Signatures of Tsunami in the Coastal Landscape - Tsunami - page 57

the crest of a tsunami wave is only sustained for a few
minutes at most. Once a critical velocity is reached, bedrock
erosion commences. The spin-up process causes vortex
erosion to develop and terminate quickly, as is demon-
strated by the fact that some potholes are only partially
formed. Whirlpools, such as the one in Fig. 3.26 , are
formed instantaneously in the space of minutes rather than
by the cumulative effect of many wave events. Whereas
mini-vortices in tornadoes can freely circumscribe paths
around the wall of the tornado, those in whirlpools are
constrained by the bedrock they are eroding.
This chapter has attempted to show that a myriad of dis-
tinct signatures produced by tsunami exist besides the
descriptions of anomalous sediment layers that pervade the
current literature. The most impressive of these additional
signatures is produced by bedrock sculpturing. Most of the
descriptions of individual signatures presented in this chapter
indicate that they do not occur as isolated features but appear
in combination with each other to form spatially organized
suites that dominate some coastal landscape—such as rocky
headlands. The description of these varied tsunami-generated
landscapes constitutes the focus of Chap. 4 .

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