-sea environments. The extreme conditions support chemosynthetic ecosystems, where microbes and specialized fauna like tube worms and clams derive energy from chemical reactions involving hydrogen sulfide rather than sunlight, forming isolated oases of biodiversity on the otherwise barren seafloor.^[44]^[45]^[46] Seismic and volcanic activity is pervasive along oceanic divergent boundaries, characterized by frequent low-magnitude earthquakes (typically below 6.0) triggered by crustal extension and faulting within the rift zone. Volcanism is dominated by basaltic eruptions that produce pillow lavas—rounded, tube-like formations—as molten material extrudes and cools rapidly in seawater, building the ridge's elevated topography. These processes occur in axial volcanic ridges or grabens, with eruptions often linked to dike intrusions that propagate along the spreading center, contributing to the continuous renewal of the oceanic crust at rates of 2-10 cm per year.^[10]^[1]^[47] Spreading at mid-ocean ridges is occasionally asymmetric, with one flank of the ridge advancing faster than the other due to offsets from transform faults that connect ridge segments or variations in underlying mantle flow. Transform faults, which accommodate lateral shear between spreading segments, can lead to oblique spreading and crustal thickness disparities, where one side may exhibit more intense faulting or magmatism. Such asymmetry is observed in regions like the Mid-Atlantic Ridge, influencing the overall geometry of the ridge system.^[48]^[49] Bathymetric profiles across mid-ocean ridges reveal a characteristic pattern where seafloor depth shallows to 2-3 km at the ridge axis before progressively deepening to over 5 km at distances of 100-200 km away, driven by thermal cooling and subsidence of the oceanic lithosphere. As newly formed hot crust conducts heat to the overlying seawater, it contracts and thickens, causing the seafloor to sink according to models like the half-space cooling approximation, which predicts subsidence proportional to the square root of age. This results in smoother, broader abyssal plains farther from the ridge, contrasting the rugged axial terrain.^[50]^[51]^[52]

Continental Features

Continental divergent boundaries manifest as rift zones where the lithosphere stretches and thins, leading to the formation of rift valleys through extensional tectonics. These valleys are primarily grabens—downdropped blocks bounded by normal faults—often accompanied by half-grabens on one side and elevated horsts on the other, creating a characteristic topographic asymmetry. The East African Rift exemplifies this block faulting, where repeated extension has produced deep basins flanked by uplifted shoulders.^[16]^[53]^[54] Volcanism at continental rifts arises from partial melting of the asthenosphere due to lithospheric thinning and upwelling, resulting in bimodal suites dominated by alkaline basalts and rhyolites. Alkaline basalts, enriched in sodium and potassium, erupt as fissure-fed flows or cinder cones, reflecting low-degree melting of a garnet-bearing mantle source, while rhyolites form from crustal anatexis or fractionation of mafic magmas. In the Rio Grande Rift, for instance, this volcanism has produced extensive plateaus of basaltic lavas interspersed with silicic ignimbrites, contributing to the region's volcanic landscape.^[55]^[56]^[57] Sedimentary basins develop within these rift depressions as subsidence creates accommodation space for accumulating clastic sediments eroded from surrounding highlands and volcaniclastics from ongoing eruptions. These basins often exhibit syn-rift architecture, with wedge-shaped deposits thickening toward active faults, including alluvial fans, lacustrine shales, and fluvial sands that record the evolving tectonic environment. The rift basins of the Basin and Range Province illustrate this, where thick sequences of Tertiary sediments preserve evidence of episodic extension and basin filling.^[58]^[59]^[60] Uplift along rift margins results from isostatic rebound of the thinned lithosphere and flexural response to loading by sediments and volcanics, forming prominent shoulder escarpments that bound the rift axis. Erosion of these uplifted flanks produces pediments—gently sloping erosion surfaces—and deepens valleys through fluvial incision, enhancing the relief contrast. In the Baikal Rift, such escarpments rise over 1,000 meters above adjacent basins, with pediment development reflecting long-term denudation rates of approximately 5-15 meters per million years.^[16]^[61] The Red Sea represents a young continental rift in transition toward oceanic spreading, where axial extension has flooded the rift floor with seawater while preserving continental crust and rift features like evaporite-filled basins and volcanic islands. This immature stage highlights how prolonged divergence can evolve from terrestrial rifting to marine conditions without fully maturing into an ocean basin.^[62]^[63]^[64]

Examples

Oceanic Examples

The Mid-Atlantic Ridge exemplifies a slow-spreading oceanic divergent boundary, extending approximately 16,000 kilometers from Iceland in the north to Bouvet Island in the south, where the Eurasian and North American plates diverge from the African and South American plates at an average rate of about 2.5 centimeters per year.^[1] This slow spreading rate results in a prominent axial rift valley, typically 20 to 30 kilometers wide and 1 to 3 kilometers deep, characterized by rugged terrain and frequent exposure of mantle-derived peridotite due to limited magmatic supply.^[65] The ridge's segmented structure includes transform faults that offset the axis, contributing to its overall linearity and the formation of fracture zones perpendicular to the spreading direction.^[1] In contrast, the East Pacific Rise represents a fast-spreading divergent boundary, primarily separating the Pacific Plate from the Nazca, Cocos, and North American plates along a roughly 9,000-kilometer axis from the Gulf of California southward to near 55°S latitude, with spreading rates varying from 6 to 16 centimeters per year.^[66] Faster spreading leads to smoother topography without a deep rift valley, as continuous magma supply builds a broad, elevated axial high and creates overlapping spreading centers where adjacent segments interact without forming transform faults.^[67] These overlapping centers, observed particularly between 9°N and 19°S, facilitate efficient crustal accretion and result in shorter, more dynamic ridge segments compared to slower-spreading systems.^[68] The discovery of oceanic divergent boundaries began in the 1950s through echo-sounding surveys that mapped the continuous, rugged topography of mid-ocean ridges, revealing their global extent and central position in ocean basins.^[12] By the 1960s, shipboard magnetometer measurements detected symmetric magnetic anomalies flanking the ridges, which were interpreted as stripes recording reversals in Earth's magnetic field during seafloor spreading, providing key evidence for plate tectonics.^[69] These findings, pioneered by researchers like Harry Hess and Frederick Vine, confirmed that new oceanic crust forms at ridges and migrates away at predictable rates.^[70] An example of ultra-slow spreading is the Gakkel Ridge in the Arctic Ocean, where the North American and Eurasian plates diverge at rates less than 1.5 centimeters per year, resulting in prolonged amagmatic segments with limited volcanism and widespread serpentinization of mantle rocks.^[71] This ridge's variable crustal thickness, often thinner than 4 kilometers in amagmatic zones, highlights how reduced melt production at ultra-slow rates exposes ultramafic rocks and alters typical ridge morphology.^[72] Ongoing monitoring of oceanic divergent boundaries relies on deep-sea submersibles such as Alvin, which since the 1970s has enabled direct observation of ridge-axis processes, including the hydrothermal vents that emerge along these boundaries and support unique chemosynthetic ecosystems.^[73] These expeditions have mapped volcanic eruptions, faulting, and fluid circulation in real time, enhancing understanding of crustal formation dynamics.^[74]

Continental Examples

The East African Rift System (EARS) represents one of the most prominent active continental divergent zones, spanning approximately 3,000 km from the Afar Triple Junction in Ethiopia southward into Mozambique.^[75] Rifting initiated around 25 million years ago during the Oligocene-Miocene transition, driven by mantle upwelling and associated with widespread volcanism that separated the African continent into the Nubian and Somalian plates. This system features two main branches: the Eastern Branch, characterized by deep rift valleys and alkaline volcanism, and the Western Branch, with shallower basins and sediment-filled lakes such as Lake Tanganyika, which stretches 650 km and reaches depths exceeding 1,400 m.^[76] Notable volcanoes like Mount Kilimanjaro, formed by rift-related magmatism, rise over 5,800 m and exemplify the system's volcanic activity, though currently dormant.^[77] In North America, the Basin and Range Province exemplifies a mature continental extensional regime, covering much of the western United States from the Sierra Nevada to the Colorado Plateau. Extension began around 30 million years ago in the Oligocene, intensifying during the Miocene with widespread normal faulting that created a distinctive landscape of alternating mountain ranges and basins.^[78] The crust has thinned to as little as 20-30 km in places due to this stretching, accompanied by high-angle normal faults that accommodate up to 100% extension in some areas, leading to metamorphic core complexes and Basin and Range topography.^[79] The Baikal Rift Zone in Siberia, Russia, is an active incipient rift system where the Eurasian Plate is extending, forming the world's deepest continental rift lake. Lake Baikal, reaching 1,637 m in depth, occupies a narrow graben basin within the rift, which has been developing since the late Oligocene around 25-30 million years ago.^[80] Ongoing divergence occurs at an average rate of about 4 mm per year, as measured by geodetic and seismic data, resulting in continued basin subsidence and fault activity.^[80] Ancient continental divergent boundaries are preserved in geological remnants, such as those associated with the opening of the Iapetus Ocean during the late Proterozoic to earliest Cambrian around 570 million years ago. This rifting split the supercontinent Rodinia, creating a proto-Atlantic ocean basin through crustal thinning and normal faulting along an axis that extended across what is now eastern North America.^[81] Remnants include sedimentary sequences of the Lynchburg Group and overturned horst-graben structures in the Blue Ridge Province of Virginia, which record the initial rift valley formation before the ocean's later closure during the Paleozoic.^[81] Continental rift zones pose significant human impacts, including seismic hazards from normal faulting and geothermal resources from elevated heat flow. In regions like the East African Rift and Basin and Range, earthquakes occur frequently along active faults, with magnitudes up to 7 or greater, threatening populations in rift valleys.^[82] Conversely, thinned crust and mantle upwelling enable geothermal energy extraction, as seen in rift-related hot springs and volcanic fields that support power generation and direct heating applications.^[83]

Relation to Plate Tectonics

Interactions with Other Boundaries

Divergent boundaries often intersect with transform boundaries at points known as triple junctions, where three tectonic plates meet, facilitating complex interactions in plate motion. A prominent example is the ridge-transform-ridge (RTR) triple junction, which connects two segments of a mid-ocean ridge via an intervening transform fault, allowing for the accommodation of differential spreading rates between ridge sections. These junctions are typically unstable and evolve over time, migrating along the boundaries as plates adjust, often transitioning to more stable configurations like transform-ridge-transform (TRT). For instance, the Mendocino Triple Junction off the coast of northern California exemplifies a ridge-transform-convergent junction involving the Pacific, North American, and Gorda plates, where the Gorda Ridge (divergent), Mendocino Fracture Zone (transform), and Cascadia Subduction Zone (convergent) meet, and the transform fault offsets the divergent spreading.^[1]^[84] Transform faults serve as offset segments that link en echelon portions of divergent ridges, enabling lateral shear motion that prevents the ridges from aligning continuously across the globe. These faults, such as those along the Mid-Atlantic Ridge, produce characteristic zig-zag patterns in the seafloor and are sites of frequent shallow earthquakes due to the sliding of plates past one another. By connecting divergent segments, transform faults maintain the continuity of plate divergence while accommodating the spherical geometry of Earth, with offsets ranging from tens to hundreds of kilometers. The [San Andreas Fault](/page/San Andreas Fault) in California illustrates this interaction, acting as a transform boundary that links the East Pacific Rise divergent zone with the Juan de Fuca Ridge.^[1]^[85]^[86] The creation of new oceanic crust at divergent boundaries is intrinsically linked to convergent boundaries through a feedback mechanism involving subduction, where the lithosphere generated at ridges is recycled back into the mantle after approximately 100-200 million years. This cycle balances global tectonic forces, as the rate of crust production at spreading centers—typically 2-10 cm per year—matches the consumption at subduction zones, preventing unchecked expansion of the ocean basins. For example, crust formed at the Mid-Atlantic Ridge is subducted along the Peru-Chile Trench, demonstrating how divergent processes supply material for destructive margins.^[1]^[2]^[87] Divergent boundaries can emerge evolutionarily following the cessation of continental collisions at convergent zones, as post-collisional extension leads to lithospheric thinning and rifting. This transition occurs when compressive forces wane, allowing underlying mantle upwelling to drive divergence, often initiating within orogenic belts. The Afar Depression in Ethiopia provides a key example of this rift-to-ridge evolution, where the continental rift system at the Afar Triple Junction is progressively developing into an oceanic spreading center, linking the Red Sea and Gulf of Aden divergent boundaries as Arabia separates from Africa at rates of about 1-2 cm per year.^[85]^[88]^[1]

Global Implications

Divergent boundaries play a pivotal role in the supercontinent cycle, driving the fragmentation of large landmasses through extensional rifting. The breakup of the supercontinent Pangaea, which began approximately 200 million years ago, exemplifies this process, as divergent plate boundaries formed within the continental interior, leading to the gradual separation of what are now the modern continents.^[89] This rifting initiated the opening of the Atlantic Ocean and facilitated the redistribution of continental crust over hundreds of millions of years, influencing global geography and climate patterns on a planetary scale.^[42] These boundaries are essential to Earth's thermal equilibrium, as divergence at mid-ocean ridges enables the release of a significant portion of the planet's internal heat—estimated at around 20% through hydrothermal circulation along the ridge axes.^[90] This heat loss, primarily from mantle upwelling and magmatic activity, regulates global tectonic activity and modulates the cooling of the Earth's interior over geological time.^[91] Additionally, divergent zones contribute to biodiversity hotspots, particularly in continental rift lakes, where isolated aquatic environments act as evolutionary cradles. For instance, the East African Rift lakes, such as Tanganyika, Malawi, and Victoria, host extraordinary speciation events in cichlid fishes, with over 1,200 endemic species arising from adaptive radiations driven by the unique ecological niches formed during rifting.^[92]^[93] The resource implications of divergent boundaries are profound, yielding valuable mineral deposits and renewable energy sources. Hydrothermal vents along oceanic ridges precipitate polymetallic sulfide deposits rich in copper, zinc, gold, and silver, formed by the interaction of hot, mineral-laden fluids with seawater at divergent plate margins.^[94]^[95] On continents, rift systems like the East African Rift offer significant geothermal energy potential, harnessing heat from shallow magmatic intrusions to generate power, with untapped resources estimated to exceed 10 gigawatts in the region alone.^[96] Advancements in recent research have enhanced understanding of divergent boundary dynamics through satellite geodesy techniques. GPS and InSAR measurements precisely track surface deformation and spreading rates, revealing millimeter-scale annual movements along active rifts, such as those in Iceland's propagating ridge systems.^[97]^[98] Studies from the 2020s have further illuminated the role of microplates in rift evolution, using numerical modeling to demonstrate how linkage between rift segments forms rotating continental microplates, as observed in the East African Rift's Victoria microplate, which influences local strain distribution and tectonic stability. Recent 2025 research has updated constraints on the Victoria microplate's Euler pole, indicating possible strain accommodation ahead of rift termini.^[99]^[100]^[101]

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Jul 19, 2023 · Here, we investigate the influence of plate boundary geometry and viscosity, asthenosphere viscosity, and the relative contribution of upper and ...
[38]
The Oceanic Crust and Seafloor - University of Hawaii at Manoa
As old oceanic crust is subducted and melted into magma, new oceanic crust in the form of igneous rock is formed at mid-ocean ridges and volcanic hotspots. This ...
[39]
Rifting - an overview | ScienceDirect Topics
With distance from the divergent plate boundary, the continental margin will become cooler, collect sediment, and isostatically sink to create a passive ...
[40]
Emplacement of dikes, sills and crustal magma chambers at ...
May 10, 1990 · For the fastest spreading ridges the initial thickness of a sill that is to develop into a crustal chamber need only attain 20 m, whereas at the ...
[41]
The mean composition of ocean ridge basalts
Mar 6, 2013 · The mean composition of MORB is determined using a global dataset of elements, trace elements, and isotopes, and is more enriched than early ...
[42]
Divergent Plate Boundary—Passive Continental Margins
Feb 11, 2020 · Mature Ocean Basin The transitions from thick continental to thin oceanic crust are passive continental margins because they are far away from ...
[43]
Mid-ocean Ridges - Woods Hole Oceanographic Institution
Some mid-ocean ridges exhibit slow separation rates, with tectonic plates separating less than 40 millimeters (about 1.5 inches) per year. Other locations ...
[44]
What is a hydrothermal vent? - NOAA's National Ocean Service
Jun 16, 2024 · “Black smokers” are chimneys formed from deposits of iron sulfide, which is black. “White smokers” are chimneys formed from deposits of ...Missing: mid- | Show results with:mid-
[45]
Hydrothermal vents - NOAA/PMEL
Hydrothermal vents are hot springs on the ocean floor, heated by magma. They include 'black smokers' with 'smoke' and diffuse vents with warm water.
[46]
Hydrothermal Vents - Dive & Discover
In 1979, scientists in Alvin dove to the Mid-Ocean Ridge in the eastern Pacific. A spectacular sight greeted them. Clouds of what looked like black smoke were ...Missing: smokers | Show results with:smokers
[47]
Plate Tectonics and Volcanoes - National Park Service
Jun 8, 2022 · Volcanoes form at divergent boundaries where plates rip apart, convergent boundaries where one plate subducts, and hotspots where rising mantle ...
[48]
[PDF] Evidence for weak oceanic transform faults - Woods Hole ...
[2] Oceanic transform faults are fundamental features of the mid-ocean ridge spreading system. ... normal fault planes becomes asymmetrical across the ends.
[49]
Mechanism of progressive broad deformation from oceanic ...
Nov 27, 2021 · Oceanic transform faults (TFs) are commonly viewed as single, narrow strike-slip seismic faults that offset two mid-ocean ridge segments.
[50]
Thermal Evolution of the Oceanic Lithosphere - SERC (Carleton)
Oct 12, 2015 · Plot the predicted seafloor bathymetry from the half-space cooling model as a function of distance from the ridge axis assuming a spreading half ...<|separator|>
[51]
[PDF] Part I – Ocean basin depth profile - Purdue University
As observed in the ocean profile, the ocean depth increases away from the MOR. This subsidence of the oceanic lithosphere could be caused by cooling of the ...
[52]
[PDF] Ocean Bathymetry and Plate Tectonics
The large-scale bathymetry is dominated by cooling and subsidence of the plates as they slide away from the ridge axes. (Data derived from sparse ship soundings ...
[53]
Geological Rift Models
Structurally, rift valleys are block-fault graben (valleys created when a block of the earth sinks), bordered by horst mountains on either side (horsts are ...
[54]
Tectonic Landforms and Mountain Building - National Park Service
Dec 28, 2020 · When divergent plate motion occurs beneath a continental crust, rift structures and normal faults form. This continental rifting causes valleys ...
[55]
Igneous Rocks & Plate Tectonics - Tulane University
Nov 12, 2003 · Small volumes of alkali basalt have also erupted in Iceland. This alkaline volcanism occurs on top of the tholeiitic basalts and erupts in ...
[56]
Magmatic history of Red Sea rifting: Perspective from the central ...
The dikes and volcanic rocks consist of a bimodal mafic-felsic suite with transitional subalkaline to alkaline chemistry. Although no unique petrogenetic model ...
[57]
[PDF] Temporal and spatial magmatic evolution of the Rio Grande rift
Between 30 Ma and 20 Ma, volcanism was dominated by weakly alkaline to calc-alkaline basalts and basaltic andesites, although lavas as evolved as 69% SiO ...
[58]
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.
[59]
[PDF] Preliminary Catalog of the Sedimentary Basins of the United States
For this report, rift basins are those basins that form within continental masses as a result primarily of extensional forces, resulting in a normal-fault ...
[60]
[PDF] Tectonics of Sedimentary Basins
Rifts are fault-bounded troughs where the lithosphere is reduced, acting as sediment receptacles preserving tectonic environment records.
[61]
[PDF] Rates of erosion and landscape change along the Blue Ridge ...
Oct 13, 2016 · Uplift occurs along a rift axis, creating an escarpment and asymmetric drainage divide, and topography is maintained as the divide migrates away ...
[62]
[PDF] Origins of Coastal Uplift in San Diego and Orange Counties
Rift shoulders are typically asymmetrical with a steep escarpment facing the rift and gradually decreasing elevation along a concave-up slope away from the rift ...<|control11|><|separator|>
[63]
Transition from continental rifting to oceanic spreading in the ...
Mar 10, 2021 · The Red Sea is part of the large “Afro-Arabian rift system” that propagates from the Dead Sea to Mozambique and is considered among the youngest ...
[64]
Northern Red Sea: Nucleation of an oceanic spreading center within ...
Jun 25, 2019 · The northern Red Sea is an amagmatic continental rift in which an oceanic spreading center is beginning to develop.
[65]
[PDF] Geological Evolution of the Red Sea: Historical Background, Review ...
The Red Sea is part of an extensive rift system that includes from south to north the oceanic. Sheba Ridge, the Gulf of Aden, the Afar region, the Red Sea, ...
[66]
The Mid-Ocean Ridge - University of California, Santa Barbara
In contrast, the axis of a slow-spreading ridge is characterized by a rift valley a few kilometers deep and about 20 to 30 kilometers wide. In the early 1980's, ...
[67]
Fast: 10-20 cm/yr | Volcano World | Oregon State University
Fast-spreading mid-ocean ridges move 100-200 mm/yr. The East Pacific Rise is perhaps the best studied fast-spreading mid-ocean ridge.
[68]
Fast-Spreading Center - Lithosphere - Syracuse University
Bathymetric map of the fast-spreading East Pacific Rise, spreading segments, transforms, overlapping spreading centers, and abyssal hills. upper oceanic ...
[69]
Overlapping spreading centres: new accretion geometry on the East ...
Based on wax model studies of spreading centres, we suggest here that transform faults fail to develop at fast spreading centres where the lateral offsets are ...
[70]
Achievements in Marine Geology and Geophysics - NCBI - NIH
The data collected by Ewing and others showed that the mid-ocean ridges were clearly the youngest part of the seafloor. ... ridge magnetic anomalies. The ...
[71]
Continental Drift and Seafloor Spreading - Dive & Discover
In the 1950s and 1960s, marine geologists such as Bruce Heezen, Marie Tharp, and Henry Menard used data from echo sounders to map ocean ridges in the North ...
[72]
[PDF] An ultraslow-spreading class of ocean ridge
The ultraslow-spreading ridges consist of linked magmatic and amagmatic accretionary ridge segments. The amagmatic segments are a previously unrecognized class ...
[73]
Highly variable magmatic accretion at the ultraslow-spreading ... - NIH
Results from a high-resolution ocean-bottom seismometer experiment at the ultraslow-spreading Gakkel Ridge show unexpected highly variable crustal thickness and ...
[74]
History of Alvin - Woods Hole Oceanographic Institution
From there the ship and submersible returned to the East Pacific Rise for two studies of hydrothermal, volcanological and geochemical processes near Ocean ...
[75]
The Discovery of Hydrothermal Vents : 1977 - Astounding Discoveries
Mar 9, 1977 · In 1977, ANGUS detected a temperature spike, and Alvin found the first hydrothermal vent with 8°C water and a dense biological community.Missing: 1970s | Show results with:1970s
[76]
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 ...
[77]
Rift Lakes and Paleoclimate - Lesson 10: East African Rifting
Lake Tanganyika is the seventh biggest lake in the world, with an area of about 34 000 km². The lake is 650 km long and up to 60 km wide. The maximum depth is ...Missing: examples | Show results with:examples<|separator|>
[78]
Lesson 10: East African Rifting
You are probably familiar with one or more of the African volcanoes already. Mounts Kenya and Kilimanjaro are both major volcanic mountains, although neither ...
[79]
[PDF] Studies of Geology and Hydrology in the Basin and Range Province ...
Basin and range extension began about 30 m.y. ago. (Price and Henry, 1984), but basin formation did not occur until several million years later. Isotopic ...
[80]
[PDF] Geometry and magnitude of extension in the Basin and Range ...
Aug 15, 2018 · The Basin and Range Province is a clas sic locality of continental extension, and it is ideal for analyzing factors that control the.
[81]
baikal region russia: Topics by Science.gov
Rifting started ca. 30 Ma ago and is still active with a present-day average extension rate of about 4 mm/yr. With a depth of 1637 m, Lake Baikal is the ...
[82]
Geol Evol Virginia-Cross Section B
But during the latest Proterozoic and earliest Cambrian, North America and "Africa" start to rift apart forming the new Proto-Atlantic (also called Iapetus) ...
[83]
[PDF] The Rio Grande Rift
Continental rifts are potential sites of hydrocarbon reserves, geothermal resources, and mineral deposits. They are also places of significant earthquake hazard ...
[84]
[PDF] Rift Zones as a Case Study for Advancing Geothermal Occurrence ...
Feb 11, 2013 · The average heat flow within the Baikal Rift is relatively low, 40-75 mW/m2, compared with 100-115 mW/m2 in the Rio Grande, Rhine, and Kenya ...
[85]
[PDF] TRIPLE JUNCTIONS
The relation of these velocity lines to the velocity of the two plates depends upon whether the boundary is a trench, transform, or ridge. Marbles rolling along.Missing: divergent | Show results with:divergent
[86]
Plate Tectonics - Tulane University
Aug 26, 2015 · Divergent Plate boundaries, where plates move away from each other. Convergent Plate Boundaries, where plates move toward each other.Missing: key | Show results with:key
[87]
Transform Plate Boundaries - Geology (U.S. National Park Service)
Feb 11, 2020 · The grinding action between the plates at a transform plate boundary results in shallow earthquakes, large lateral displacement of rock, and a ...
[88]
Age of the Seafloor - Science On a Sphere - NOAA
Very little of the sea floor is older than 150 million years. This is because the oldest sea floor is subducted under other plates and replaces by new surfaces.
[89]
The Afar Triple Junction and sea-floor spreading - NASA ADS
The Afar depression is generally agreed to represent oceanic crust, part of the Red Sea-Gulf of Aden floor produced by drift of Arabia from Africa. ... From the ...
[90]
Supercontinents – Geology 101 for Lehman College (CUNY)
Pangaea has been breaking apart since about 200 million years ago. Divergent plate boundaries formed within the continents to cause them to rift apart. The ...
[91]
Quantitative estimate of heat flow from a mid‐ocean ridge axial ...
Aug 24, 2014 · Hydrothermal circulation transfers heat from newly formed oceanic crust into the overlying ocean, removing more than 88% of the total heat of ...
[92]
Heat from Earth's core could be underlying force in plate tectonics
Jan 17, 2017 · The researchers estimate up to approximately 50 percent of plate dynamics are driven by heat from the Earth's core and as much as 20 terawatts ...
[93]
East African cichlid fishes | EvoDevo | Full Text - BioMed Central
Jan 5, 2023 · Research has largely focused on East African cichlids of the Rift Lakes Tanganyika, Malawi, and Victoria that constitute the biodiversity hotspots of cichlid ...
[94]
The Impact of the Geologic History and Paleoclimate on the ...
This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks.
[95]
[PDF] Factsheet: Hydrothermal Vents - NOAA Ocean Exploration
Areas where tectonic plates are moving apart from one another are called divergent plate boundaries, ... towers as well as mineral-rich deposits on the seafloor.
[96]
Mining of deep-sea seafloor massive sulfides: A review of the ...
Rapid precipitation of metal sulfides from their host hydrothermal fluid in tight systems leads to chimney formation, with chimney collapse and coalescence ...
[97]
The East African Rift Realising the Regions Geothermal Potential
Nov 17, 2020 · Geothermal potential of the East African Rift has been largely unrealised due to various challenges. Adequate policies and regulatory ...
[98]
Integration of GPS and InSAR Data for Resolving 3‐Dimensional ...
Mar 20, 2020 · We develop an algorithm to integrate GPS and InSAR data for a 3-dimensional crustal deformation field at the Earth's surface.
[99]
Geodetic investigation of plate spreading along a propagating ridge
We utilize new terrestrial (dry-tilt) and space (GPS and InSAR) geodetic data to investigate the nature of plate spreading and magma-tectonic interaction.2 Methods · 2.1 Gps Data Collection And... · 2.6 Torfajökull Volcano
[100]
(PDF) Formation of Continental Microplates Through Rift Linkage
Here we focus on microplate formation and their temporal evolution in continental rift settings. To this aim, we employ the geodynamic finite element software ...<|control11|><|separator|>
[101]
Victoria continental microplate dynamics controlled by the ...
The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In ...