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Earth’s Mantle and Sea Level Changes

25 May 2013

You could knock me down with a napkin. Funny thing but after reading David Pratt, who said that heat flow from the mantle caused changes in the crust, uplift and subsidence, we have a press release from Syracuse University in the US where Prof Robert Moucha argues the mantle affects long term sea level rise activities as a result of uplift, and/ or subsidence – see http://phys.org/print288539123.html

He says there is a prehistoric shoreline from Virginia to Florida, dating back to an interglacial episode, and is in some places 280 feet above the modern sea board. The shoreline was carved by waves more than 3 million years ago (geochronological dates). How might this be consistent with the consensus as axial change is out of the question? Moucha says the shoreline has been uplifted by over 200 feet which means it has very little to do with short sheets melting and sea levels rising. In addition, the shoreline is not flat – or uniform along its course. It is distorted. This reflects the pushing motion from beneath, from the mantle. This is almost exactly what David Pratt envisaged – pressure from beneath the crust causing uplift, or conversely, subsidence. Moucha thinks this is a cautionary discovery from those that rely almost exclusively on cycles of glacial advance and retreat in their study of sea level changes. Climate scientists take note. Moucha also adds – 3 million years ago average global temperature was 2 to 3 degrees higher but co2 in the atmosphere was similar to the modern world. Wow. What is all the doomsaying about? Quite how he calculates average global temperatures 3 million years ago is not discussed but we may safely assure us he did not include catastrophism in his sums.

The Moucha et al paper is in the May 15th issue of Science Express and some idea of what he envisages can be found in th statement, 'the N American east coast has always been thought of as a passive margin' (referring to large areas mostly bereft of tectonic activity and a long way from the Mid Ocean Ridge) and continues, 'we have challenged the  traditional view of passive margins by showing thjrough observations and numerical simulations, they are subject to long term deformation in response to mantle flow.' However, the influences are subsumed in the Plate Tectonics theory according to J Mitrovica of Harvard (a co-author) but the group used seismic tomography (see also Pratt on this technology from the post two days ago) as well as computer modelling (see also Pratt on this). Moucha and team hope to apply their modelling technique to the Appalachian mountain chain – also a region of passive geology (but 200 million years ago very active). Have they been affected by Mantle pressure, causing uplift, more so in some parts than in others, and so on.


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