Figure 2. Landscape disturbances caused by the 1980 Mount St. Helens eruption. (A) Hummocky debris-avalanche deposit in upper North Fork Toutle River valley, June 1980. Foreground field of view is ~3 km across. Photograph by H. Glicken. (B) Tephra-mantled hillslope within area swept by blast pyroclastic density current (PDC) (cf. Fig. 1). Stumps are ~0.5 m wide. Photograph by U.S. Geological Survey (USGS), 1980. (C) Tephra-mantled hillslope within blow-down zone of blast PDC and thick valley fill in Smith Creek (cf. Fig. 1). Note person in circle for scale. Photograph by Lyn Topinka, USGS, September 24, 1980. (D) Tephra-mantled landscape east of volcano beyond zone of blast PDC, summer 1980. The tree trunks are ~0.5 m across. Photograph courtesy of Joe Antos, University of Victoria. (E) Pyroclastic-flow deposits mantling debris-avalanche deposit in upper North Fork Toutle River valley. Individual flow lobes are ~30-50 m across. Photograph by Lyn Topinka, USGS, September 30, 1980. (F) Lower Toutle River valley, transformed from cobble-bedded channel to smooth, sand-bedded channel by large lahar. Field of view is ~80 m across. Photograph by Lyn Topinka, USGS, July 6, 1980. From Major and Mark (2006).
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Uploaded: Dec21 09