Opening of the North Atlantic Ocean

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Opening of Central and North Atlantic from 170 Ma to the present Central atlantic.png
Opening of Central and North Atlantic from 170 Ma to the present

The opening of the North Atlantic Ocean is a geological event that has occurred over millions of years, during which the supercontinent Pangea broke up. As modern-day Europe (Eurasian plate) and North America (North American Plate) separated during the final breakup of Pangea in the early Cenozoic Era, [1] they formed the North Atlantic Ocean. Geologists believe the breakup occurred either due to primary processes of the Iceland plume or secondary processes of lithospheric extension from plate tectonics.

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Animation of the rifting of the supercontinent Pangea Pangea animation 03.gif
Animation of the rifting of the supercontinent Pangea

Rocks from the North Atlantic Igneous Province have been found in Greenland, the Irminger Basin, Faroe Islands, Vøring Plateau (off Norway), Faroe-Shetland Basin, Hebrides, Outer Moray Firth and Denmark. [2] The supercontinent known as Pangea existed during the late Paleozoic and early Mesozoic eras and began to rift around 200 million years ago. [3] [4] Pangea had three major phases of breakup. The first major phase began in the Early-Middle Jurassic, taking place between North America and Africa. [5] The second major phase of breakup began in the Early Cretaceous. The South Atlantic Ocean opened around 140 million years ago as Africa separated from South America, and about the same time, India separated from Antarctica and Australia, forming the central Indian Ocean.[ citation needed ] The final major phase of breakup occurred in the early Cenozoic, as Laurentia separated from Eurasia. [5] As the two plates broke free from each other, the Atlantic Ocean continued to expand. [5]

Iceland plume theory

Plume hypothesis for continental breakup. Active upwelling heats and weakens crust and creates magmatism. Plume 2.jpg
Plume hypothesis for continental breakup. Active upwelling heats and weakens crust and creates magmatism.

The Iceland plume is a mantle plume under Iceland that carries hot material from the deep within Earth's mantle upwards to the crust. The rising hot material weakens the lithosphere, making the separation of plates easier. [6] The flow of hot plume material creates volcanism under the continental lithosphere. Iceland extends across the Mid-Atlantic Ridge. The Mid-Atlantic Ridge is a divergent plate boundary, and it separates the Eurasian and North American plates. The ages of the earliest volcanic rocks from this plume lie in the late Paleocene, and both sides of the Atlantic Ocean contain these rocks. [7] Since these rocks have been dated to the late Paleocene, this lines up with the time of breakup of the North Atlantic continent, so some think it could have been a contributing factor. [7]

Plate tectonics

This theory views volcanism as the resultant of lithospheric processes rather than heat from the mantle rising up. [6] Instead of heat coming up from deep in the mantle, volcanic anomalies come from a shallow source. [6] [8] Volcanism thus occurs where the crust is easier to break up because it has been stretched by lithospheric extension, allowing melt to reach the surface. [9] Volcanic anomalies are created by plate tectonics such as spreading plate boundaries or subduction zones. [9] The location of the volcanism is governed by the stress field in the plate and the amount of melt is governed by the fusibility of the mantle beneath. [6] Plate tectonics can explain most of the volcanism on Earth.

Active vs. passive plates

Active rifting, such as is formed by the Iceland plume, is driven by hotspot or mantle plume activity. From deep within the Earth, hot mantle rises to force doming of the crust. [10] This causes thinning of the crust and lithosphere, then melting and underplating occur. [10] Finally, there is rifting at the crest of the domed crust and volcanism occurs. [10] In passive rifting, driven by plate tectonics, the crust and lithosphere extend as a result of plate boundary forces such as slab pull. [10] Far field stresses thin the crust and lithospheric mantle, and hot asthenospheric mantle passively enters the thinned area. [10] The upwelling of asthenosphere is not involved in the actual rifting process. The upward flow of the asthenosphere results in decompression melting, magmatic underplating and some volcanism that may occur in the rift area. [10]

See also

Related Research Articles

<span class="mw-page-title-main">Plate tectonics</span> Movement of Earths lithosphere

Plate tectonics is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by geoscientists after seafloor spreading was validated in the mid-to-late 1960s.

<span class="mw-page-title-main">Convergent boundary</span> Region of active deformation between colliding tectonic plates

A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

<span class="mw-page-title-main">Mantle plume</span> Upwelling of abnormally hot rock within Earths mantle

A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian Traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries.

<span class="mw-page-title-main">Large igneous province</span> Huge regional accumulation of igneous rocks

A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive and extrusive, arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.

<span class="mw-page-title-main">Iceland hotspot</span> Hotspot partly responsible for volcanic activity forming the Iceland Plateau and island

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<span class="mw-page-title-main">Passive margin</span> Transition between oceanic and continental lithosphere that is not an active plate margin

A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin. A passive margin forms by sedimentation above an ancient rift, now marked by transitional lithosphere. Continental rifting forms new ocean basins. Eventually the continental rift forms a mid-ocean ridge and the locus of extension moves away from the continent-ocean boundary. The transition between the continental and oceanic lithosphere that was originally formed by rifting is known as a passive margin.

<span class="mw-page-title-main">Magmatism</span> Emplacement of magma on the outer layers of a terrestrial planet, which solidifies as igneous rocks

Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of magma or lava. Volcanism is the surface expression of magmatism.

<span class="mw-page-title-main">Geology of Iceland</span>

The geology of Iceland is unique and of particular interest to geologists. Iceland lies on the divergent boundary between the Eurasian plate and the North American plate. It also lies above a hotspot, the Iceland plume. The plume is believed to have caused the formation of Iceland itself, the island first appearing over the ocean surface about 16 to 18 million years ago. The result is an island characterized by repeated volcanism and geothermal phenomena such as geysers.

<span class="mw-page-title-main">East Australia hotspot</span>

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The term "mesoplates" has been applied in two different contexts within geology and geophysics. The first is applicable to much of the Earth's mantle, and the second to distinct layering within the Earth's crust.

<span class="mw-page-title-main">Delamination (geology)</span> Loss of the portion of the lowermost lithosphere from the tectonic plate to which it was attached

In geodynamics, delamination refers to the loss and sinking (foundering) of the portion of the lowermost lithosphere from the tectonic plate to which it was attached.

Non-volcanic passive margins (NVPM) constitute one end member of the transitional crustal types that lie beneath passive continental margins; the other end member being volcanic passive margins (VPM). Transitional crust welds continental crust to oceanic crust along the lines of continental break-up. Both VPM and NVPM form during rifting, when a continent rifts to form a new ocean basin. NVPM are different from VPM because of a lack of volcanism. Instead of intrusive magmatic structures, the transitional crust is composed of stretched continental crust and exhumed upper mantle. NVPM are typically submerged and buried beneath thick sediments, so they must be studied using geophysical techniques or drilling. NVPM have diagnostic seismic, gravity, and magnetic characteristics that can be used to distinguish them from VPM and for demarcating the transition between continental and oceanic crust.

Volcanic passive margins (VPM) and non-volcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on Earth as the result of the formation of ocean basins via continental rifting. Initiation of igneous processes associated with volcanic passive margins occurs before and/or during the rifting process depending on the cause of rifting. There are two accepted models for VPM formation: hotspots/mantle plumes and slab pull. Both result in large, quick lava flows over a relatively short period of geologic time. VPM's progress further as cooling and subsidence begins as the margins give way to formation of normal oceanic crust from the widening rifts.

<span class="mw-page-title-main">Volcanism of Northern Canada</span> History of volcanic activity in Northern Canada

Volcanism of Northern Canada has produced hundreds of volcanic areas and extensive lava formations across Northern Canada. The region's different volcano and lava types originate from different tectonic settings and types of volcanic eruptions, ranging from passive lava eruptions to violent explosive eruptions. Northern Canada has a record of very large volumes of magmatic rock called large igneous provinces. They are represented by deep-level plumbing systems consisting of giant dike swarms, sill provinces and layered intrusions.

This is a list of articles related to plate tectonics and tectonic plates.

<span class="mw-page-title-main">Geology of Cape Verde</span>

Cape Verde is a volcanic archipelago situated above an oceanic rise that puts the base of the islands 2 kilometers (1.2 mi) above the rest of the seafloor. Cape Verde has been identified as a hotspot and the majority of geoscientists have argued that the archipelago is underlain by a mantle plume and that this plume is responsible for the volcanic activity and associated geothermal anomalies.

Tectonic subsidence is the sinking of the Earth's crust on a large scale, relative to crustal-scale features or the geoid. The movement of crustal plates and accommodation spaces produced by faulting brought about subsidence on a large scale in a variety of environments, including passive margins, aulacogens, fore-arc basins, foreland basins, intercontinental basins and pull-apart basins. Three mechanisms are common in the tectonic environments in which subsidence occurs: extension, cooling and loading.

A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials.

<span class="mw-page-title-main">Plate theory (volcanism)</span>

The plate theory is a model of volcanism that attributes all volcanic activity on Earth, even that which appears superficially to be anomalous, to the operation of plate tectonics. According to the plate theory, the principal cause of volcanism is extension of the lithosphere. Extension of the lithosphere is a function of the lithospheric stress field. The global distribution of volcanic activity at a given time reflects the contemporaneous lithospheric stress field, and changes in the spatial and temporal distribution of volcanoes reflect changes in the stress field. The main factors governing the evolution of the stress field are:

  1. Changes in the configuration of plate boundaries.
  2. Vertical motions.
  3. Thermal contraction.

Intraplate volcanism is volcanism that takes place away from the margins of tectonic plates. Most volcanic activity takes place on plate margins, and there is broad consensus among geologists that this activity is explained well by the theory of plate tectonics. However, the origins of volcanic activity within plates remains controversial.

References

  1. ↑ "Pangea". Encyclopædia Britannica Online. Encyclopædia Britannica Inc. 7 Nov 2012.
  2. ↑ Jolley, D. W.; Bell, B. R. (2002). "The evolution of the North Atlantic Igneous Province and the opening of the NE Atlantic rift". In Jolley, D. W.; Bell, B. R. (eds.). The North Atlantic Igneous Province: Stratigraphy, Tectonic, Volcanic and Magmatic Processes (PDF). Vol. 197. The Geological Society, London, Special Publications. pp. 1–13. Retrieved 10 December 2016.
  3. ↑ Lovett, Richard A. (September 5, 2008). "Supercontinent Pangaea Pushed, Not Sucked, Into Place". National Geographic News. Archived from the original on September 10, 2008. Retrieved 10 December 2016.
  4. ↑ Condie, K. C. (1989). Plate Tectonics and Crustal Evolution (3rd ed.). Pergamon Press. ISBN   9780080348742.
  5. 1 2 3 Merali, Z.; Skinner, B. J. (2009). Visualizing Earth Science. Wiley. ISBN   978-0-470-41847-5.
  6. 1 2 3 4 Foulger, G. R. (2010). Plates vs. Plumes: A Geological Controversy. Wiley-Blackwell. ISBN   978-1-4051-6148-0.
  7. 1 2 White, R. S.; McKenzie, D. P. (1989). "Magmatism at rift zones: The generation of volcanic continental margins and flood basalts" (PDF). Journal of Geophysical Research: Solid Earth. 94 (B6): 7685–7729. Bibcode:1989JGR....94.7685W. doi:10.1029/JB094iB06p07685 . Retrieved 10 December 2016.
  8. ↑ Foulger, Gillian R. (2005-02-08). "Iceland & the North Atlantic Igneous Province" . Retrieved 2012-10-14.
  9. 1 2 Lundin, Erik. "The Iceland "Anomoaly" - An Outcome of Plate Tectonics". StatoilHydro ASA, Research Centre. Retrieved Nov 7, 2012.
  10. 1 2 3 4 5 6 Pirajno, Franco (2000). Ore Deposits and Mantle Plumes. Kluwer Academic Publishers. pp. 221–223. ISBN   9780412811401.
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