Ben Oostdam's


page 30



It appears that the first breakthrough
was the MOR; memories of the expanding earth hypothesis? (right)
NOTE: take the word "breakthrough" very literally, because Hess and Dietz do away with the artificial MOHO boundary and identify the seafloor as the moving upper solidified part of the convection cell!
(below) This was the model Dietz presented at the first seminar on
sea-floor spreading at SIO (1961):

We eager graduate students "attacked" him, saying that the MOR was in one Ocean (the Atlantic) and the trenches in the other (the Pacific). I suggested that "properties" on either side of the MOR would be symmetric (thinking of increase in sediment thickness with age, but nothing else...); were they? His reply always was the same: "I do not know, this is just an "armchair model", but we can go out and test it!" And that was done, unfortunately without me, because I had other problems to solve.
Many more detailed models about the MOR followed through the 1960's and 1970's. But I recall one other problem we had: who would "lift the rug" at the subduction zone so that the ocean sediments could be "swept underneath?" One answer - much later - was "offscraping" (right), and I think Arnold Bouma will recognize the toothpaste like layers not unlike Alpine sedimentary rocks
subduction zones
BLO fecit 20021026 - NOTE (January 10, 2009): also used as BLO story # 433 because it was one of the ten most visited webpages on my site.