Degree Year

1975

Document Type

Thesis

Degree Name

Bachelor of Arts

Department

Geology

Advisor(s)

Norman Grant

Keywords

Quezaltenango, Guatemala, Subducted, Central American Quaternary, Volcano, Plates, Cocos, Caribbean, Middle American, Trench

Abstract

The city of Quezaltenango is located in southwestern Guatemala, approximately 100 kilometers WNW of Guatemala City. The volcanic features of this area represent a portion of the Central American Quaternary volcanic chain. This chain seems to be controlled by the underthrusting of the Cocos plate beneath the Americas and Caribbean plates, which occurs in the Middle American trench. The two overriding plates, which in the Caribbean finds topographical expression in the Cayman Trough. Molnar and Skyes have suggested that faults in eastern Guatemala may represent the continental extension of the transform. Stoiber and Carr feel that this plate boundary is currently rather inactive. Thus, plate convergence in the Middle American Trench seems to be the dominant tectonic feature. Stoiber and Carr have shown that the associated seismic zone dips at an angle of 30 degrees from the trench to a depth of 100 kilometers. At this point a drop in seismic activity occurs which they attribute to the beglnnlng of melting in the subducted plate. Below 150 kilometers seismicity is evident again, but its position indicates a sharp increase in the dip of the seismic zone. They suggest that the steep dip at the depth where melting occurs may account for the linearity of the volcanic chain.

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