Theopening of the North Atlantic Ocean is ageological event that has occurred over millions of years, during which thesupercontinentPangea broke up. As modern-day Europe (Eurasian Plate) and North America (North American Plate) separated during the final breakup of Pangea in the earlyCenozoic Era,[1] they formed the NorthAtlantic Ocean. Geologists believe the breakup occurred either due to primary processes of theIceland plume or secondary processes oflithospheric extension fromplate tectonics.
Rocks from theNorth Atlantic Igneous Province have been found inGreenland, theIrminger Basin,Faroe Islands,Vøring Plateau (off Norway),Faroe-Shetland Basin,Hebrides, OuterMoray Firth andDenmark.[2] The supercontinent known asPangea existed during the latePaleozoic and earlyMesozoic eras and began torift around 200 million years ago.[3][4] Pangea had three major phases of breakup.
TheIceland plume is amantle plume underIceland 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 createsvolcanism under thecontinental lithosphere. Iceland extends across theMid-Atlantic Ridge. The Mid-Atlantic Ridge is adivergent plate boundary, and it separates the Eurasian and North American plates. The ages of the earliest volcanic rocks from this plume lie in the latePaleocene, 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]
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, allowingmelt to reach the surface.[9] Volcanic anomalies are created by plate tectonics such as spreading plate boundaries orsubduction 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 rifting, such as is formed by theIceland 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 andlithosphere, then melting andunderplating 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 asslab pull.[10] Far field stresses thin the crust and lithospheric mantle, and hot asthenospheric mantle passively enters the thinned area.[10] The upwelling ofasthenosphere is not involved in the actual rifting process. The upward flow of the asthenosphere results indecompression melting, magmatic underplating and some volcanism that may occur in the rift area.[10]