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Atlas Pg. 12 Meso-American Fault Zone, Honduras, Guatemala, El Salvador Strike slip faults, volcanoes, deforestation Significance: Guatemala, Honduras, and El Salvador lie near the junction of three tectonic plates; geologic forces at this junction create a shear zone across Meso-America. Several large faults and concentrated volcanic activity together effect the geological dynamics of the region. The Meso-American tectonic complexity, rugged terrain, dense vegetation, and volatile political situation have made regional fieldwork difficult. Orbital photographs illustrating the details of regional faulting and volcanism will serve to intergrate existing geological field knowledge that has been obtained during recent times. Passes over the volcanic arc along the Pacific coast will provide the opportunity to document eruptions that may otherwise be unreported during the continuing period of political instability. Photography of the region will be used to assess deforestation and to map current vegetative cover throughout Central America. Repetitive photography will allow monitoring of environmental modifications which include erosion, siltation, riverine and costal changes. Physical Characteristics: The Polochic and Motagua strike-slip faults that cross southern Guatemala, link the Cayman Trough with a triple plate junction off the coast of Mexico in the Gulf of Tehuantepec. A similar strike-slip fault, the Guayape Fault, splits Honduras near the southern border with Nicaragua. Between these fault systems are uplifted and down dropped crustal blocks. Densely wooded ridges and aligned agricultural river valleys from the surface expression of the faulting. The Pacific Volcano Belt paralleling the west coast is a chain of Mt. Fuji-like volcanoes, many of which are active, interspersed with caldera lakes. Observation Techniques: Concurrent, near-vertical stereoscopic views with the 50 mm and 100 mm lenses will supply ideal regional coverage. Use the 250 mm lens for detailed views of volcanoes and fault segments. Stereo oblique views along the ridges and valleys are helpful in determining structural alignment. Photography with color infrared film will best define the areas of deforestation. The area is frequently cloudy so any photographic opportunity in clear weather should be maximized. We currently have very few useful photographs of Guatemala (that country now has high priority). [[image]] Map illustrating the major faults: P - Polochic M - Motagua G - Guayape HD - Faults comprising the Honduras depression Center Point: 14.5°N, 88.5°E 144
