EVIDENCE OF PLUMESThe first paper wasthe comprehensive review by Ian Campbellof the theory of mantle plumes. Review shows that mantle plume theory makesnumerous testable predictions which are both quantitative and exacting.
Thehypothesis correctly predicts that; rapid initial volcanism from the plume headis followed by reduced volcanism from the plume tail, the size of the flattenedplume head in the upper mantle is 2000 to 2500 km across, flood volcanismpreceded by domal uplift. Campbellconcludes the excellent agreement between the predictions made from plumetheory and the observations made from large igneous provinces and hotspottracks leaves little room for doubt that the plume hypothesis is correct.Michael Story et al. present new / ages for the early tertiary lavas of EastGreenland and the Faeroe Islands (part of the North Atlantic Igneous Provinces)and used these with published data to estimate melt production rates leading upto, during and following continental break-up between Greenland and Europe. Theauthors show that following commencement of volcanism at ?61 Ma, volcanic activity was irregular until 55.7 ± 0.5 Ma when the averagemelt production rate increased by more than an order of magnitude (from <100to >3000 /kmof rift/Ma).
This increase coincided with continental rifting between Europeand Greenland and shallow decompression melting of hot mantle. It is concludedthat a start-up mantle plume head and tail model, with moderate excesstemperature (?T?100 °C) and active upwelling, bestexplains the time, spatial and compositional aspects of volcanism in thisprovince.Saunders et al (2003) cite Hawaii insupport of the model, In Hawaii despite the very high lithostatic pressuresfound at 70-80 km the plume heat source was able to produce melting. The basaltproduction rate at Hawaii currently is 0.13 /a, which is lower than an average productionduring lifetime of the island at 0.013 /a.
Saunderspoints out that at a modern mid ocean ridge where asthenosphere is within fewkilometers of the earth surface with melting rates at 104 km long, 1 km wideand 1cm/a spreading ridge produce magma at an average rate of 1.2 /a (McLean M.D. 1996).
This average volume of melt reaching the surface of Hawaii