North Atlantic Igneous Province

Formation

Isotopic dating indicates the most active magmatic phase of the NAIP was between c. 60.5 and c. 54.5 Ma (million years ago) (mid-Paleocene to early Eocene) – further divided into Phase 1 (pre-break-up phase) dated to c. 62–58 Ma and Phase 2 (syn-break-up phase) dated to c. 56–54 Ma.

Continuing research also indicates that tectonic plate movement (of the Eurasian, Greenland, and North American plates), regional rifting events, and seafloor spreading between Labrador and Greenland may have begun as early as c. 95–80 Ma, c. 81 Ma, and c. 63–61 Ma respectively (late Cretaceous to early Paleocene).

Studies have suggested that the modern day Iceland hotspot corresponds to the earlier 'North Atlantic mantle plume' that would have created the NAIP. Through both geochemical observations and reconstructions of paleogeography, it is speculated that the present day Iceland hotspot originated as a mantle plume on the Alpha Ridge (Arctic Ocean) c. 130–120 Ma, migrated down Ellesmere Island, through Baffin Island, onto the west coast of Greenland, and finally arrived on the east coast of Greenland by c. 60 Ma.

Extensive outpourings of lava occurred, particularly in East Greenland, which during the Paleogene was then adjacent to Britain. Little is known of the geodynamics of the opening of the North Atlantic between Greenland and Europe.

As the Earth's crust was stretched above the mantle hotspot under stress from plate rifting, fissures opened up along a line from Ireland to the Hebrides and plutonic complexes were formed. Hot magma over 1000 °C surfaced as multiple, successive and extensive lava flows covered over the original landscape, burning forests, filling river valleys, burying hills, to eventually form the Thulean Plateau, which contained various volcanic landforms such as lava fields and volcanoes. There was more than one period of volcanic activity during the NAIP, in between which sea levels rose and fell and erosion took place.

Volcanic activity would have started with volcaniclastic accumulations, like volcanic ash, quickly followed by vast outpourings of highly fluid basaltic lava during successive eruptions through multiple volcanic vents or in linear fissures. As mafic low viscosity lava reached the surface it rapidly cooled and solidified, successive flows built up layer upon layer, each time filling and covering existing landscapes. Hyaloclastites and pillow lavas were formed when the lava flowed into lakes, rivers and seas. Magma that did not make it to the surface as flows froze in conduits as dikes and volcanic plugs and large amounts spread laterally to form sills. Dike swarms extended across the British Isles throughout the Cenozoic. Individual central complexes developed with arcuate intrusions (cone sheets, ring dikes and stocks), the intrusions of one centre cut through earlier centres recording magmatic activity with time. During intermittent periods of erosion and change in sea levels, heated waters circulated through the flows altering the basalts and deposited distinctive suites of zeolite minerals.

Activity of the NAIP 55 million years ago may have caused the Paleocene–Eocene Thermal Maximum, where a large amount of carbon was released into the atmosphere and the Earth substantially warmed. One hypothesis is that the uplift caused by the NAIP hotspot caused methane clathrates to dissociate and dump 2000 gigatons of carbon into the atmosphere.