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88 OCEANOGRAPHY IN THE NEXT DECADE 



A basic description of the nature and evolution of many conti- 

 nental margins is available today. However, understanding of the 

 dynamics of margin development has not grown at the same rate. 

 Knowledge of continental margin structure and motion has pro- 

 gressed, but understanding of the margins is limited by the need 

 to understand the basic physical processes that accompany mar- 

 gin formation. Continental margins research must embrace a unified 

 approach that emphasizes the important role of process-oriented 

 interdisciplinary programs. Further, margins cross the shoreline, 

 and such efforts will further enhance the developing synergism 

 with Earth scientists involved in land and ocean research. 



Fault Dynamics and Lithospheric Deformation 



Any approach to the problems associated with lithospheric 

 deformation demands the use of many tools. A wide-ranging field- 

 mapping program is needed specifically to establish the link be- 

 tween surface deformation and deformation in the lower crust. 

 For example, the configuration of large faults at depth in the crust 

 and the structural fabric associated with distributed deformation 

 in the upper mantle must be established by large-scale seismic 

 imaging and tomographic techniques. Laboratory studies are also 

 essential to establishing the constitutive laws for frictional be- 

 havior of both large deformation zones and discrete fault zones 

 and defining their variability with strain, strain rate, and fluid 

 content. Models of fluid flow in deforming porous media and 

 methods to relate the models to observable quantities for field 

 observation are required. 



Mantle Dynamics and Extension 



Understanding the interaction between mantle processes and 

 lithospheric extension will require a focused muitidisciplinary ef- 

 fort. Wide-ranging field-mapping programs must be designed to 

 establish specific links between surface deformation and deforma- 

 tion in the lower crust. Large geophysical experiments will be 

 needed to define the modern structure of rifts and margins and 

 the thermal and dynamic state of mantle beneath young, pres- 

 ently active rifts. This work must be combined with geological 

 mapping and thorough geochemical studies of magniatic systems 

 to determine the nature of mantle sources, the history of melting, 

 and fractionation The development of shear-wave techniques 



