Bjaerke Continental drift animation Page 2.

About project The reconstruction of continental movements presented here was worked out by Håkon Arnesatd Bjærke between 1928 and 1970. A short version of his manuscript was published in Håkon A. Bjærke and Tor Bjærke, 1997, The earths moving continents. Continental movements from the Cambrian to the present. Arnestad Bjærke began systematic collection of geological data for his project on continental drift in 1928 at the age of eigthteen. The work was finished in 1970. The oldest map present in the final manuscript is dated 1937. The idea behind this project was relatively simple: to trace the continental movements back in time based on all relevant geological information available (structural geology, paleontology, lithostratigraphy etc.). The reconstruction was based on a few basic concepts: 1. The lithosphere consists of continental units resting on a continuous substratum. Consequently continental margins are lifted up relatively to the interior of the continents. 2. As continental units separate, uplift of margins take place. As a continental unit approaches another unit, subsidence of intermediate sea floor and adjacent margins occurs. 3. Subsidence caused by approaching continental units and further increased by input of sediment from adjacent continents is the mechanism for formation of geosynclines. Colliding continental units contribute and fold sediments into narrow zones. 4. The formation of fold zones therefore always requires that two separate continental units are involved. 5. Rifting and separation of continental units cause uplift along bordering margins. If rifting occurs along a previously folded zone, mountain chains are formed due to uplift of accumulated low density material. Complex rift systems may be formed, sometimes leaving fragmented or partly fragmented zones as free-lying structural elements. 6. Major compressional (folding) and tensional (rifting) phases are typically of episodic character. 7. Paleobiogeography reflects previous relative position of continental units, distribution of land and sea, and climatic zones. The reconstruction of continental movements was based on these concepts, starting with the present and going back in time, taking into account all the large scale structural features, folding and rifting phases, and drawing upon available fossil evidence to test the suggested movements. When the movements had been established he tested the idea that centrifugal forces could have been the driving force creating the calculated movements. This idea was not unique. Several of the leading geologists suggested the same idea during the 1920s. The hypothetical pole positions were tested against paleoclimatological observations and available paleomagnetic pole positions, and he found that the idea was supported by the data. Arnestad Bjærkes results are essentially different from all current geological theories. He continued to work, however, according to his original hypotheses. The theory of plate tectonics did not change his attitude as it was not relevant to the geological observations. His guiding principle was continuity. Any constellation of the continents had to have a direct connection with the previous and the following. The results as presented in the animation involve a double or triple set of movements. The continents move relatively to the ocean floor and its continuation below the continents. The rotational axis moves relatively to the lithosphere either because the entire planet changes position relatively to the spin axis, or the lithosphere is moving relatively to the spinning core. Plate tectonics is regarded as the response of the lithosphere adjusting to the continuous relative shift of the rotational axis. The animation was made using Autocad 3ds max 5. A scene with four identical overlapping, partly transparent spheres was created. The spheres could be rotated independantly allowing elements to be moved relatively to each other. All elements that were moved had to be retraced using Right Hemisphere Deep Paint 3D. The result being a series of 2D maps in non-projected format. The maps were manipulated in a graphic program to get an acceptable quality. However, memory restrictions did not allow a higher resolution. A series of maps, one for each million years, were made. To explain the movements it was (as in the original theory) assumed that centrifugal forces are responsible for the continental movements. The poles are placed where they most efficiently contribute to the movements. It turned out that the relative pole movements roughly follow a circle 100 degrees wide (80-120 degrees). However, an abrupt change had to be introduced at 204 ma where the circle is offset nearly 90 degrees away from the previous. Due to the rigid system offered by the software, minor movements have been neglected. They may, however, add up to considerable distances. The position of the continents can therefore not be regarded as absolute in relation to present longitude/latitude grid. A number of questions regarding these minor movements, the positions of separate terranes and microcontinents, structural relationships, and detailed timing of certain events have yet to be solved. For a more detailed understanding of structural relationships it is recommended to study the maps in the 1997 paper. Tor Bjaerke Stavern, 2011