Sur submarine slide, Monterey Fan, central California

The Sur debris slide and associated debris flow cover more than 1000 km² of the eastern part of Monterey submarine fan and extend from the base of the continental slope near the apex of the fan to the Monterey fan valley. The flow is generally confined between the continental slope and remnants of an older channel (Monterey East fan valley). The hummocky surface of the debris slide and diffuse echo returns from the surface of the nearly acoustically transparent debris flow, as seen in 3.5 kHz profiles, are common to large submarine slides described from passive-margin continental-slope and rise deposits. Piston cores from the Sur slide recovered contorted and sheared fan turbidite units as well as clast- and matrix-supported mudlump debris flows. The cores show that the slide debris is overlain by 0.23–0.87 m of mud and turbidite sand that limit the age of the slide to latest Holocene, although more than one stage of emplacement is possible.     

The Stability of Andradite, Hedenbergite, and Related Minerals in the System Ca--Fe--Si--O--H

Phase relations for the bulk compositions 3CaO·2FeO_x·3SiO₂+excessH₂O and CaO·FeO_x·2SiO₂+excess H₂O were determinedusing conventional hydrothermal techniques with solid phaseoxygen buffers to control fO₂. Andradite, Ca₃Fe³⁺₂Si₃O₁₂, synthesized above 550 °C hasan average unit cell edge, a_o, of 12.055±0.001 Å,and an index of refraction, n, of 1.887±0.003. Belowthis temperature, a_o increases whereas n decreases, indicatingthe formation of a member of the andradite-hydroandradite solidsolution. At 2000 bars P_fluid andradite is stable above an f_O2of 10¹⁵ bar at 800 °C and 10-³² bar at 400 °C. At lowerf_O2 andradite+fluid gives way at successively lower temperaturesto the condensed assemblages magnetite+wollastonite, kirschsteinite(CaFe²⁺SiO₄)+ wollastonite and kirschsteinite+xonotlite (Ca₆Si₆O₁₇(OH)₂). Synthetic hedenbergite, CaFe²⁺Si₂O₆, has average unit cell dimensionsof a_o = 9.857± 0.004 Å, b_o = 9.033±0.002Å, c_o = 5.254±0.002 Å and ß = 104.82°±0.03°,and refractive indices of n = 1.731±0.003 and n = 1.755±0.005.At 2000 bars P_fiuid, hedenbergite is stable below an f_O2 of10-¹³ bar at 800 °C and 10-²⁸ bar at 400 °C. Above thesef_O2 values, hedenbergite+O₂ breaks down to andradite+magnetite+quartz. The mineral pair andradite +hedenbergite thus limit the f_O2range possible for their joint formation under equilibrium conditions. The hydration of wollastonite to xonotlite occurs at much lowertemperatures than previous experimental work indicated. A tentativehigh temperature limit for this reaction is set at 185°±15°C and 5000±25 bars and 210°±15 °Cand 2000±20 bars. Inasmuch as the growth of xonotlitefrom wollastonite + H₂O was never accomplished, this high temperaturelimit does not represent an equilibrium univariant curve. Nine phases were encountered in the study of andradite and hedenbergite.They are andradite, hedenbergite, magnetite, wollastonite, kirschsteinite,xonotlite, quartz, ilvaite, and vapor (fluid). An invariantpoint analysis using the method of Schreinemakers shows thetopologic relations of the reactions involved. The resultinggrid can be used to interpret natural occurrences.     

The role for a geographical information system in a large environmental project

Abstract

A geographical information system (GIS) has proved to be a valuable tool in the Direct/Delayed Response Project—a comprehensive examination of the future, long-term chemical response of surface waters to acidic deposition. The role of the GIS within the project includes aggregation, analysis and display of various forms, scales and projections of environmental data related to acidic deposition. The GIS is particularly valuable for effectively communicating key scientific findings and results of regional, national and international importance to a diverse audience.     

Seismic modeling of Tertiary sandstone clinothems, Spitsbergen

Two-dimensional seismic modelling has been undertaken on an overall progradational succession of sloping mudstone and sandstone units from the Palaeogene of Spitsbergen. The modelling shows that the main geometric features of the section would be resolved at 1500 m depth (with frequencies below 60 Hz, which is common in seismic data at these depths). However, interference between the base and top of lithological units gives lateral amplitude variations and discrepancies between the seismic image and the geometrical model. This is particularly prominent in low-frequency models. Terminations of reflectors, resembling toplap and onlap, may be interpreted, but are artefacts of the general convergence of lithological units present in the geometrical model. The geological section causes a seismic pattern resembling sigmoid progradational seismic facies. Two-dimensional seismic modelling is an efficient tool in bridging the gap between outcrop observations and subsurface data. Hence, modelled outcrop sections are important as reference points' for improved seismic stratigraphic interpretation.     

GARDENS ARE US,WE ARE NATURE: TRANSCENDING ANTIQUITY AND MODERNITY*

ABSTRACT. The history of gardens and the history of humans are linked inextricably, especially in the context of environment. As people and their institutions have changed, so too have gardens. This brief essay illustrates some important aspects in the evolution of gardens, exploring three seemingly discrete, but actually interconnected, notions: the antiquity of gardens, combining archaeological data with ethnographic parallels; the role of gardens in the changing spatial manifestations of agriculture, from dump heaps to amber waves of grain; and the transformation of domestic space, the literal and figurative reconstruction of garden fences into house walls. Changes are discussed as inadvertent products, rather than as consequences of deliberate actions. Modern ideas about categorizing landscapes are challenged further. The nature/culture dualism is a myth even at the household scale, as is our traditional way of looking at the world.     

Modelling spatially and temporally distributed phenomena: new methods and tools for GRASS GIS

Abstract

The concept of GRASS (Geographic Resources Analysis Support System) as an open system has created a favourable environment for integration of process based modelling and GIS. To support this integration a new generation of tools is being developed in the following areas: (a) interpolation from multidimensional scattered point data, (b) analysis of surfaces and hypersurfaces, (c) modelling of spatial processes and, (d) 3D dynamic visualization. Examples of two applications are given-spatial and temporal modelling of erosion and deposition, and multivariate interpolation and visualization of nitrogen concentrations in the Chesapeake Bay.     

PROMOTIONAL IMAGERY OF GLACIER NATIONAL PARK*

ABSTRACT. The Great Northern Railway vigorously encouraged visitation to Glacier National Park between 1911 and 1930. We reconstruct the railway's promotional imagery of Glacier through an assessment of 796 photographs used by the company to publicize park landscapes and activities. Seven themes in the photographs—Native Americans, scenery, recreation, wildlife, the Wild West, park management, and personalities—reveal a useful portrait of how Glacier National Park was marketed with images of the American West mass distributed for decades by one of the nation's most influential corporations.