Application of Landsat satellite imagery to monitor land‐cover changes at the Athabasca Oil Sands,Alberta, Canada

A major advantage of satellite remote sensing is that the imagery acquired provides a synoptic view of the landscape. Thus, repeat coverage by the satellite on a regular basis permits the detection of changes in land‐cover over time. This study demonstrates the application of remote sensing technology to the monitoring of mining activities at the Athabasca Oil Sands region of Alberta, Canada. First, we describe the techniques used to match a time sequence of Landsat imagery, both spatially and spectrally, to ensure that the spectral changes through time are due to land‐cover variations. A series of spectral trajectories were then extracted to assess changes in land‐cover through time. Secondly, a land‐cover classification was produced from the baseline 1984 imagery and, using historic and future mine extents, the classification was analyzed to determine the proportion of each land‐cover type affected through development. Results of the analysis indicate that since 1984 there has been a larger reduction in mixedwood dense and broadleaf vegetation classes than mixedwood sparse or dense conifer stands in the area. Based on the delineations of mine‐site activity, the area of woodland and wetland habitat subject to development has increased from approximately 2,520 hectare (ha) in 1984 to 32,930 ha in 2005.     

Indifference towards national identity: what young adults think about being English and British*

ABSTRACT. National identity should be sharply distinguished from nationalism. People speak by reference to a general and assumed membership of a country, and routine markers of behaviour and style may exhibit this sense of membership. This matter‐of‐fact acceptance of ‘national’ membership does not guarantee enthusiasm for the ‘nation’ and it cannot be taken as a signal of nationalism, banal or otherwise. While theoretical statements and assumptions often suggest that national identity is fundamental to individuals in contemporary societies, empirical investigation of people talking about national identity uncovers some broad strands of indifference and hostility towards national identity in general, and towards British and English identities in particular. This may reflect young adults' wish not to appear ‘nationalist’ just as many would wish not to appear racist. But the level of apathy and antagonism towards national identity among young adults suggests that we ought to reconsider any assumption that national identity is ‘normally’ a powerful and important marker, embraced with enthusiasm.     

City networks: breaking gridlocks or forging (new) lock‐ins?

There is today a global recognition that we live in an ‘urban age’ of near‐planetary urbanization where cities are at the forefront of all sorts of agendas. Yet little attention is offered to the active role of cities as political drivers of the urban age. There might today be more than two hundred ‘city networks’ globally, with thousands of para‐diplomatic connections actively defining relations between cities, international organization and corporate actors. This actively networked texture of the urban age shapes all areas of policy and, not least, international relations, and holds much promise as to possible urban solutions to global challenges. Based on an overview of a representative subset of this mass of city‐to‐city cooperation (n=170), this article illustrates the landscape of city networking, its issue areas and institutional shapes, and its critical features. As we argue, city networks today are faced by a crucial challenge: while trying to overcome state‐centric ‘gridlocks’ cities are, at the same time, building both political–economic as well as very material ‘lock‐ins’. We need to pay serious attention to this impact of city diplomacy in international affairs, developing a greater appreciation of the path dependencies and responsibilities this diplomatic activity purports.     

Permeability of the continental crust: dynamic variations inferred from seismicity and metamorphism

The variation of permeability with depth can be probed indirectly by various means, including hydrologic models that use geothermal data as constraints and the progress of metamorphic reactions driven by fluid flow. Geothermal and metamorphic data combine to indicate that mean permeability ( k ) of tectonically active continental crust decreases with depth ( z ) according to log  k  ≈ −14–3.2 log  z , where k is in m² and z in km. Other independently derived, crustal-scale k – z relations are generally similar to this power-law curve. Yet there is also substantial evidence for local-to-regional-scale, transient, permeability-generation events that entail permeabilities much higher than these mean k – z relations would suggest. Compilation of such data yields a fit to these elevated, transient values of log  k  ≈ −11.5–3.2 log  z , suggesting a functional form similar to that of tectonically active crust, but shifted to higher permeability at a given depth. In addition, it seems possible that, in the absence of active prograde metamorphism, permeability in the deeper crust will decay toward values below the mean k – z curves. Several lines of evidence suggest geologically rapid (years to 10³ years) decay of high-permeability transients toward background values. Crustal-scale k – z curves may reflect a dynamic competition between permeability creation by processes such as fluid sourcing and rock failure, and permeability destruction by processes such as compaction, hydrothermal alteration, and retrograde metamorphism.     

Permeability of continental crust influenced by internal and external forcing

The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability–depth relations) on a very large scale? Here we argue that large‐scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing – fluxes induced by metamorphism, magmatism, and mantle degassing – is dominant, whereas in the shallow crust, external forcing – the vigor of the hydrologic cycle – is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near‐lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near‐hydrostatic fluid pressures are the norm. We use first‐order calculations and numerical modeling to explore the hypothesis that upper‐crustal permeability is influenced by the magnitude of external fluid sources, much as lower‐crustal permeability is influenced by the magnitude of internal fluid sources. We compare model‐generated permeability structures with various observations of crustal permeability.