Pioneers of Marine Geology: Identifying the Basic Questions
5
with the motions and forces deep within the Earth. It is no coincidence that a geophysicist fIrst fonnulated a global hypothesis for ocean-margin morphology which
proved to be viable: the meteorologist Alfred Wegener (Fig. 0.1.4).
A. Wegener became intrigued with the parallelism of the coast lines bordering the
Atlantic Ocean (a phenomenon noted already in 1801 by the famous naturalist-explorer, Alexander von Humboldt). It seemed to Wegener that the continents looked
like puzzle pieces which belong together. He then leamed quite by accident that
paleontologists had invoked fonner land bridges between the shores facing each other
across the Atlantic to explain striking similarities between the fossil records of both
sides of the ocean. After an extensive literature search, he became convinced that the
continents had once been joined, and had broken up after the Paleozoic. Replacing
the concept of land bridges with his hypothesis of continental drift, he started the
"debate of the century" in geology with an article in 1912 (Oeol. Rdsch. 23: 276), and
especially with his book The Origin of Continents and Oceans (Braunschweig, 1915,
in Gennan). He envisioned granitic continents floating in basaltic mantle magma like
icebergs in water (Fig. 0.2a), and drifting about on the surface of Earth in response to
unkown forces derived from the rotation of the planet.
Wegener's hypothesis, in modified fonn, is now an integral part of sea-floor
spreading and plate tectonics (Chap. 1), the ruling theories explaining the geomorphology and geophysics of the ocean floor and of the crust of the Earth in general. It
was the work of sea-going geophysicists which eventually led to the acceptance of
plate tectonis. The pioneering efforts of E. C. Bullard (Fig. 0.1.11) on earth magnetism, heat flow, and seismic sunreying, and of M. Ewing (Fig. 0.1.9) and his associates
in all aspects of marine geophysics were of central importance in this development
(although M. Ewing did not himself advocate sea-floor spreading). These scientists
also were instrumental in elucidating the structure of continental margins (M. Ewing
et al., 1937, Geophysical Investigations in the Emerged and Submerged Atlantic
Coastal Plain, Bull Oeol Soc Am, 51, p 909; E. C. Bullard and T. F. Gaskell, 1941,
Submarine Seismic Investigations, Proc Royal Soc, Ser A 177, P 476).
The turning point in the scientific revolution which shook the earth sciences, and
which culminated in plate tectonics is generally taken to be the seminal paper of H.
H. Hess, History of Ocean Basins, published in 1962. Hess (Fig. 0.1.10) started his
distinguished career working with the Dutch geophysicist, F. A. Vening-Meinesz, on
the gravity anomalies of deep-sea trenches. These investigations resulted in the hypothesis that trenches may be surface expressions of the downgoing limbs of mantle
convection cells. As a naval officer, Hess discovered and mapped a great number of
flat-topped seamounts, whose morphology suggested widespread sinking of the sea
floor. Stimulated by subsequent discoveries on the Mid-Ocean Ridge (rift morphology, heat flow, and others) he proposed his idea of the sea floor being generated at
the center of the Mid-Ocean Ridge (Fig. 0.3 d), moving away and downward as it
ages, finally to disappear into trenches. The tenn "sea-floor spreading" was introduced by R. Dietz (in 1961) for this postulated phenomenon. Sea-floor spreading,
and its offspring plate tectonics have since become the basic framework within which
the data of marine geology are interpreted.
5
with the motions and forces deep within the Earth. It is no coincidence that a geophysicist fIrst fonnulated a global hypothesis for ocean-margin morphology which
proved to be viable: the meteorologist Alfred Wegener (Fig. 0.1.4).
A. Wegener became intrigued with the parallelism of the coast lines bordering the
Atlantic Ocean (a phenomenon noted already in 1801 by the famous naturalist-explorer, Alexander von Humboldt). It seemed to Wegener that the continents looked
like puzzle pieces which belong together. He then leamed quite by accident that
paleontologists had invoked fonner land bridges between the shores facing each other
across the Atlantic to explain striking similarities between the fossil records of both
sides of the ocean. After an extensive literature search, he became convinced that the
continents had once been joined, and had broken up after the Paleozoic. Replacing
the concept of land bridges with his hypothesis of continental drift, he started the
"debate of the century" in geology with an article in 1912 (Oeol. Rdsch. 23: 276), and
especially with his book The Origin of Continents and Oceans (Braunschweig, 1915,
in Gennan). He envisioned granitic continents floating in basaltic mantle magma like
icebergs in water (Fig. 0.2a), and drifting about on the surface of Earth in response to
unkown forces derived from the rotation of the planet.
Wegener's hypothesis, in modified fonn, is now an integral part of sea-floor
spreading and plate tectonics (Chap. 1), the ruling theories explaining the geomorphology and geophysics of the ocean floor and of the crust of the Earth in general. It
was the work of sea-going geophysicists which eventually led to the acceptance of
plate tectonis. The pioneering efforts of E. C. Bullard (Fig. 0.1.11) on earth magnetism, heat flow, and seismic sunreying, and of M. Ewing (Fig. 0.1.9) and his associates
in all aspects of marine geophysics were of central importance in this development
(although M. Ewing did not himself advocate sea-floor spreading). These scientists
also were instrumental in elucidating the structure of continental margins (M. Ewing
et al., 1937, Geophysical Investigations in the Emerged and Submerged Atlantic
Coastal Plain, Bull Oeol Soc Am, 51, p 909; E. C. Bullard and T. F. Gaskell, 1941,
Submarine Seismic Investigations, Proc Royal Soc, Ser A 177, P 476).
The turning point in the scientific revolution which shook the earth sciences, and
which culminated in plate tectonics is generally taken to be the seminal paper of H.
H. Hess, History of Ocean Basins, published in 1962. Hess (Fig. 0.1.10) started his
distinguished career working with the Dutch geophysicist, F. A. Vening-Meinesz, on
the gravity anomalies of deep-sea trenches. These investigations resulted in the hypothesis that trenches may be surface expressions of the downgoing limbs of mantle
convection cells. As a naval officer, Hess discovered and mapped a great number of
flat-topped seamounts, whose morphology suggested widespread sinking of the sea
floor. Stimulated by subsequent discoveries on the Mid-Ocean Ridge (rift morphology, heat flow, and others) he proposed his idea of the sea floor being generated at
the center of the Mid-Ocean Ridge (Fig. 0.3 d), moving away and downward as it
ages, finally to disappear into trenches. The tenn "sea-floor spreading" was introduced by R. Dietz (in 1961) for this postulated phenomenon. Sea-floor spreading,
and its offspring plate tectonics have since become the basic framework within which
the data of marine geology are interpreted.