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Everything You Wanted to Know About Flood Basalt Provinces but were Afraid to Ask

Wednesday, February 6, 2008
Anne
Jay (Open University, UK)

Basalt lava flows play an important part in the geology and geomorphology of all the terrestrial planets. The most continually active basaltic volcano on Earth, Hawaii, has average eruption rates of 0.1 km3 yr-1 mostly in the form of pahoehoe and some 'a'a. However, in the past, approximately every 30 million years the Earth experiences volcanic eruptions with an average eruption rate of 1-2 km3 yr-1 (averaged over 1 million years). These eruptions are known as large igneous provinces, but when they occur mainly on the continents they are referred to as continental flood basalt provinces.

These massive out-pourings of (mostly) tholeiitic basalt have volumes greater than 1 106 km3, and can have lava flows of up to 1000 km long. Although the eruption rate is only an order of magnitude larger than that of current-day Hawaii, it is thought that the lava was erupted in a series of intense eruptions decades long, followed by periods of quiescence. It is also thought that these large eruptions could have caused global climate change on a grand scale, with links to mass extinctions.

My research focuses mainly on the Deccan Traps, a continental flood basalt province in India. It erupted at the same time as the Cretaceous-Tertiary Mass extinction (when the dinosaurs went extinct) and has therefore been linked to it. To try and understand how many eruptions formed the Deccan Traps, I have investigated the structure and type of lava flows and the basalt architecture (i.e. how all the lava flows fit together in 3-d space). From this we now understand a lot more about the internal structure of large piles of lava and how complex the stratigraphy can be.

Using the Deccan traps as an example I will explain where all the lava comes from, how it is erupted, how it is emplaced and what this could mean for future investigations of thick piles of lave be it on Earth or other planets.

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