TABLE 2-3 Dynamics of Oceanic Lithosphere and Imaging the Earth's Interior: Areas Where Observatories Are Very Useful to Investigate a Particular Scientific Problem and Where They Are Useful

Observatory science is VERY USEFUL to investigate the following:

  • Global earth structure;

  • Seismogenesis at subduction zone megathrusts;

  • Ridge-crest processes and creation of oceanic crust; and

  • Oceanic volcanism.

Observatory science is USEFUL to investigate the following:

  • Upper mantle dynamics;

  • Ocean plate kinematics;

  • Plate deformation; and

  • Geologic hazard mitigation.

To address the science where observatories are very useful, development or improvement of the following sensors is needed:

  • Long-range, multi-mission, multi-sensor AUVs (including docking capability);

  • Advanced ROVs with improved manipulator and cable-laying capability;

  • Borehole and buriable broadband seafloor seismometers;

  • Seafloor geodetic sensors (strain, tilt, gravity);

  • Borehole fluid pressure/composition and samplers; and

  • In situ biological and chemical sensors.

vection in Earth's mantle (layered versus whole mantle) and the existence and origin of distinct mantle geochemical reservoirs. These topics will be major focuses of future research.

The nature and origin of hotspots and their interaction with the lithosphere are other important questions in mantle dynamics. New paleo-magnetic data are inconsistent with the idea of “fixed” hot spots and geochemical data appear to be compatible with a variety of different origins for hot spots, including the 670 km discontinuity, a boundary between different geochemical reservoirs in the lower mantle, or the core-mantle boundary (CMB). The CMB is compositionally and perhaps dynamically the most dramatic boundary within the earth and it has been proposed as the origin of hot spots and the graveyard of subduction zones. Future studies will be aimed at determining the role of the CMB in the larger-scale dynamics of Earth's mantle.

The earth's inner core, which comprises less than 1 percent of Earth's volume, is the last frontier of solid-earth geophysics. Data that sample this region must travel through the remaining 99 percent of Earth's volume; thus,

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