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The British Tertiary Volcanic Province (BTVP) synonymous with the term British Tertiary Igneous Province (BTIP), was a time of intense volcanic activity 52-63 million years ago in Britain in the Paleogene and early Eocene period. During the break up of the supercontinent Pangea, as the North American Plate and Eurasian Plate rifted apart to form the North Atlantic Ocean, Britain sat above a mantle plume (hotspot). 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 1000oC surfaced as multiple, successive and extensive lava flows covered over the original landscape, burning forests, filling river valleys, burying hills, to eventually form a lava plateau named the Thulean Plateau, which contains various volcanic landforms such as lava fields and volcanoes. There was more than one period of volcanic activity during the BTVP, in between which sea levels rose and fell and erosion took place.

The BTVP within the Thulean Plateau
The Thulean Plateau, also synonymous with The North Atlantic Igneous Province and The Thulean Province, was a vast basaltic lava plain that possibly extended over 1,800,000 km2 (700,000 sq mi), which was broken up during the formation of the Atlantic Ocean, leaving remnants existing in the BTVP of Northern Ireland, northwestern Scotland and scattered bits in England and Wales, and outside the BTVP in the Faroe Islands, bits of northwestern Iceland, eastern Greenland and western Norway. Extensive outpourings of lava occurred, particularly in East Greenland, which during the Tertiary period was then adjacent to Britain. Little is known of the geodynamics of the opening of the North Atlantic between Greenland and Europe, but studies have suggested, but is hotly debated, that the modern day Iceland hotspot corresponds to the earlier 'North Atlantic mantle plume' that would have created the Thulean plateau. The BTVP, particularly West Scotland, provides relatively easy access, compared to the largely inaccessible basalt fields of West Greenland, to deeply eroded relics of the central volcanic complexes. So the BTVP is a window into understanding igneous intrusion, evolution of magma, controls of episodic volcanic activity, mechanism and driving force behind ocean opening, hotspot relations to ocean formation and more.



Volcanic and igneous landforms and their extent within the BTVP
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, sucessive 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 Dike (geology) and Volcanic plug and large amounts spread laterally to form Sill (geology). Dike swarms extended across the British Isles throughout the Tertiary. Individual central complexes developed with arcuate intrusions ( cone sheets, ring dykes 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.

Locations of Major Intrusion Complexes within the BTVP:
===Locations of Submarine Central Complexes within the BTVP :===
 * Lundy Island
 * Carlingford, County Louth
 * Mourne Mountains
 * Slieve Gullion -Ring of Gullion AONB
 * Arran
 * Mull
 * Ardnamurchan
 * Rùm
 * Eigg
 * Skye
 * St Kilda
 * Rockall
 * Anton Dohrn Seamount
 * Rosemary Bank
 * Blackstones Bank
 * Brendan
 * Erlend

Other notable locations with spectacular igneous landforms within the BTVP:

 * Giant's Causeway - Polygonal basalt columns, which seen from above are large hexagonal pavements
 * Canna and Sanday - Basalt lava field with great thicknesses of boulder conglomerate, examples of periods of erosion of fast flowing rivers in between the lava flows.
 * Rathlin Island - Lower and Upper Tertiary Lava flows
 * Fingal's Cave on the Isle of Staffa - Polygonal basalt columns eroded to form a cave
 * Ailsa Craig - Volcanic plug
 * Cleveland Dyke, North Yorkshire - Dyke swarm related to the Mull intrusive complex
 * The dike complexes of the BTVP contain many examples of dolerite dike swarms found throughout the British Isles.

BTVP historically studied
The intensity of scientific investigation within the BTVP has made it one of the most historically important and deeply studied igneous provinces in the world. Basalt petrology was born in the Scottish Hebrides in 1903 lead by the eminent British Geologist 'Sir Archibald Geikie'. From the outset Giekie studied the geology of Skye and other Western Isles taking a keen interest in volcanic geology and in 1871 he presented the Geological Society of London with an outline of the 'Tertiary Volcanic History of Britain'. Post Geikie many have tried, and continue to study and understand, the BTVP, and in doing so have advanced knowledge in geology, minerology and in more recent decades geochemistry and geophysics.

Synonymous or related names

 * British Tertiary Igneous Province (BTIP)
 * British Paleogene Igneous Province (BPIP)
 * Thulean Plateau
 * Brito-Arctic province (BAP)
 * North Atlantic Igneous Province (NAIP)
 * North Atlantic Tertiary Province (NATP)
 * North Atlantic Volcanic Province (NAVP)
 * North Atlantic Basalt Province (NABP)
 * North Atlantic Tertiary Volcanic Province (NATVP)