Comment on “Late Cenozoic sea level and the rise of modern rimmed atolls” by Toomey et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 451: 73–83

© 2016 Elsevier B.V. Toomey et al. (2016) present a credible new model to explain variations in the formation of Pacific Ocean atolls through the Late Cenozoic, thus accounting for contemporary differences in atoll morphology. While we do not contradict the primary influences of dissolution and sedimentation processes, we suggest that the influence of submarine landsliding should not be ignored. Multiple slope failures exist on the flanks of many atolls. When large submarine landslides affected a significant portion of a palaeo-atoll rim, this had the potential to open up an atoll lagoon allowing much freer circulation between the lagoon and the ocean. Our atoll flank collapse model therefore provides an additional mechanism for an enclosed atoll lagoon to become a ‘leaking bucket’ system and an atoll more likely to evolve into the ‘empty bucket’ form with later sea-level rise. Submarine landsliding adds additional support for the new model of atoll formation proposed by Toomey et al

Electrical Analogue Computer for the Heat Pump

(Taken from the Summary) Because of the complex behavior of a cylindrical heat source-sink under intermittent operating conditions, analysis by analytical means is very difficult. Therefore an electrical analogy computer consisting of a distributed resistance capacitance model was designed and built. It was shown analytically that the behavior of this computer model was the same as that of the heat system. That the model was a true analogy is verified by the fact that data obtained from this model could be used to check certain heat flow problems previously solved by analytical means. Data were obtained for a cylindrical heat source in an infinite medium. These data were used to check the analytical solution presented by A. Gemant. A generator was designed and built which could be used to solve two dimensional heat flow problems involving intermittent operation. Its theory of operation was set forth and the circuit diagram presented. With such equipment one may obtain numerical answers to many two dimensional problems

Tsunamigenic slope failures: the Pacific Islands ‘blind spot’?

© 2015, Springer-Verlag Berlin Heidelberg. We discuss issues related to a recognised shortcoming in existing tsunami hazard assessments for Pacific Island Countries and Territories (PICTs), that of tsunamigenic slope failures (TSFs). Currently, TSFs are most likely underrepresented as sources in existing tsunami databases for two key reasons. First, relatively low magnitude earthquakes associated with subduction zones are generally assigned as the tsunamigenic source, as opposed to the TSFs they generate. A reassessment of such ‘anomalous tsunamis’ may yield clues that serve to reassign their tsunamigenic source. Second, there are thousands of oceanic islands and seamounts scattered across the Pacific and flank collapse of volcanic edifices such as these is a largely unquantified tsunamigenic threat. However, while it is now possible to model such TSFs, this is unlikely to happen in the near future because of the lack of detailed bathymetry and landslide mass data. Recent developments in the identification of past tsunamis in the Pacific Islands have developed a unique range of indicators that can be used for identifying such events. These are geological, oral tradition and archaeological components that include, but are not limited to, a modified Darwinian model of atoll formation, coastal megaclasts, oral traditions of vanished islands and giant waves, and the abandonment of prehistoric coastal sites. As such, the most logical way forward is to use the multiple indicators available to us to identify evidence of past tsunamis

Late Wisconsinan And Holocene Sedimentation Of Silverhope Valley, British Columbia

Sixty-eight bedrock and sediment exposures, six lake bottom cores, and twenty-six bulk samples of river gravels were studied by various stratigraphic methods including: radiocarbon and caesium dating, tephrochronology and lithofacies analysis to interpret late Wisconsinan and Holocene deposits in the Silverhope Creek drainage basin.;Late Wisconsinan evidence suggests that during the downwasting and retreat of the Cordilleran Ice Sheet between approximately 11 500 and 11 000 years BP, there was one minor readvance and two smaller standstill/oscillations. During deglaciation a dead ice-dammed lake formed in front of the retreating ice mass. Partial lake drainage occurred initially by catastrophic flooding through dead ice into the contiguous Chilliwack valley over a low pass. Subsequent lake levels were controlled by dead ice decay, hummocky terrain, ice marginal drainage and height of the retreating ice mass. Final drainage occurred as a small outburst into the Fraser valley. Tributary glaciers appear to have retreated at different rates and to be, at times, temporarily covered by water.;Burial of Mazama tephra found in paraglacial alluvial fans suggests that following deglaciation, meltwater reworking of glacial sediments was more rapid on the west side of the drainage basin.;Landslide-damming (probably not seismic-generated) of Silver Lake appears to have taken place around 1100 A.D. Radiocarbon ages indicate that sedimentation in the lake occurred at a rate of about 0.14 cm a{dollar}\sp{lcub}-1{rcub}{dollar} until 1946, with Silverhope Creek forming a delta into the southwest side of the lake. In 1946, diverted flows built a new delta into the southeast side of Silver Lake at the commencement of major logging activity and road construction around and to the south of Silver Lake. Caesium-137 traces indicate that post-1946 sedimentation rates have increased to approximately 2.75 cm a{dollar}\sp{lcub}-1{rcub}.{dollar} Rates do not appear to have declined significantly in the last twenty to thirty years.;Analysis of in-channel gravels from Silverhope Creek indicates that human activity (logging and road construction) has site specific influences on particle size distribution. However, most disequilibriums in the general trend of downstream fining have been inherited from previous glaciation and the landslide-damming of Silver Lake. A tentative model of Holocene sedimentation for this unique drainage basin indicates that sediment yield is both episodic (lake-forming mass movement event and human impact) and perhaps subject to climatic asymmetry

Major typhoon phases in the upper Gulf of Thailand over the last 1.5 millennia, determined from coastal deposits on rock islands

© 2018 Elsevier Ltd and INQUA Rapid growth of Asian megacities, exemplified by the megacity of Bangkok, Thailand, with a population of over 10 million inhabitants, means that an increasing number of people are living in low-lying coastal areas exposed to hazards such as typhoons. While Bangkok has always been considered not to be at risk from typhoon strikes, recent discoveries of elevated carbonate boulder deposits have started to question this assumption. This work reports on findings from the islands of Ko Khang Khao and Ko Phai, farther north and west than earlier studies, and adds to the existing body of evidence for prehistorical typhoon-driven high energy marine inundation (HEMI) events penetrating northwards into the Bay of Bangkok. Elevated carbonate boulder deposits up to 6 m amsl indicate that these were emplaced by waves generating onshore minimum flow velocities between 3.0 and 5.5 m/s, consistent with typhoon-impacted coastlines elsewhere in the tropical Asia-Pacific region. When viewed in conjunction with other data from the Bay of Bangkok their chronologies indicate age clusters around four major phases of activity in AD 600–700, AD 900–1000, AD 1150–1250 and AD 1400–1650. At 250 years duration, the last phase of activity was the longest, but it has also been followed by the longest period of quiescence that has coincided with rapid urban growth in and around the city of Bangkok. The re-occurrence of typhoon-driven HEMI events on the scale of the prehistorical events reported here would threaten all the low-lying coasts in the Bay of Bangkok, including the Chao Phraya delta, and as such these results indicate an urgent need to re-evaluate coastal hazards for the region

Is Bangkok at risk of marine flooding? Evidence relating to the historical floods of AD 1785 and 1983

© 2020, Springer Nature B.V. Thailand’s low-lying capital city Bangkok is a dense metropolis, one of Asia’s rapidly growing ‘megacities’, and home to over 10 million residents. Bangkok’s location on the sinking Chao Phraya Delta means it has a high susceptibility to river flooding. However, the possible contribution of marine incursion to river flooding is not as widely recognised and needs further consideration. We therefore re-examine the historically documented floods in AD 1785 and 1983. Available evidence suggests that the superposition of different flood behaviours was important during both events. Attention is drawn to the evidence for, and contributory roles played by, astronomical spring tides, meteorological tides, storm waves and possibly storm surge. These marine effects can exacerbate river floods caused by seasonal peak flows in the tidal lower Chao Phraya River during the early north-east monsoon. For future management of flood risk, it is therefore necessary to recognise that Bangkok has a compound flood-risk profile that includes both hydrometeorological and marine influences. The significance of marine influences on Bangkok’s flood risk is likely to increase in future with continuing eustatic sea-level rise and subsidence of the Chao Phraya Delta

The Bauer scarp ridge jump: a complex tectonic sequence revealed in satellite altimetry

We investigate here the ridge jump that led to abandonment of the Galapagos Rise and formation of the Batter scarp during the initiation of the present day configuration of the East Pacific Rise since the lower Miocene. We use recently available high-resolution satellite-derived gravity data to investigate in detail the tectonic structure of the eastern Pacific from the Equator to 20%. With this data, we identify fracture zones, abandoned spreading ridges, scarps, and other seafloor features that provide evidence for discerning tectonic history. Based on our structural interpretation of the satellite-derived gravity field, we make the following conclusions: (1) The Galapagos Rise spreading center appears to have originated by opening of the Marquesas/Mendana transform complex as a result of the change in spreading direction following breakup of the Farallon Plate. (2) The Galapagos Rise was not the sole locus of spreading following plate reorganization at ~ 20 Ma through to the initiation of the Bauer scarp at ~ 8 Ma, as had been previously hypothesized. Rather, it and a second western spreading axis were likely active concurrently, forming a counterclockwise-rotating Bauer Microplate at a much earlier stage than thought previously. (3) The Bauer scarps are pseudofaults associated with northward rift propagation. Propagation proceeded in several stages. A first propagator emanating from the Garrett transform complex stalled at the future location of the Wilkes transform creating an area of complex morphology near its northern tip. A second propagator, also emanating from the Garrett complex followed in the first’s wake and broke through the complex region. At this point the propagation proceeded very rapidly to the northern end of the Bauer Microplate (the Gallego fracture zone, later to become the Yaquina transform fault). Ridge propagation continued north in two more stages, creating the Gofar and Quebrada transforms at the terminus of each stage

Palaeotsunamis in the Sino-Pacific region

© 2020 Elsevier B.V. Palaeotsunami research in the Sino-Pacific region has increased markedly following the 2011 Tōhoku-oki tsunami. Recent studies encompass a variety of potential sources and cover a full range of research activities from detailed studies at individual sites through to region-wide data collation for the purposes of database development. We synthesise palaeotsunami data from around the region drawing on key examples to highlight the progress made since 2011. We focus on a wide range of spatial and temporal scales, from region-wide to local events, from multi-millennial site records to estimates of magnitude and frequency along national coastlines. The review is based on sub-regions but in reviewing the combined records highlights common events and anomalies. In doing so we identify future research opportunities and notable findings arising from our review

Defining tsunamis: Yoda strikes back?

© 2016 Elsevier B.V. Charting the journey of the term tsunami through to its nearly ubiquitous global use today is not simply a case of determining when it was borrowed from Japanese. It represents an almost 1400 year journey from the earliest historical Japanese reference to waves generated by the AD684 Hakuho-Nankai earthquake to a 95.7% usage by international media to describe the 2010 Chilean tsunami. The gradual rise of the term\u27s usage parallels changes in Japanese society from an educated elite in Kyoto writing down oral event descriptions from various prefectures, to the spread of newspapers, an increasing Western influence and a preference within the education system.The widespread use of the term tsunami throughout Japan was not truly achieved until the same decade that it was adopted by Western scientists to describe the 1946 Alaskan tsunami in Hawaii. The alternative term kaishou most likely became less popular simply because it was more difficult to understand in Japanese. While there has been a rapid uptake in Western science, and ultimately its wider adoption, this has been aided greatly by two major events to affect the Hawaiian Islands in 1946 (Alaskan) and 1960 (Chilean). During this time the meaning of the term has also changed with semantic narrowing focusing in on the definition we know today. Along the way there have been casualties, with terms such as kaishou now rarely, if ever, appearing. Other terms, which speak volumes about not only the richness of the Japanese language, but also of Japanese experience with tsunamis in the past, now offer us the opportunity to use appropriate qualifying terms to describe the nature of an event. A souteigai-tsunami is an unexpectedly large event whereas a yoda is a small one

Anthropogenic disruption to the seismic driving of beach ridge formation: The Sendai coast, Japan

© 2015 Elsevier B.V. The expected geomorphic after-effects of the Mw 9.0 Tōhoku-oki earthquake of 11 March 2011 (eastern Japan) are summarized by a schematic model of seismic driving, which details seismogenic disturbances to sediment systems that affect the rate or timing of sediment delivery to coastlines over timescales of 102-104years. The immediate physical environmental responses to this high-magnitude earthquake included a large tsunami and extensive region-wide slope failures. Normally, slope failures within mountain catchments would have significant impacts on Japan\u27s river and coastal geomorphology in the coming decades with, for example, a new beach ridge expected to form within 20-100years on the Sendai Plain. However, human activity has significantly modified the rate and timing of geomorphic processes of the region, which will have impacts on likely geomorphic responses to seismic driving. For example, the rivers draining into Sendai Bay have been dammed, providing sediment traps that will efficiently capture bedload and much suspended sediment in transit through the river system. Instead of the expected ~1km of coastal progradation and formation of a ~3m high beach ridge prior to the next large tsunami, it is likely that progradation of the Sendai Plain will continue to slow or even cease as a result of damming of river systems and capture of river sediments behind dams. The resulting reduction of fluvial sediment delivery to the coast due to modification of rivers inadvertently makes seawalls and other engineered coastal structures even more necessary than they would be otherwise