Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil

Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,...     

Land Changes Fostering Atlantic Forest Transition in Brazil: Evidence from the Paraíba Valley

The Atlantic Forest biome has only 13 percent of its pristine vegetation cover left. This article analyzes the consequences of land changes on forest cover in the Paraíba Valley, São Paulo state, Brazil, from 1985 to 2011. Multitemporal satellite image classifications were carried out to map eight land use and land cover classes. The forest cover increased from 2,696 km² in 1985 to 4,704 km² in 2011, mostly over areas of degraded pastures. The highest rates of afforestation were observed within protected areas around eucalyptus plantations. On the other hand, deforestation processes were concentrated on areas covered by secondary forests. Socioeconomic changes taking place in particular Brazilian settings, such as industrialization and agricultural modernization, allied to the Paraíba Valley's natural biophysical constraints for agricultural production, have led the region to experience a remarkable case of forest transition.     

Broadening participation,creating community,and learning that it never goes as planned

This paper presents the experience of a service-learning course which used community geography to study a proposed research and community center in DeKalb, IL. The center was proposed as a jointly-developed project by the Northern Illinois University and local governmental entities. The original goal of the course was to explore the viability of the proposed project and solicit feedback from the community through traditional engaged planning and public participation. As students began interacting with university and residential communities, it became clear that both communities had input for the center, and found similarities in their experiences and perceptions. While noted divisions in interest groups are known in DeKalb, both communities found themselves surprisingly interested in meaningful discussion to better understand each other through their shared experiences. In response, our theoretical approach shifted to community geography. Students, university employees, and local residents introduced and analyzed questions together as researchers and participants, and developed recommendations to address shared concern. Students then prepared a report advocating for those concerns to submit to university and community leaders. Following the evolution of this project, this paper presents lessons learned and areas for application of community geography as a pedagogical technique, as an important component of geography curriculum, and as a research framework for town-gown relationship inquiry.

     

Numerical modeling of Maranhão Gulf tidal circulation and power density distribution

Ocean Dynamics - Marine resources are outstanding among renewable energy for their wide occurrence and diverse possibilities of exploitation. The tidal resource can be harnessed by the use of both...     

Paleo-stratigraphic permeability anisotropy controls supergene mimetic martite goethite deposits

The Hamersley Basin in Western Australia is one of the world's largest iron ore-producing regions, hosting two types of ore in banded iron formations: the high-grade martite-microplaty haematite and the supergene martite-goethite ores. With the high-grade ores almost entirely mined in the last decade, the supergene ores have more recently become the dominant resource of interest. Consequently, understanding the genesis of these martite-goethite deposits is a critical step for exploration. Yet, although various models exist, there is still no consensus on how these mineral resources formed, complicating the prediction of resource volume and location. Here, we show that the paleo-stratigraphic permeability anisotropy (with higher permeability along strata than across) controls the supergene mimetic enrichment transport process and, subsequently, the mineralisation distribution. We introduce a flow model that implicitly represents strata with a potential function that orients the permeability tensor accurately. The numerical solver uses automatic mesh adaptivity to deliver robust solutions. By accurately reproducing the mineralisation patterns in specific deposits, we identify and quantify the paleo-water table level and permeability anisotropy ratio as the two main controlling parameters for the mineralisation distribution. These insights provide new timing constraints for the mineralisation and the physical process of iron enrichment, suggesting much more potential mineralisation volume in the paleo-reconstructed zones than previously anticipated. These flow models allow us to draw geological conclusions with few a priori assumptions required for the genetic model in which the transport component is dominant. The predictive power of this methodology will allow targeted drilling to narrow down the prospective areas and lower exploration costs. Furthermore, the methodology's generality applies to other commodities in sedimentary basins involving supergene processes and will improve our understanding of various genetic models.     

Submarine groundwater discharge: A large, previously unrecognized source of dissolved iron to the South Atlantic Ocean

This paper reports the initial results of a study of groundwater and coastal waters of southern Brazil adjacent to a 240 km barrier spit separating the Patos Lagoon, the largest coastal lagoon in South America, from the South Atlantic Ocean. The objective of this research is to assess the chemical alteration of freshwater and freshwater–seawater mixtures advecting through coastal permeable sands, and the influence of the submarine discharge of these fluids (SGD) on the chemistry of coastal waters. Here we focus on dissolved iron in this system and use radium isotopic tracers to quantify SGD and cross-shelf fluxes. Iron concentrations in groundwaters vary between 0.6 and 180 μM. The influence of the submarine discharge of these fluids into the surf zone produces dissolved Fe concentrations as high as several micromolar in coastal surface waters. The offshore gradient of dissolved Fe, coupled with results for Ra isotopes, is used to quantify the SGD flux of dissolved Fe from this coastline. We estimate the SGD flux to be 2 × 10⁶ mol day^− 1 and the cross-shelf flux to be 3.2 × 10⁵ mol day^− 1. This latter flux is equal to about 10% of the soluble atmospheric Fe flux to the entire South Atlantic Ocean. We speculate on the importance of this previously unrecognized iron input to regional ocean production and on the potential significance of this source to understanding variations in glacial–interglacial ocean production.     

Bragg diffraction and the iron crust of cold neutron stars

If cooled-down neutron stars have a thin atomic crystalline–iron crust, they must diffract X-rays of appropriate wavelength. If the diffracted beam is to be visible from Earth (an extremely rare but possible situation), the illuminating source must be very intense and near the reflecting star. An example is a binary system composed of two neutron stars in close orbit, one of them inert, the other an X-ray pulsar. (Perhaps an “anomalous” X-ray pulsar or magnetar, not powered by gas absorption from the companion or surrounding space, would be the cleanest example.) The observable to be searched for is a secondary peak added (quasi-) periodically to the main X-ray pulse. The distinguishing feature of this secondary peak is that it appears at wavelengths related by simple integer numbers, λ,λ/2,λ/3,…,λ/n because of Bragg’s diffraction law.