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.