Search Results

Two glacier avalanches from Mount Huascarán killed 4,000 people and destroyed the town of Ranrahirca and killed 15,000 people and devastated the city of Yungay in 1970, making it the most deadly glacier disaster in world history. Because these avalanches were unpredictable and uncontrollable, the Peruvian government tried more forcefully than it had during previous decades to implement hazard zoning to reduce disaster vulnerability in the Callejón de Huaylas. Local residents with different risk perceptions, however, successfully resisted zoning plans. In the process, glacier and glacial lake science became contested knowledge that various social groups sought to control. Ironically, locals opposed zoning to limit state intervention in their communities. But by inhabiting hazard zones they ultimately became even more dependent on state programs to monitor Cordillera Blanca glaciers and drain glacial lakes. As glacier experts tried to protect populations, they mediated between the centralized state and various local populations.

This chapter considers systems of interacting agents placed on networks. The agents — spins, oscillators, interacting individuals, etc. — occupy the nodes of networks and interact with each other through network links. In more complicated situations, these agents, in turn, influence their network substrates, and so the pair, a network and the system of agents, co-evolve. The chapter discusses unusual phenomena in these cooperative systems on complex networks. In particular, the Ising model on networks is considered, various synchronization phenomena, and basic game theory models. Finally, avalanches and other abrupt phenomena in many-particle systems on complex networks are touched upon.

This chapter begins with a survey of early experimental results — the Planck spectrum, the photoelectric effect, and Compton scattering — that are usually presented as evidence for the existence of photons. The photon concept is indeed sufficient to explain these results, but it is not necessary. There are semi-classical models that explain the same data without introducing photons. The crucial experiment, in which light consisting of a single photon reflects from a beam splitter, depends on the essential indivisibility of photons, and it excludes all semi-classical descriptions of light. This discussion is followed by a preview of modern methods of production and detection of individual photons, e.g., spontaneous down conversion and Silicon avalanche-photodiode counters, together with an introduction to the quantum theory of light based on the correspondence principle.

This chapter first discusses which parameters determine sensor sensitivity, and then explains the basic semiconductor physics relevant to radiation detectors. Statistical limits to energy resolution are discussed with a simple derivation of the Fano factor. Semiconductor doping and pn-junctions are explained and applied to the formation of extended detector volumes. Quantitative expressions describing charge transport and collection times are derived. The mechanism of induced charge is explained and applied to multi-electrode structures, such as strip and pixel detectors (Ramo's theorem). Charge collection in the presence of trapping and alternate sensor materials is discussed. Avalanche gain is described and applied to photodiodes. The second half of the chapter explains the basics of electronic signal acquisition with voltage, current, or charge-sensitive amplifiers. The relationship between pulse rise time and frequency response is explained together with the basic amplifier parameters that limit bandwidth. In closing, the importance of amplifier input impedance is shown.

This chapter discusses the occurrence of natural disturbances and their significant effects on the forests. It focuses on two disturbances that are the most important and widespread occurrences in the Klamaths: fire and water. The chapter first discusses the fire histories of the Klamath Mountains and interactions of various species and their adaptations to fire. It examines the effects of twentieth-century fire exclusion, the loss of fire-tolerant trees due to selective harvest, and plantation forestry. The chapter then discusses the negative and positive effects of floods on forests. It also describes other disturbances such as insects, pathogens, strong winds, drought, snow avalanches, and earthquakes.

This chapter discusses the montane and subalpine coniferous forests and other vegetation of the Sierra Nevada and Cascade Ranges in California, vegetation patterns and environmental factors that affect distribution, and the role fire in spatial pattern and landscape. It also discusses some of the factors affecting vegetation, such as insects and pathogens, wind and avalanches, invasive species, air pollution, and logging.

This book investigates complex systems that are idealizations of naturally occurring phenomena characterized by the autonomous generation of structures and patterns at macroscopic scales. It provides material and guidance to allow the reader to learn about complexity through hands-on experimentation with complex systems with the aid of computer programs. Each chapter thus presents a simple computational model of natural complex phenomena ranging from avalanches and earthquakes to solar flares, epidemics, and ant colonies. This introductory chapter explains what complexity is, with emphasis on the fact that defining it is not a simple endeavor, and that it is not the same as randomness or chaos. It also shows that open dissipative systems are complex and clarifies what natural complexity means. Finally, it describes the computer programs listed in this book and suggests materials for further reading about complexity.

This chapter describes a simple computational idealization of a sandpile. When sand trickles slowly through your fingers, a small conical pile of sand forms below your hand. Sand avalanches of various sizes intermittently slide down the slope of the pile, which is growing both in width and in height but maintains the same slope angle. The pile of sand is a classic example of self-organized criticality. The chapter first provides an overview of the sandpile model before discussing its numerical implementation and a representative simulation involving a small 100-node lattice. It then examines the invariant power-law behavior of avalanches and the self-organized criticality of a sandpile. The chapter includes exercises and further computational explorations, along with a suggested list of materials for further reading.

This chapter considers the occurrence of traffic jams in the flow of moving automobiles as an example of complex collective behavior emerging from the interactions of system elements. It begins with a discussion of the basic design principle of an automobile traffic model and the numerical implementation of the model using the Python code. It then describes a representative simulation involving an ensemble of 300 cars initially at rest and distributed randomly, with a mean spacing of 10 units. It also examines how the traffic jam model behaves, traffic jams as avalanches, and the self-organized criticality of car traffic. The chapter includes exercises and further computational explorations, along with a suggested list of materials for further reading.

There are at least three justifications for the examination of the geomorphology of the area in which ecosystem studies are conducted. First, the present landscape and the materials that make it up provide the substrate on which ecosystem development occurs and may impose constraints, such as where soil resources are limited, on that development. Second, the nature of the landscape and the geomorphic processes acting on it often define a large part of the disturbance regime within which ecosystem processes occur (Swanson et al. 1988). Third, the processes of weathering, erosion, sediment transport, and deposition that define geomorphic dynamics within the landscape are themselves ecosystem processes, for example, involving the supply of resources to organisms. In this last context, it is noteworthy that drainage basins (also called watersheds or catchments) were recognized as units of scientific study during a similar time period in both geomorphology and ecology (Slaymaker and Chorley 1964; Bormann and Likens 1967; Chorley 1969). The drainage basin concept, the contention that lakes and streams act to integrate ecological and geomorphic processes, remains important in both sciences and underlies the studies in Green Lakes Valley reviewed here. Over the past 30 years, Niwot Ridge and the adjacent catchment of Green Lakes Valley have been the subject of much research in geomorphology. Building on the studies of Outcalt and MacPhail (1965), White (1968), and Benedict (1970), work has emphasized the study of present-day processes and dynamics, especially of mass wasting in alpine areas. These topics have been reviewed by Caine (1974, 1986), Ives (1980), and Thorn and Loewenherz (1987). Studies of geomorphic processes have been conducted in parallel with work on Pleistocene (3 million to 10,000 yr BP) and Holocene (10,000 yr BP to present) environments in the Colorado Front Range (Madole 1972; Benedict 1973) that have been reviewed by White (1982). This chapter is intended to update those reviews in terms that complement the presentation of ecological phenomena such as nitrogen saturation in the alpine (chapter 5) as well as to refine observations and conclusions of earlier geomorphic studies.

The Missing Witnessis set in the Swiss alps and features a romance plot aborted by a jealous villain and saved by the servant Genevieve, the ‘missing witness’ of the title. It offers a wonderful example of an extended sensation scene involving not one, but two hand-to-hand fight scenes on a treacherous mountain pass, the first ending with the hero seeming to plunge to his death and the second with an avalanche engulfing the heroine and the stage. Unfortunately the play was hastily withdrawn when the actor playing Gustave, Mr. J. F. Stephenson, misjudged his ‘sensation leap’ and broke his leg only three weeks after its opening at the Alexandra Theatre in Liverpool. Here we follow the printed edition of the text as published by John and Robert Maxwell, Braddon’s husband and stepson.Aided by these familial arrangements Braddon had become adept at managing and maintaining control over her published work, so there was no need for her to engage with another theatrical publisher.

Western European countries are subject to natural phenomena that can cause disasters. Their origins are various: geophysical (earthquakes), hydrometeorological (sea storms, floods, and avalanches), or geomorphologic (landslides). They are fairly widespread but less frequent and of relatively low intensity compared with other regions of the world; for example, an earthquake in France or Belgium is not likely to be as violent as in Greece or Japan. Some of the countries concerned, such as France and Germany, are subject to all the hazards mentioned above, while Denmark and The Netherlands are seldom exposed to earthquakes and never to avalanches because they have no mountains. Man is not responsible for phenomena such as earthquakes, but contributes significantly to the onset and aggravation of other hazards, and is sometimes largely responsible for the direct and indirect consequences, having built and maintained installations in ‘risk’ sectors. The number of victims and the cost of the damage may be high, depending on the circumstances, the intensity, and the duration of the phenomenon. Western European countries have experienced real natural disasters in the distant or recent past. Floods following a storm wave in The Netherlands in 1953 were responsible for some 2,000 deaths and damage amounting to over 3 billion Euros. Two hundred people died in the most destructive flood ever known in France in 1930 in the Tarn (Ledoux 1995). Natural phenomena such as these can recur with at least the same intensity but may entail much greater damage because of increased human occupation in the sectors concerned: the flooding submerges zones which are much more urbanized than they were in the nineteenth century. Whether prevention measures are taken depends on the level of risk which the populations concerned are prepared to accept. These measures should be associated with spatial and temporal forecasts and preceded by an analysis of the processes for these phenomena to be fully understood. In order to remove the ambiguities and the inaccuracies of terminology that are observed all too often, it is necessary in the first instance to define ‘geomorphic hazards and natural risks’, particularly in terms of the notions of risk, hazards, and vulnerability.

The cryosphere refers to the Earth’s frozen realm. As such, it includes the 10 percent of the terrestrial surface covered by ice sheets and glaciers, an additional 14 percent characterized by permafrost and/or periglacial processes, and those regions affected by ephemeral and permanent snow cover and sea ice. Although glaciers and permafrost are confined to high latitudes or altitudes, areas seasonally affected by snow cover and sea ice occupy a large portion of Earth’s surface area and have strong spatiotemporal characteristics. Considerable scientific attention has focused on the cryosphere in the past decade. Results from 2 ×CO2 General Circulation Models (GCMs) consistently predict enhanced warming at high latitudes, especially over land (Fitzharris 1996). Since a large volume of ground and surface ice is currently within several degrees of its melting temperature, the cryospheric system is particularly vulnerable to the effects of regional warming. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that there is strong evidence of Arctic air temperature warming over land by as much as 5 °C during the past century (Anisimov et al. 2001). Further, sea-ice extent and thickness has recently decreased, permafrost has generally warmed, spring snow extent over Eurasia has been reduced, and there has been a general warming trend in the Antarctic (e.g. Serreze et al. 2000). Most climate models project a sustained warming and increase in precipitation in these regions over the twenty-first century. Projected impacts include melting of ice sheets and glaciers with consequent increase in sea level, possible collapse of the Antarctic ice shelves, substantial loss of Arctic Ocean sea ice, and thawing of permafrost terrain. Such rapid responses would likely have a substantial impact on marine and terrestrial biota, with attendant disruption of indigenous human communities and infrastructure. Further, such changes can trigger positive feedback effects that influence global climate. For example, melting of organic-rich permafrost and widespread decomposition of peatlands might enhance CO2 and CH4 efflux to the atmosphere. Cryospheric researchers are therefore involved in monitoring and documenting changes in an effort to separate the natural variability from that induced or enhanced by human activity.

The raw facts alone make mountains worthy of geographic interest: mountains constitute 25 per cent of the earth’s surface; they are home to 26 per cent of the world’s populace; and generate 32 per cent of global surface run-off (Meybeck et al. 2001). More than half the global population depends directly on mountain environments for the natural resources of water, food, power, wood, and minerals; and mountains contain high biological diversity; hence they are important in crop diversity and crop stability (Ives 1992; Smethurst 2000; UNFAO 2000). Elevation, relief, and differences in aspect make mountains excellent places to study all processes, human and physical: high energy systems make mountains some of the most inhospitable of environments for people and their livelihoods, and strikingly distinct changes in environment over short distances make mountains ideally suited to the study of earth surface processes. Mountains are often political and cultural borders, or in some cases, political, cultural, and biological islands. With ever-increasing populations placing ever-increasing environmental pressure on mountains, mountain environments are heavily impacted and are therefore quickly changing. Moreover, they are more susceptible to adverse impacts than lowlands and are degrading accordingly. Whatever environmental change or damage happens to mountain peoples and environments then moves to lower elevations, thus affecting all. Three seminal texts indicate an ongoing interest in mountain geography: the oldest, Peattie (1936), is still in print; the newest, Messerli and Ives (1997) is contemporary; and Price (1981) is now being rewritten. Indeed, mountain geography as a field in its own right has led to the recent formation of the Mountain Geography Specialty Group of the Association of American Geographers (Friend 1999). With increasing importance placed on sustainability science (Kates et al. 2001), mountain geography is at the cutting edge of inter- and multidisciplinary research that serves to unify rather than further specialize scholarly geography (Friend 1999). The United Nations proclaimed 2002 the International Year of Mountains and has devoted an entire chapter (13) of its Agenda 21 from the Rio Earth Summit to mountain sustainable development (Friend 1999; Ives and Messerli 1997; Ives et al. 1997a, b; Messerli and Ives 1997; Sène and McGuire 1997; UNFAO 1999, 2000).

In August of 1992, Hurricane Andrew battered south-eastern Florida, causing fifty-eight deaths, and more than $27 billion in property losses (National Climatic Data Center 1999). The following year, widespread flooding occurred within the Upper Mississippi River basin, inundating 5.3 million hectares during the worst flood to affect much of the region in this century. The Northridge earthquake (magnitude 6.7) led to sixty-one deaths and more than $20 billion in property damage and loss in 1994. A year later, Kobe, Japan, experienced a magnitude 6.9 earthquake. Despite massive efforts to prepare for such events, more than 6,000 lives were lost, and $150–200 billion in property damage was experienced. In 1998, Hurricane Mitch devastated Honduras, Nicaragua, and other parts of Central America. More than 5,600 people died in Honduras alone and approximately 70,000 homes were damaged. In Nicaragua, more than 850,000 people were affected, with approximately 2,860 deaths. Estimates of losses in agriculture, housing, transportation and other infrastructure are in excess of $1.3 billion dollars (United Nations Office for the Coordination of Humanitarian Affairs 1998). These are just a few, albeit particularly devastating, events that continued to focus our attention in the 1990s on hazards and disasters. The widespread news media coverage of these disaster events provided a backdrop for fictional portrayals as Hollywood rediscovered the disaster movie genre. With enhanced special effects and big-named stars, popular films such as Twister, Volcano, Dante’s Peak, Armageddon, Deep Impact, Titanic, and A Civil Action added a different slant to the media coverage of disasters and the public’s perception of hazards throughout the decade. The public’s interest and fascination in actual disasters also propelled several books to the bestseller list (Barry 1997; Junger 1997; Larson 1999). Both the fictional representations and the consequences of real disasters illustrate the shift in our understanding of the forces at work in such events. Some of the damage in Hurricane Andrew, for example, is attributed to inadequate enforcement of building standards. In Kobe, structures engineered to withstand seismic activity failed, prompting concern about just how safe infrastructure is in tectonically active areas. And Hurricane Mitch’s devastating toll cannot be explained solely by the storm. Decades of land abuse and a combination of social, political, and economic factors combined with the storm to cause the severe losses.

The idea of Canadian Studies runs counter to recent economic trends that challenge the salience of the boundary between Canada and the United States. Books such as Nine Nations of North America (Garreau 1981) declare that the boundary is an irrelevant curiosity from a bygone era. Regional boundaries are more important than national boundaries when studying the geography of North America. Canada is viewed as nothing more than the “thirteenth Federal Reserve District” of the United States (Kindleberger 1987: 16). These statements suggest that Canada is not different from the United States, so why study geography from a Canadian perspective? One response is that the study of Canada endures because scholars persist in the idea that events (and the perception of events) in Canada differ from those elsewhere in North America. This chapter emphasizes research conducted by members of the Canadian Studies Specialty Group (CSSG) of the Association of American Geographers (AAG) between the late 1980s to the present. However, where relevant, we also include research conducted by other AAG members, scholars from the Association for Canadian Studies in the United States (ACSUS), and in some cases, Canadian and other scholars who have published in American journals. While we intend to present a comprehensive survey, it is by no means exhaustive. Our goal is to identify some major themes and diverse ways that Canadian geography has been studied in the United States. The chapter examines research conducted from the late 1980s to the present, and is organized around six themes: (1) economic geography and free trade; (2) political geography of national identities; (3) urban and social geography; (4) Canada’s regions: historical and cultural perspectives; (5) physical geography; and (6) the future of Canadian Studies. The deregulation of the Canadian economy accelerated with the implementation of the Canada-United States Free Trade Agreement (FTA) in 1989 and the North American Free Trade Agreement (NAFTA) in 1994. Free trade influenced much of the recent research done on Canada’s economic geography. Prior to the FTA, Americans paid little attention to the Canadian economy (Romey 1989). The neglect stems from the lack of controversy between Canada and the United States.

This chapter mainly discusses plastic flow in FCC crystals, where dislocations are intrinsically highly mobile, going from elementary dislocation mechanisms to dislocation microstructures and the mechanical response. Experimental aspects and the current state of the art in modelling are discussed. The elementary mechanisms are phonon drag, which governs free-flight velocities between obstacles, dislocation interactions and especially intersections and reactions, as well as cross-slip, which is a poorly known, complex and multiform core mechanisms. The formation of dislocation patterns and their properties have not been modelled convincingly until now. The strain-hardening stages are semi-quantitatively understood, except at very large strains, and are reasonably well described by dislocation-based continuous models. The recent discovery of intermittent flow and dislocation avalanches has triggered a lot of activity, and constitutes a breakthrough with many potential consequences.

The chapter covers photodetectors for photons in the optical and near UV range (about 200 nm to 700 nm). Important for particle and astroparticle experiments are photodetectors which detect light generated in scintillation or Cherenkov detectors, for example. The detection of photons always starts with the generation of an electron by photoeffect at a photocathode. The photoelectron can then be either multiplied in a photomultiplier tube by secondary electron emission or the cathode could be the surface of a semiconductor detector; both techniques can also be combined in hybrid photodetectors. A relatively new semiconductor detector is the silicon photomultiplier using an avalanche operation mode to obtain sufficiently large signals. In the last section the different photodetectors are compared and are assigned to typical applications according to their properties.