North Atlantic Tertiary Province Flashcards
When did the NATP occur?
Occurred during the early Phanerozoic Eon (Palaeogene - Neogene). Roughly 65 - 23 MYA
What occurred during this period?
The expansion of the Atlantic Ocean, separating the America’s and Europe. This created the mid-Atlantic ridge.
How did ocean crustal expansion occur?
A Oceanic - Oceanic divergent/constructive plate boundary powered by a massive mantle plume pushed between the two plates causing the ridge to rise and push away from each other whilst subsequent construction of new oceanic crust was occurring. this created crustal weaknesses in the form of fractures creating a path for magma to rise through the asthenosphere.
What evidence is there to suggest the existence of the NATP in the UK?
The stretching of the crust as the Atlantic Ocean formed created weaknesses in the surface of the rock, at right angles to the direction of tension. Lava rising up through the cracks formed vertical sheet intrusions – known as dykes – across northern England, southern Scotland and the Inner Hebrides. If they reached the surface, these formed fissure eruptions, covering large areas of land with lava. This produces a feature known as a ‘flood basalt’. These cover most of Skye, Mull and Northern Ireland. The Giant’s Causeway in Northern Ireland, and Fingal’s Cave on the Isle of Staffa, are well known examples. These basalts are famous for their hexagonal columns. This is an effect of the cooling of the lava,
which in the same way as mud cracks form, has led to joints that reach down towards the centre of the flow and produces columns. Some of the volcanic activity was explosive, leaving behind accumulations of large blocks of volcanic material (agglomerates) and ashes.
What are laterites and how do they form?
The basaltic laterites of Northern Ireland were formed by extensive chemical weathering of basalts during a period of volcanic activity. Percolating waters caused degradation of the
parent basalt ( iron rich) and preferential precipitation by acidic water through the lattice left the iron and aluminium ores.
