Document Type
Article
Publication Date
11-10-1990
Abstract
Major volcanoes of the Southern Washington Cascades (SWC) include the large Quaternary stratovolcanoes of Mount St. Helens (MSH) and Mount Adams (MA) and the Indian Heaven (IH) and Simcoe Mountain (SIM) volcanic fields. There are significant differences among these volcanic centers in terms of their composition and evolutionary history. The stratovolcanoes consist largely of andesitic to dacitic lavas and pyroclastics with minor basalt flows. IH consists dominantly of basaltic with minor andesite lavas, all erupted from monogenetic rift and cinder cone vents. SIM has a poorly exposed andesite to rhyolite core but mainly consists of basaltic lavas erupted from numerous widely dispersed vents; it has the morphology of a shield volcano. Distribution of mafic lavas across the SWC is related to north‐northwest trending faults and fissure zones that indicate a significant component of east–west extension within the area. There is overlap in eruptive history for the areas studied, but it appears that peak activity was progressively older (MSH (Ka), IH (mostly
Identifier
10.1029/JB095iB12p19561
Publisher
American Geophysical Union
Repository Citation
Leeman, W. P., Smith, D. R., Hildreth, W., Palacz, Z., & Rogers, N. (1990). Compositional diversity of late Cenozoic basalts in a transect across the southern Washington Cascades: Implications for subduction zone magmatism. Journal of Geophysical Research: Solid Earth, 95(B12), 19561-19582. http://doi.org/10.1029/JB095iB12p19561
Publication Information
Journal of Geophysical Research: Solid Earth