Game-Based Virtual Worlds as Decentralized Virtual Activity Systems

There is widespread interest in the development and use of decentralized systems and virtual world environments as possible new places for engaging in collaborative work activities. Similarly, there is widespread interest in stimulating new technological innovations that enable people to come together through social networking, file/media sharing, and networked multi-player computer game play. A decentralized virtual activity system (DVAS) is a networked computer supported work/play system whose elements and social activities can be both virtual and decentralized (Scacchi et al. 2008b). Massively multi-player online games (MMOGs) like World of Warcraft and online virtual worlds like Second Life are each popular examples of a DVAS. Furthermore, these systems are beginning to be used for research, development, and education activities in different science

Is Australia a tectonically stable continent? Analysis of a myth and suggested morphological evidence of tectonism

Occasional references to the relative tectonic instability of the Australian continent have been published over the last hundred years or so. Youthful tectonic forms were described from various parts of the continent throughout that period. Despite this, it was repeatedly claimed that the shield lands in particular were tectonically stable, and as recently as this century reference has been made to a concept embracing a tectonically inert continent. However, some 60 years ago, the accumulated evidence convinced E.S. Hills that in Australia all land surfaces, including the shield lands, and even recent alluvial plains, were tectonically disturbed. This conclusion was reinforced by analyses of seismicity and faulting; by regional geological mapping that revealed widely distributed tectonic forms and especially fault-related features, many of them of neotectonic age; by technological advances that allow faulting episodes to be closely dated; by the recognition of underprinting; and by the realization that many minor forms, previously unrecognized or attributed to other mechanisms or processes, are associated with crustal stress and are of tectonic origin. Thus, while Australia is a relatively stable continent, it is subject to widespread small-magnitude earth movements. Ironically, in view of earlier thinking, neotectonic forms may be better developed and preserved on the shields than elsewhere.C. R. Twidal

The Rhyolitic Plateau of the Marifil Formation (Jurassic): A Gondwana Paleosurface in the Southeastern Portion of the Northern Patagonian Massif

Along the southeastern border of the Northern Patagonian Massif of the provinces of Río Negro and Chubut, an extensive surface is presently called the “Rhyolitic” or “Ignimbritic Plateau.” This large geomorphological unit has a geographical extension which exceeds 50,000 km2 and it is located between 40°30′ and 44° lat. S and between the Atlantic Ocean coast and 67°30′ long. W. It is characterized by a smooth topography of low and rounded hills, shallow endorheic basins, and a poorly integrated drainage network. The drainage network is mostly nonfunctional and roughly coincident with the bedrock fracture system. Bedrock is almost exclusively composed of the acid volcanic and pyroclastic rocks of the Marifil Formation of Early to Middle Jurassic age. A significant proportion of the identified positive landforms present form and nature very similar to that of “bornhardts,” as defined by Twidale (Revista de la Asociación Geológica Argentina 62(1):139–153, 2007), basically for granites. Bornhardts are uncovered dome hills (Twidale, Revista de la Asociación Geológica Argentina 62(1):139–153, 2007) which are usually frequent in Gondwana landscapes (Fairbridge, Encyclopedia of geomorphology. Ronald, New York, 1968). Furthermore, the ubiquitous presence of “corestones” (isolated, large, rounded boulders), which are taken as indicators of an ancient, deep weathering front, supports the hypothesis that these paleosurfaces were generated by long-term, intense chemical weathering processes. The deep weathering would have occurred over at least 25 Ma, between the Middle and Late Jurassic, under a hot and moist paleoenvironment and under extremely stable tectonic conditions. The mobilization, denudation, and later sedimentation of the regolith/saprolite formed under such conditions would have taken place during several erosion episodes, mostly under tectonic forcing, between the Late Jurassic and the Late Cretaceous. The important clay and other secondary mineral accumulations (some of them significant sources of uranium) in the region would have a direct genetic relationship with the development of these paleosurfaces. From the Late Miocene onwards, the colder and drier conditions that were imposed in the region by the uprising Andes and the establishment of mountain glaciers and ice caps during numerous glaciations allowed the modification of this landscape by hydro-eolian processes which generated the widely distributed endorheic depressions (locally known as “bajos sin salida”) by deflation and occasionally reworked the surviving rocky hills by abrasion.Fil: Martinez, Oscar A.. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Rabassa, Jorge Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin