Abstract ........................................................ 1
Introduction .................................................... 2
Landslide .................................................... 4
Lava-Dome Effusion Rates ..................................... 6
Rock Type, Grain Size, Grain Shape .............................. 6
Chronology ...................................................... 8
Radiocarbon Ages ............................................. 8
Tephra and Tephrochronology .................................. 8
Geomorphology ............................................... 14
Distinguishing Lithic Pyroclastic Flows from Lahars in
Proximal Areas ........................................... 15
On Map "Units" .............................................. 15
Synopsis of Geologic History ................................... 17
Pre-Augustine Mesozoic Rocks ................................... 18
Pleistocene to Late Holocene Materials ......................... 19
Pleistocene Deposits ........................................ 19
Landslide Block .......................................... 20
Glacial Deposits ......................................... 20
Basaltic and Rhyolitic Deposits .......................... 21
Pleistocene and Holocene Pumiceous Fall and Pyroclastic-
Flow Deposits ............................................... 22
Lava Domes of Uncertain Late Holocene Age ................... 23
Kamishak Dome (Dome K) ................................... 23
Domes F and P ............................................ 23
Prehistoric Summit Domes ................................. 23
Lava Flows ............................................... 24
Prehistoric Deposits of Late Holocene Age ...................... 24
Deposits Older Than Tephra G (about 2,500-2,10014C yr
B.P.) ....................................................... 25
East Point Debris-Avalanche Deposit(s) ................... 25
Deposits Between Tephras G and I (about 2,100-1,80014C yr
B.P.) ....................................................... 25
Yellow Cliffs Debris-Avalanche Deposit ................... 25
Southeast Point Debris-Avalanche Deposit ................. 25
Deposits Between Tephas I and H (about 1,700-1,40014C yr
B.P.) ....................................................... 25
Northeast Point Debris-Avalanche Deposit ................. 25
Northeast Bench Debris-Avalanche or Lahar Deposit ........ 28
Diamictatop Landslide Block .............................. 28
Deposits Between Tephras H and С (about 1,450-1,10014C yr
B.P.) ....................................................... 29
South Point Debris-Avalanche Deposit ..................... 29
Long Beach Debris-Avalanche Deposit ...................... 29
Southwest Pyroclastic Fan ................................ 30
Southeast Pyroclastic Fan ................................ 31
North Bench Debris-Avalanche Deposit ..................... 31
Deposits Between Tephras С and M (about 1,000-75014C yr
B.P.) ....................................................... 32
Lagoon Debris-Avalanche Deposit .......................... 32
Pumiceous Pyroclastic-Flow Deposit ....................... 34
Lithic Pyroclastic-Flow (or Lahar?) Deposit .............. 34
Deposits Between Tephras M and В (about 750-40014C yr
B.P.) ....................................................... 34
Pyroclastic-Flow and Lahar Deposits ...................... 34
Southeast Beach Debris-Avalanche Deposit ................. 34
Deposits Younger than Tephra В (younger than about 40014C
yr B.P.) .................................................... 34
West Island Debris-Avalanche Deposit ..................... 34
Rocky Point Debris-Avalanche Deposit ..................... 39
Unassigned Debris-Avalanche Deposits ..................... 39
North Slope Lava Flow .................................... 40
Beach and Eolian Deposits ................................... 40
Historical Deposits ............................................ 40
1812 Eruption ............................................... 42
1883 Eruption ............................................... 42
Burr Point Debris-Avalanche Deposit ...................... 44
Pyroclastic-Flow and Surge Deposits ...................... 47
Lava Dome ................................................ 48
Discussion ............................................... 48
1935 Eruption ............................................... 49
Lava Dome ................................................ 49
Flank Deposits ........................................... 49
1963-64 Eruption ............................................ 49
Lava Dome ................................................ 49
Pyroclastic-Flow and Lahar Deposits ...................... 49
Ballistics ............................................... 50
1976 Eruption ............................................... 50
Pyroclastic-Flow, Surge, and Lahar Deposits .............. 50
1986 Eruption ............................................... 52
Lava Dome and Agglutinate ................................ 52
Pyroclastic-Flow and Lahar Deposits ...................... 52
Occasional Small Events ..................................... 55
2006 Eruption ............................................... 56
Nonvolcanic Deposits ........................................ 56
Talus and Stream Deposits ................................ 56
Eolian Deposits .......................................... 56
Beach Deposits ........................................... 56
Tidal-Flat Deposits and Marsh Deposits ................... 57
Comparison to Previous Geologic Map ............................ 57
Précis of Eruptions ............................................ 57
High-Energy Flows From Insular Setting ......................... 58
Pyroclastic Density Currents ................................ 58
Debris Avalanche and Surge ("Blast") ........................ 58
Augustine's Debris Avalanches ............................ 58
Mobility and Speed of Volcanic Debris Avalanches ......... 59
Tsunami ..................................................... 62
Augustine Island, 6 October 1883 ......................... 62
Analysis of 6 October 1883 Records ....................... 63
Evidence on Augustine Island for Augustine Tsunami ....... 66
Evidence on Mainland for Augustine Tsunami ............... 66
Sparseness of Mainland Evidence for Augustine Tsunami .... 67
Numerical Simulation of Augustine Tsunami ................ 68
Can Augustine Generate Large Tsunami? .................... 68
Hazards ........................................................ 69
Acknowledgments ................................................ 70
References Cited ............................................... 70
Plates [in pocket]
1. Map showing the geology of Augustine Island, Alaska.
2. Map showing measured sections on Augustine Island and
Shuyak Island, Alaska.
Figures
1. Index maps of Cook Inlet area, Alaska and Augustine
Island ...................................................... 2
2. Photo looking south-southwest of Augustine Volcano .......... 4
3. Oblique aerial photo looking northeast of Augustine
Island and Augustine Volcano ................................ 6
4. Plot of chemical composition analyses of volcanic rocks
(whole-rock analyses) and tephra (glass-separate
analyses) from Augustine Island ............................. 7
5. Summary of mean annual wind directions 1949-62 ............. 12
6. Tephra stratigraphy overlying flowage deposits on
Augustine Island just north of southeast gully ............. 13
7. Isopach maps of coarse pumiceous tephra-layers on
Augustine Island ........................................... 14
8. Graph showing thickness of some sheets of tephra erupted
from volcanoes in western United States plotted against
distance downwind .......................................... 15
9. Summary of eruptive history of Augustine Volcano based
on data in this report ..................................... 16
10. Sketch showing in profile development of arrested sea
cliffs at Augustine Island ................................. 16
11. Map showing offshore distribution of debris avalanches
off Augustine Volcano based on seaward extent of
conspicuously hummocky submarine topography ................ 18
12. Oblique aerial photo looking north-northwest of
Augustine Volcano .......................................... 19
13. Photo showing Naknek Formation (Jurassic) on south side
of Augustine Island ........................................ 20
14. Photo showing great landslide block capped by layered
Augustine-volcanic debris, south coast Augustine Island .... 21
15. Photo showing view north of glacial till containing
striated exotic stones and associated glacial drift (g)
overlain by dacitic fall pumice of Augustine Volcano ....... 21
16. Photo looking eastward showing bedded olivine-basalt
hyaloclastite at or near base of discontinuously exposed
volcanic materials of Augustine Volcano .................... 22
17. Photo showing basaltic hyaloclastite overlain by dacite
pumice on south flank of Augustine Island .................. 22
18. Photo showing pumice-fall deposit from Augustine
interbedded with distal thin beds of Pleistocene glacial
outwash, south-southwest flank of volcano .................. 23
19. Oblique aerial photo looking toward east-southeast of
Augustine Volcano summit area including landslide-
truncated prehistoric summit-dome complex .................. 24
20. Photos showing details within East Point debris-
avalanche deposit .......................................... 26
21. Photo showing view of sea cliff along Augustine Island
east shore ................................................. 27
22. Photo showing Southeast Point and Northeast Point
debris-avalanche deposit ................................... 27
23. Schematic sketch of coastal cliffs along east side of
Augustine Island showing stratigraphic relations of four
oldest debris-avalanche deposits ........................... 27
24. Photo showing view west of hummocky surface of Northeast
Point debris-avalanche deposit ............................. 28
25. Oblique aerial photo looking west-southwestward of
prominent huge-boulder "mound" area of hummocky
Northeast Point debris-avalanche deposit, Augustine
Island ..................................................... 28
26. Oblique aerial photo looking west-northwestward of
Augustine's Northeast Point debris-avalanche deposit and
apparently overridden sea cliff ............................ 29
27. Photo showing nine-meter megaclast of summit-dome
porphyritic andesite forming a single hummock of Long
Beach debris-avalanche deposit on lower southwest flank
of Augustine Island ........................................ 30
28. Photo looking northwest of boulders on southeast
pyroclastic fan of Augustine Island ........................ 31
29. Vertical aerial photo of Augustine's north flank showing
dome complex, North Slope lava flow and the debris-
avalanche deposits ......................................... 32
30. Oblique aerial photo looking south-southeast showing
North Slope lava flow, arrested sea cliff cut in North
Bench debris-avalanche deposit, Rocky Point debris-
avalanche deposit, and 1883 debris-avalanche levee
across and below the lava flow ............................. 33
31. Photo looking west-northwest from high on cone of
Augustine Volcano showing West Island, one of the
largest of Augustine's debris-avalanche deposits ........... 34
32. Photo showing oblique aerial view southwestward of
Augustine Volcano and its offshore West Island ............. 35
33. Photo showing coastal sea cliff exposing interior of
debris-avalanche hummock on West Island, just off
Augustine Island ........................................... 35
34. Photo looking southeastward of southwest side of
central core of high conical hummocks of West Island
debris-avalanche deposit ................................... 36
35. Stratigraphic section showing succession atop debris-
avalanche hummock on southwest coast of West Island ........ 36
36. Sketch map showing details of Grouse Point area,
Augustine Island ........................................... 37
37. Oblique aerial photos of oddly planed-off hummocks on
southwest part of West Island, at Augustine Island ......... 38
38. Photo looking northeast of southwestmost part of
Augustine's West Island showing oddly flattened
hummocks ................................................... 38
39. Photo showing Bouldery diamict of debris-avalanche
levee resting atop North Slope lava flow, north flank of
Augustine Volcano .......................................... 39
40. Photos and a sketch of Augustine Volcano showing large-
scale effects to summit area by 1883 eruption .............. 41
41. Photographic portraits of George Davidson .................. 42
42. Oblique aerial photo of Augustine Volcano from the
north showing hummocky deposit about Burr Point
deposited by landslide of 6 October 1883 ................... 44
43. Photos showing eastern cluster of hummocks of 1883 Burr
Point debris avalanche, Augustine Island ................... 45
44. Schematic sketch of stratigraphic relations at seaside
hummocks east of Burr Point ................................ 46
45. Oblique aerial photos of Augustine Volcano showing
1935,1883 and 1935 domes ................................... 47
46. Photo of Augustine Volcano from southwest showing large
steaming dome and below it a light-colored fan of
debris ..................................................... 48
47. Photo looking south-southeast of summit-dome complex
showing 1976 dome nested below summit ...................... 49
48. Photos looking westward of Augustine Volcano summit
area ....................................................... 50
49. David A. Johnston's "isodroop" curve from an experiment
of melting plastic like that at Burr Point hut in the
1976 eruption .............................................. 51
50. Photo looking southward in then-new 1986 dome and lava-
flow tongue at its base .................................... 52
51. Photo looking north-northeast of Augustine's 1935 and
1986 domes, from 1964 dome ................................. 53
52. Photo showing lithic-fall beds at summit domes of
Augustine Volcano that bury the former rough-surfaced
crescent of the 1976 dome .................................. 53
53. Photo looking southwest of moving 1986 pyroclastic flow
that issued from collapsing lava dome flowing down lower
Augustine's north flank near Burr Point .................... 54
54. Photo looking east on lower north flank of Augustine
Island showing imbricated boulders stacked by 1986
flood ...................................................... 55
55. Sketch map of largest deposits of the January-April
2006 eruption .............................................. 55
56. Plot of fall versus runout for volcanic debris
avalanches from around the world ........................... 59
57. Profiles of large landslides ............................... 60
58. Schematic sketch illustrating how the stilling well in
tide gauges causes a decrease in recorded wave height
and a delay in recorded peak height from the actual
wave ....................................................... 62
59. Tide-gauge marigram from St. Paul (Kodiak), Alaska on 6
October 1883 showing arrivals of wave train of air wave
and of tsunami from Augustine .............................. 62
60. Map showing tsunami travel times from north flank of
Augustine Island ........................................... 63
61. Timing of contemporary records of initial events in
morning 6 October 1883 eruption of Augustine Volcano ....... 64
62. Plot of variation in tidal ranges at Kodiak, Seldovia,
and English Bay, Alaska .................................... 65
63. Photo showing 1883 tsumani and ashfall deposits near
Nanwalek ................................................... 66
64. Photo of core from Beluga Lagoon near Homer with sand-
gravel bed of 1883 Augustine tsunami ....................... 67
Tables
1. Summary of previous geologic work bearing on description
of rocks and deposits at Augustine Volcano .................. 5
2. Radiocarbon ages and stratigraphy of tephra layers at
Augustine Volcano ........................................... 9
3. Stratigraphy of coarse pumiceous "marker-bed" tephra
layers and debris-avalanche deposits at Augustine
Volcano .................................................... 12
4. Some historical tsunami caused by nonvolcanic landslides
and by volcanic debris avalanches .......................... 61
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