Title

Tsunamis, hurricanes and neotectonics as driving mechanisms in coastal evolution (Proceedings of the Bonaire Field Symposium, March 2-6, 2006. A contribution to IGCP 495)

Document Type

Book

Publication details

Scheffers, A & Kelletat, D (eds), Tsunamis, hurricanes and neotectonics as driving mechanisms in coastal evolution (Proceedings of the Bonaire Field Symposium, March 2-6, 2006. A contribution to IGCP 495), E Schweizerbart, Stuttgart, Germany, Zeitschrift fur Geomorphologie Supplementband, vol. 146.

Abstract

Using field oberservations and remote sensing data from the Indian Ocean Tsunami 2004 impact at Banda Aceh and Lhok Nga districts (Indonesia) F.Lavigne, R.Paris, P.Wassmer, Ch.Gomez, D.Brunstein and 11 other Co-authors present a field data-based methodology to calibrate simulation codes for tsunami inundation models. The presented preliminary results are part of the French-Indonesian TSUNAMIRISQUE programme with the aim to improve existing flood models and to propose accurate risk maps along coastal areas.

The volume offers an excellent overview to the state of the art in tsunami- and paleotsunami research. The papers present many impressive details about investigation methods, the differentiation of storm- and tsunami-wave generated deposits, about patterns, timing and extent of extreme paleo-tsunami impacts, which are illustrated at a wide variety of coastal sites. All in all this volume will be a great help for an ongoing research on ancient tsunami and storm impacts along coastal sites, and for a more accurate determination of extreme wave risk areas. Therefore, the volume should have a wide readership not only within the geomorphological and geological community.

The study of modern and ancient tsunami impacts on coastal areas is becoming increasingly important, not only since the December 24, 2004 Indian Ocean Tsunami has devasted many coastal communities in SE Asia, but also since human societies have settled there and coastal population density has increased. Obviously, a prediction of future tsunami impacts and their run up heights along all coastlines of the world makes it necessary to understand the processes and also the frequency and extension of tsunami events happened in the past. Learning from the past is one of the most important aspects in recent tsunami- and paleo-tsunami research.

In the first paper A. Scheffers presents a compressed review of sedimentary impacts, ages and run-up extensions of Holocene tsunami events from several islands of the Intra-Americas Seas (Aruba, Bonaire, Curacao, Barbados, Guadeloupe, Anguilla, St. Martin/St. Maarten, Bahamas) and from Southern Europe coasts (Cyprus, Turkey, Crete, Mallorca, Spain, Portugal).

E.Robinson, D.-A. C.Rowe & S.A.Khan focus on wave-emplaced boulders on Jamaica’s rocky shores and made some comparisons with similar deposits in Grand Cayman. They discuss e. g. the effects of submarine landslides for local tsunami events as well as the extent of hurricane-generated movement of boulders weighing up to 33 tons.

S. Scheffers, A. Scheffers, U.Radtke, D. Kelletat, K. Staben&R. Bak describe dramatic tsunami–impacts with long-lasting phase-shift on coral reef ecosystems at Bonaire (southern Caribbean) during the Holocene. They hypothize that gaps in the spatial distribution of coral reefs around the globe, where obviously the environmental conditions for coral reef growth are good, may be due to tsunami impacts.

Megablocks of Middle and Younger Holocene age were identified and dated along the shorelines around the Tripoli islands and Byblos, northern Lebanon, by Ch.Morhange, N. Marriner & P.A.Pirazzoli. The authors assume a tsunami origin for most of the megablocks, and emphasize that they have been displaced by high-energetic waves from tsunami events generated in outer tsunamigenic areas, and not by vertival movements of the Lebanese coast.

A. Scheffers gives a detailed description of the coastal transformation during and after the sudden neotectonic uplift in Western Crete (Greece), that happened on July 365 AD and has been documented in a great variety of uplifted littoral forms.

A fault-Model for the AD 365 destructive earthquake and tsunami in the Eastern Mediterranean is presented by S. C. Stiros&A.Drakos. Their preferred model indicates that the up to 9 m coastal uplift of Western Crete and the large scale destructions at many coastal sites in the Eastern Mediterranean were associated with a single giant submarine earthquake from the Hellenic (Aegean) Arc SW of Crete. They assume an unusual magnitude of at least 8. 5.

A. Vött, M.May, H. Brückner & S.Brockmüller give a detailed description of Late Holocene tsunami impacts along the northern coast of Lefkada Island (NW Greece). They used geomorphological mapping and vibracoring in deposits near the modern coast to find different types of sedimentary relicts of paleo-tsunamis like e. g. washover and breakthrough fan sediments (crevasse splay) deposited into lagoonal environments and dislocated mega-blocks, blocks and stones. Absolute age estimations are based on 14C-AMS dating of plant remains or marine organism. The authors postulate at least two mega-tsunami impacts at 1,000 cal BC and 1,000–1,400 cal AD, and two smaller events at 300 cal BC and 430 cal AD.

G.Mastronuzzi, C. Pignatelli&P. Sansò discuss the value of boulder fields as a morphological indicator of paleo-tsunamis in the Mediterranean Sea focusing on the differentiation between storm- and tsunami-accumulated boulders. The authors emphasize that the geomorphological feature as well as local topography, transporting wave character, size, weight and lithological properties of boulder assemblages have to consider before using them as indicators of a tsunami impact. The presence of a single large boulder, of which the weight is below local limits, as well as imbrication, arrangement in groups or rows could also result from deposition by extreme storm waves.

F. J.Gracia, C.Alonso, J. Benavente, G. Anfuso & L. Del-Río summarize different coastal records of the 1755 Tsunami waves along the south SW Spanish Atlantic coast. The authors describe in detail different erosional and depositional tsunami and storm records preserved at different locations from the Guadalquivir river in the North up to Los Lances Bay inthe South.

A. Scheffers discusses the origin of Mega-ripples or “dunes” in coarse clastic tsunami deposits along the coastlines of the Caribbean islands Curaçao and Bonaire (Netherlands Antilles). The author states that the mega-ripples are caused by water flow predominantly with onshore direction and assumes a tsunamigenic origin of these features.

The last two papers deal with the December 26, 2004 Indian Ocean Tsunami. B. M. Richmond, B. E. Jaffe, G. Gelfenbaum&R.A.Morton give an excellent description of the geological impacts of this tsunami on Indonesia, Sri Lanka, and the Maldives. The analysis of the observed morphological changes and of the sediment depositions as well as the water level measurements have been used to reconstruct locally variable tsunamigenic processes.

Using field oberservations and remote sensing data from the Indian Ocean Tsunami 2004 impact at Banda Aceh and Lhok Nga districts (Indonesia) F.Lavigne, R.Paris, P.Wassmer, Ch.Gomez, D.Brunstein and 11 other Co-authors present a field data-based methodology to calibrate simulation codes for tsunami inundation models. The presented preliminary results are part of the French-Indonesian TSUNAMIRISQUE programme with the aim to improve existing flood models and to propose accurate risk maps along coastal areas.

The volume offers an excellent overview to the state of the art in tsunami- and paleotsunami research. The papers present many impressive details about investigation methods, the differentiation of storm- and tsunami-wave generated deposits, about patterns, timing and extent of extreme paleo-tsunami impacts, which are illustrated at a wide variety of coastal sites. All in all this volume will be a great help for an ongoing research on ancient tsunami and storm impacts along coastal sites, and for a more accurate determination of extreme wave risk areas. Therefore, the volume should have a wide readership not only within the geomorphological and geological community.

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