Geology

The Cenozoic evolution of South American topography is marked by episodes of large-scale uplift and subsidence not readily explained by lithospheric deformation. The drying up of the inland Pebas system, the drainage reversal of the Amazon river, the uplift of the Sierras Pampeanas and the uplift of Patagonia have all been linked to the evolution of mantle flow since the Miocene in separate studies. Here we investigate the evolution of long-wavelength South American topography as a function of subduction history in a time-dependent global geodynamic model. This model is shown to be consistent with these inferred changes, as well as with the migration of the Chaco foreland basin depocentre, that we partly attribute to the inboard migration of subduction resulting from Andean mountain building. We suggest that the history of subduction along South America has had an important influence on the evolution of the topography of the continent because time-dependent mantle flow models are consistent with the history of vertical motions as constrained by the geological record at four distant areas over a whole continent. Testing alternative subduction scenarios reveals flat slab segments are necessary to reconcile inferred Miocene shorelines with a simple model paleogeography. As recently suggested, we find that the flattening of a subduction zone results in dynamic uplift between the leading edge of the flat slab segment and the trench, and in a wave of dynamic subsidence associated with the inboard migration of the leading edge of flat subduction. For example, the flattening of the Peruvian subduction contributed to the demise of Pebas shallow-water sedimentation, while continental-scale tilting also contributed to the drainage reversal of the Amazon River. The best correlation to P-wave tomography models for the Peruvian flat slab segment is obtained for a case when the asthenosphere, here considered to be 150 km thick and 10 times less viscous than the upper mantle, is restricted to the oceanic domain.

Assateague Island, MD-VA has experienced many breaching events throughout its history as a result of extratropical and tropical storm impacts. An analysis of historical documents (e.g. historical maps and NOS & NOAA T-sheets), aerial imagery (e.g.
true color and false-color infrared), LIDAR data, and an in-depth literature review of former tidal inlets of Assateague Island produced an updated inlet chronology of the mixed-energy, wave-dominated barrier island. Eleven former tidal inlets and breach zones were identified from north to south: Northern Assateague Breach zone, North Sinepuxent Inlet, Sandy Point Inlet, North Beach Inlet, Sinepuxent Inlet, Fox Hills and Winter Quarter Breach zone, Slough Inlet, Green Run Bay Inlet, Green Run Inlet, Cherry Tree Inlet, and Swan Pool Breach zone. Evidence of former tidal inlets and breaches include such geomorphic features as recurved spit ridges, relict flood-tidal
deltas and flood channels, inlet channel scars (topographic low areas of immature vegetation), relict inlet ponds, and inlet-closure ridges. Inlet-closure ridges were also utilized to develop a five-stage life-cycle model of the former Green Run Inlet, as
well as a three-stage life-cycle model of the former Sinepuxent Inlet. Inlet-closure ridges are more subtle than recurved spit ridges, with the tallest inlet-closure ridge being equivalent in height to the shortest recurved spit ridge. Recurved spit ridges
were also observed decreasing in height toward the inlet throat within the former inlets. In total, 34% of Assateague Island is estimated to contain tidal inlet fill.

На основе анализа литературы по изучению овражной эрозии на территории Саратова и его окрестностей отмечены основные методики и результаты исследований за более чем 130-летний период, а также направления современного изучения. Определен современный уровень изученности овражной эрозии территории

We present a method for determining soil-bound organic carbon, which we define as soil carbon having no carbonate, charcoal, litter fragments, or root fragments. Carbonates are removed by exposing the soil sample to acid vapor until the δ13C values reach a constant value. Charcoal, litter, and root fragments are removed by flotation. Rocks and other large debris are removed by inspection and sieves. Organic carbon and nitrogen concentrations of the processed soil are determined quantitatively using high-temperature flash combustion gas chromatography. At the Duke Free-Air CO2 Enrichment (FACE) site, our technique showed that the variability in litter-free soil was less than the variability in soil that contained litter and root fragments. Isolating the soil-bound fraction reduced the uncertainty of soil carbon uptake due to CO2 enrichment by a factor of about 20. This analytical technique will help researchers quantify the flux of carbon between soil and the atmosphere and discern how changing climate, CO2 levels, nutrient availability, and land use alter this flux.

This research adds data to the growing body of literature examining how agricultural practices influence soil carbon levels and crop yield. We collected 20 soil samples each from three adjacent plots of land on a farm in Brighton, Iowa (60 samples total). These cultivated sites all shared the same silty loam soil characteristics, and included three different methods of soybean farming: conservation tillage (also known as no-till drilling), conventional tillage, and organic farming, where tillage is used to excess. The no-till drill method produced 15% more soybeans than conventional tilling and 110% more soybeans than the organic method. The mean levels of soil carbon were the highest in the no-till drill plots. The drill method plots had 41% more soil carbon than conventionally-tilled plots and 48% more carbon than the organic plots. The carbon difference is statistically significant (P=0.01). The drill method produced the highest
crop yield and preserved more soil organic carbon than either the conventional or organic methods.

Due to the domestic use of the river water, the rivers have become highly contaminated and is currently not a clean source for drinkable water. This provides a need to find an alternative source of clean, drinkable water. We focused on the highland catchment areas to derive the needed drinkable water  in  hope  this  would  relieve  the  Ethiopian  people's  needs.  This  work  is  made  of  six chosen drainage  sub-basins  of Ethiopia seeking  for  clean  water resource.  The study  shows that these sub- basins  receive  abundant  volumes  of  water  that  reaches  an  average  between  0.78  billion to 10.02 billion  cubic  meters annually.  To  use this  water properly this morphometric analysis seeks to find the optimum location for constructing dams.
http://gisedu.colostate.edu/WebContent/nr505/ethiopia2009/nr505_fall09_team13_Amrouni_Newby/index.html

در این مقاله به بررسی زمین ساخت فعال نسبی حوضه صوفی چای بر اساس شاخص های زمین ریختی به وسیله نرم افزار Global Mapper و Arc GIS پرداخته شده است. شاخص های محاسبه شده عبارتند از: شاخص طول-شیب رودخانه(SL)، انتگرال فرازسنجی (Hi)، نسبت عرض کف دره به ارتقاع آن (Vf)، شکل حوضه زهکشی (Bs)، وپیچ و خم پیشانی کوه (Smf)، عدم تقارن حوضه زهکشی(Af) و در نهایت بررسی این ویژگی ها با هم به عنوان شاخص زمین ساخت فعال نسبی (Iat) که ترکیبی از شاخص های بالا است محاسبه می شود. منطقه مورد مطالعه در جنوب آتشفشان سهند در شمال غرب ایران قرار دارد این مناطق به علت پر جمیت بودن و وجود ساختار ها و گسلهای زیاد که عامل بروز حوادث و بلایای طبیعی زیاد درگذشته بوده است، بستری مناسبی برای بررسی زمین ساخت فعال نسبی منطقه و پیش گیری از چنین حوادثی در آینده است. حوضه صوفی چای به لحاظ سطح فعالیت نسبی تکتونیکی در مرحله فعال تکتونیکی قرار دارد و بر اساس شواهد بدست آمده از بالا دست حوضه به سمت پایین دست از شدت فعالیت تکتونیکی¬کاسته می شود.