A REVIEW OF THE ORIGINS OF SUBPARALLEL RIDGES AND TROUGHS - GENERALIZED MORPHOLOGICAL PREDICTIONS FROM TERRESTRIAL MODELS

The morphologies of ridges and troughs on Earth and the processes involved in their formation are reviewed for application to sets of subparallel ridges and troughs on outer planet satellites, We consider tension fracturing, normal faulting, thrust faulting, buckle folding, strike-slip tectonism, fissure eruption, wall diapirism, surface folding of a flow, and near-surface (laccolithic) intrusion. The landform characteristics and geologic associations predicted of each process are generalized to be independent of planet-specific parameters. We find that the combinations of landforms derived from each process are unique, making each distinguishable in the idealized case. Morphological parameters most diagnostic of formational process are ridge and trough cross-sectional shape, termination style, and incipient character. The characteristics described are useful in constraining the origin of ridge and trough terrains observed in Voyager images and will aid in analysis of high-resolution images from the Galileo and Cassini spacecraft.