HR: 11:50h
AN: OS21D-07    [PDF]
TI: Progress in Tsunami Deposit Research- What Should Mega-tsunami deposits look like?
AU: * Keating, B H
EM: keating@soest.hawaii.edu
AB: Large landslide scars and debris flows surround ocean islands. It has been proposed that these landslides could trigger "Giant Waves." However, the basic tenets of the Giant Wave Hypothesis have proven problematic. What characteristics should mega-tsunami deposits display? Tsunamis are depositional and erosional in desultory fashion. Numerous studies, show that tsunami derived deposits share many characteristics, e.g. sand sheets, marine shells deposited in subaerial settings, boulder deposits, etc. Sediments fine inland and upland (a distribution pattern not unique to tsunami). Tsunami deposits could be restricted to a single event, or alternately the backwash could erode and mix materials from multiple events (e.g. material in wave cut notches). It is difficult to differentiate between tsunami and storm deposits. Modern cementation of coral and basalt clasts on rocky shores today resemble proposed paleo-tsunami deposits. Tsunami deposits reflect their local source. Although tsunami deposits should reflect the carrying power of the waves, they can only do so if material of the appropriate size and density is present to reflect that carrying power. Complicating the situation, uplift can expose conglomerates above sea level. Although subsidence is characteristic of many oceanic islands, it should not be assumed to dominate in all cases.Tsunami deposits are ephemeral (easily eroded by normal beach processes, mixed with soils, and remobilised by anthropogenic activity) and many of their most diagnostic features can disappear within years after an event.
DE: 3020 Littoral processes
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 4558 Sediment transport
DE: 4564 Tsunamis and storm surges
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting