analogue modeling of overlapping spreading centers insights into their propagation and coalescence abstract the propagation and segmentation of mid ocean ridges is studied using centrifuged analogue models built with non linear materials the deformation of the brittle ductile model is controlled by diapiric uprise of buoyant analogous asthenospheric material induced by a centrifugal body force this linear upwelling laterally stretches the model mantle that in turn induces failure in the upper layer simulating the brittle crust arrays of fractures initiate within zones of high stress concentration above the diapir fractures propagate laterally in a direction perpendicular to the maximum tensile the minimum principal stress secondary tension cracks initiate in the vicinity of parent fracture tips through going fractures that crosscut the model surface develop by short fractures propagating toward each other and coalescing in different types of patterns the overlap overstep and inclination of fractures developed at the initial stage of extension control their subsequent growth and coalescence non overlapping sub parallel fractures propagate along nearly straight paths and coalesce to produce a single planar fracture if overlapping fractures are parallel they propagate towards each other along curved paths that enclose an intervening elliptical core of intact material fracture curvature in this case results from crack crack interaction and is similar to that of overlapping spreading centers oscs observed along mid ocean ridges overlapping non parallel fractures tend to coalesce by one of their tips propagating sub parallel to the spreading direction toward the other fracture such offsets can serve as models for the development of the orthogonal ridge transform fault patterns common along mid ocean ridges

effect of moisture and temperature conditions on the decay rate of a purple mudstone in southwestern china soil formation and geomorphology are primarily influenced by the rock decay which in turn is strongly determined by moisture and temperature conditions however it remains unclear whether rock decay is dominated by thermal stresses or by hydration disintegration and there is little information on mudstone decay rate in southwestern china this study hypothesized that rock decay is dominated by hydration mechanism and focused on the physical decay characteristics of typical purple mudstones using a combination of field and laboratory based experiments the bedrock of a penglaizhen group j 3 p in yanting county sichuan province southwestern china was exposed and covered with nylon fabric in situ soil depths of 10 20 40 and 60 cm were laid on this nylon fabric in 2003 and the decay rate the quantity of clastic particles 2 mm that were decayed from the bedrock in t km 2 yr 1 under the nylon fabric was measured both in 2005 and 2009 in addition fresh mudstones sampled from the matoushan group k 2 m the tuodian group j 3 t and the lufeng group j 1 l in yuanmou county shuangbai county and lufeng county of yunnan province southwestern china respectively were subjected to alternating applications of moisture temperature and their interaction seven treatments in the laboratory and their decay ratios the mass of decayed rock of 2 mm clastic particles to sampled rock mass in percent were measured in 2010 in the field the decay rate of the bedrock showed a significant p 0 05 positive relationship with both the daily moisture and temperature variation at the interface between the soil and bedrock in the laboratory results showed that the effect of moisture variation but not temperature alternation on rock decay was apparent suggesting that purple rock decay is dominated by hydration mechanism freezing thawing in particular affects the sampled rocks because it causes more spalling and fracturing the j 3 t rock had the highest decay ratio because it had the highest clay mineral content and porosity of the three rock types hierarchical clustering analysis suggested that the variation of moisture content and h2o phase solid or liquid within rock plays a key role in rock decay processes both field and laboratory studies consistently showed that the alteration of wetting drying and freezing thawing as well as moisture content substantially influenced rock decay c 2012 elsevier b v all rights reserved

the role of ph in red stratum mudstone disintegration in the three gorges reservoir area china and the associated micromechanisms abstract the well known slide prone red stratum mudstones in the three gorges reservoir tgr area are currently undergoing sharp changes in i water level driven by the impounding discharging operation of the three gorges dam and ii the rain water h concentration driven by recent rapid industrial agricultural development and these changes are expected to impact geohazards this potential impact emphasizes the importance of understanding the role of ph in the drying wetting disintegration of red stratum mudstones although many investigations have focused on the role of ph in mudstone disintegration the red stratum mudstones in the tgr area differ from mudstones elsewhere and the role of ph has seldom been studied in these rocks this work adds to the limited body of research by 1 experimentally investigating the possible role of ph in red stratum mudstone drying wetting disintegration and 2 revealing the micromechanisms responsible for this role in the experiment six disintegration performance indexes and two mechanical indexes i e particle size gradation slake durability index decay constant surface energy box dimension fractal dimension cohesion and friction angle were monitored throughout the disintegration process a tri piecewise linear fractal model is proposed to better describe the particle size distribution this research shows that the acid enhancements stimulate the disintegration of red stratum mudstones and significantly affect shear strength in comparison alkaline environments inhibit the mudstone fragmentation and slightly degrade the shear strength two possible micromechanisms and three potential effects of acid or alkaline agents are presented to account for the role of ph the findings provide insights into the potential geohazard impacts of sharp changes in the exposure environment i e water level and h concentration of the red stratum mudstones in the tgr area

architecture of normal faults in the rift zone of central north iceland this work examines the architecture and propagation of normal faults that accommodate extension in the rift zone of central north iceland it is based on a structural study of portions of three grabens their normal faults and dilational fractures in basaltic lavas of the fremri namur and dyngjufjol volcanic systems we analyzed the shape throw and dilation along faults in order to infer their possible evolution the shape of throw profiles departs from elliptical varying along each fault with throw being lower at the fault and segment tips propagation of fault segments is accommodated by dilational fractures nucleating at their respective tips segments link by lateral propagation of one or both tips or by the development of intervening linking segments two orders of fault segmentation indicate that the present throw accumulated by many increments as the fault scarps changed their geometries faults have large dilational components weakly correlated with fault throw and length

weathering and soil formation rates based on geochemical mass balances in a small forested watershed under acid precipitation in subtropical china abstract accurate weathering and soil formation rates in natural environment and their quantitative dependences on environmental factors remain poorly understood despite their significance in the understanding of biogeochemical cycling and for the development of sustainable land use strategies in the present study rates of weathering and soil formation on granite and their dependences on acid precipitation were studied in a small forested watershed fengxingzhuang fxz in subtropical china using geochemical mass balance equations and multiple regression analysis atmospheric input from wet and dry deposition and stream output through runoff were monitored from march 2007 to february 2010 the physical and chemical properties of soil and granite rock were also determined the results show that acid precipitation is very severe in the fxz forested watershed by bringing in h both directly from strong acids 741 mol ha 1 yr 1 and indirectly from nitrogen and sulfur transformations 831 mol ha 1 yr 1 which serves as an important driving force for weathering and soil formation the fxz forested watershed currently remains as a net sink for hydrogen ion inorganic nitrogen sulfur potassium and aluminum with a mean of 0 07 1 60 1 48 0 10 and 0 44 g m 2 yr 1 respectively and a net source for dissolved silicon sodium calcium and magnesium with a mean of 5 33 2 95 1 04 and 0 34 g m 2 yr 1 respectively based on geochemical mass balance equations the weathering rate of granite r in the fxz forested watershed is 1 04 0 65 t ha 1 yr 1 but varying according to the changes in environmental conditions such as rainfall amount air temperature and h input within different seasons correspondingly soil formation rate s is 0 95 0 69 t ha 1 yr 1 which equals to 0 066 0 048 mm yr 1 of soil depth suggesting a base for establishing the soil loss tolerance value in the granitic region of subtropical china acid precipitation significantly promotes weathering and soil formation by the input of rainfall and h although air temperature effects occur simultaneously a proposed model that quantitatively describes weathering and soil formation rates is a combined product of rainfall amount x 1 h input x 2 and air temperature x 3 resulting from multiple regressions r 0 00045 x 1 0 026 e 0 0022 x 2 0 012 e 0 0459 x 3 s 0 00035 x 1 0 029 e 0 002 x 2 0 016 e 0 0424 x 3 which improves the prediction from simple linear regression

dike induced faulting in rift zones of iceland and afar geodetic data and field observations demonstrate that the emplacement of dikes in volcanic rift zones frequently generates normal faulting and graben subsidence at the earth9s surface elastic modeling of the vertical ground surface displacements above dikes and faults indicates that the extent of graben subsidence can be achieved only if fault slip extends virtually to or beyond the dike plane at depth a mechanical model that includes dikes and frictional faults shows that dike opening tends to compress and lock faults located to either side of the dike therefore slip extending into or beyond the dike cavity must occur either 1 on faults that intersect the dike near its top above the zone of dike induced compression or 2 on faults that slip ahead of the dike as it propagates laterally data from iceland indicate that slip occurred on deep faults that presumably slipped in advance of the laterally propagating dike

viscoelastic deformation of lunar impact basins implications for heterogeneity in the deep crustal paleo thermal state and radioactive element concentration 1 diverse geological characteristics found for the three major lunar provinces i e the feldspathic highlands terrane fht the south pole aitken terrane spat and the procerallum kreep terrane pkt strongly suggest their distinctly different thermal histories quantitative differences among these provinces in their early thermal histories and crustal radioactive element concentrations however are highly unknown one of the few observables that retain a record of the ancient lunar thermal structure is the viscoelastic state of impact basins this study investigates the long term evolution of basin structures using global lunar gravity field data obtained by kaguya tracking and derives constraints for 1 the paleo thermal state of impact basins and for 2 crustal column averaged radioactive element concentrations for each province our calculation results indicate that impact basins in the central anorthositic region of the fht i e the fht an require a very cold interior dt dr 20 k km 1 on the surface this result strongly suggests that the deep portion of the thick farside highlands crust is highly depleted in radioactive elements th 0 5 ppm indicating that the th rich spa basin floor crust is clearly different from the lower crust underneath the fht an and cannot be accounted for by simple exposure of the lower crust our analysis also indicates that the observed basin structure allows as high as 6 ppm of column averaged th concentration in the crust inside the pkt these results indicate that radioactive element concentrations deep in the crust probably vary greatly region by region similarly to those observed on the surface

determination of easily accessible metal fractions in rocks by batch leaching with acid cation exchange resin the easily accessible fraction of metals in rocks is derived from leaching experiments aliquots of rock powders are mixed with ion exchange resin and distilled water the ph self adjusts to a value of 3 after batch leaching times of 2 48 hr at 70 c the resin is quantitatively separated from the rock powder and eluted with 4 n hno3 the metal contents of the leachates are determined and related to the respective contents of the whole rock the leaching kinetics of each element is related to that of a reference element aluminium is most commonly chosen as a reference element because it is considered to represent the dissolution behaviour of the main rock forming minerals the easily accessible trace element fraction eat is given as the percentage of leached element at 1 al dissolution these eat values are reproducible and independent from grain size and sample resin ratio the procedure is tested on basaltic glass and variably altered gneisses the glass shows congruent release of all metals a slightly crystalline glass of the same chemical composition displays heterogeneous leaching behaviour the leaching kinetics of variably altered gneisses provide insight into the mineralogical siting of elements and their accessibility to fluids consequences for rb sr dating of rocks are discussed

dynamics of volcanic systems in iceland example of tectonism and volcanism at juxtaposed hot spot and mid ocean ridge systems volcanic systems are swarms of tectonic fractures and basalt volcanoes formed as a result of plate pull as the plates are pulled apart associated with the mid ocean ridges and the magma dynamics of the iceland mantle plume most systems are 40 150 km long 5 20 km wide and develop a central volcano they supply magma to all eruptions in iceland data obtained in the last few years have greatly improved our knowledge of their volcanotectonic environment as a result the geometry of the plume is better constrained and the crust previously considered thin 10 km is now modeled as thick 20 40 km depending on the location of the volcanic systems their activity either decreases or increases faulting in the two main seismic zones from this we can infer that emplacement of the feeder dike to the largest historical eruption in iceland that of laki in 1783 increased shear stress in the south iceland seismic zone and almost certainly triggered the largest m 7 1 in 1784 historical earthquake in ic

the effect of land plants on weathering rates of silicate minerals abstract land plants and their associated microbiota directly affect silicate mineral weathering in several ways by generation of chelating ligands by modifying ph through production of co2 or organic acids and by altering the physical properties of a soil particularly the exposed surface areas of minerals and the residence time of water in laboratory experiments far from equilibrium 1 mm oxalate a strong chelator of al has a negligible effect on the dissolution rate of alkali feldspars but some effect on calcic feldspars and olivine by analogy to oxalate the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small except perhaps in microenvironments adjacent to roots and fungal hyphae the effect of ph on silicate mineral dissolution rate depends on ph below ph 4 5 the rate increases with decreasing ph in the circumneutral region the rate is ph independent and at ph values above around 8 the rate increases with increasing ph vegetation should thus cause an increase in weathering rate through the ph effect only where the ph is below 4 5 as an overall generalization the effect of plants on weathering rate through changes in soil solution chemistry is probably small for granitic rocks it may be greater for more mafic rocks it is the release of ca and mg from mafic rocks that has the greatest influence on the global co2 budget the effect of changes in soil physical properties on weathering rate can be major by binding fine particles plants can greatly increase weathering rates in areas of high physical erosion where erosion rates are lower the effect of plants is less clear on long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water a major unknown in estimating the effect of the advent of land plants on weathering rates is the nature thickness particle size distribution permeability of the regolith on the pre silurian continents the indirect effect of vegetation through changing the regional distribution of precipitation may be as important as the direct effects

influence of soil development on the geomorphic evolution of landscapes an example from the transverse ranges of california soil development can significantly influence the topographic evolution of a tectonically deforming mountain piedmont faults and folds associated with the north frontal thrust system deform piedmont sediments of variable compositions along the north flank of the san bernardino mountains the topographic expressions of folds with similar structural characteristics diverge appreciably primarily as a function of differences in sediment composition and associated soil development soils with petrocalcic horizons in limestone rich deposits are resistant to erosion and anticlinal folds form prominent ridges folds forming in granite derived deposits with argillic soil horizons are eroded and or buried and are therefore topographically less pronounced we propose that these landform contrasts can be explained by differences in soil controlled hydrologic and erosion characteristics of deposits without calling upon changes in tectonic style along the mountain front

impacts of simulated acid solution on the disintegration and cation release of purple rock mudstone in southwest china abstract rock disintegration and cation release not only impact on terrestrial geomorphology but also provide nutrients for plants further fractal theory has been widely used to characterize the distribution of fragments in rocks for measuring the degree of disintegration yet the effects of an acidic environment on the trajectory of fractal dimensions of rock disintegration and cation release are not fully clear therefore to investigate the impacts of a solution s ph on disintegration and cation release from the purple rock in southwest china a series of laboratory experiments were performed by soaking the purple rocks in solutions with phs from 2 5 to 7 0 over 24 treatment cycles the results show that the lower the ph the fewer cycles required to obtain a stable fractal dimension the fractal dimension of purple rock under different ph values approached three after 24 treatment cycles until decay ratios the mass of decayed rock of 90 acidic treatment increased cation release especially when the ph value of the solution was below 3 5 compared with a deionised water soaking solution the amounts of k na ca2 and mg2 were increased by 4 92 1 27 1 12 and 1 08 times with ph values of 2 5 3 5 4 5 and 5 6 soaking solution respectively at the disintegration stage in addition the release of ca2 and mg2 were more sensitive to acid than that of k and na and ca2 weathering occupied the dominant position in the cation weathering rates moreover due to disintegration processes that transformed each rock sample into fragments fresh surfaces were exposed from which cations were liberated creating a significant p

crust generated above the iceland mantle plume from continental rift to oceanic spreading center since the north atlantic continental breakup in the early tertiary the process of rifting above a mantle plume has produced large thicknesses of igneous crust we report results of an integrated offshore onshore seismic study of the crust and upper mantle along a transect of the aseismic faroe iceland ridge between the continental fragment beneath the faroe islands and the present day spreading center in northeast iceland normal incidence seismic data provide an image of the uppermost crust which is complemented by a velocity model from streamer refraction analyses these data together image four sedimentary basins up to 400 m deep along the crest of the ridge the streamer refraction velocity model in turn forms the uppermost section of a full crustal velocity model derived from travel time modeling of air gun and explosive data the compressional to shear wave velocity ratio in the crust of the faroe iceland ridge is 1 77 0 02 similar to that of eastern iceland the moho beneath the faroe iceland ridge lies at a depth of 25 30 km crust of 25 30 km thickness requires an upper mantle potential temperature elevated 200 250 c above normal if formed by passive adiabatic decompression melting of the mantle or a somewhat less elevated temperature if as is likely there is a component of active convection in the underlying mantle plume core

comparison of seafloor tectonic fabric at intermediate fast and super fast spreading ridges influence of spreading rate plate motions and ridge segmentation on fault patterns we have conducted a comparative study of the tectonic morphology of young seafloor using seamarc ii side scan sonar surveys of the intermediate spreading ecuador rift the fast spreading east pacific rise epr 8 30 10 n and the super fast spreading epr 18 19 s we find that characteristics of fault populations are not only a function of spreading rate but also vary along axis within individual ridge segments i e with proximity to large and short offset discontinuities we also find that fault azimuths can be used to examine plate kinematics on a finer scale than can be obtained using magnetic data alone most of the variation in fault populations with spreading rate can be explained by an inverse relationship between spreading rate and thickness of the brittle layer for example regions of super fast spreading are characterized by the largest numbers of short faults the smallest average fault spacing and throw and the highest fault density in addition clusters of short closely spaced antithetic faults subsidiary to long master inward dipping faults are common within the super fast spreading area presumably the result of a thinner weaker brittle layer faults facing away from the ridge axis occur in increasing numbers with increasing spreading rate such that few outward facing faults are found at slow to intermediate rates and approximately equal numbers of inward and outward facing faults are observed at the fastest rates rapid thickening of the brittle layer with distance from the ridge may account for the predominance of inward facing faults at slower spreading rates outward facing faults at all spreading rates have shorter mean lengths and lower vertical offsets these differences may reflect the shorter time outward facing faults are active owing to increasing strength of the lithosphere with distance from the ridge fault lengths and spacings in all areas approximate exponential distributions the extensional strain represented by fault populations is calculated from the displacement and length distributions of faults and strain estimates of 4 are obtained for each area assuming that fault spacing reflects fracture depth extent where faults initiate we infer a brittle layer thickness of 1 km when faulting begins fault populations are examined for ridge segment scale variations in amagmatic extension we see evidence for greater amagmatic extension associated with long term reduced magma supply along the eastern third of the ecuador rift evidence for local increased brittle extension is also found within 15 km of transform faults discordant zones left by overlapping spreading centers oscs are characterized by low fault abundances at oscs discrete events of ridge tip propagation may accommodate extension taken up elsewhere along the ridge by normal faulting fault azimuths do appear to be useful indicators of plate motion within the epr 8 30 10 n area fault trends record a recent change in pacific cocos plate motion 3 6 at 1 m y consistent with magnetic anomaly and fault lineation data from elsewhere along the northern epr within the ecuador rift fault azimuths scatter within 3 of predicted trends and are consistent with constant spreading about one pole for the past 1 5 m y

contribution of volcanism and tectonism to axial and flank morphology of the southern east pacific rise 17 10 17 40 s from a study of layer 2a geometry multichannel seismic images from the east pacific rise 17 10 17 40 s are used to study the geometry of seismic layer 2a in the near axis region wave equation datuming is applied to stacked common midpoint data to remove the distorting effects of seafloor topography on the layer 2a event processed stacks are compared with seafloor morphology and tectonic fabric imaged in side scan sonar data assuming layer 2a corresponds with the extrusive crust these data are used to study the relationship between volcanism and tectonism in the accumulation of the extrusive layer and to assess the contribution of extrusives to ridge crest and ridge flank morphology we find variations in axial thickening of layer 2a which imply twofold variation in the width of the extrusive layer accumulation zone as well as systematic changes in the pattern of accumulation of this layer on the ridge flanks the layer 2a horizon mimics abyssal hill relief consistent with a horst and graben origin for this topography short wavelength variations in the thickness of layer 2a are superimposed on this relief which we attribute to volcanic modification of tectonic topography at the edge of the neovolcanic zone the integrated off axis thickness of layer 2a is correlated with ridge cross sectional area and indicates persistent 100 000 years spatial gradients in extrusive layer thickness systematic changes in the cross axis shape of the ridge observed over distances of 5 10 km cannot be attributed to the extrusive layer and it appears that axial structure beneath the volcanics governs the cross axis morphology of the ridge

rock mass characterization by fractal dimension fractal theory is used in the present study to develop a more reliable method for rock mass characterization field studies have been carried out in opencast mines of dolomite limestone fluorite sandstone and shale in coalmines fractal dimension of blasted fragments dfrag and in situ rock blocks din situ is calculated using size distribution curves according to schumann s model based on the co relation between uniaxial compressive strength ucs and dfrag it is observed that change in fractal dimension is nominal beyond the ucs value of 20 from the co relation between bieniawaski s rock mass rating rmr and din situ it is found that there is a sharp increase in fractal dimension for rmr greater than 40 co relation between rmr and dfrag din situ shows that as rmr increases dfrag din situ ratio decreases rock mass classification based on fractal geometry is suggested

quantitative fault studies on the east pacific rise a comparison of sonar imaging techniques a synthesis is presented of published statistics on the lengths scarp heights and spacing of normal faults on the flanks of the east pacific rise epr between 19 s and 21 n nine data sets are included which were collected at different times employing one of four different sonar mapping systems the scripps deep tow instrument seamarc i seamarc ii and gloria with widely ranging data collection capabilities the epr in this region is morphologically quite similar and in some cases the data sets were obtained from the same area of the seafloor it is assumed therefore that data collection procedure and system resolution have had a greater influence on the fault statistics observed than varying tectonic processes we try to account for these sampling effects such that quantitative comparisons of fault development at midocean ridges may then be made we discuss the problem of identifying faults in sonar images and the errors associated with measurements of the relevant parameters we also investigate the statistical properties of the fault populations and derive expressions for correcting observed values of the population means at finite resolution to obtain the corresponding values at infinite resolution the theoretical predictions compare well with the results of a decimation procedure applied to real data sets to simulate diminishing resolution we also discuss the effects that surveying geometry can have on the interpretation of fault lengths the data synthesis is augmented by an analysis of the correlation between scarp height and fault length for areas near 3 5 s and 12 n on the epr the correlation which we find to be linear is used to estimate 1 the minimum operational fault target size for each of the four mapping systems and 2 the topography due to faulting in an area where only fault lengths are known

on the persistence of weathering abstract the term weathering has been in use for a very long time but it has come to mean different things to different people and hence as scientific short hand it no longer functions here we question the tenets underpinning the most common usage of the term and note that the climate process linkage implicit to the term is often missing and amounts to misdirection rather than climate as the primary driver behind specific weathering processes it is argued that rock properties constitute the dominant control further a case is made for reconsideration of our present bipartite mechanical chemical division of weathering processes and of the weathering processes currently deemed to be those that occur as process studies become evermore reductionist in nature so the functionality of the term comes more and more into question the linkage between process and landform the scaling up attribute is seen as a current weakness and one that will become more confusing as reductionist approaches continue as a way forward it is suggested that weathering stripped of specific preconceived notions of specific processes be envisaged as a function of energy transfer and be investigated in that light identification of new processes as well as restructuring of known processes particularly when considering weathering on other planets is a potential outcome of such an approach with a process foundation rooted in energy transfer rock decay provides a better umbrella term and liberates researchers from the inescapable conceptual baggage implicit to the term weathering

the calculation of base cation release from mineral weathering in soils derived from palaeozoic greywackes and shales in upland uk abstract weathering rates for soil profiles and catchments developed on greywacke and shale parent materials have been calculated using four common methods cited in the literature conservative element depletion the profile model catchment input output mass balance budgets and the magic model a comparison of the results suggests that for any single method the results are consistent however comparison between methods suggests a greater variation and systematic difference between weathering rates calculated from soil profiles compared to those calculated on a catchment basis the reason for these differences and the implications for acidification and critical load work are discussed

the effect of ph of water and mineralogical properties on the slake durability degradability of different rocks from the lesser himalaya india slake durability is an important geotechnical parameter and is a measure of degradability of rocks due to the process of mechanical and chemical breakdown it is closely related to the mineralogical composition and the texture of the rocks in this paper mineralogical examination along with slake durability tests under variable ph conditions both in acidic and alkaline environments on the limestone shale and siltsone were evaluated to understand the relationship between mineralogy and the degradability of rocks the study revealed that rocks rich in calcium carbonate and or magnesium carbonate are adversely affected in the acidic environment whereas the rocks rich in quartz feldspar and muscovite are independent of the ph of the slaking fluid which in turn is more influenced by the texture of the constituent minerals it has also been observed that fine grained rocks are more susceptible to degrade in comparison to the coarse grained rocks

geometry formation and development of tectonic fractures on the reykjanes peninsula southwest iceland abstract a study was made of 903 fractures most of which are of postglacial age on the reykjanes peninsula some 120 fractures belonging to the vogar fissure swarm he completely within the same postglacial lava flow and were studied in great detail for the vogar fractures 75 are pure tension fractures and 25 are normal faults the average length of the vogar fractures is 611 m the average width is 0 6 m the average spacing measured perpendicular to the average strike n54e of fractures is 456 m the estimated average depth is of the order of several hundreds of meters and the average throw of the faults is 2 3 m all major fractures on the peninsula appear to have formed by coalescence of smaller fractures as a result of absolute tensile stress the fractures group into four fissure swarms each being a part of a volcanic system which it is proposed is fed by an elongated partially molten magma reservoir located at a depth of about 8 km beneath the peninsula it is suggested that a slight magmatic pressure increase in these reservoirs and resulting uplift and tensile stress at the surface is the main cause of postglacial fracture formation

formation of segmented normal faults a 3 d perspective the interpretation of fault kinematics from geometric data is an essential step in developing an understanding of the growth of fault systems constraints on fault geometry are however often restricted to 2 d maps or cross sections in this article we consider the extent to which kinematic interpretations of faulting benefit from a 3 d rather than 2 d geometrical perspective concentrating on relay zones and segmented normal fault arrays we suggest that very different interpretations of their evolution arise from the recognition that the propagation directions of faults and fault segments will rarely be contained within the inspection plane of 2 d data a 3 d perspective favours an interpretation in which the segments of a fault array are kinematically interrelated from their initiation individual segments in such systems may link into a single fault surface out of the plane of inspection or may be unconnected in 3 d we argue that this interpretation which conflicts with the often suggested model of incidental overlap of originally isolated faults should be the preferred model for the generation and growth of segmented normal fault arrays

quantitative determination of the effect of temperature on mudstone decay during wet dry cycles a case study of purple mudstone from south western china although temperature is considered a key factor influencing rock decay little is known about the quantitative relationship between a rock s decay rate and temperature which makes it difficult to quantitatively predict the rate of rock decay under varied temperature during wetting drying cycle conditions thus the aim of the present paper was to observe the decay rate of various purple mudstones and to develop a model with which to calculate their decay rates under varied temperature conditions three types of purple mudstone were sampled from the tuodian group j 3 t matoushan group k 2 m and lufeng group j 1 l located in the chuxiong district of yunnan province south western china all samples were manually cut into cubes of 50 x 50 x 50 mm before being subjected to 39 wetting drying cycles in a 2 mm sieve under artificial constant temperature natural daily temperature variation and artificial temperature alternation minimum and maximum treatments in the laboratory decay rates were calculated by weighing the mass remaining in the sieve after each treatment cycle the results showed that the decay rates of the tested rocks rose with an increase in temperature and temperature difference maximum minimum with the rank order of decay rate being j 3 t k 2 m j 1 l quantitative analysis revealed rock decay rate to be significantly related to temperature by a power function and exponentially related to temperature difference our results suggested that temperature difference has a stronger effect on purple mudstone decay than that of temperature magnitude during the wetting drying processes c 2015 elsevier b v all rights reserved

determination of mineral surface area in relation to the calculation of weathering rates the release of base cations by the weathering of soil minerals provides the primary buffer against the detrimental impact of acid deposition on the soil the rate of release of base cations will be governed by mineral composition and the exposed surface area of mineral grains in theory it is possible to calculate the surface area of a mixture of grains on the basis of particle size and geometry an alternative is the use of correlations it has been suggested sverdrup et al 1990 nordic council of ministers 98 that mineral surface area can be related to soil particle size distribution via a simple empirical equation this contribution compares the surface areas of soils as calculated by geometric equations and sverdrup s equation with actual bet measurements the equations tested do not appear to be applicable to the soils used in the current work modified versions of the equation suggested by sverdrup applied to subsets of our data based on sites and soil types yield better results for the soils used in the current work statistically significant improved fits are obtained when soil mineralogy as well as soil texture is taken into account