Years before the advent of plate
tectonics"•the widely accepted theory,
developed in the mid-1960’s, the holds
that the major features of Earth’s surface
are created by the horizontal motions
of Earth’s outer shell, or lithosphere"•
a similar theory was rejected by the
geological community. In 1912, Alfred
Wegener proposed, in a widely debated
theory that came to be called continental
drift, that Earth’s continents were mobile.
To most geologists today, Wegener’s
The origin of Continents and Oceans
appears an impressive and prescient
document, containing several of the
essential presumptions underlying plate
tectonics theory: the horizontal mobility
of pieces of Earth’s crust; the essential
difference between oceanic and conti-
nental crust; and a causal connection
between horizontal displacements and
the formation of mountain chains. Yet
despite the considerable overlap
between Wegener’s concepts and the
later widely embraced plate tectonics
theory, and despite the fact that conti-
nental drift theory presented a possible
solution to the problem of the origin of
mountains at a time when existing expla-
nations were seriously in doubt, in its
day Wegener’s theory was rejected
by the vast majority of geologists.
Most geologists and many historians
today believe that Wegener’s theory
was rejected because of its lack of an
adequate mechanical basis. Stephen
Jay Gould, for example, argues that
continental drift theory was rejected
because it did not explain how continents
could move through an apparently solid
oceanic floor. However, as Anthony
Hallam has pointed out, many scientific
phenomena, such as the ice ages, have
been accepted before they could be fully
explained. The most likely cause for the
rejection of continental drift"•a cause
that has been largely ignored because
we consider Wegener’s theory to have
been validated by the theory of plate
tectonics"•is the nature of the evidence
that was put forward to support it. Most
of Wegener’s evidence consisted of
homologiesâ€"similarities of patterns and
forms based on direct observations of
rocks in the field, supported by the use
of hammers, hand lenses, and field note-
books. In contrast, the data supporting
plate tectonics were impressively
geophysicalâ€"instrumental determinations
of the physical properties of Earth gar-
nered through the use of seismographs,
magnetometers, and computers.
The author of the passage discusses the "essential presumptions" (see highlighted text) of "The origin of Continents and Oceans" most likely in order to
(A)indicate features of Wegener's theory that caused it to be doubted in its day
(B)show why Wegener's theory is now regarded as prescient
(C)indicate differences between plate tectonics and the theory of continental drift
(D)cite features of the theory of continental drift for which no evidence was available in Wegener's day
(E)point out aspects of Wegner's theory that were accepted well before the advent of plate tectonics
Please provide explanation with your answer.
tectonics"•the widely accepted theory,
developed in the mid-1960’s, the holds
that the major features of Earth’s surface
are created by the horizontal motions
of Earth’s outer shell, or lithosphere"•
a similar theory was rejected by the
geological community. In 1912, Alfred
Wegener proposed, in a widely debated
theory that came to be called continental
drift, that Earth’s continents were mobile.
To most geologists today, Wegener’s
The origin of Continents and Oceans
appears an impressive and prescient
document, containing several of the
essential presumptions underlying plate
tectonics theory: the horizontal mobility
of pieces of Earth’s crust; the essential
difference between oceanic and conti-
nental crust; and a causal connection
between horizontal displacements and
the formation of mountain chains. Yet
despite the considerable overlap
between Wegener’s concepts and the
later widely embraced plate tectonics
theory, and despite the fact that conti-
nental drift theory presented a possible
solution to the problem of the origin of
mountains at a time when existing expla-
nations were seriously in doubt, in its
day Wegener’s theory was rejected
by the vast majority of geologists.
Most geologists and many historians
today believe that Wegener’s theory
was rejected because of its lack of an
adequate mechanical basis. Stephen
Jay Gould, for example, argues that
continental drift theory was rejected
because it did not explain how continents
could move through an apparently solid
oceanic floor. However, as Anthony
Hallam has pointed out, many scientific
phenomena, such as the ice ages, have
been accepted before they could be fully
explained. The most likely cause for the
rejection of continental drift"•a cause
that has been largely ignored because
we consider Wegener’s theory to have
been validated by the theory of plate
tectonics"•is the nature of the evidence
that was put forward to support it. Most
of Wegener’s evidence consisted of
homologiesâ€"similarities of patterns and
forms based on direct observations of
rocks in the field, supported by the use
of hammers, hand lenses, and field note-
books. In contrast, the data supporting
plate tectonics were impressively
geophysicalâ€"instrumental determinations
of the physical properties of Earth gar-
nered through the use of seismographs,
magnetometers, and computers.
The author of the passage discusses the "essential presumptions" (see highlighted text) of "The origin of Continents and Oceans" most likely in order to
(A)indicate features of Wegener's theory that caused it to be doubted in its day
(B)show why Wegener's theory is now regarded as prescient
(C)indicate differences between plate tectonics and the theory of continental drift
(D)cite features of the theory of continental drift for which no evidence was available in Wegener's day
(E)point out aspects of Wegner's theory that were accepted well before the advent of plate tectonics
Please provide explanation with your answer.
