Article and Photosby Arthur E. Berman,editor@hgs.orgFrom the Editor February, 2005 The Northern Sumatra Earthquake of 2004:Forty Years of Ignoring Plate TectonicsDiscuss the significance of the calc-alkaline series.That was the only question on my petrology mid-term examination in 1975. It was perhaps the most penetrating question I have ever been asked as a geologist. It is also the only exam question I remember from my academic years.I went to the professor, Dr. Rudy Epis, after he returned the exams to discuss my low grade with him. I had written everything I knew about the granitic rocks that make up the calc-alkaline series and it was all correct. What I had failed to do was to answer the question. I had not discussed the significance of the calc-alkaline series.I did not address the “granite problem.” Granite is a light-colored, relatively light-weight rock that contains a lot of quartz. Most of the Earth is made up of basaltic material, the opposite of granite: a dark, heavy rock without much quartz. Based on the overall composition of the Earth, there is just too much granite, and most of it is found on the continents. This has puzzled geologists since the science of geology began.It is understandable that the typical victim of the recent tsunami disaster in the Indian Ocean did not anticipate the tragic events that are still unfolding there. It is inexcusable that their leaders and governments made no effort to inform and prepare their citizens for the inevitability of an event like this during the forty years since the articulation of the plate-tectonic model.Epis explained that he was looking for a plate-tectonic explanation to the granite problem. Basically, the plate-tectonic model says that the Earth is a great factory. Earth is constantly recycling mostly oceanic, basaltic crust into ocean-trench subduction zones and generating granite by a kind of distillation process.That discussion with Dr. Epis transformed me. I was awed, even overwhelmed, by the way his mind worked and the power of a scientific model—the plate-tectonic model, in this case—to collapse complexity into simplicity. I knew about plate tectonics and the calc-alkaline series separately. I had simply not connected the two in the elegant way he had. I entered his office a student concerned about a grade and left, in some way, a geologist. He made me see, perhaps for the first time, the importance of critical thinking. I promised myself to never again fail to seek the question within the question.I thought about the conversation with Rudy Epis in early December 2004 as I began reading Simon Winchester’s Krakatoa, The Day the World Exploded: August 27, 1883. Winchester’s book is an entertaining, popular explanation of plate tectonic theory in the context of a cataclysmic volcanic explosion that occurred in Indonesia 121 years ago. Krakatoa had a profound affect on Victorian consciousness because invention of the telegraph made news of the eruption immediately known around the world.On December 26, 2004, the Northern Sumatra Earthquake occurred in the same tectonic neighborhood as Krakatoa. The world is stunned by the death and destruction that is coming to light from the earthquake and ensuing tsunami. The difference between the past and present seismic events in Indonesia is that we understand the current disaster because of the plate-tectonic model; in 1883, however, geology did not yet have an Earth model or context to explain Krakatoa to a frightened and confused world.Plate Tectonics and a Restless EarthPlate tectonics was not new in 1975 when I was studying petrology from Rudy Epis, but it was a model still considered optional by many geologists: as with all new ideas, it takes time before any but the innovator and early adopter groups embrace a new invention (Berman, 2004k). The plate-tectonic model began in 1915 when Alfred Wegener published his observations on the fit between the continents minus the intervening, present-day ocean basins (the relationship had, in fact, been previously noted as early as 1620 by Francis Bacon). Wegener supported his theory of “continental drift,” that the continents had, at one time, been connected, with abundant and convincing biological evidence. Wegener’s work was scorned and ridiculed by the scientific community presumably because there was no mechanism to de-couple the crust from the underlying mantle and core of the Earth. Thomas Chamberlin, the American geologist famous for his address Method of Multiple Working Hypotheses (HGS Bulletin, v. 47, no. 2) apparently abandoned his thesis when he commented in 1923 on Wegener’s work, “If we are to believe this hypothesis we must forget everything we learned in the last seventy years and start over again,” (Winchester, 2003). Plate tectonics was revived after World War II due to wartime advances in measurement technology and instrumentation. A new Earth model evolved and was articulated in a series of key papers, notably by Dietz (1961), Wilson (1965), and Cox et al (1967). The breakthrough came in late 1965 when Brent Dalrymple presented findings at a meeting of the Geological Society of America: he showed an exact match between terrestrial paleomagnetic measurements and seafloor magnetic reversal bands that had been identified in post-war ocean basin surveys (Figure 1). “It was indeed a revelation...and the start of a revolution in Earth science!” (Donnenfield and Howell, 2004).A mechanism was discovered for a crust in dynamic and perpetual motion, de-coupled from and, at the same time, interacting with the underlying mantle and core (Figure 2). Wegener’s concept was validated. The crust is divided into tectonic plates that move carrying continents along with them (Figure 3). Earth’s crust is constantly being destroyed and regene