Geodynamics: Progress and Prospects

activity Afar Africa anomalies associated Atlantic basalts basement basins belt beneath block boundary central changes complex composition continental continents crust crustal deep depth detailed determined direction early earth earthquakes East eastern evidence evolution extending fault Figure floor flow folded formation formed further Geodynamics Geol geological Geophys geophysical gravity Iceland important indicate interpretation island late lines lithosphere lower magnetic major maps margin material measurements mechanism Mesozoic movements nature needed northern observed oceanic origin Pacific period phases phonolites plate Plateau positive possible present pressure problems processes produced Project recent region relative rift rise rocks sediments seismic seismic refraction separation similar southern spreading structure studies subduction subsidence suggest surface tectonic thick trend uplift upper mantle velocity vertical volcanic Walvis Ridge wave western zone