Monitoring land surface and cover in urban and peri-urban environments using digital aerial photography

This paper describes the development of a system for decimetre-scale monitoring of land-surface and land-cover in urban and peri-urban environments. We describe our methodology that comprises the application of highly automated processing and analysis methods to digital aerial photography. The approach described in this paper addresses a monitoring need by providing the ability to generate change information at a spatial resolution suitable for urban, peri-urban and coastal areas, where an increasing percentage of the worlds’ population dwells. These areas are dynamic, with many environmental issues associated with planning, service provision, resource management and allocation, as well as monitoring regulatory compliance. We present a system based on standardised data and methods, which is able to track and communicate changes in features of interest in a way that has not been previously possible. We describe the methodology and then demonstrate its feasibility by applying it to geographic areas of planning and policy relevant size (the order of tens of thousands of square kilometres). We demonstrate the approach by applying it to the problem of urban forest assessment.     

Net deficits and the case for aquacultural geography

Summary The crisis in capture fisheries has placed an increased onus on aquaculture to supply the world fish demand. The advancing role of culture relative to capture fisheries has precipitated environmental and socio-economic transformations. Geographers have paid scant attention to these developments. This paper provides a literature review and proffers a research agenda for aquacultural geography.     

A new look at the Martian “violet haze” problem II. “Blue clearing” in 1969

The 1969 apparition of Mars has been extensively observed by the International Planetary Patrol Program. Using this material, the distribution of “blue clearing” in phase angle has been examined for four Martian bright area-dark area pairs. Arabia-Syrtis Major showed a smooth variation with a maximum at opposition. Zephyria-Mare Cimmerium showed a similar behavior except for a period around 20° before opposition. Memnonia-Mare Sirenum showed a rather steady decline from 20° before opposition to 30δ after opposition, except for an increase around 11° after opposition. Xanthe-Nilokeras showed a rather erratic behavior.Arabia-Syrtis Major underwent a strong diurnal variation in blue clearing near opposition. Xanthe-Nilokeras showed a diurnal variation throughout the apparition nearly identical to that of Arabia-Syrtis Major near opposition. Mare Cimmerium and Mare Sirenum are not well suited for showing a diurnal variation.The systematic error in these data due to the effects of astronomical “seeing” is discussed quantitatively.     

Sudbury Breccia (Canada): a product of the 1850 Ma Sudbury Event and host to footwall Cu–Ni–PGE deposits

The Sudbury Structure, formed by meteorite impact at 1850 Ma, consists of three major components: (1) the Sudbury Basin; (2) the Sudbury Igneous Complex, which surrounds the basin as an elliptical collar; and (3) breccia bodies in the footwall known as Sudbury Breccia. In general, the breccia consists of subrounded fragments set in a dark, fine-grained to aphanitic matrix. A comparison of the chemical composition of host rocks, clasts and matrices indicates that brecciation was essentially an in-situ process. Sudbury Breccia forms irregular-shaped bodies or dikes that range in size from mm to km scale. Contacts with the host rocks are commonly sharp. The aspect ratio of most clasts is approximately 2 with the long axes parallel to dike walls. The fractal dimension (Dr)=1.55. Although there appears to be some concentration of brecciation within concentric zones, small Sudbury Breccia bodies within and outside these zones have more or less random strikes and steep dips. Sudbury Breccia bodies near an embayment structure tend to be subparallel to the base of the Sudbury Igneous Complex. Sudbury Breccia occurs as much as 80 km from the outer margin of the Sudbury Igneous Complex. In an inner zone, 5 to 15 km wide, breccia comprises 5% of exposed bedrock with an increase in brecciation intensity in embayment structures. Sudbury Breccia may be classified into three types based on the nature of the matrix: clastic, pseudotachylite and microcrystalline. Clastic Sudbury Breccia, the dominant type in the Southern Province, is characterized by flow-surface structures. Possibly, a sudden rise in pore pressure caused explosive dilation and fragmentation, followed by fluidization and flowage into extension fractures. Pseudotachylite Sudbury Breccia, mainly confined to Archean rocks, apparently formed by comminution and frictional melting. Microcrystalline Sudbury Breccia formed as a result of the thermal metamorphism, of the North Range footwall, by the Sudbury Igneous Complex. This produced a zone, approximately 1.2 km wide, wherein the matrix of the breccia either recrystallized or, locally, melted. An overprint of regional metamorphism obliterated contact effects in the South Range footwall. The Ni–Cu–PGE magmatic sulphide deposits may be classified into four types based on structural setting: Sudbury Igneous Complex–footwall contact, footwall, offset, and sheared deposits. Sudbury Breccia is the main host for footwall deposits (e.g., McCreedy East, Victor, Lindsley). Sudbury Breccia locally hosts mineralization in radial (e.g., Parkin and Copper Cliff) and concentric (e.g., Frood–Stobie) offset dikes.     

Vertical seismic profile at Pike's Peak, Saskatchewan, Canada: turning rays and velocity anisotropy

First-arrival traveltimes from a multi-offset vertical seismic profile (VSP) were used to estimate velocity anisotropy in the presence of a vertical velocity gradient. A numerical model consisting of two layers with vertical velocity gradients of 3.1 and 1.2 s⁻¹, respectively, and global anisotropy parameters of =0.12±0.02 and δ=0.30±0.06 yielded first-arrival traveltimes that matched the observed traveltimes well. Shallow receivers were found to be crucial for constraining the vertical velocity field and for determining the parameters of anisotropy at depth.     

The estuarine chemistry and isotope systematics of U in the Amazon and Fly Rivers

Natural concentrations of ²³⁸U and δ²³⁴U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land–sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates.On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0–16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (1 m) zones of Fe(III)—and, to a lesser degree, Mn(IV)—reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved ²³⁸U profile co-varied closely with Mn(II). Isotopic variations as evidenced in δ²³⁴U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the δ²³⁴U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched δ²³⁴U values represent a riverine surface complexation product that is actively involved in Mn–Fe diagenetic cycles and surface complexation reactions.In the Fly River estuary, ²³⁸U appears to exhibit a reasonably conservative distribution as a function of salinity. The absence of observed U removal does not necessarily imply non-reactivity, but instead may record an integration of concurrent U removal and release processes. There is not a linear correlation between δ²³⁴U vs. 1/²³⁸U that would imply simple two component mixing. It is likely that resuspension of bottom sediments, prolonged residence times in the lower reaches of the Fly River, and energetic particle–colloid interactions contribute to the observed estuarine U distribution. The supply of uranium discharged from humid, tropical river systems to the sea appears to be foremost influenced by particle/water interactions that are ultimately governed by the particular physiographic and hydrologic characteristics of an estuary.     

Shoreline development,longshore transport and surface wave dynamics,Pleistocene Lake Bonneville,Utah

Point of the Mountain spit and Fingerpoint spit are two of the largest geomorphic features of Pleistocene Lake Bonneville of the western Great Basin, USA. The spits and their associated shorelines show distinctly different geomorphic expression and genesis; this is a function of their positions within the lake and the dynamics of the waves and storms that formed them. Mapping of geomorphic features, geometry of erosional features, and detailed lithologic analysis of shoreline deposits are used to determine dominant modes of sediment erosion and deposition. The Point of the Mountain spit, located in the eastern portion of the basin, was formed as a result of highly fractured bedrock in a salient of the Wasatch Front being exposed to wave trains that approached from the north‐northwest causing north‐to‐south longshore sediment transport. Shoreline development and sediment transport on the southern portion of the spit were minimal. The Fingerpoint spit, located on an island in the northwest portion of the basin, was formed by bidirectional longshore sediment transport as the result of waves that approached from both the north‐northeast and the south‐southwest. Spit development is a function of surface wave energy and direction which in turn is the integrated result of wind direction, wind intensity, and fetch. Wave transport direction determined from ?eld measurements at Point of the Mountain spit corresponds very well to the direction of maximum fetch (c. 200 km). For the Fingerpoint spit, the hypothesized wave transport direction from the south corresponds with the direction of maximum fetch (c. 350 km). However, wave energy transport from the north had limited fetch (c. 100 km), implying that wind intensity from the north was relatively large. The geometry of the two large Bonneville spits suggests the predominant wind direction from storms during the Pleistocene was from the north and points the way for future studies that can aid in further understanding the nature of Pleistocene wind ?elds in the Great Basin. Copyright © 2004 John Wiley & Sons, Ltd.     

Interdiffusion of hydrous dacitic and rhyolitic melts and the efficacy of rhyolite contamination of dacitic enclaves

Effective binary diffusion coefficients of Si during the interdiffusion of hydrous, 3 and 6% H₂O, dacitic and rhyolitic melts have been determined at 1.0 GPa, 1100°–1400°C. Water is shown to enhance diffusivities by one to two orders of magnitude above dry Si diffusivities in the same compositional system for SiO₂ compositions 65–75wt%. The effect of silica content on diffusion is small and typically within experimental error. With 3% H₂O in the melts the Arrhenius equation for Si diffusion at 70% SiO₂ is: $${\text{D = }}2.583\operatorname{x} 10^{ - {\text{ }}8} {\text{ }}\exp ( - 126.5/R{\text{T}})$$ where D is the diffusivity in m²/s, the activation energy (126.5) is in kJ/mol, R is in J/mol and T in Kelvin. Although less-well constrained, the Si diffusivity at 70% SiO₂ with 6% H₂O in the melts can be described by: $${\text{D = }}2.692\operatorname{x} 10^{ - {\text{ }}7} {\text{ }}\exp ( - 131.4/R{\text{T}})$$ The activation energies for diffusion are substantially below the activation energy of 236.4kJ/mol measured during anhydrous interdiffusion in the same system (Baker 1990). The decrease in activation energy with the initial addition of 3% water and the relative insensitivity of the activation energy to the additional water is related to the abundance of OH species in the melt, and the reduction of (Si,Al)-O bond strengths due to the interaction of hydroxyls with the (Si,Al)-O network. Changes in the pre-exponential factor of Arrhenius equations are attributed to the abundance of H₂O species in the melts. No decoupling of non-alkalies from SiO₂ during interdiffusion of the two melts was observed, although alkalies diffuse much more rapidly than non-alkalies (but were not measured quantitatively in this study) and can become decoupled. Interdiffusion of Si and all non-alkalies is demonstrated to be predictable, at least to within a factor of ten, by the Eyring equation. Using the diffusion data of this study for nonalkalies and of other studies for alkalies and Sr isotopes the contamination of a host rhyolitic magma by dacitic enclaves, 5 and 50 cm radius, has been modeled for temperatures of 1000°, 900°, and 800° C with water contents of 3 and 6%. Even when the effects of phenocrysts on diffusion in the dacitic enclaves are estimated the results of the modeling demonstrate that significant contamination is possible in the case of small enclaves, and even large enclaves have the potential to affect the composition of their host magma in geologically short times.