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And the rapid rise of natural catastrophes in vulnerable developing countries is easily explained. Despite attention being drawn to the problem in the 1990s through the UN International Decade for Natural Disaster Reduction (IDNDR) initiative, prospects for reducing the impact of natural hazards on the populations of developing countries in the short to medium term look bleak. The follow-up UN programme - the International Strategy for Natural Disaster Reduction (ISDR) - is admirable in both...

Forecast for the future

Broadly speaking, the forecast for the twenty-first century and beyond is not, from a natural hazard perspective, a particularly promising one. Although increased losses from weather and climate extremes have been explained away in terms of human factors such as greater vulnerability and wealth concentration (e.g. Changnon et al., 2000), it is likely that continued anthropogenic global warming will result in more extreme, and therefore more hazardous, meteorological phenomena. Observations of...

Natural hazards the human dimension

The impact of natural hazards on society is clearly on the rise, although it still falls far below that due to environmental degradation and, in particular, civil strife (Fig. 8.1). Figures for the period 1900-90 indicate that almost 90 per cent of disaster-related deaths over the period can be attributed to war and famine, with all the natural hazards together making up the remainder. Notwithstanding this, the numbers of people affected by natural hazards during the 1970s and 1980s fell little...

Environmental change and natural hazards the impact in the twentyfirst century

From the perspective of the first year of a new millennium, the impact of rapid-onset geophysical hazards over the course of the next century is difficult to forecast, particularly in light of the major uncertainties attached to predictions of environmental change over this period. Perhaps some constraints can be imposed, however, on the basis of climate change impact forecasts made in a recent report by the UK Meteorological Office (1999) (Box 8.1), and based upon the second Hadley Centre...

Chapter summary

In this short concluding chapter we look to the future and address the issue of how contemporary environmental change driven by anthropogenic global warming might lead to an increase in hazard. We examine one recent forecast for climate change over the next 80 years and explore its hazard implications. We also look at the human dimension and evaluate the critical role increasing vulnerability plays in exacerbating the impact of natural hazards on human society. In conclusion, we present a...

Environmental effects of impact events

The scale of environmental damage due to an impact event is not simply a reflection of the impactor size. Morrison et al. (1994) observe that it is the kinetic energy of the impactor that is its most significant property, which is a function of both object size and velocity. All other parameters being equal, a large object will have a greater kinetic energy and be more destructive than one of smaller dimensions (Fig. 7.6 Table 7.3). Owing to their much higher velocities, however, long-period...

The impact record on Earth

The dynamic nature of the Earth provides conditions that are far from ideal for the preservation of impact structures. Seventy per cent of the planet's surface is covered with water, and perhaps 50 per cent of the land surface has been altered sufficiently over geological time to eradicate evidence of all but the very largest collisions. This leaves only 15 per cent of the Earth's surface suitable for preserving the evidence of most past impacts. Around 165 impact sites have now been...

Recognising the impact threat

As at November 2000, 278 potentially hazardous asteroids (PHAs) had been identified in orbits close enough to threaten collision with the Earth at some time in the future (NASA NEO Program http neo.jpl.nasa.gov neo pha.html), and this number is increasing almost weekly. The Earth is constantly being bombarded by debris from space, most of which burns up in the atmosphere. Once or twice a century, however, objects in the 50-m size range penetrate the atmospheric shield and either impact on the...

Perspectives on future sealevel change

The worrying element of anthropogenic sea-level change is that it involves a considerable time lag between the forcing agent, for example greenhouse gas (GHG)-induced planetary warming, and the response of the system. The corollary of this is that even if we reduced GHG emissions to zero today, the warming resulting from previous emissions would still be sufficient to cause a substantial rise in global sea level over the coming century. To illustrate this, the UK Meteorological Office (1999)...

Sealevel change as a trigger of natural hazards

Significantly elevated sea levels are now widely recognised as being an inevitable consequence of the current period of global warming. In this chapter we address the causes and scale of past sea-level fluctuations, particularly during the late Quaternary and, most recently, in the twentieth century. We look forward through examining sources of future sea-level rise and projections for elevated sea levels over the next few thousand years. Uncertainties in such forecasts are considered, arising...

Volcanoes and mass extinctions

The largest eruptions of all are not in fact of the explosive variety, but involve instead the relatively quiet effusion of gigantic volumes of basaltic lava. Such continental flood basalt (CFB) eruptions occur - as the name suggests - on continental crust and are typically associated with mantle plumes or 'hot spots'. The volumes involved are often in excess of 1,000,000 km3, or over 300 times the volume of Toba ejecta, and the areas of the flows are typically of the order of hundreds of...

Volcanic supereruptions and environmental change

Alongside asteroid and comet impacts, volcanic super-eruptions - registering 8 on the Volcanic Explosivity Index - are capable of triggering rapid and dramatic changes to the Earth's physical environment. Over the past 2 Table 5.5 Phenomena associated with Irish tree-ring width minima (Source Sadler and Grattan, 1999) Table 5.5 Phenomena associated with Irish tree-ring width minima (Source Sadler and Grattan, 1999) Hekla 3 eruption (Iceland) Greenland ice core acidity peak. 1120 50 bc...

Volcanoes and climate

In the context of global warming, it is crucial that we are able to evaluate the.role of volcanic activity in the operation of the global climate system, and to understand the processes and mechanisms involved. This is of particular importance as the surface cooling associated with single large eruptions or multiple, temporally adjacent, smaller volcanic events can be sufficient to mask - at least temporarily - the impact of human activity on the climate due to greenhouse gas emissions. There...

Water and slope failure

We have seen that a slope becomes less stable when it contains more water. Four key mechanisms by which water can induce instability are by reducing the effective normal stress, liquefying mixtures of soil and fine-grained rock, chemically weathering a rock, and enhancing rock cracking. 4.6.1 Reducing the effective normal stress The overlying surfaces of a failure plane are rough and uneven and can resist movement by interlocking their small-scale surface irregularities (like the teeth of...

Types of landslide

Landslides are unstable mixtures of soil and rock. They occur when the pull of gravity overcomes natural slope resistance. This situation typically arises when slope resistance is reduced below a critical value by some combination of chemical weathering, increased fluid pressure in rock and soil (e.g. after persistent rainfall), and the undercutting of the base of a slope, either by natural erosion or by human activity. Bulk soil resistance may also vary significantly according to the amount...

Sealevel change as an initiator of seismicity and volcanism

During the Quaternary, the continental margins were subjected to major stress changes as the enormous variations in ocean volume repeat edly loaded and unloaded the crust. These stress changes have been implicated in triggering a range of potentially hazardous phenomena, including increased tectonism and seismicity (e.g. Nakada and Yokose, 1992), enhanced volcanic activity (e.g. Rampino et al, 1979 Wallmann et al, 1988 McGuire et al., 1997), and landslide formation (e.g. Weaver and Kuijpers,...

Changing sea levels and natural hazards

Sea levels have changed throughout geological time (e.g. Haq et al., 1987) in response to a range of different and sometimes interacting isostatic, eustatic and tectonic processes (Dawson, 1992 Box 6.1). Natural hazards related to such sea-level change are surprisingly many and varied, and the relationship between the two is often far from clear. Broadly speaking, rising sea levels can be expected to increase the threat to coastal zones, primarily owing to the inundation or flooding of...

Recent environmental change

Studies of surface temperature change, utilising a range of proxy measurements, reveal that the planet has been significantly warmer during the past 70 years than at any time in the past millennium (Jones et al.f 1998). Furthermore, the warming has accelerated in the past three decades, and 14 of the 15 warmest years on record have occurred since 1980, with 1998, followed by 1997 and 1995, being the warmest ever. Mean global temperatures are now higher than at any time since ad 1400. Reliable...

Effect of environmental change on global rates of landsliding

A recurring theme of this chapter is the importance of water in destabilising slopes and in influencing how quickly and how far a landslide can travel. A key feature is the length of time for which rock and soil remain saturated with water. The amount and duration of water retention increase as the rate of water supply becomes ever greater than the rate of water escape from a slope. Of these two factors, it is the rate of water supply that appears generally to be more susceptible to...

Extratropical cyclones an overview

Extratropical cyclones generally have less destructive power than do tropical cyclones or tornadoes, but are able to provide damaging winds over a wide area, and also wave damage in coastal areas. The wind speed tends to be higher in open country, on hills and over the sea, though topographic features can increase speeds locally. The wave hazard depends on the wind's fetch the distance of water over which the wind blows and duration, as well as its speed. Extratropical cyclones are described at...

Changing sea levels submarine landslides and collapsing ocean islands

It would perhaps be surprising if large and rapid changes in sea level did not have a destabilising influence on continental margins and ocean islands, and both sea-level falls and rises have been implicated in catastrophic submarine landslides and sediment failures e.g. Weaver and Kuijpers, 1983 Prior et al, 1986 Masson and Weaver, 1992 Roberts and Cramp, 1996 Maslin et al, 1998 Rothwell et al, 1998 Alibes et al, 1999 and collapses of the flanks of ocean islands e.g. McGuire et al, 1997 ....

Sluggish deformation

Ventnor Blocks Slope Stability

Significant movement decimetres to metres over timescales of days to years almost invariably involves deformation of soil or clay-rich rock. Slower movements metres per 10-100 years or more often involve also the deformation of apparently hard crustal rock, whether sedimentary, igneous or metamorphic. The second group of movements occurs mostly on mountains Jahn, 1964 and volcanoes Borgia, 1994 , but though important geomorphologic-ally, they do not constitute a major hazard. Accordingly, we...

Eruption characteristics and environmental impact

The potential for a volcanic eruption to have a significant impact on the environment is eruption characteristics and environmental impact 91 dependent upon a number of factors, the most important of which are size, explosivity, magma chemistry and geographical location. In very broad terms, volcanoes can be divided into effusive and explosive types, with eruptions of the former being dominated by lava flow formation and the latter by the more energetic expulsion of disrupted magma pyroclastic...

Volcanoes and Ice

'Fire and ice' have long been linked in some way or other, and as far back as 1975 Kennett and Thunell proposed, on the basis of the tephra content of deep-sea cores, that a dramatic and global increase in explosive volcan-ism coincided with the glacially dominated Quaternary. The precise nature of the link between volcanism and glaciation remains problematical, however, and while some authors e.g. Bray, 1976, 1977 Rampino and Self, 1992 suggest that volcanic activity is able to initiate or...

Contents

Chapter I Natural hazards an introduction I 1.1 What are natural hazards 1 1.2 Natural hazards and environmental change 2 1.3 Natural hazard impacts a historical perspective 5 1.4 A natural hazards primer 10 1.5 Recent environmental change 14 Chapter 2 Windstorms in a warmer world 18 2.1 Weather-related natural hazards and climate change 18 2.2 Observing and predicting trends in weather-related hazards 23 2.3 Mid-latitude storminess in a warmer world 29 2.4 Tropical cyclones, tornadoes,...

Box The effect of a shift in the mean on extreme event exceedance frequency for a normal distribution

When a normal distribution experiences a relatively small type B shift in its mean see main text , the relative change in extreme event exceedance frequency or exceedance probability can be surprisingly large. There are three aspects to this effect The relative change in exceedance frequency is steep function of the shift in the mean Relatively small changes in the mean value produce very large relative changes in the exceedance frequency or exceedance probability of extreme events. For...

Volcanoes as initiators of past environmental change notes of caution

Within the current intellectual climate of neo-catastrophism and punctuated equilibrium see Chapter 7.1 , it has become fashionable to explain any dramatic change, either in the environment or in human history, in terms of anomalous physical events, of which asteroid and comet impacts and volcanic eruptions are most popularly invoked. Eruptions clearly have an impact on both weather and climate, but Sadler and Grattan 1999 urge more critical appraisal of the evidence for the link between...

Setting the scene the new catastrophism

Before Charles Darwin proposed his revolutionary model to explain the diversity of life on the Earth, the general consensus, both scientific and populist, held that the planet and all life upon it had been created - exactly as it appeared - near-instantaneously and at the whim of a deity. Any subsequent changes, such as Noah's flood, were interpreted as sudden, devastating events sent by the aforementioned deity to chastise humankind for one misdemeanour or another. In short, catastrophism was...