Exploration Insights September 2020 | Page 28

Exploration Insights | 15
relative motion of continental land masses by GPS . These techniques have helped shape our comprehension of the Earth as a dynamic planet with its lithosphere segmented into plates .
In the late 1960s , the plate tectonic theory was formulated , showing that the relative motion of plates on a spherical Earth is accommodated along plate boundaries ( Mckenzie and Parker , 1967 ; Le Pichon , 1968 ). One implication of the theory is that the Earth preserves a constant volume by replacing the amount of lithosphere consumed at destructive plate boundaries ( e . g . volcanic arcs ) with the creation of lithosphere at mid-ocean ridges . This laid geometrical constraints on the motion of the tectonic plates at the Earth ’ s surface back through geological time ( e . g . Dewey and Bird , 1970 ).
Since the 1970s , full plate tectonic models have been developed . These are dynamic maps that represent the motions of discrete pieces of crust on the surface of a sphere — the Earth .
nter - Scientific Visualization Studio , Smithsonian Institution , Global Change se Advanced Research Projects Agency ( DARPA ), Dynamic Media Associates
In the second part of the 20 th century , the improvement of instrumental observations led to : the contextualization of magnetic anomalies on the ocean seafloor ( Hess , 1962 ); the recording of natural seismicity ; and the measuring of tectonic stress ( e . g . from borehole breakout ) or , more recently , observing the
The essential components of a plate tectonic model are :
A set of geodynamic units ( GDUs ), which represent fragments of the lithosphere ( present day ) which each have a singular tectonic evolution
A rotation pole table that associates each fragment with a series of rotation poles , enabling transformations (“ reconstructions ”) to be carried out from their present-day position to their paleo-positions
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Figure 1 > Initial attempts at plate reconstructions were essentially paleogeographic maps dealing with singular snapshots of time . A ) A fit between Africa and South America first proposed in 1587 , by Dutch map maker Abraham Ortelius . B ) Reconstruction of the continental fit before the opening of the Atlantic Ocean by Antonio Snider-Pellegrini , 1858 . C ) The well-known initial maps of Pangaea by Alfred Wegner , 1929 .