Augustine Southeast Beach Debris Avalanche
Start: 760 yBP ± 60 Years [1]
Stop: 380 yBP ± 20 Years [1]
Event Type: Not an eruption
Description: From Waitt and Beget (1996): "Between about 700 and 400 yr B.P. (between tephra layers M and B) a debris avalanche swept to the sea on the west and a small one on the south-southeast. Large lithic pyroclastic flows shed to the southeast; smaller ones descended exiting swales on the southwest and south."
"A boulder diamict exposed in upper part of bluffs along Southeast beach (unit MBas) is studded with angular in situ blocks as large as 2.5 m, as large as 6 m as lag on beach, and as large as 7 m in the surf zone seaward. The diamict is overlain by B tephra and underlain by M and C tephras. These tephras overlie unit HCpe that forms most of bluff. Adjacent lahar or pyroclastic-flow deposits (units MBlp and MBpl) are flatter surfaced and contain angular lithic andesite clasts no larger than 2 m."
"During this prehistoric period numerous domes must have been emplaced at the summit, repeatedly renewing the source for catastrophic debris avalanches. Remnants of these older domes form the east and south sides of the present summit-dome complex. Below the summit area at least three domes were emplaced on the upper flanks, one on the south (Karnishak dome), two on the northwest (domes "I' and "H"). Another undated and nearly buried dome or lava flow diversifies the upper south flank."
"A boulder diamict exposed in upper part of bluffs along Southeast beach (unit MBas) is studded with angular in situ blocks as large as 2.5 m, as large as 6 m as lag on beach, and as large as 7 m in the surf zone seaward. The diamict is overlain by B tephra and underlain by M and C tephras. These tephras overlie unit HCpe that forms most of bluff. Adjacent lahar or pyroclastic-flow deposits (units MBlp and MBpl) are flatter surfaced and contain angular lithic andesite clasts no larger than 2 m."
"During this prehistoric period numerous domes must have been emplaced at the summit, repeatedly renewing the source for catastrophic debris avalanches. Remnants of these older domes form the east and south sides of the present summit-dome complex. Below the summit area at least three domes were emplaced on the upper flanks, one on the south (Karnishak dome), two on the northwest (domes "I' and "H"). Another undated and nearly buried dome or lava flow diversifies the upper south flank."
References Cited
[1] Volcanic processes and geology of Augustine Volcano, Alaska, 2009
Waitt, R.B., and Beget, J.E., 2009, Volcanic processes and geology of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1762, 78 p., 2 plates, scale 1:25,000, available at http://pubs.usgs.gov/pp/1762/ .[2] Provisional geologic map of Augustine Volcano, Alaska, 1996
Waitt, R. B., and Beget, J. E., 1996, Provisional geologic map of Augustine Volcano, Alaska: U.S. Geological Survey Open-File Report 96-0516, 44 p., 1 plate, scale 1:25,000.
map in GIF format 21 KB 
full-text PDF 2.6 MB
map sheet 295 MB! [3] Preliminary volcano-hazard assessment for Augustine Volcano, Alaska, 1998
Waythomas, C. F., and Waitt, R. B., 1998, Preliminary volcano-hazard assessment for Augustine Volcano, Alaska: U.S. Geological Survey Open-File Report 98-0106, 39 p., 1 plate, scale unknown.
full-text PDF 2.08 MB
map sheet plate 3.14 MB [4] Cyclic formation of debris avalanches at Mount St Augustine volcano, 1992
Beget, J. E., and Kienle, J., 1992, Cyclic formation of debris avalanches at Mount St Augustine volcano: Nature, v. 356, n. 6371, p. 701-704.Complete Eruption References
Preliminary volcano-hazard assessment for Augustine Volcano, Alaska, 1998
Waythomas, C. F., and Waitt, R. B., 1998, Preliminary volcano-hazard assessment for Augustine Volcano, Alaska: U.S. Geological Survey Open-File Report 98-0106, 39 p., 1 plate, scale unknown.
full-text PDF 2.08 MB
map sheet plate 3.14 MB 
Provisional geologic map of Augustine Volcano, Alaska, 1996
Waitt, R. B., and Beget, J. E., 1996, Provisional geologic map of Augustine Volcano, Alaska: U.S. Geological Survey Open-File Report 96-0516, 44 p., 1 plate, scale 1:25,000.
map in GIF format 21 KB
full-text PDF 2.6 MB
map sheet 295 MB! 
Cyclic formation of debris avalanches at Mount St Augustine volcano, 1992
Beget, J. E., and Kienle, J., 1992, Cyclic formation of debris avalanches at Mount St Augustine volcano: Nature, v. 356, n. 6371, p. 701-704.
Volcanic processes and geology of Augustine Volcano, Alaska, 2009
Waitt, R.B., and Beget, J.E., 2009, Volcanic processes and geology of Augustine Volcano, Alaska: U.S. Geological Survey Professional Paper 1762, 78 p., 2 plates, scale 1:25,000, available at http://pubs.usgs.gov/pp/1762/ .