The role of Serendipidy in Research

When discussing the possibility that certain forms of glacial motion might be caused by cycles of expansion and contraction, resulting from variations in insolation energy entering the glacial ice, I referred to the exchanges in the mid-19thC between Henry Moseley and James Croll that I had uncovered to see if anyone else had put forward a similar explanation for glacial movement. On the basis of a related explanation for the motion of lead sheet moving down roofs having slopes insufficient for gravity to overcome the frictional forces, Moseley had suggested that similar thermal mechanics could be responsible for some forms of glacial motion. In the ensuing discussions of Moseley's "crawling theory", a contemporary glaciologist's summed up the mid 19thC discussions as to whether thermal expansion and contraction could have any role in the motion of glaciers, as having been "demolished" by James Croll. Previous blogs have attempted to show that rather than disagreeing with Moseley, James Croll concurred that changes in thermal condition within the glaciers could well provide part of the explanation for their movement. Sadly, Henry Moseley died before he had the chance to answer some of the more vehement criticisms from other contemporaneous geologists. I therefore consider it a clan responsibility to argue the case as I am sure Moseley would have done had he lived long enough!  

James Croll was a self taught Scottish geologist who had earlier provided the first credible explanation for the glacial and inter-glacial periods, occurring within the very long cycles of ice-ages, in terms of the synchronous variations in the Earth's elliptic orbit and the inclination of the Earth's axis of rotation relative the ecliptic plane. I mention this again since it was the weird clan/familial coincidence that first alerted me to the possibility that these long term glacial and inter-glacial period (circa 20 to 110ka) might be inducing similarly long term thermal ratchet phenomena within the Earth's crust. In the next few blogs I will attempt to establish how many of the dynamic processes that have shaped and continue to shape the Earth's lithosphere might have as their origin the influence of these long term and other very long term variations in Earth climate. I will be suggesting that the massive changes in the distribution of ice and water that accompany the circa 120Ma periodicity of the ice-ages and the intervening hot-house conditions could help to explain not just the horizontal tectonic processes but crucially help to account for the cycles of vertical tectonics, whereby deep sediments from oceanic crust rise to become continental crust, only to be eroded and eventually sink down to again become part of the oceanic crust. I will attempt to show that the phasing of these continental wide rises and falls, sometimes referred to as epirogeny, appears to be closely synchronous with the phasing of the recorded ice-ages. Furthermore, with periodicities 3 orders of magnitude less it will also be argued that the changes in surface ice and water conditions accompanying the shorter period glacials and inter-glacials within an ice-age might also be exercising significant influence on horizontal tectonics and especially near surface behaviour.

In presenting another explanation for the dynamic evolution of the Earth's crust, a recurring theme of the next few posts, it will be suggested that plate tectonics, the dominant paradigm in geology, may be in need of reappraisal.