World's Coastlines Research Articles

A PROJECTION OF THE WORLD COASTLINE

Abstract A formula is derived from the spherical Transverse Mercator equation suitable for the combined projection of the world coastline within a finite area using two different central meridians.

Global coastal hazards from future sea level rise

A rise of sea level between 0.3 and 0.9 m by the end of the next century, caused by predicted greenhouse climate warming, would endanger human populations, cities, ports, and wetlands in low-lying coastal areas, through inundation, erosion and salinization. The consequences of a global sea level rise would be spatially non-uniform because of local or regional vertical crustal movements, differential resistance to erosion, varying wave climates, and changeable longshore currents. Although many factors can influence sea level, leading to a noisy record, various studies utilizing tide-gauge data find an average global rate of sea level rise of 1–2 mm/yr, over the last 100 years. This trend is part of a general rise over the last 300 years, since the low point of the Little Ice Age. Sea level rise may accelerate 3–8 times over present rates, within the next century. The permanently inundated coastal zone would extend to a depth equivalent to the vertical rise in sea level. Major river deltas, coastal wetlands and coral islands would be most affected. Episodic flooding by storm waves and surges would penetrate even farther inland. Beach and cliff erosion will be accentuated. Saltwater penetration into coastal aquifers and estuaries could contaminate urban water supplies and affect agricultural production. Research on relative risks and impacts of sea level rise on specific localities is still at an early stage. Development of a global coastal hazards data base, intended to provide an overview of the relative vulnerabilities of the world's coastlines, is described in this paper. To date, information on seven variables, associated with inundation and erosion hazards, has been compiled for the U.S., and parts of Canada and Mexico. A coastal vulnerability index (CVI) has been designed to flag high risk coastal segments. Preliminary results are presented for the eastern United States, as a test case.

Global coastal hazards from future sea level rise

A rise of sea level between 0.3 and 0.9 m by the end of the next century, caused by predicted greenhouse climate warming, would endanger human populations, cities, ports, and wetlands in low-lying coastal areas, through inundation, erosion and salinization. The consequences of a global sea level rise would be spatially non-uniform because of local or regional vertical crustal movements, differential resistance to erosion, varying wave climates, and changeable longshore currents.Although many factors can influence sea level, leading to a noisy record, various studies utilizing tide-gauge data find an average global rate of sea level rise of 1–2 mm/yr, over the last 100 years. This trend is part of a general rise over the last 300 years, since the low point of the Little Ice Age. Sea level rise may accelerate 3–8 times over present rates, within the next century.The permanently inundated coastal zone would extend to a depth equivalent to the vertical rise in sea level. Major river deltas, coastal wetlands and coral islands would be most affected. Episodic flooding by storm waves and surges would penetrate even farther inland. Beach and cliff erosion will be accentuated. Saltwater penetration into coastal aquifers and estuaries could contaminate urban water supplies and affect agricultural production.Research on relative risks and impacts of sea level rise on specific localities is still at an early stage. Development of a global coastal hazards data base, intended to provide an overview of the relative vulnerabilities of the world's coastlines, is described in this paper. To date, information on seven variables, associated with inundation and erosion hazards, has been compiled for the U.S., and parts of Canada and Mexico. A coastal vulnerability index (CVI) has been designed to flag high risk coastal segments. Preliminary results are presented for the eastern United States, as a test case.

Sea-level rise and shore nourishment: a discussion

The role of sea-level rise in the long-term evolution of the world's coastlines is generally acknowledged in a qualitative sense. Hence it is logical that it is taken into account in the design of shore nourishment schemes. However, because of the large-scale character (in both time and space), it is difficult to quantify its impacts. The state-of-the-art in deductive modelling does not allow for an approach based purely on mathematical physics. Therefore, an alternative approach is proposed, utilizing conceptual models which are made quantitative and validated with the aid of inductive ideas, such as those inferred from observed or through analogy expected behaviour. An example is a conceptual LSCE model in which sea-level rise is one of the “sinks” acting on the active zone of a coastal cell. This model describes the coastal evolution at the time scale of the sea-level rise. At a somewhat smaller time scale, say the lifetime of an individual nourishment, a profile behaviour model, deductive or inductive and defined for a specific site and a specific class of situations and phenomena, can be the appropriate answer. With the aid of these design tools one does not have to fall back in the too simple and usually false assumption that shoreline retreat before and after a nourishment is the same. This allows us to include the increased effects of an accelerated sea-level rise to predict the longevity of shore nourishment. Thus, the conceptual model approach appears to be promising. Designing shore nourishment specifically to compensate for the effect of sea-level rise requires a good understanding of the coastal evolution on the longer time and space scales. Because of the uncertainties associated with these large scales this requires flexibility which, fortunately, can be achieved by combining shore nourishment with appropriate monitoring. Thus, shore nourishment is an effective mechanism to prevent shore retreat due to long-term sea-level rise.

Why Are Ancient Rocky Shores so Uncommon?

The geologic history of rocky shore biotas has been neglected by paleontologists. Under present conditions of high continentality, rocky shores account for more than 33% of the world's coastline. They are generally located on shores facing narrow continental shelves, where the pattern of global plate tectonics exerts much influence over their regional concentration. The highest frequency of rocky shores occurs on islands associated with hot spots, island arcs, and convergent-plate margins associated with subduction. Rocky shores situated in these settings are subject to recycling, so their remains are rare in the stratigraphic record. Some passive continental margins, including those along newly rifted oceans and those with low rates of sedimentation, exhibit frequencies of rocky shores as high or higher than those found on many convergent-plate margins. These have a good chance of being retained in the stratigraphic record for geologically significant periods of time. Epicontinental flooding reduces the overall extent of rocky shores during major high stands in sea level, but unconformable surfaces produced by the fluctuation between marginal seas and epicontinental seas are a common feature in the stratigraphic record. These surfaces are the only stable archives of rocky-shore biotas. Ancient rocky shores are rarely described in the paleontological and geological literature because unconformable surfaces are seldom excavated in three-dimensional relief. Important data are easy to overlook in cross-sectional slices of limited extent.

Coastline Changes: A Global Review

Coastline Changes is a first attempt to describe and analyse the pattern of advance and retreat on the world's coastlines in recent decades. Summarising and illustrating the evidence for coastline changes and discussing possible explanations, it provides valuable background for further detailed, local studies of coastline changes, an analytical framework for the elucidation of process and change in coastal environments, and a stimulus for the on-going mapping and measurement of changes on coastlines. Explanations of coastline changes are demonstrated to be typically multiple and the relative importance of relevant factors to vary from one section to another.

Methodologies for Geology: G. K. Gilbert and T. C. Chamberlin

THE HEROIC AGE OF AMERICAN GEOLOGY came to an end in 1928 with the publication of The Two Solar Families by Thomas Chrowder Chamberlin and the posthumous printing of Grove Karl Gilbert's Studies of Basin Range Structure. Both born in 1843, these two men had spanned the era which witnessed the creation of the institutional and intellectual foundations of American geology. Along with James Dwight Dana, John Newberry, and William Morris Davis they were among the American architects of the new sciences. It was Gilbert and Chamberlin whoabove and beyond their monographs and their tireless labors in the new institutional workshops of the science-gave the geology of this era its classic formulations of scientific methodology. Traditionally their papers, especially Gilbert's Inculcation of Scientific by Example (1886) and Chamberlin's Method of Multiple Working Hypotheses (1897), have been viewed as dealing with the same problems of scientific geology. In one sense this is correct: both men were responding to the inundation of information about the earth which was pouring in from all the continents of the globe. The opening up of the continental interiors to the eyes of science may be dated conveniently from the voyages of Cook, which rounded out the mappa mundi of the world's coastlines. The wave of exploration which swelled out of Western civilization from that time until the conquest of the poles has been termed the Second Great Age of Discovery by William Goetzmann. The natural sciences which exfoliated from natural history beginning in the late eighteenth century were a response to the stimulus of the new information being generated. Not only was information of new kinds, it also flowed in increasing volume; the data base that astronomy had accumulated over millennia geology acquired in decades. When Gilbert and Chamberlin wrote their influential essays, they were reacting to this milieu. The Second Age of Discovery had not only multiplied the information base of geology, it had shattered the correspondences and relationships which had held the old systems of knowledge together. Philosophies of method had to provide some new mechanism which could, in particular, preserve the concept of causality.

The navy's hydrographer and the International Federation of Surveyors

Abstract The Royal Navy had, by the middle of the nineteenth century, mapped nine-tenths of the world's coastlines. Today hydrography is an affair of international co-operation, through the Federation Internationale de Geometres (International Federation of Surveyors); and it is also a more sophisticated affair than sounding depths with lead weights or plotting positions by visible beacons.