Abstract Despite creating one of Earth's most iconic landforms, and having been studied since antiquity, river meandering is currently explained by several alternative models that remain debated. This is partly because observers have deconstructed meanders to a set of properties thought to be fundamental or significant for meandering, but each of these underpinning properties is itself complex and in turn requires analysis of its causes and mechanisms. This philosophical contribution aims to provide a perspective on the state of the science that makes a rigorous interrogation into what ‘causation’ actually means, and explores what a systems perspective can elucidate about meandering phenomena. We approach the problem through a discussion of the variety of ways in which previous researchers have tackled the problem of meandering, from a channel and floodplain perspective, on Earth and Mars, in the field and laboratory, and at the present day through to the ancient stratigraphic record. It is evident that river meandering has numerous causal pathways rather than a single set of necessary and sufficient conditions. A systemic view on the evolution of plant species shows that their feedbacks on river pattern likewise have several pathways. Employing the conceptual apparatus of the philosophy of science will move us towards a more consensual synthesis of river meandering.

Abstract Marine geological and geophysical data from Alpha Ridge in the Arctic Ocean are sparse because of thick perennial sea-ice cover, which prevents access by most surface vessels. Rare seismic data in this area, acquired largely from drifting ice-camps, had shown the hemipelagic drape that covers most of the ridge is highly disrupted within a large (>90 000 km 2 ) south central region. Here, evidence of pronounced seafloor erosion and debris flows infilling seafloor lows was previously interpreted to be the result of a possible bolide impact. In recent years, several icebreaker expeditions have successfully acquired multibeam bathymetry and sub-bottom profiler data in the western segment of this region. Analysis of these data reveals a complex seafloor morphology characterized by ridges and troughs, angular blocks and escarpments as well as seismic facies characterized by hyperbolic seafloor reflections, and convoluted to incoherent and transparent sub-bottom reflectivity. These features are interpreted as evidence of sediment mass movement with varying degrees of lateral transport deformation. At least two episodes of failure are interpreted based on the presence of both buried and surficial mass-transport features. As multiple events are interpreted, seismicity is the most plausible trigger mechanism rather than bolide impact.

Abstract Tsunami present a significant geohazard to coastal and water-body marginal communities worldwide. Tsunami, a Japanese word, describes a series of waves that, once generated, travel across open water with exceptionally long wavelengths and with very high velocities before shortening and slowing on arrival at a coastal zone. Upon reaching land, these waves can have a devastating effect on the people and infrastructure in those environments. With over 12 000 km of coastline, the British Isles is vulnerable to the tsunami hazard. A significant number of potential tsunami source areas are present around the entire landmass, from plate tectonic boundaries off the Iberian Peninsula to the major submarine landslides in the northern North Sea to more localized coastal cliff instability which again has the potential to generate a tsunami. Tsunami can be generated through a variety of mechanisms including the sudden displacement of the sea floor in a seismic event as well as submarine and onshore landslides displacing a mass of water. This review presents those impacts together with a summary of tsunami triggers and UK case histories from the known historic catalogue. Currently, apart from some very sensitive installations, there is very little in the UK in the way of tsunami management and mitigation strategies. A situation that should be urgently addressed both on a local and national level.

Abstract With its rich lithological variation, upland, lowland and coastal settings, and past climatic changes, the UK presents a wide variety of landslide features that can pose significant hazards to people, construction and infrastructure, or simply add to landscape character and conservation value of an area. This chapter describes and defines the nature and extent of this landsliding; the causes, effects and geological controls on failure; and their mitigation and stabilization. A risk-based approach to landslide management is outlined with qualitative and semi-quantitative methodologies described. Numerous case studies are presented exemplifying landslide and slope stability hazards in the UK.

Abstract Fast-moving, rainfall-induced debris-flow events are relatively common in the mountainous areas of the UK. Their impacts are largely, although by no means exclusively, economic and social. They often sever (or delay) access to and from relatively remote communities for services and markets for goods; employment, health and educational opportunities; and social activities. Specific forms of economic impact are described and their extent is defined by the vulnerability shadow. The mechanisms of rainfall-induced, fast-moving debris flows are considered to bridge between slow mass movements and flood phenomena. The occurrence of debris flows is largely restricted to mountainous areas and a series of case studies from Scotland is briefly described. Hazard and risk assessment are briefly considered and a strategic approach to risk reduction is described. The latter allows a clear focus on that overall goal before concentrating on the desired outcomes and the generic approach to achieving those outcomes. The effects of climate change on debris-flow hazard and risk are also considered and it is concluded that, in Scotland, increases in debris-flow frequency and/or magnitude are most likely and that increases in the risks associated with debris flows are also likely.

Abstract The NW African continental margin is well known for the occurrence of large-scale but infrequent submarine landslides. The aim of this paper is to synthesize the current knowledge on submarine mass wasting off NW Africa with a special focus on the distribution and timing of large landslides. The described area reaches from southern Senegal to the Agadir Canyon. The largest landslides from south to north are the Dakar Slide, the Mauritania Slide, the Cap Blanc Slide, the Sahara Slide and the Agadir Slide. Volumes of individual slides reach several hundreds of cubic kilometres; run-outs are up to 900 km. In addition, giant volcanic debris avalanches are widespread on the flanks of the Canary Islands. All headwall areas are complex with clear indications of multiple failures. The most prominent similarity between all investigated landsides is the existence of widespread glide planes that follow the stratigraphy, which points to weak layers as most important preconditioning factor for the failures. Landslides with volumes larger than 100 m 3 are close to being evenly distributed over time, contradicting previous suggestions that landslides off NW Africa occur at periods of low or rising sea level. The risk associated with the landslides off NW Africa, however, is relatively low due to their long recurrence rates.

ABSTRACT What causes recurrent mass extinctions of life? We find that the ages of 10 of the 11 well-documented extinction episodes of the last 260 m.y. show correlations, at very high confidence (>99.99%), with the ages of the largest impact craters or the ages of massive continental flood-basalt eruptions. The four largest craters (≥100 km diameter, impact energies ≥3 × 10 7 Mt trinitrotoluene [TNT]) can be linked with recognized extinction events at 36, 66, 145, and 215 Ma, and with stratigraphic distal impact debris correlative with the extinctions. The ages of 7 out of 11 major flood-basalt episodes can be correlated with extinction events at 66, 94, ca. 120, 183, 201, 252, and 260 Ma. All seven flood-basalt–extinction co-events have coincident volcanogenic mercury anomalies in the stratigraphic record, closely linking the extinctions to the volcanism. Furthermore, the seven major periods of widespread anoxia in the oceans of the last 260 m.y. are significantly correlated (>99.99%) with the ages of the flood-basalt–extinction events, supporting a causal connection through volcanism-induced climate warming. Over Phanerozoic time (the last 541 m.y.), the six “major” mass extinctions (≥40% extinction of marine genera) are all correlated with the ages of flood-basalt episodes, and stratigraphically with related volcanogenic mercury anomalies. In only one case, the end of the Cretaceous (66 Ma), is there an apparent coincidence of a “major” mass-extinction event with both a very large crater (Chicxulub) and a continental flood-basalt eruption (the Deccan Traps). The highly significant correlations indicate that extinction episodes are typically related to severe environmental crises produced by the largest impacts and by periods of flood-basalt volcanism. About 50% of the impacts of the past 260 m.y. seem to have occurred in clusters, supporting a picture of brief pulses of increased comet or asteroid flux. The largest craters tend to fall within these age clusters. Cross-wavelet transform analyses of the ages of impact craters and extinction events show a common, strong ~26 m.y. cycle, with the most recent phase of the cycle at ~12 Ma, correlating with a minor extinction event at 11.6 Ma. The stream of life flows so slowly that the imagination fails to grasp the immensity of time required for its passage, but like many another stream it pulses irregularly as it flows. There are times of quickening, the expression points of evolution, which are almost invariably coincident with some great geologic change, and the correspondence so exact and so frequent that the laws of chance may not be invoked by way of explanation. —Richard Swann Lull ( Organic Evolution , New York, Macmillan, 1929, p. 693)

Abstract Large lateral variations in pore-fluid pressures and associated overpressures occur in the compartmentalized Lower Triassic Bunter reservoir rocks in the Terschelling Basin (northern Dutch offshore). This study describes the main controlling factors on the distribution of these overpressures by combining seismically derived structural interpretations with pressure data. The most important controlling factor is considered to be the presence and type of both lateral and vertical permeability barriers. Lateral permeability barriers are formed by Zechstein salt and faults. The most effective vertical permeability barrier for maintaining high overpressures is the Upper Triassic Röt evaporite. Overpressures of more than 30 MPa are observed in the Bunter compartments where the Röt is present and laterally continuous. Overpressures are lower than 15 MPa in compartments where the Röt was affected by Mid-Cimmerian erosion. Based on structural observations, it is concluded that the highly overpressured compartments became fully hydraulically restricted during the Late Jurassic and Early Cretaceous. Calculations show that subsequent sedimentary loading, during the Cretaceous and Cenozoic, was able to generate the observed overpressures.

Abstract: Volcanism of Late Cretaceous–Miocene age is more widespread across the Zealandia continent than previously recognized. New age and geochemical information from widely spaced northern Zealandia seafloor samples can be related to three volcanotectonic regimes: (1) age-progressive, hotspot-style, low-K, alkali-basalt-dominated volcanism in the Lord Howe Seamount Chain. The northern end of the chain ( c. 28 Ma) is spatially and temporally linked to the 40–28 Ma South Rennell Trough spreading centre. (2) Subalkaline, intermediate to silicic, medium-K to shoshonitic lavas of >78–42 Ma age within and near to the New Caledonia Basin. These lavas indicate that the basin and the adjacent Fairway Ridge are underlain by continental rather than oceanic crust, and are a record of Late Cretaceous–Eocene intracontinental rifting or, in some cases, speculatively subduction. (3) Spatially scattered, non-hotspot, alkali basalts of 30–18 Ma age from Loyalty Ridge, Lord Howe Rise, Aotea Basin and Reinga Basin. These lavas are part of a more extensive suite of Zealandia-wide, 97–0 Ma intraplate volcanics. Ages of northern Zealandia alkali basalts confirm that a late Cenozoic pulse of intraplate volcanism erupted across both northern and southern Zealandia. Collectively, the three groups of volcanic rocks emphasize the important role of magmatism in the geology of northern Zealandia, both during and after Gondwana break-up. There is no compelling evidence in our dataset for Late Cretaceous–Paleocene subduction beneath northern Zealandia. Supplementary material: Trace element compositions of zircons and whole-rock chemical compositions obtained by previous studies are available at: https://doi.org/10.6084/m9.figshare.c.3850975

Abstract The LUSI mud volcano in the sub-district of Porong, Sidoarjo, East Java, Indonesia started to erupt on 29 May 2006. An almost continuous eruption of a mixture of mud, water and gas has occurred around this area since this date. The eruption triggered vertical and horizontal ground deformation. From June 2006 to December 2010, 14 global positioning system campaigns were conducted to observe the ground deformation using c . 50 stations sparsely located up to 10 km from the eruption centre. Field observations of cracks, terrestrial laser scanning and geo-electrical measurements have also been used to infer the ground deformation signature around the LUSI mud volcano. More than 150 pairs of interferograms generated from 66 ALOS PALSAR images from June 2006 to December 2009 have also been used to study the ground deformation caused by the LUSI mud volcano. The LUSI mud eruption began only 200 m from where the Lapindo Inc. oil company was drilling for oil and gas. The drilling may have pierced a deeper high-pressure zone, causing an underground blow-out of the drillhole into a hydrofracture. Alternatively, the magnitude 6.3 Yogyakarta earthquake, which was located c . 275 km from the eruption site and occurred two days before the LUSI eruption, may have shaken the area sufficiently to cause the eruption by reactivating a fault in the region and liquefying the mud. These two hypotheses for triggering the mud volcano have been argued vehemently and still remain controversial. The ground deformation signatures provide important clues to understanding the trigger for the eruption and to solve this controversy. Co-seismic fault reactivation has its own typical ground deformation signature. This study used global positioning system and InSAR techniques, as well as field observations of cracks, terrestrial laser scanning and geo-electrical measurements, to determine the signature of ground deformation around the LUSI mud volcano and to explain the triggering mechanism.