Mountain building processes in the Central Andes

False color composite images of the Thematic Mapper (TM) bands 5, 4, and 2 were examined to make visual interpretations of geological features. The use of the roam mode of image display with the International Imaging Systems (IIS) System 600 image processing package running on the IIS Model 75 was very useful. Several areas in which good comparisons with ground data existed, were examined in detail. Parallel to the visual approach, image processing methods are being developed which allow the complete use of the seven TM bands. The data was organized into easily accessible files and a visual cataloging of the quads (quarter TM scenes) with preliminary registration with the best available charts for the region. The catalog has proved to be a valuable tool for the rapid scanning of quads for a specific investigation. Integration of the data into a complete approach to the problems of uplift, deformation, and magnetism in relation to the Nazca-South American plate interaction is at an initial stage

Dynamic interaction between tectonic plates, subducting slabs, and the mantle

Mantle convection models have been formulated to investigate the relation between plate kinematics and mantle dynamics. The cylindrical geometry models incorporate mobile, faulted plate margins, a phase change at 670 km depth, non-Newtonian rheology, and tectonic plates. Models with a variety of parameters indicate that a relatively stationary trench is more likely to be associated with a subducted slab that penetrates into the lower mantle with a steep dip angle. However, a subducted slab that is deflected above the 670-km phase change with a shallow dip is more likely to be associated with a margin that has undergone rapid retrograde trench migration. This relation between slab morphology and plate kinematics is consistent with seismic tomography and plate reconstruction of western Pacific subduction zones. The efficiency of slab penetration through the 670-km phase change is controlled by both the buoyancy of the subducting plate and the mobility of the overriding plate. While older subducting plates have a greater propensity for slab penetration, trench mobility reduces the propensity for slab penetration. Smaller overriding plates have a greater mobility. When subducted slabs approach the bottom thermal boundary layer, hot fluid is pushed aside, and plumes form on the periphery of slab accumulations. There are sharp temperature contrasts between the subducted slab and the thermal boundary layer at the core mantle boundary (CMB). Old subducted slabs and a thermal boundary layer lead to large-scale lateral structure near the CMB

Tectonics of the central Andes

Acquisition of nearly complete coverage of Thematic Mapper data for the central Andes between about 15 to 34 degrees S has stimulated a comprehensive and unprecedented study of the interaction of tectonics and climate in a young and actively developing major continental mountain belt. The current state of the synoptic mapping of key physiographic, tectonic, and climatic indicators of the dynamics of the mountain/climate system are briefly reviewed