نتایج جستجو برای: mechanical weathering
تعداد نتایج: 242214 فیلتر نتایج به سال:
Over millions of years, the oxidation of organic carbon contained within sedimentary rocks is one of the main sources of carbon dioxide to the atmosphere, yet the controls on this emission remain poorly constrained. We use rhenium to track the oxidation of rock-bound organic carbon in the mountain watersheds of New Zealand, where high rates of physical erosion expose rocks to chemical weatherin...
In situ quantification of localizedweathering processes on basalt flows inNewMexico andHawaii demonstrates that small-area factors can be more important than other more readily observable factors. Further, it demonstrates that the factorial concept of the Pope Boundary-Layer weathering model is partially solvable, that organicweathering can accentuate glassweathering (with implications for clim...
It has been proposed that increased rates of chemical weathering and the related drawdown of atmospheric CO on the 2 Ž . continents may have at least partly contributed to the low CO concentrations during the last glacial maximum LGM . 2 Variations in continental erosion could thus be one of the driving forces for the glacialrinterglacial climate cycles during Quaternary times. To test such an ...
A model for the combined long-term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the GEOCARB III model [Berner R.A., Kothavala Z., 2001. GEOCARB III: a revised model of atmospheric CO2 over Phanerozoic time. Am. J. Sci. 301, 182–204] for CO2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation o...
–Carbon bound in gibbsite, collected from a residual weathering profile developed on a Paleozoic granite in the Georgia Piedmont, was examined for its C content and found to be geologically young. The study site, located at the Panola Mountain Research Watershed, has developed a granite–saprolite–soil regolith in which C-gibbsite model ages deep within the profile (C-horizon) average about 8000...
Mitochondrial DNA analysis of skeletal material is invaluable in forensic identification, although results can vary widely among remains. Previous studies have included bones of different ages, burial conditions, and even species. In the research presented, a collection of human remains that lacked major confounders such as burial age, interment style, and gross environmental conditions, while ...
The weathering hypothesis states that teen childbearing among African American women is rationalized given greater early exposure to poor physical health and shortened life spans that result from the physical consequences of social inequality in African American communities (i.e., “weathering”). This paper tests a simple yet unexplored test of the basic assumption of the weathering hypothesis: ...
Fossil and phylogenetic evidence indicates legume-rich modern tropical forests replaced Late Cretaceous palm-dominated tropical forests across four continents during the early Cenozoic (58-42 Ma). Tropical legume trees can transform ecosystems via their ability to fix dinitrogen (N2) and higher leaf N compared with non-legumes (35-65%), but it is unclear how their evolutionary rise contributed ...
We tested antlers of Coues white-tailed (Odocoileus virginianus couesi) and mule deer (O. hemionus) in various stages of natural decomposition to determine the degree of weathering that cast antlers could endure and still yield usable DNA. Based on physical characteristics, we partitioned antlers into 7 weathering categories ranging from freshly cast (class 1) to having been exposed to weatheri...
Critical Zone (CZ) research investigates the chemical, physical, and biological processes that modulate the Earth's surface. Here, we advance 12 hypotheses that must be tested to improve our understanding of the CZ: (1) Solar-to-chemical conversion of energy by plants regulates flows of carbon, water, and nutrients through plant-microbe soil networks, thereby controlling the location and extent...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید