Computer simulations of pyroclastic flows from dome collapse

We present a method of simulating both the avalanche and surge components of pyroclastic flows generated by lava collapsing from a growing Pelean dome. This is used to successfully model the pyroclastic flows generated on 12 May 1996 by the Soufriere Hills volcano, Montserrat. In simulating the avalanche component we use a simple 3-fold parameterisation of flow acceleration for which we choose values using an inverse method. The surge component is simulated by a 1D hydraulic balance of sedimentation of clasts and entrainment of air away from the avalanche source. We show how multiple simulations based on uncertainty of the starting conditions and parameters, specifically location and size (mass flux), could be used to map hazard zones.

Rapid climate change: an overview for economists

The possibility of future rapid climatic changes is a pressing concern amongst climate scientists. For example, an abrupt collapse of the ocean's Thermohaline Circulation (THC) would rapidly cool the northern hemisphere and reduce the net global primary productivity of vegetation, according to computer models. It is unclear how to incorporate such low-probability, high-impact events into the development of economics policies. This paper reviews the salient aspects of rapid climate change relevant to economists and policy makers. The main scientific certainties and uncertainties are clearly delineated, with the aim of guiding economics goals and ensuring that they retain fidelity to their scientific underpinnings.

Why we need new spectacles: Mapping the experiential dimension in prehistoric Cretan landscapes

The Bronze to Iron Age transition in Crete, a period of state collapse and insecurity, saw the island's rugged, high-contrast topography used in striking new ways. The visual drama of many of the new site locations has stimulated significant research over the last hundred years, with explanation of the change as the main focus. The new sites are not monumental in character: the vast majority are settlements, and much of the information about them comes from survey. Perhaps as a result, the new site map has not been much studied from phenomenological perspectives. A focus on the visual and experiential aspects of the new landscape can offer valuable insights into social structures at this period, and illuminate social developments prefiguring the emergence of polis states in Crete by c. 700 BC. To develop, share and evaluate this type of integrated study, digital reconstructive techniques are still under-used in this region. I highlight their potential value in addressing a regularly-identified shortcoming of phenomenological approaches-their necessarily subjective emphasis.

Resistivity imaging survey of the Roman barrows at Bartlow, Cambridgeshire, UK

Resistivity imaging was carried out on four large Roman barrows at Bartlow in Cambridgeshire. The geophysical survey formed part of a wider research project designed to record and assess the landscape context of the largest surviving Roman burial mounds in Britain. The barrows today range in height from 6.6 m to 13.2 m and their steep profile loosed particular practical and modelling challenges. Data were obtained using a Campus Geopulse resistance meter with up to 50 electrodes spaced at 1 m intervals and lines up to 76 m long. A total of 24 lines was obtained. Topographic corrections were applied to the pseudosections, whichwere inverted using Res 2 Dinv and Res3 Dinv. Resistivity imaging was particularly successful in identifying evidence for the antiquarian explorations of the site. Central collapse features or in-filled tunnels image as high resistance features in all barrows and in one (Barrow IV) there is also a low resistance feature in the approximate position of a known antiquarian tunnel. Barrow VI had a thick covering of high-resistivity that may relate to nineteenth century landscaping and reconstruction of this monument. Resistivity imaging also revealed possible evidence for ancient revetments in all four large barrows. Copyright (c) 2006 John Wiley & Sons, Ltd.

Conical sedimentary structures, trace fossils or not? Observations, experiments, and review

Conical sedimentary structures are widespread in the geological column. Those that are mediated by organisms (or organic matter) can be attributed to seven principal processes, which are investigated by experiment and/or field observations: (1) sand collapse into a cavity (decomposed body, open shaft, or gallery), (2) upward (escape) or downward locomotion by an organism through the sediment, (3) upward adjustment (equilibration), (4) casting of coelenterates' excavations, (5) organism-mediated soft-sediment deformation in heterolithic sediment, (6) biodeformational small and large excavations by organisms, and (7) fluid (gas or liquid) escape structures. Footprint loading may also be included. Criteria are given to distinguish between these processes. Dewatering pipes are best recognized by a zone of deformed and fluidized sediment at the base, and association with non-life (lethal) facies. Care must be used in assigning specimens to ichnotaxa, and it is generally necessary to slab, and also to carry out stratinomic investigation in the field.

The rise of urban tourism in Havana since 1989

This article looks at the development of urban tourism in Havana, Cuba, in the period since the collapse of state socialism in the USSR and Eastern Europe. It provides an interesting case study of the adoption of an outward-oriented state development policy in the context of a socialist state. The dramatic rise of urban-based tourism in Havana since 1989 is described, followed by a review of the socio-economic impacts of such tourism. These include: income generation; job creation; the rise of the informal economy, including crime and prostitution; increased migration to the primary city, along with spatial concentration on the coastal strip, and associated environmental impacts. In conclusion, the article considers the fat that the promotion of tourism has returned Havana to some of the conditions that existed in the city Socialist Revolution in 1959.

City Profile: Havana

Since 1989, after 40 years of curbing urban development and under-investment in urban infrastructure, Havana is slowly regaining its primacy as Cuba's, and indeed one of the Caribbean's. major tourist destinations. This profile focuses on the urban change undergone by Havana since the introduction of the socalled'Special Period' in 1.989, following the collapse of State socialism in the USSR and Eastern Europe. A particular emphasis is placed on the role played by international tourism as a catalyst for socio-economic and environmental change in Havana in the 1990s. The profile also reviews the main urban development and governance issues that Havana is likely to face in the future. (c) 2005 Elsevier Ltd. All rights reserved.

Elevated marine deposits in Bermuda record a late Quaternary megatsunami

Deposits of coral-bearing, marine shell conglomerate exposed at elevations higher than 20 m above present-day mean sea level (MSL) in Bermuda and the Bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage (MIS) I I, ca. 360-420 ka before present. On the strength of this evidence, a sea level highstand more than 20 m higher than present-day MSL was inferred for the MIS I I interglacial, despite a lack of clear supporting evidence in the oxygen-isotope records of deep-sea sediment cores. We have critically re-examined the elevated marine deposits in Bermuda, and find their geological setting, sedimentary relations, and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period. Rather, these deposits, which comprise a poorly sorted mixture of reef, lagoon and shoreline sediments, appear to have been carried tens of meters inside karst caves, presumably by large waves, at some time earlier than ca. 310-360 ka before present (MIS 9-11). We hypothesize that these deposits are the result of a large tsunami during the mid-Pleistocene, in which Bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll. Likely causes for such a megatsunami are the flank collapse of an Atlantic island volcano, such as the roughly synchronous Julan or Orotava submarine landslides in the Canary Islands, or a giant submarine landslide on the Atlantic continental margin. (c) 2006 Elsevier B.V. All rights reserved.

Why we need new spectacles: Mapping the experiential dimension in prehistoric Cretan landscapes

The Bronze to Iron Age transition in Crete, a period of state collapse and insecurity, saw the island's rugged, high-contrast topography used in striking new ways. The visual drama of many of the new site locations has stimulated significant research over the last hundred years, with explanation of the change as the main focus. The new sites are not monumental in character: the vast majority are settlements, and much of the information about them comes from survey. Perhaps as a result, the new site map has not been much studied from phenomenological perspectives. A focus on the visual and experiential aspects of the new landscape can offer valuable insights into social structures at this period, and illuminate social developments prefiguring the emergence of polis states in Crete by c. 700 BC. To develop, share and evaluate this type of integrated study, digital reconstructive techniques are still under-used in this region. I highlight their potential value in addressing a regularly-identified shortcoming of phenomenological approaches-their necessarily subjective emphasis.

Growth of the lava dome and extrusion rates at Soufrière Hills Volcano, Montserrat, West Indies: 2005–2008

The third episode of lava dome growth at Soufrière Hills Volcano began 1 August 2005 and ended 20 April 2007. Volumes of the dome and talus produced were measured using a photo-based method with a calibrated camera for increased accuracy. The total dense rock equivalent (DRE) volume of extruded andesite magma (306 ± 51 Mm3) was similar within error to that produced in the earlier episodes but the average extrusion rate was 5.6 ± 0.9 m3s−1 (DRE), higher than the previous episodes. Extrusion rates varied in a pulsatory manner from <0.5 m3s−1 to ∼20 m3s−1. On 18 May 2006, the lava dome had reached a volume of 85 Mm3 DRE and it was removed in its entirety during a massive dome collapse on 20 May 2006. Extrusion began again almost immediately and built a dome of 170 Mm3 DRE with a summit height 1047 m above sea level by 4 April 2007. There were few moderate-sized dome collapses (1–10 Mm3) during this extrusive episode in contrast to the first episode of dome growth in 1995–8 when they were numerous. The first and third episodes of dome growth showed a similar pattern of low (<0.5 m3s−1) but increasing magma flux during the early stages, with steady high flux after extrusion of ∼25 Mm3

Clastic and core lava components of a silicic lava dome

The formation of a lava dome involves fractionation of the lava into core and clastic components. We show that for three separate, successive andesitic lava domes that grew at Soufrière Hills volcano, Montserrat, between 1999 and 2007, the volumetric proportion of the lava converted to talus or pyroclastic flow deposits was 50%–90% of the lava extruded. Currently, only 8% of the total magma extruded during the 1995–2007 eruption remains as core lava. The equivalent representation in the geological record will probably be even lower. Most of the lava extruded at the surface flowed no further than 150–300 m from the vent before disaggregation, resulting in a lava core whose shape tends to a cylinder. Moderate to high extrusion rates at the Soufrière Hills domes may have contributed to the large clastic fraction observed. Creating talus dissipates much of the energy that would otherwise be stored in the core lava of domes. The extreme hazards from large pyroclastic flows and blasts posed by wholesale collapse of a lava dome depend largely on the size of the lava core, and hence on the aggregate history of the partitioning process, not on the size of the dome.