Exploration Insights September 2020 | Page 15

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 A B C © 2020 Halliburton 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.