Geoscience Reference
In-Depth Information
Fig. 7.4 Location map of Lituya
Bay, Alaska
-150°
-140°
-130°
Anchorage
Valdez
60°
Prince William
Sound
Gulf of Alaska
55°
Queen Charlotte
Island
50°
Disenchantment Bay
Skagway
Glacier
Bay
Yakutat
Lituya
Bay
Juneau
0
100 km
Rockslide
Cascade
Glacier
Lituya Glacier
Gilbert Inlet
79
99
Fish Lake
524
67
38
69
53
17 182
61
40
49
207
37
64 49 168
27
Crillon Inlet
24
37
North Crillon Glacier
21
40
10
26
30
Height of
run-up (m)
Tsunami
inundation
11
59
Cenotaph
Island
La Chaussee Spit
0
1
2
3 km
the volume of water nor the rate at which the lake drained was
sufficient to allow such a high wave to develop. Besides, the
maximum wave run-up did not occur near the discharge point
for any Jökulhlaups or glacier water bursting from the glacier.
The tsunami appears to have been created by a sudden
impulsive rockfall. Within 50-60 s of the earthquake,
30.5 9 10 6 m 3 of consolidated rock dropped 600-900 m
from the precipitous northeast shoreline of Gilbert Inlet into
the bay (Fig. 7.5 ). The impact of this rockfall was analogous
to that of a meteoroid crashing into an ocean—a phenomenon
that will be described in Chap. 9 . The impact not only dis-
placed an equivalent volume of water, it also created a large
radial crater in the bottom sediments of the lake that left an
arcuate ridge up to 250 m from the shoreline (Pararas-Cara-
yannis 1999 ). The sudden displacement of water and sedi-
ment sheared 400 m off the front of Lituya Glacier and flung it
high enough into the air that a distant observer reported seeing
the glacier lift above a ridge that had hidden it from view.
 
Search WWH ::




Custom Search