deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

tsunami deposits in a lacustrine sequence of the sanriku coast northeast japan abstract lacustrine deposits of the pacific coast of northeast japan consisting mostly of black organic mud contain intercalated thin beds of well sorted medium sand examination of the deposits from a coastal site of sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds transported from the littoral environment by a great flooding of seawater the mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis each with a maximum rise of 1 m or more above sea level

new findings of bronze age homogenites in the ionian sea geodynamic implications for the mediterranean abstract holocene homogenites similar in character and stratigraphic position to those previously recorded in the ionian basin and related to the gigantic tsunami originating from santorini bronze age eruption are described from a core transect crossing the deformation front of the mediterranean ridge east of victor hensen seahill investigations on grain sizes and carbonate content carried out on three cores from three different areas of the ionian basin encompassing the bronze age homogenite revealed important similarities and some differences the most obvious difference concerns the carbonate content which is minimum at the base of the unit in a core close to the messina abyssal plain whereas it is maximum in cores from the western mediterranean and calabrian ridges characterized by the typical cobblestone topography a terrigenous versus pelagic nature of the components is documented and a distal versus local provenance is inferred homogenites are critically compared with unifites a type of re sediment recently described from the eastern mediterranean comparison includes in particular a source and sediment transport and b triggering mechanism a substantial difference exists between the sedimentation patterns of the ionian and levantine basins seaward of the calabrian and hellenic arcs in the latest quaternary and the difference contains a clear geodynamic message sedimentation rates increase from the late pleistocene to the holocene in the ionian basin whereas they decrease in the levantine basin the glacio eustatic signal is well expressed in the levantine basin where the source areas are situated consistently in the south or on a passive type aseismic continental margin north african margin in the ionian basin on the contrary the glacioeustatic signal is totally obscured by the strong tectonic signal from the active northern continental margin of the mediterranean

a sand sheet deposited by the 1964 alaska tsunami at port alberni british columbia the stratigraphic record of 137cs activity in a tidal marsh at port alberni british columbia suggests that a widespread sand sheet just below the marsh surface was deposited by the tsunami from the great alaska earthquake of 1964 we propose by analogy that similar deeper sand sheets at port alberni also may have been deposited by earthquake induced tsunamis

tsunami sedimentation associated with the lisbon earthquake of 1 november ad 1755 boca do rio algarve portugal a description is given of a distinctive marine deposit at boca do rio on the algarve coast of portugal it is proposed here that the sediment accumulation was deposited by the tsunami generated by the lisbon earthquake of 1 november ad 1755 the deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave regimes these include laterally continuous sand layers chaotic pebble horizons large amounts of gravel sized shell debris and distinctive assemblages of marine microfossils a preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup the use of tsunami sediments as time synchronous marker horizons is also discussed

sudden probably coseismic submergence of holocene trees and grass in coastal washington state growth position plant fossils in coastal washington state imply a suddenness of holocene submergence that is better explained coseismic lowering of the land than be decade or century long rise of the sea these fossils include western red cedar and sitka spruce whose death probably resulted from estuarine submergence close to 300 years ago rings in eroded bark free trunks of the red cedar show that growth remained normal within decades of death rings in buried bark bearing stumps of the spruce further show normal growth continuing until the year of death other growth position fossils implying sudden submergence include the stems and leaves of salt marsh grass entombed in tide flat mud close to 300 years ago and roughly 1 700 and 3 100 years ago the preservation of these stems and leaves shows that submergence and initial burial outpaced decomposition which appears to take just a few years in modern salt marshes in some places the stems and leaves close to 300 year old are surrounded by sand left by an extraordinary landward directed surge probably a tsunami from a great thrust earthquake on the cascadia subduction zone

holocene relative sea level changes on the margin of a glacio isostatically uplifted area an example from northern caithness scotland evidence is presented for holocene relative sea level changes on the margin of a glacio isostatically uplifted area the lower wick river valley northern caithness scotland lithostratigraphic b

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

a thick holocene homogenite from the ionian abyssal plain eastern mediterranean abstract a homogenite layer thicker than 12 m holocene in age occurs in the ionian abyssal plain the graded sandy base is 1 3 m thick most of the layer is structureless and homogeneous in grain size and mineral composition the most remarkable components are siltsized grains composed of aragonite needles they are interpreted as skeleton fragments of the green alga halimeda sp the homogenite covers an area of at least 1100 km 2 and assuming a minimum thickness of 10 m comprises a volume of 11 km 3 the source of the material of the homogenite is a matter of speculation very likely it has been remobilized from different areas around the ionian abyssal plain as triggering event a tsunami generated by the collapse of the santorini caldera about 3500 yrs b p is assumed

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

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

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

subduction arc reversal and the origin of porphyry copper gold deposits in island arcs the tertiary quaternary porphyry copper gold deposits of the southwest pacific rim particularly in luzon mainland papua new guinea bougainville guadalcanal and fiji mostly formed after a reversal of arc polarity where this reversal has not occurred e g new zealand and japan porphyry copper gold deposits are absent or scarce hence older porphyry copper gold deposits may be useful clues to tectonic history enrichment of magmas in gold may have resulted from two stage melting the tectonic setting of porphyry copper gold deposits differs from that inferred for volcanic hosted massive sulfide deposits

coseismic slip distribution of the 2003 mw 6 6 san simeon earthquake california determined from gps measurements and seismic waveform data 1 we combine geodetic and seismic data sets to constrain the coseismic slip distribution of the mw6 6 san simeon earthquake which occurred in the central california coast ranges on december 22 2003 we use continuous and survey mode gps observations along with seismic waveform data from the california integrated seismic network cisn we invert both data sets for the distribution of finite fault slip in a layered earth model the inversion results indicate that the rupture extends to the southeast of the epicenter for approximately 25 30 km and occurred in a relatively shallow depth range between 1 to 10 km the average and peak slip are 0 61 m and 2 37 m respectively the scalar seismic moment is 7 85e18 nm and the static stress drop 1 7 mpa this thrust earthquake is characterized by its shallow along strike extended slip

coastal sedimentation associated with the december 12th 1992 tsunami in flores indonesia this paper presents the result of a detailed granulometric investigation of sediments deposited by a modern tsunami the 1992 tsunami in flores indonesia eyewitness accounts indicate that sediments were deposited upon coastal lowlands over wide areas as a result of the tsunami inundation distinctive vertical and lateral variations in particle size composition are characteristic features of the tsunami deposits and these are intimately related to sedimentary processes associated with flood inundation the geomorphological and sedimentary evidence is used here to establish a preliminary model of tsunami sedimentation this information is believed to be of great value in understanding sedimentary processes associated with tsunami flooding and in the interpretation of palaeo tsunami deposits

sedimentation et fracturation de haute energie en milieu recifal tsunamis ouragans et cyclones et leurs effets sur la sedimentologie et la geomorphologie d un atoll motu et hoa a rangiroa tuamotu pacifique se abstract a longitudinal festoon fracture of the reef flat widened by slow biological and mechanical erosion transverse along the grooves divides the nw coral rim of rangiroa tuamotu se pacific into colossal blocks 15 10 5 m 1500 t the elaboration of these blocks can be attributed to the dislocation of the top of the reef flat by catastrophic events tsunamis or hurricanes typhoons in the sw and s pacific the shifting of these blocks mega boulders would necessitate a considerable amount of energy and at present we cannot decide which one of these phenomena was responsible various examples observed in the pacific are cited to illustrate abrupt changes in the sea level these could be attributed either to meteorological events hurricanes cyclones or typhoons or to seismic events of very high energy ground sea or tsunamis the reader is reminded of the different characteristics that these phenomena produce this study is mainly concerned with tsunamis especially the frequency of their occurrence energy and effects on the coasts of small oceanic islands hurricanes cyclones and typhoons roughly originate from the n ne and e whereas tsunamis originate from all directions except from se s and sw angle these very high energy events hurricanes and tsunamis seem then to be responsible for 1 the decreasing grain size of the coral rim sediments from the ocean to the lagoon through the range of colossal blocks smaller boulders scree gravels coarse and fine sands 2 the sedimentary accretion of the motu itself at each very high energy so called catastrophic event they are also responsible for the preservation of the two characteristic geomorphic forms of an atoll motu and hoa 3 finally the alternation motu hoa motu etc on the coral rim this alternation seems to result from the interaction between oceanic disturbances hurricanes or tsunamis and the water volume which must flow over the coral rim the transported material the reef flat and the angle of incidence between the swell and the coast during these catastrophic events

catastrophic wave erosion on the southeastern coast of australia impact of the lanai tsunamis ca 105 ka sand barriers along the coast of southern new south wales dating from the last interglacial have been almost completely destroyed most probably by a catastrophic tsunami evidence for catastrophic wave erosion can also be traced to heights of at least 15 m above present sea level on coastal abrasion ramps these erosional features lie above the range of effective erosion by contemporary storm waves and cannot be attributed to either eustatic fluctuations or local uplift chronological evidence for the timing of the destruction of the last interglacial barriers suggests that tsunamis generated by the submarine slide off lanai in the hawaiian islands 105 ka traveled across the pacific and eroded this coast

evidence for a large earthquake and tsunami 100 400 years ago on western vancouver island british columbia abstract a peaty marsh soil is sharply overlain by a sand sheet and intertidal mud at tidal marshes near tofino and ucluelet vancouver island british columbia foraminifera and vascular plant fossils show that the buried soil was submerged suddenly and was covered quickly by sand radiocarbon ages place this event between 100 and 400 yr ago the coastal subsidence suggested by the submergence occurred in an area of net late holocene emergence perhaps during the most recent great earthquake on the northern part of the cascadia subduction zone the sand sheet overlying the peaty soil records the tsunami triggered by this earthquake similar stratigraphic sequences of about the same age have been reported from estuaries along the outer coasts of washington and northern oregon suggesting that hundreds of kilometers of the cascadia subduction zone may have ruptured during one or a series of plate boundary earthquakes less than 400 yr ago

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

linking tsunami deposits submarine slides and offshore earthquakes abstract the recognition that many tsunamis are associated with coastal sedimentation has been of great value in the study of tsunamis prehistorically geological investigation of such sediments has resulted in the identification of a series of palaeotsunamis that appear to have taken place in different areas of the world in most cases however it has proved difficult to link former tsunamis to specific source mechanisms studies of modern tsunamis have also faced difficulties in the recognition of the specific source mechanisms for example offshore earthquakes may trigger submarine slides that combine to produce complex patterns of tsunami flooding at the coast

tektite bearing deep water clastic unit at the cretaceous tertiary boundary in northeastern mexico the hypothesis of cretaceous tertiary k t boundary impact on yucatan mexico predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves an outcrop along the arroyo el mimbral in northeastern mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic marl sequence deposited at more than 400 m water depth the marls were found to be unsuitable for determining magnetostratigraphy but foraminiferal biostratigraphy places the clastic unit precisely at the k t boundary we interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact the elastic unit comprises three main subunits 1 the basal spherule bed contains glass in the form of tektites and microtektites glass spherules replaced by chlorite smectite and calcite and quartz grains showing probable shock features this bed is interpreted as a channelized deposit of proximal ejects 2 a set of lenticular massive graded laminated beds contains intraclasts and abundant plant debris and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water 3 at the top several thin ripple beds composed of fine sand are separated by clay drapes they are interpreted as deposits of oscillating currents perhaps a seiche an iridium anomaly 921 23 pg g is observed at the top of the ripple beds our observations at the mimbral locality support the hypothesis of a k t impact on nearby yucatan

low sea level emplacement of a very large late pleistocene megaturbidite in the western mediterranean sea large volume turbidites termed megaturbidites or megabeds result from catastrophic slope failures and the associated downslope transport of enormous quantities of sediment from continental margins to the deep sea such large sediment failures can generate tsunamis and in terrains underlain by gas hydrates clathrates may be associated with the release of substantial amounts of the greenhouse gas methane it has been proposed that the megaturbidite events may be triggered by seismic activity or may result from gas hydrate release itself caused by a lowering of hydrostatic pressure on clathrates as a result of low sea level previous conclusions on the significance of sea level change however have been conditional because of the lack of absolute times of turbidite emplacement here we use accelerator mass spectrometry radiocarbon dating in five widely spaced cores to constrain the date of emplacement of a large volume 500 km3 bed in the balearic basin of the western mediterranean this turbidite is exceptional in its magnitude and represents the main sedimentation event in the balearic basin over the past 100 kyr our data provide an estimate of 22 000 calendar years before present for emplacement of the megabed a time when sea level stood at its lowest level during the last glacial maximum the coincidence of these dates is consistent with emplacement due to clathrate destabilization caused by low sea level although other triggering mechanisms such as seismic shock cannot be ruled out