origin of minor limestone shale cycles climatically induced or diagenetic the opinion is widely held that each limestone bed in minor limestone shale cyclic sequences however modified subsequently by diagenesis reflects an environmental event on the assumption that this is true attempts have recently been made to relate limestone shale cycles to climatic variations affected by milankovitch orbital cycles a test is proposed and illustrated mainly with reference to the blue lias formation of dorset england that appears to indicate that many limestones can be produced solely by rhythmic unmixing of caco 3 during diagenesis unless such limestones can be clearly distinguished from those that record genuine environmental signals orbital cycle analysis based on such sequences will give meaningless results

field survey report on tsunami disasters caused by the 1993 southwest hokkaido earthquake detailed field work at okushiri island and along the southwest coast of hokkaido has revealed quantitatively 1 the advancing direction of tsunami on land 2 the true tsunami height i e height of tsunami excluding its splashes as measured from the ground and 3 the flow velocity of tsunami on land in heavily damaged areas when a japanese wooden house is swept away by tsunami bolts that tie the house to its concrete foundation resist until the last moment and become bent towards the direction of the house being carried away the orientations of more than 850 of those bent bolts and iron pipes all that can be measured mostly at okushiri island and fell down direction of about 400 trees clearly display how tsunami behaved on land and caused serious damage at various places the true tsunami height was estimated by using several indicators such as broken tree twigs and a window pane the flow velocity of tsunami on land was determined by estimating the hydrodynamic force exerted on a bent handrail and a bent down guardrail by the tsunami through in situ strength tests

tsunami deposits from the 1993 southwest hokkaido earthquake and the 1640 hokkaido komagatake eruption northern japan the southwest hokkaido tsunami of july 12th 1993 left continuous onshore sand deposits along the west coast of oshima peninsuka hokkaido northern japan we investigated spatial distribution and lithofacies of the new tsunami deposits for its identification of ancient tsunami deposits an eyewitness acount and bent plants helped our interpretation of the onshore tsunami behavior we regard the following properties as typical of the coastal tsunami sand deposits 1 the deposits cover the surface almost continuously on gentle topography 2 deposit thicknesses and mean grain sizes descrease with distance from the sea 3 deposit thicknesses and lithofacies vary greatly across local surface undulation 4 graded bedding reflecting tsunami runup and backwash is present in thick deposits 5 the deposits are widely distributed along the coast and extend inland several tens of meters to 100 m we examined a candidate for the paleo tsunami deposits associated with the 1640 komagatake eruption and confirmed that the similar patterns are typical of ancient tsunami deposits

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

micromorphological analysis of coastal sediments from willapa bay washington usa a technique for analysing inferred tsunami deposits tsunami deposits are provisionally distinguished in the field on the basis of anomalous sand horizons fining up and fining landward coupled with organic rich fragmented backwash sediments in this paper micromorphological features of a sediment sequence previously interpreted as being of tsunami origin are described these characteristics are shown to be consistent with the macro scale features used elsewhere but show additional details not seen in standard stratigraphies including possible evidence for individual waves possibly wave magnitude progression organic fragment alignment and intraclast microstructures although replication and more complete studies are needed this analysis confirms the identification of a tsunami in willapa bay in ca 1700 ad while demonstrating a widely applicable technique for confirming or refuting possible tsunami deposits

a holocene tsunami deposit in eastern scotland a thin regionally extensive laterally persistent sand layer identified within the holocene coastal sequences of eastern scotland dated to 7000 years bp is suggested to be a tsunami deposit the likely source of the tsunami wave is the earthquake induced second storegga slide on the norwegian continental slope at least 750 km northeast of the deposit

tsunamis in the new zealand archaeological record abstract historical and geological records both indicate tsunami inundation of new zealand in the 700 years since the first human settlement in addition maori oral traditions refer to unusual waves that might have been tsunami waves although the accounts are open to other interpretations tsunami evidence has rarely been proposed from archaeological sites primarily because of a limited understanding of the requisite evidence and environmental context we list a criteria suggesting possible tsunami inundation of archaeological sites based upon geoarchaeological data and use them in a case study from the archaic maori occupation site at wairau bar the list is possibly incomplete but indicates that archaeological investigations can gain from assessments of changing environmental conditions through time at any individual site our intention is not to prove tsunami inundation rather it is to point to archaeological sites as possible sources of information we highlight the potential of the wairau bar site for further investigation

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

a tsunami about 1000 years ago in puget sound washington water surged from puget sound sometime between 1000 and 1100 years ago overrunning tidal marshes and mantling them with centimeters of sand one overrun site is 10 kilometers northwest of downtown seattle another is on whidbey island some 30 kilometers farther north neither site has been widely mantled with sand at any other time in the past 2000 years deposition of the sand coincided to the year or less with abrupt probably tectonic subsidence at the seattle site and with landsliding into nearby lake washington these findings show that a tsunami was generated in puget sound and they tend to confirm that a large shallow earthquake occurred in the seattle area about 1000 years ago

analysis of environmental controls on tsunami deposit texture abstract tsunamis transport large amounts of sediment and can leave recognisable signatures in the landscape the form and composition of onshore tsunami deposits are a function of wave dynamics sediment availability and characteristics of the local environment the latter of which also partially controls preservation of the deposit this research reviews these relationships in a global context and assesses the connection between tsunami deposit particle size and four controlling parameters climate temperature and rainfall density of tsunami sediments degree of coastal protection and distance between tsunami source and sediment deposition an international dataset of tsunami deposit locations and texture was compiled from published literature and existing databases values for environmental variables were calculated for each location from global datasets of temperature rainfall coastline shape and tsunami source locations spearman s rank order correlation principal component analysis pca and hierarchical cluster analysis ca were used to analyse relationships between these variables pca results show an inverse relationship between particle size and sediment density climate variables and distance from source ca results support this suggesting a cluster structure controlled primarily by particle size and secondly by climate and sediment density these relationships can be explained by the influence of the environment on antecedent morphology and the composition of sediments available for tsunami transport

tsunamis caused by offshore active faults and their deposits abstract this paper reviews the variable features of coastal tsunamis caused by offshore active faults along the eastern margin of the japan sea emjs based on the historical records and modern observations of earthquakes and tsunamis tsunami deposits discovered along the emjs coast were also introduced and categorized depending on their sedimentary environments the offshore active faults which are densely distributed along the emjs and generate tsunamis are originated from the opening of the japan sea back arc basin during the late oligocene to miocene period the magnitudes of the earthquakes that caused large tsunamis in the emjs were under 8 0 the size of the fault plane approximately equal to the tsunami source area was approximately 10 100 and several tens of kilometers in length the slip distance of the reverse type faults was less than 20 m the sedimentary characteristics and depositional processes of tsunami deposits were obtained from deposits in various environments such as coastal lowlands marine terraces coastal lagoons and inland ponds certain unique approaches used to identify tsunami deposits were reviewed such as gravel layers that intercalate inorganic soils and a holocene marine terrace dinoflagellate cysts and foraminiferal linings which are potentially derived from the sea and chemical features e g the ca2 mg2 ratio as indicators of seawater inflow into a coastal lagoon the spatial distribution and recurrence of earthquakes and tsunamis in the emjs were found based on previous paleo tsunami studies the difference between tsunami deposits caused by offshore active faults and those by megathrust earthquakes only manifests itself in the horizontal and vertical directions but not in the sedimentary environments and structures the data thus inferred can be used for the estimation of offshore active fault models and validation of previous tsunami disaster reconstructions in the future

traces of tsunami preserved in inter tidal lacustrine and marsh deposits some examples from northeast japan the japan sea earthquake of may 26 1983 triggered a large scale tsunami that surged over the coast of ne japan and caused considerable damage the tsunami resulted in peculiar sedimentary processes on the coast depending on the hydraulic scale of the tsunami three kinds of sedimentary processes were recognized each of which left unique deposits such deposits are expected to remain in sedimentary sequences preserving remarkable sedimentary facies borehole samples drilled at different localities in coastal regions have been examined to detect traces of ancient tsunamis sedimentological and geochemical studies of the samples reveal that layered deposits similar to those developed by the tsunami of the japan sea earthquake are common in the drilled cores estimated ages of these deposits are exactly equivalent to the dates of ancient tsunamis documented in historical records these results show that the invasion of tsunamis is recorded in coastal depositional sequences from analyses of long borehol

sources and transportation modes of the 2011 tohoku oki tsunami deposits on the central east japan coast abstract we evaluated sediment sources of the 2011 tohoku oki tsunami deposits along a 4500 m inland transect from the central east japan coast using grain size mineralogy and foraminifera analyses the tsunami run up height in our study area was 13 to 20 m near the coastline 1 4 to 2 8 m in the middle of the valley and 1 3 m around the inundation limit the inundation distance was around 4800 m the deposits are composed of sand and mud and show a fining and thinning trend mineral composition of the tsunami deposits was similar to that of coastal dune and beach deposits indicating that most of the tsunami sediment originated from there a minor foraminifera population in the deposit 15 specimens per 5 g of sample compared with 100 specimens per 1 g for typical marine sediment indicates that marine sediment source was not dominant topography played an important role in sediment transport process and deposit distribution the run up wave accelerated faster in concave topography became more erosive and resulted in a thin deposit in topographic lows we infer that the deposits up to 2300 m from the coastline were deposited by bedload and suspension whereas suspension was responsible for deposits farther inland

geologic evidence for earthquakes during the past 2000 years along the copalis river southern coastal washington evidence for several prehistoric earthquakes is present in deposits less than 2000 years old that crop out at the copalis river estuary 47 07 2 n 124 09 7 w the deposits show that land subsided decimeters into the intertidal zone on as many as three occasions and that sand vented while the land underwent little or no subsidence on another occasion the evidence for earthquake induced subsidence consists of buried marsh and forest soils that evince sudden estuarine submergence attended on at least one occasion by a landward directed surge of sandy water this combination of submergence and surge implies subsidence and tsunami exposed evidence for subsidence and tsunami along the copalis river is strong for a time within a few decades of 300 years ago moderate for a time 1400 1900 years ago and weak subsidence or lacking tsunami for an intermediate time also about 1400 1900 years ago the history of sudden submergence and tsunami in the past 2000 years at the copalis river estuary resembles that shown by buried soils farther south in coastal washington at grays harbor and willapa bay the history can be explained most simply by great mw of 8 or 9 thrust earthquakes at the boundary between the juan de fuca and north america plates with one or two earthquakes occurring 1400 1900 years ago and another close to 300 years ago the evidence for earthquake induced venting along the copalis river consists of sand intrusions and vented sand volcanoes the sand rose through muddy estuarine deposits at least 3 m thick entraining these deposits in fragments as much as 0 3 m long intrusion occurred at one or more times in the past 2000 years and at least some of the venting occurred 900 1300 years ago the sand bodies do not imply artesian flow of flood pressured groundwater because the sand vented forcefully and infrequently through a lowland that probably lacked natural levees the earthquake implied by the venting of sand 900 1300 years ago could have come from a source below above or at the boundary between the juan de fuca and north america plates if from the subducted juan de fuca plate the implied earthquake was farther west or larger than the largest earthquakes within that plate during the past 100 years evidence permitting a source within the north america plate includes a fault scarp an uplifted tideflat and landslides near puget sound dating from the interval 700 1700 years ago a plate boundary source would explain buried soils whose estuarine submergence and burial imply coseismic subsidence for parts of coastal washington in the interval 600 1300 years ago however stratigraphy shows that little or no coseismic subsidence occurred along the copalis river during the venting 900 1300 years ago if a plate boundary earthquake struck coastal washington 900 1300 years ago the earthquake produced a different distribution of land level change than did the plate boundary earthquakes inferred for 1400 1900 and 300 years ago

onshore tsunami deposits caused by the 1993 southwest hokkaido and 1983 japan sea earthquakes onshore tsunami deposits resulting from the 1993 southwest hokkaido and 1983 japan sea earthquakes were described to evaluate the feasibility of tsunami deposits for inferring paleoseismic events along submarine faults tsunami deposits were divided into three types based on their composition and aerial distribution a deposits consisting only of floating materials b locally distributed siliclastic deposits and c widespread siliclastic deposits the most widely distributed tsunami deposits consist of the first two types type c deposits are mostly limited to areas where the higher tsunami runup was observed the scale of tsunami represented by vertical tsunami runup is an important factor controlling the volume of tsunami deposits the thickest deposits about 10 cm occur behind coastal dunes to produce thick siliclastic tsunami deposits a suitable source area such as sand bar or dune must be available in addition to sufficient vertical tsunami runup estimation of the amounts of erosion and deposition indicates that tsunami deposits were derived from both onshore and shoreface regions the composition and grain size of the tsunami deposits strongly reflect the nature of the sedimentary materials of their source area sedimentary structures of the tsunami deposits suggest both low and high flow regimes consequently it seems very difficult to identify tsunami deposits based only on grain size distribution or sedimentary structure of a single site in ancient successions

geomorphological effects of tsunami run up and backwash abstract geomorphological processes associated with tsunami run up and backwash are highly complex to date most studies have considered the sedimentology of palaeo tsunamis while almost no detailed studies have been undertaken in areas known to have been affected by tsunamis in recent times research on contemporary tsunamis show that coastal landscapes may be greatly altered not only by direct tsunami run up orthogonal to the shoreline but also by episodes of vigorous backwash and by water flow sub parallel to the coastline the combined effect of these processes produces hitherto unrecognised coastal landforms that are dominated by the effects of high magnitude erosion and deposition deposition of large boulders is also associated with severe tsunamis while in adjacent areas run up processes often result in the deposition of continuous and discontinuous sediment sheets in many instances the upper limit of sediment deposition lies well below the upper limit of wave run up which is frequently marked by a well defined zone of stripped vegetation and soil the processes described have considerable implications for models of coastal evolution it may even be the case that the evolution of particular stretches of coastline are dominated by such high magnitude low frequency events

coastal sedimentation associated with the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract with wave heights of 30 m and runups reaching 50 m a s l and 6 km inland the december 26 2004 tsunami in sumatra was one of the largest tsunamis in recorded human history in this paper we present a description of the event in the lhok nga bay west coast of banda aceh and an interpretation of the tsunami sand deposits mostly based upon grain size analysis the 3 5 km long transect of lampuuk displays two landward fining thinning and sorting sequences the thickest cross sections of the first sequence of deposits 0 1 5 km inland suggest a deposition by three consecutive runups inflows and a final backwash return flow or outflow from 1 5 to 3 5 km inland the record is dominated by the second and highest wave 15 30 m normally graded couplets or triplets of layers were used to identify the runup of each wave the topmost layers interpreted as the backwash deposition describe a seaward sequence of increasing mean grain size and decreasing degree of sorting the local effects of the topography could be identified thickest deposits in the topographic lows 50 80 cm great spatial variations in thickness and upper laminated texture when the sedimentation was limited by steep slopes landward coarsening and very poor sorting at the wave breaking point bimodal grain size distributions reflecting different sources of sediments finally by coupling the longitudinal and vertical trends of the 26 cross sections we propose a model of sediment transport and deposition in a large tsunami wave

sedimentological and geoarchaeological evidence of multiple tsunamigenic imprint on the bay of palairos pogonia akarnania nw greece abstract this paper presents evidence of multiple tsunami impact on the bay of palairos pogonia nw greece during the holocene based on detailed geo scientific studies altogether 41 vibracores were drilled to detect high energy influence in the stratigraphical record layers of coarse grained allochthonous marine deposits were found intersecting autochthonous fine grained back beach sediments in the palairos coastal plain on top of beach or marly bedrock units at pogonia beach and along the pogonia cliff section high energy deposits are associated with specific sedimentary structures such as fining upward sequences rip up clasts basal erosional contact bi to multimodal grain size distribution lamination and co existence of both well rounded and angular sharply edged components all of them typical of tsunami impact macro and microfaunal analyses revealed tsunami related input of numerous ex situ marine species and mostly angular shell debris into quiescent fresh to brackish water environments by high energy and long distance transport geophysical methods helped to find subsurface structures and to seize the lateral extent of tsunami layers ca fe ratios derived from xrf measurements were used to trace tsunami influence inland most important is the widespread spatial distribution of the tsunamites with a lateral extent between 70 m at the pogonia cliff section 200 m at pogonia beach and 1 km in the central palairos plain and overall tendencies of fining and thinning towards inland highest elevations of tsunamites were found around pogonia village at ca 7 5 m a s l vibracore data give evidence that the overall coastal evolution has been strongly affected locally even controlled by multiple high energy impact a conspicuous geoarchaeological tsunamite up to 1 5 m thick was found at pogonia cliff consisting of mixed marine sand pebbles bio erosively altered stones shell debris foraminifers and terrigenous material abundant ceramic fragments bones building material it is directly associated with the submerged remains of an ancient mole which was destroyed and its building material partly dislocated by the same event dating of tsunamites was accomplished by archaeological age determination of diagnostic sherds and by radiocarbon and luminescence dating techniques strong tsunami events were dated to the beginning of the 6th the mid 5th the 4th 3rd and the late 2nd millennia bc as well as to the 4th 3rd century bc on a regional scale the recurrence interval for large events is ca 500 1000 years at least twice during the late holocene the palairos coastal plain was flooded quasi contemporaneously from both the northern and southern side

high resolution geochemical and grain size analysis of the ad 1755 tsunami deposit insights into the inland extent and inundation phases abstract in the study of palaeotsunamis it is crucial to decipher the sedimentological record to derive intensity of past events and to infer different inundation phases to achieve this goal it is important to apply high resolution techniques that allow magnifying intra deposit details at a sub centimetric scale that otherwise would not be perceived consequently valuable information could be overlooked in this work we applied successfully high resolution geochemical and grain size analyses xrf core scanning and image analysis respectively to the ad 1755 tsunami deposit this quartz sand enriched in bioclast deposit exhibiting high si al and ca ti was recognized in the coastal stratigraphic sequence of salgados lagoon due to its contrasting composition when compared with the under and overlying mud layers with scarce bioclasts exhibiting low si al and ca ti in the absence of textural evidence the identification of peaking concentrations of cl s and br all major constituents of sea salt in a continuous muddy sequence allowed slightly extending farther inland the limit of inundation in addition grain size analysis data attested the fining inland of the deposit furthermore despite the macroscopic massive structure of the tsunami deposit throughout the lagoon grain size results revealed more complexity and allowed inferring up to four depositional sequences directly associated with the ad 1755 tsunami inundation

hydro and morpho dynamic modeling of breaking solitary waves over a fine sand beach part i experimental study abstract the objectives of this work are 1 to examine the mechanisms that influence tsunami erosion and deposition mechanisms in the littoral zone via physical simulations of breaking solitary waves over a fine sand beach and 2 to provide experimental data for validation of numerical models to predict tsunami erosion and deposition processes the experiments were carried out in a 48 8 m 2 16 m 2 1 m wave flume the flume was instrumented to observe free surface elevations cross shore velocities suspended sediment concentrations vertical and cross shore pore pressure gradients near the shoreline and morphological changes in addition wave sediment interactions were observed via underwater video cameras the results are systematically analyzed to investigate the roles of wave breaking bore runup wave drawdown and wave induced pore pressure variations on tsunami erosion and deposition processes the studies showed that the wave plunging on a thin layer of water prior to reaching the shoreline did not cause much sediment suspension while the waterjet impinging directly on the beach entrained substantial amounts of sand the suspended sediments were subsequently pushed up the slope by fluid momentum as the broken wave transformed to a turbulent bore a small net deposition region was observed near the maximum runup point where both the flow velocity and the water depth were near zero a significant amount of the sediment transport occurred during the wave drawdown in the form of thick sheet flow which resulted in net erosion of the shore face and the beach a hydraulic jump formed near the wave breaking region toward the end of the drawdown which caused most of the suspended sand to deposit in the wave breaking region consequently breaking solitary waves over a sloping fine sand beach led to net erosion of the shore face and the beach net deposition in a small region immediately seaward of the max excursion point and net deposition in the wave breaking zone

superimposed orogenesis and metallogenesis in sanjiang tethys the sanjiang tethyan area experienced the superpoimsed transition from tethyan tectonic evolution in late paleozoic to continental collision orogeny in cenozoic resulting in the accumulation of massive multi stage mineralizations and large amounts of metallic industrial ore deposits the complex metallogenic evolution of this area finds expression in the following aspects large amounts of complex superimposed and reworked ore deposits were developed on the proterozoic substrate of rigid continental segment with special metallic associations of sn cu sn pb zn and fe cu volcanics hosted massive sulfide deposits were developed throughout the evolution of tethyan lithosphere from continental margin rift cu through initial ocean basin cu zn ocean arc cu zn pb and interarcual rift valley or back arc basin pb zn ag to rift basin caused by arc continental collision cu pb zn island type porphyry copper deposits at the tethyan stage were replaced by continental type porphyry copper deposits at the collision orogeny stage metallic ore forming belt and gigantic ore deposits of world class such as the yulong porphyry cu mo metallogenic belt the lanping zn pb cu ag metallogenic belt the ailaoshan au metallogenic belt the chuanxi ree metallogenic belt the tengchong lianghe sn metallogenic belt were generated explosively during the collision orogeny in cenozoic although successful researches on tectonic and metallogenic cheracteristics have been conducted for the sanjiang tethyan metallogenic domain many important scientific problems remain unsolved such as precise time limits and internal connections between tectonic superposition continental accretion and convergence and collision and transformation the control of geological setting over mineralization the constraint of the crust mantle interaction on the formation of ore deposit clusters and the anomalous concentration of large amounts of ore materials space time structure material structure and genetic type of ore deposits of the typical metallogenic system the development mechanism of metallogenic systems and the formation mechanism of large sized ore deposits it is obvious that the solution of these problems will be a great breakthrough in the study of the tectonic evolution and metallogenesis of the sanjiang tethyan metallogenic domain

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

the storegga slides evidence from eastern scotland for a possible tsunami abstract the second storegga slide on the continental slope off western norway has been dated at between 8000 and 5000 yrs b p a prominent sand layer in flandrian holocene deposits along the coast of eastern scotland and dated at approximately 7000 yrs b p may have been deposited by a tsunami generated by the slide the altitude and stratigraphy of the layer allow estimates to be made of the magnitude of the earthquake which initiated the slide

tsunami deposits beneath tidal marshes on vancouver island british columbia thin sheets of sand occur within holocene mud and peat deposits beneath tidal marshes at tofino ucluelet and port alberni on vancouver island british columbia the sand sheets are extensive and have sharp upper and lower contacts in most cases they consist of moderately sorted massive sand and silty sand with abundant wood and other plant detritus at port alberni the thickest sheet has gravel and is graded the upper two sand sheets in the tofino ucluelet area and possibly the third are also present at port alberni eyewitness accounts and 137 cs analysis suggest that the uppermost thinnest sand was deposited by the tsunami triggered by the great alaska earthquake in 1964 the next oldest sand sheet has been radiocarbon dated at our data suggest that large tsunamis have struck the southern british columbia coast several times during the late holocene and that some were much larger than the 1964 tsunami which caused about 10 million damage 1964 canadian dollars to communities on vancouver island because such tsunamis can be expected in the future they pose a hazard to people and property in some coastal areas

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

tsunamis as geomorphic crises lessons from the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract large tsunamis are major geomorphic crises since they imply extensive erosion sediment transport and deposition in a few minutes and over hundreds of kilometres of coast nevertheless little is known about their geomorphologic imprints the december 26 2004 tsunami in sumatra indonesia was one of the largest and deadliest tsunamis in recorded human history we present a description of the coastal erosion and boulder deposition induced by the 2004 tsunami in the lhok nga bay located to the west of banda aceh northwest sumatra the geomorphological impact of the tsunami is evidenced by beach erosion some beaches have almost disappeared destruction of sand barriers protecting the lagoons or at river mouths numerous erosion escarpments typically in the order of 0 5 1 5 m when capped by soil and more than 2 m in dunes bank erosion in the river beds the retreat along the main river is in the order of 5 15 m with local retreats exceeding 30 m large scars typically 20 50 cm deep on slopes dislodgement of blocks along fractures and structural ramps on cliffs the upper limit of erosion appears as a continuous trimline at 20 30 m a s l locally reaching 50 m the erosional imprints of the tsunami extend to 500 m from the shoreline and exceed 2 km along riverbeds the overall coastal retreat from lampuuk to leupung was 60 m 550 000 m 2 and locally exceeded 150 m over 276 000 m 3 of coastal sediments were eroded by the tsunami along the 9 2 km of sandy coast the mean erosion rate of the beaches was 30 m 3 m of coast and locally exceeded 80 m 3 m the most eroded coasts were tangent to the tsunami wave train which was coming from the southwest the fringing reefs were not efficient in reducing the erosional impact of the tsunami the 220 boulders measured range from 0 3 to 7 2 m large typically 0 7 1 5 m with weights from over 50 kg up to 85 t we found one boulder less than 1 m large at 1 km from the coastline but all the others were transported less than 450 m 30 m and the moderate tsunamis height