Epilog
305
graphy (pennitting the detection of inhomogeneities) and the discovery of basin-size
isotopic provinces proved crucial. Vigorous discussion about the style of mantle
convection (e. g., the relative importance of shallow and deep convection and the role
of mantle plumes) continues.
The proper description of ridge-crest processes depends on mapping the magma
chambers which underlie the crest like large pearls on a string, and on measuring the
emissions of gases and fluids. Details of topography become available as acoustic
swath-mapping, using mUltiple source and microphone arrangements, becomes almost routine. Geologists now "look" at the sea floor here at the ridge crest and
elsewhere with giant "acoustic searchlights", opening up new frontiers of marine
geomorphology.
For understanding processes within the subduction zone, the detection of fluid
overpressure along overthrust faults, and of seeps along the continental slope, were
very important. Thus, the role offluid circulation within the crust has become a topic
of intensive research.
Regarding the debate about the processes controlling evolution, the iridium spike
at the Cretaceous-Tertiary boundary (reported in 1980) provided a rallying point. This
debate, bolstered by the study of pelagic sediments on land and on the deep-sea floor,
has led to a re-evaluation of the tenets of classic unifonnitarianism, and has emphasized the crucial importance of episodic events in Earth history, especially concerning
the role of impacts of extraterrestrial bolides. It is as though geologists suddenly
realized that Earth is not an isolated fortress in space, but is vulnerable to bombardement - as illustrated by the surface of our Moon.
For Quaternary climate history the discovery of ice age carbon dioxide fluctuations in polar ice (likewise reported in 1980) was of primary importance. The tie-in to
the deep-sea carbonate record proved to be highly instructive regarding the ocean's
role in controlling atmospheric C02. This topic has become the subject of intense
research efforts.
In the continental margins, especially in the passive ones, sea level fluctuations are
recorded in the geometry of sediment bodies of vast volumes. Some of these bodies
contain petroleum and other resources, which has greatly stimulated four-dimensional
basin analysis using the new insights gained from plate tectonics.
History, it is said, is a guide to destiny. First marine geophysics, and, more recently, marine geology and stratigraphy have led the way back to a global view of the
evolution of Earth and its life. The next step in this development is to achieve
detailed correlation between the record in the sea and that on land. Sequence-stratigraphy, magnetic stratigraphy, and bio- and chemostratigraphy will have to be greatly
refined for the purpose, and accurate dating of events becomes crucial. Only with
such tools in hand can we attempt synchronous global reconstructions of paleo-environments, to elucidate with some exactness the complex interactions of the many
processes governing climate change (Fig. E.l). For geologists, the answer to questions of cause and effect must be sought by detennining "before" and "after" across
oceans and continents, with ever-increasing resolution. As we expand our knowledge
of rates of changes in Earth history and the forces controlling them, we gain fun-
305
graphy (pennitting the detection of inhomogeneities) and the discovery of basin-size
isotopic provinces proved crucial. Vigorous discussion about the style of mantle
convection (e. g., the relative importance of shallow and deep convection and the role
of mantle plumes) continues.
The proper description of ridge-crest processes depends on mapping the magma
chambers which underlie the crest like large pearls on a string, and on measuring the
emissions of gases and fluids. Details of topography become available as acoustic
swath-mapping, using mUltiple source and microphone arrangements, becomes almost routine. Geologists now "look" at the sea floor here at the ridge crest and
elsewhere with giant "acoustic searchlights", opening up new frontiers of marine
geomorphology.
For understanding processes within the subduction zone, the detection of fluid
overpressure along overthrust faults, and of seeps along the continental slope, were
very important. Thus, the role offluid circulation within the crust has become a topic
of intensive research.
Regarding the debate about the processes controlling evolution, the iridium spike
at the Cretaceous-Tertiary boundary (reported in 1980) provided a rallying point. This
debate, bolstered by the study of pelagic sediments on land and on the deep-sea floor,
has led to a re-evaluation of the tenets of classic unifonnitarianism, and has emphasized the crucial importance of episodic events in Earth history, especially concerning
the role of impacts of extraterrestrial bolides. It is as though geologists suddenly
realized that Earth is not an isolated fortress in space, but is vulnerable to bombardement - as illustrated by the surface of our Moon.
For Quaternary climate history the discovery of ice age carbon dioxide fluctuations in polar ice (likewise reported in 1980) was of primary importance. The tie-in to
the deep-sea carbonate record proved to be highly instructive regarding the ocean's
role in controlling atmospheric C02. This topic has become the subject of intense
research efforts.
In the continental margins, especially in the passive ones, sea level fluctuations are
recorded in the geometry of sediment bodies of vast volumes. Some of these bodies
contain petroleum and other resources, which has greatly stimulated four-dimensional
basin analysis using the new insights gained from plate tectonics.
History, it is said, is a guide to destiny. First marine geophysics, and, more recently, marine geology and stratigraphy have led the way back to a global view of the
evolution of Earth and its life. The next step in this development is to achieve
detailed correlation between the record in the sea and that on land. Sequence-stratigraphy, magnetic stratigraphy, and bio- and chemostratigraphy will have to be greatly
refined for the purpose, and accurate dating of events becomes crucial. Only with
such tools in hand can we attempt synchronous global reconstructions of paleo-environments, to elucidate with some exactness the complex interactions of the many
processes governing climate change (Fig. E.l). For geologists, the answer to questions of cause and effect must be sought by detennining "before" and "after" across
oceans and continents, with ever-increasing resolution. As we expand our knowledge
of rates of changes in Earth history and the forces controlling them, we gain fun-