Many theorists now doubt that heat loss from Earth’s core and radioactive decay are sufficient
by themselves to produce all the energy driving the tectonic plates whose movements have
helped shaped Earth’s surface. This leaves a loose end in current geological theory. Herbert
Shaw argues that because scientists have underestimated the input of substantial amounts of
energy from extraterrestrial impactors (asteroids and comets striking Earth), they have
difficulty accounting for the difference between the quantity of energy produced from sources
intrinsic to Earth and that involved in plate tectonics. Whereas most geologists have treated
the addition of energy through the bombardment of Earth’s surface by such impactors as a
process separate and independent from the movement of Earth’s tectonic plates, Shaw
asserts that these processes are indivisible. Shaw’s revolutionary “open-system” view
recognizes a continuum between terrestrial and extraterrestrial dynamics, whereas modern
plate tectonic theory, like the classical geology developed during the nineteenth century, is
founded on the view that Earth’s geological features have changed through gradual, regular
processes intrinsic to Earth, without reference to unique catastrophic events. Classical
geology borrowed a decisive, if unspoken, premise from Newton—the independence of Earth’s
processes from any astronomical context.
1. The author’s primary purpose is to
A. identify the influences informing a particular geological theory about the processes that
have shaped Earth’s surface
B. identify differences between two views of the extraterrestrial impactors and argue that the
phenomenon has influenced the development of plate tectonic theory
C. argue that an explanation is based on a dubious evidence and propose an alternative
explanation
D. discuss an explanation and place that explanation under theoretical context
E. suggest that apparent discrepancy poses a serious problem for a particular theory that
many have believed