SQUINTING BACK AT STRABO*

ABSTRACT. Strabo of Amasia (ca. 64 B.c.‐ca. A.D. 23) wrote the first comprehensive geography of the world known to the Greeks and Romans. Interest in Strabo and his Geography, which survives nearly intact in seventeen books, has fluctuated over the centuries among both classicists and historians of geography. After some historical background on Strabo and his reception, this essay considers the contribution of two significant recent English‐language treatments, as well as Strabo's Geography itself, and suggests ways in which the Strabonic model may have renewed relevance to the geographer's task of interpreting the oikoumene in the contemporary world.     

Global cotton and local environmental management: the political ecology of rich and poor small-hold farmers in southern Mali

This study examines the hypothesis that poor households engage in less sustainable soil management practices than rich households in a similar socioeconomic environment. This broad objective is explored in Mali's southern cotton belt through three specific research questions. First, is there empirical evidence to support the claim that poor households engage in less sustainable soil management practices than rich households? Second, what local and extra-local factors influence household agricultural management approaches in southern Mali? Third, what broader scale political and economic processes are linked to the factors that influence local-level agricultural management approaches? The author reports that soil quality measures on the farms of rich and poor households are not significantly different, refuting the conventional wisdom that the wealthy are better managers of the environment. A variety of environmentally deleterious practices are associated with export-oriented cotton production, an activity more vigorously pursued by wealthy than poor farmers. Finally, the focus on poverty in international environment and development discourse has allowed the government of Mali to avoid a serious debate on the sustainability of cotton production. The study's findings are based on household interviews describing agricultural management practices, an analysis of farm field soil measures, and discussions with donors and national policymakers.     

Transport rate of calcareous sand in unidirectional flow

This paper examines the transport of calcareous sand in unidirectional flow and its prediction through existing sediment transport models. A flume experiment of four sand samples collected on Oahu, Hawaii, provides 29 sets of sediment transport data in the bed-form and suspended transport stages. The measured transport data are compared with direct predictions from four energy-based transport models developed for siliceous particles. Corrections for the grain-size, fall velocity, and critical velocity of calcareous sand based on recent research are applied to the models and the results are compared with the direct calculations and measured data. The comparison illustrates the important role particle shape plays in the transport of calcareous sand. All four sediment transport models give consistent predictions and good agreement with the majority of the measured data. Two of the models respond positively to the corrections in both the bed-form and suspended transport stages indicating that such an approach may provide an interim solution for the transport of calcareous sand.     

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.     

A PULSED PLASMA JET ACOUSTIC SOURCE FOR PROFILING THE OCEAN FLOOR1

A plasma gun source has been successfully used to obtain sub-bottom profiles. The profiles show better penetration than with a 3-5 kHz source and more resolution than with an air gun. The plasma gun source is compact, self-contained, and requires no complex auxiliary equipment. The device was deployed from large research vessels and a small boat. The plasma gun produces sufficient acoustic energy and with its characteristically short pulse length and broad bandwidth it is an attractive sub-bottom profiler, especially in shallow fresh or salt water.     

Petrogenetic Evolution of the Torfaj?kull Volcanic Complex, Iceland I. Relationship Between the Magma Types

The Torfaj?kull volcano, Iceland's largest silicic centre, issituated close to the junction of the active, southerly propagatingEastern Rift Zone and the South Eastern Zone, an older crustalsegment. This paper provides major, trace, and some Sr isotopedata on postglacial (<10000 y) rocks, i.e., tholeiitic magmasof the Eastern Rift Zone and transitional basalts, icelandites,and rhyolites of the Torfaj?kull centre, and assesses the relationshipsbetween the magma types in terms of the development of the Icelandiccrust. Tholeiitic magmas from the Eastern Rift Zone are LILE-enrichedrelative to MORB. They have undergone extensive olivine-plagioclase-clinopyroxenefractionation at low pressures. Compared with the tholeiites,Torfaj?kull transitional basalts show LILE/HFS enrichment andhigher (⁸⁷Sr/⁸⁶Sr)₁ ratios. They define several magmatic lineagesand have equilibrated over a wide range of pressures. Both basalttypes were derived by very small degrees of partial meltingof compositionally similar mantle sources, the main differencebeing that the tholeiites were generated in the spinel Iherzolite,and the transitional basalts in the garnet lherzolite, stabilityfields, a conclusion previously reached by Meyer et al. (1985).The mantle sources may have contained LILE-enriched streaks. Low-pressure differentiation of Torfaj?kull transitional basaltproduced an iceiandite to sub-alkaline rhyolite sequence bycrystal fractionation, the rhyolites representing >90% crystallizationof parental basalts. The rhyolites were emplaced as nine separatelava fields, formed during 11 eruptive episodes. The compositionalrange within each field is limited, and, although similar, theranges define several magmatic lineages. Continued fractionationof plagioclase-alkali feldspar-clinopyroxene-magnetite-apatite-zirconassemblages generated peralkaline rhyolites in certain post-glacialeruptions. Chemical variations in the deposits from the Hrafntinnuskerperalkaline eruption were related predominantly to alkali feldsparfractionation, and the melts were erupted from a zoned magmachamber. All postglacial volcanic rocks at Torfajokull havebeen mantle derived and thus represent new additions to theIcelandic crust.