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Rock Weathering (rock + weathering)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

DIFFERENTIAL ROCK WEATHERING IN THE ,VALLEY OF THE BOULDERS', KÄRKEVAGGE, SWEDISH LAPLAND

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2008
ROBERT G. DARMODY
ABSTRACT. Kärkevagge is an alpine valley in the low arctic of Swedish Lapland. It is named after, and famous for, its large deposit of immense (c. 10,15 m) boulders that almost fill the lower valley. Above the boulder deposit, on the flanks of the valley, are more recent and generally much smaller (c. 1,3 m) individual boulders that have fallen from the valley-wall cliff face, presumably from post-glacial valley-side unloading. Some of these smaller boulders are seemingly fresh and unweathered while others have been reduced to no more than mounds in the tundra. These boulders must be younger than the larger, lower giant boulder deposit, but are not particularly recent rockfalls as they are partially buried in colluvium. Comparisons of mineralogy and chemistry indicate that the possibility exists that the incompetent, ,rotten' rocks, if not considerably older than their competent neighbors, are inherently self-destructive. They have evidence of increased sulfur content, which is a proxy for pyrite, a known weathering accelerant in Kärkevagge. [source]

Rock weathering creates oases of life in a High Arctic desert

ENVIRONMENTAL MICROBIOLOGY, Issue 2 2010
Sara Borin
Summary During primary colonization of rock substrates by plants, mineral weathering is strongly accelerated under plant roots, but little is known on how it affects soil ecosystem development before plant establishment. Here we show that rock mineral weathering mediated by chemolithoautotrophic bacteria is associated to plant community formation in sites recently released by permanent glacier ice cover in the Midtre Lovénbreen glacier moraine (78°53,N), Svalbard. Increased soil fertility fosters growth of prokaryotes and plants at the boundary between sites of intense bacterial mediated chemolithotrophic iron-sulfur oxidation and pH decrease, and the common moraine substrate where carbon and nitrogen are fixed by cyanobacteria. Microbial iron oxidizing activity determines acidity and corresponding fertility gradients, where water retention, cation exchange capacity and nutrient availability are increased. This fertilization is enabled by abundant mineral nutrients and reduced forms of iron and sulfur in pyrite minerals within a conglomerate type of moraine rock. Such an interaction between microorganisms and moraine minerals determines a peculiar, not yet described model for soil genesis and plant ecosystem formation with potential past and present analogues in other harsh environments with similar geochemical settings. [source]

Rock weathering promoted by embryonic soils in surface cavities

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2002
G. Certini
Summary The upper surfaces of trachyte outcrops and boulders in Tuscany and Latium have numerous cavities. The cavities have formed from the dislodgement of xenoliths and, if properly oriented, they collect water and accumulate mineral and organic debris. There is no drainage, and water stays in them for a long time, inducing a severe hydrological regimen, but supporting a variety of living organisms such as cyanobacteria, green algae and insects. The humic substances produced by the humification of organic matter and the organic acids released by organisms alter the underlying rock, thereby deepening and enlarging the cavities. Following the dissolution of the glassy cements, crystals detach from the matrix to join the accumulated material, where they are progressively comminuted and partly changed into clay minerals. With time, these accumulations increase in thickness sufficiently to allow the establishment of vascular plants and the development of horizons so as to become embryonic soils. We sampled the material from several such cavities and determined its chemical and mineralogical composition. We conclude that cavities contain miniature ecosystems supported by the tiny bodies of soil in them. [source]

Processes controlling rapid temperature variations on rock surfaces,

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2010
Jamie L. Molaro
Abstract In arid environments, thermal oscillations are an important source of rock weathering. Measurements of temperature have been made on the surface of rocks in a desert environment at a sampling interval of 0·375,s, with simultaneous measurements of wind speed, air temperature, and incoming shortwave radiation. Over timescales of hours, the temperature of the rock surface was determined primarily by shortwave radiation and air temperature, while rapid temperature variations, high dT/dt, at intervals of seconds or less, were determined by wind speed. The maximum values of temperature change and time spent above 2°C,min,1 increased at high measurement rates and were much higher than previously reported. The maximum recorded value of dT/dt was 137°C,min,1 and the average percentage time spent above 2°C,min,1 was ,70 ± 13%. Maximum values of dT/dt did not correlate with the maximum values of time spent above 2°C,min,1. Simultaneous measurements of two thermocouples 5·5,cm apart on a single rock surface had similar temperature and dT/dt values, but were not correlated at sampling intervals of less than 10,s. It is suggested that this is resulting from rapid fluctuations due to small spatial and timescale wind effects that are averaged out when data is taken at longer sampling intervals, ,10,s or greater. Published in 2010 by John Wiley & Sons, Ltd. [source]