A boundary between two tectonic plates runs up the entire length of the North Atlantic, this is a feature called the Mid-Atlantic Ridge, in reality a mountain chain. On one side is the North American plate, on the other is the Eurasian plate and sea floor spreading is slowly moving them apart. The North Atlantic we know today was formed during the past 60 million years. Animation Explaining How Sea Floor Spreading Moves Tectonic Plates Apart. The mid-ocean ridges combine to form a global undersea mountain system.
As well as the fault-lines where tectonic plates meet there are other fractures, punctures and lines of weakness in the earth’s crust through which molten volcanic rock, known as basaltic magma, and superheated water can be ejected with considerable force.
These fractures (known as vents) and their underlying reservoirs of molten rock can pour out enormous amounts of basaltic magma (inc. rhyolites & gabbros) that can cover huge surrounding areas in thick, flat sheets of magma; these are known as sills. If a magma outpouring occurs deep underwater the immense pressure causes mineral rich water to be squeezed from underground rocks and sediments, helping to lower the melting point of the magma and making it both more buoyant and more easily squeezed upwards. As the molten magma rises it can attract lighter elements, especially silica, so becoming the rocks we know as granites.
When large quantities of this magma spills out onto either the earth’s surface or onto the seabed, a number of gases, e.g. carbon dioxide & sulphur dioxide, accompany them and can have dramatic consequences for the oceans, climate and the environment.
These magma outpourings are known as Large Igneous Provinces. Land formations such as the Columbia Plateau in the Pacific Northwest of America and the Deccan traps (traps = stepped hills) in India are visible examples today; but the largest magma outpourings have occurred deep in ocean basins, producing gigantic features such as the Ontong Java Plateau under the western Pacific and the Kerguelen Plateau under the Indian Ocean.
Geologists categorise Large Igneous Provinces as Continental Flood Basalts, Volcanic Rifted Margins or Oceanic Plateaus and Ridges.
As well releasing magma vents can also disgorge superheated water. This happens when water is sucked down through cracks in the sea floor rock; heated by contact with the Earth's interior it is then forced by pressure up back into the ocean through vents. This water does not boil because it is under so much pressure from the tremendous weight of the ocean above and can reach temperatures that can exceed 400°C (752°F). As the water travels through the earth it becomes saturated with minerals and gases, particularly methane and hydrogen sulphide.
The North Atlantic Igneous Province (NAIP) is one of the largest such on earth and extends from Baffin Island and Greenland northwards into the Arctic, east across to Norway and southwards down to Denmark, Scotland and Northern Ireland.
Outpourings of its magma created the Scottish islands of Skye, Rhum, Eigg, Canna and the basalt columns of the Giant’s Causeway and Fingle’s Cave.
Flood basalts from this time are still widely exposed on the Faroe Islands, Greenland and Baffin Island whilst Iceland remains a volcanically active ‘hot spot’ to this day.
It is known that the NAIP was particularly active at two periods in the deep past; the first phase was between 62 - 58 million years ago, with a second phase at the time of the PETM, between 56 - 54 million years ago when the area began to be uplifted; the continental plate split apart and emitted large volumes of magma.
With hindsight, there was always a possibility that a magma outpouring would meet a large storehouse of combustible hydrocarbon fuels under or on the seabed floor, such as the vast quantities of methane contained in organic rich sediments under the seabed or methane hydrates on the sea floor.
Find Out More:
Where possible I have tried to connect links to either full copies or abstracts of the papers below. If links are broken try copying and pasting the title into Google or Google Scholar; that should help you locate an abstract at least. Also please let me know at: firstname.lastname@example.org
Layers Of Once Molten Rock Under The Atlantic Ocean Mapped. Science Daily. 2008.
Paleocene-Eocene Thermal Maximum and the Opening of the Northeast Atlantic. M. Storey et al. Science. 2007.
Volcanic Activity Triggered Deadly Prehistoric Warming. National Geographic. 2007.Ocean Floor Reveals Clues To Global Warming. Science Daily. 2004.
The Evolution Of The North Atlantic Igneous Province And The Opening Of The NE Atlantic Rift. D. Jolley et al. Geological Society of London. 2002. Abstract.
Early Eocene Evolution Of The Vøring And Lofoten-Vesterålen Passive Volcanic Margins. F. Tsikalas et al. AAPG conference: Hydrocarbon Habitat of Volcanic Rifted Passive Margins. Stavanger conference. 2002. Summary.
The Palaeocene Lava Field Of West-Central Skye. I. Williamson. Transactions of the Royal Society of Edinburgh. 1994. Abstract.
Note: Igneous provinces and the associated release of CH4 and CO2 from the volcanic activity are suspected to have played a major part in the End Permian [a.k.a Permian-Triassic] extinction event, initiated by the Siberian traps igneous province and also in the Early Jurassic extinction event, this time from the Karoo–Ferrar igneous province. Igneous Provinces, Flood Basalts and Ancient Mass Extinctions.