earth and mars water inventories as clues to accretional histories abstract the earth has 2 7 km of water on its surface its mantle contains at least 150 ppm water and probably significantly more depending on the amount of undepleted mantle and subducted crustal water that is present geologic evidence suggests that a few hundred meters of water are close to the martian surface but evidence from snc meteorites indicates that the martian mantle is very dry containing no more than about 35 ppm water part of the difference in water content of the mantles of the two planets is attributed to plate tectonics however the earth s mantle appears to contain at least several times the water content of the martian mantle even accounting for plate tectonics we attribute the difference to two possible causes the first possibility is that melting of the earth s surface during accretion as a result of the development of a steam atmosphere allowed impact devolatized water at the surface to dissolve into the earth s interior in contrast because of mars smaller size and greater distance from the sun the martian surface may not have melted so that the devolatilized water could not dissolve into the surface a second and preferred possibility is that mars like the earth acquired a late volatile rich veneer but it did not get folded into the interior as with the earth but instead remained as a water rich veneer the perception of mars as having a wet surface but a dry interior is consistent with what we know of the geologic history of mars which can be viewed as the progressive intrusion and overplating of a water rich crust by dry mantle derived volcanic rocks

characterization of some andepts and andic soils in rwanda central africa abstract the morphology chemistry and clay mineralogy of ten pedons developed on quaternary basic volcanic ashes in the northwestern highlands of rwanda under perudic to udic marginal to ustic moisture regimes are reported eight pedons have abundant al fe humus complexes allophane and imogolite and thus qualify as andepts whereas the other two pedons do not because of their halloysitic clays these last two soils are thought to be in a more advanced stage of pedogenesis and to have been formed in parent materials consisting of volcanic ash mixed with residuum from the underlying granitic and metamorphic rocks their physical chemical and clay mineralogical properties are distinctive from those of soils in kenya and tanzania the differences are discussed in relation to soil moisture regimes and petrological nature of parent ashes

chemical weathering of basalts southwest iceland effect of rock crystallinity and secondary minerals on chemical fluxes to the ocean river ground and peat water from a basaltic catchment area laxa in kjos southwest iceland were sampled and analyzed for major element concentrations to define the effect of glassy versus crystalline basalt the formation of secondary minerals and runoff on fluxes of dissolved elements to the ocean the proportions of the dissolved solids in the water samples derived from precipitation air and rock weathering were estimated the amounts of na mg ca k and s originating from precipitation were calculated from the respective solute cl marine ratios and the estimated aqueous cl originated from precipitation which was calculated using measured b content of the waters and b cl molal marine and rock ratios the rock contribution from weathering ranged from 22 to 46 percent of the total dissolved solids of the waters iron and al showed low mobility compared to na this was primarily due to consumption of these elements by ferrihydroxides allophane imogolite and clay minerals also si and to a lesser degree ca show apparent slightly lower mobility than na these results are in good agreement with these phases being dominant in the soils of the study area wada and others 1992 and the main secondary minerals of basaltic glass in iceland crovisier and others 1992 reaction progress calculations support these findings according to a model interaction of basaltic glass and meteoric water al fe and si are consumed by amorphous fe and al hydroxides and imogolite and allophane at low reaction progress with increasing reaction progress ca fe mg smectite became the primary secondary minerals limiting the mobility of ca fe mg si and al these findings suggest that the weathering in the laxa in the kjos catchment area has evolved into the beginning of the smectite weathering stage and that it is dominated by a relatively low reaction progress and a high water to rock ratio in the present study the effect of runoff and rock crystallinity was quantified for dissolved elemental fluxes temperature lithology other than rock crystallinity and rock age were similar in all of the catchment areas in this study silica ca f s al k mg and b had a very similar dependence on runoff on the other hand na fluxes were found to be less dependent on runoff and fe fluxes were found to be independent of runoff basaltic glass dissolves faster than fully crystallized basaltic rocks gislason and eugster 1987a therefore increased glass content of the primary rocks is thought to increase the leaching and elemental fluxes at constant runoff however because some of the solutes particularly al and fe were highly influenced or even controlled by the formation of secondary minerals this increasing dissolution with increasing glass content was hidden on the other hand basaltic glass was observed to enhance the fluxes of more mobile elements like na si ca f and s by a factor of 2 to 5 at a constant runoff of 200 cm yr constant vegetative cover and 0 to 100 percent glass content of the rocks the k and mg fluxes were found to be independent of rock crystallinity however runoff alone cannot explain the fluxes of these elements and it seems that vegetative cover and seasonal variations in biomass activities influence the k and mg fluxes

an assessment of the fluvial geomorphology of subcatchments in parana valles mars this paper uses a multifaceted remote sensing and morphometric approach to investigate if the surface of subcatchments in the parana valles area of mars 20 30 s 0 20 w is reflective of hydrology and sediment transport by water using digital elevation model dem data obtained from the mars orbiter laser altimeter mola three nested subcatchments were examined using a suite of terrestrial geomorphic and hydrologic statistics to determine if their shape and form lies within the known range of fluvial catchment properties on earth further an examination of statistical accuracy via an innovative pixel by pixel solution of two statistics established that despite mineralogical homogeneity confirmed by the compact reconnaissance imaging spectrometer for mars crism spectral survey erosion processes were likely to be variable across the study site the dem based methods outlined here can be employed at other sites to investigate geomorphic properties and attributes of the martian surface

properties weathering and classification of some soils formed in peralkaline volcanic ash in kenya abstract physical chemical and mineralogical properties were determined for six profiles in and west of the great rift valley in kenya data include morphology information on gross composition of horizons organic carbon cation exchange capacities extractable cations etc and detailed characterization of the clay fractions by means of transmission electron microscopy x ray diffraction infrared spectroscopy and additional techniques the three least weathered profiles nos 1 3 of table i have morphologies typical of andepts but lack certain other characteristics common to such soils their clay fractions were largely amorphous to x rays and consisted mainly of poorly ordered siliceous feoxides with virtually no allophane all of the clays contained halloysite the peralkaline nature of the ash parent material seems responsible for the clay mineralogy of the soils which differs from that generally found in andepts the high proportions of iron in the amorphous materials depart from the composition widely reported for such soils one distinctive feature was the presence of pantelleritic trachyte found in ash from a number of sites in addition to those of the profiles how the six profiles may best be classified is an open question none of the profiles qualifies as andept nor would they be included in the proposed order of andisols as presently defined modifications of the definition of andisols so as to include some of these soils would seem desirable

deep massive sulphide exploration using 2d and 3d geoelectrical and induced polarization data in skellefte mining district northern sweden geoelectrical and induced polarization data from measurements along three profiles and from one 3d survey are acquired and processed in the central skellefte district northern sweden the data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1 5 km the 2009 data were inverted previously and their joint interpretation with potential field data indicated several anomalous zones the 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area several high chargeability low resistivity zones interpreted as possible massive sulphide mineralization and associated hydrothermal alteration are revealed the 3d survey data provide a detailed high resolution image of the top 450 m of the upper crust around the maurliden east north and central deposits several anomalies are interpreted as new potential prospects in the maurliden area which are mainly concentrated in the central conductive zone in addition the contact relationship between themajor geological units e g the contact between the skellefte group and the j orn intrusive complex is better understood with the help of 2010 deep resistivity chargeability data the bottommost part of the vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to 1 km depth

halloysite smectite mixed layered clay in fluvio volcanic soils at the southern foot of mount kilimanjaro tanzania abstract the formation of kaolinite smectite mixed layered clays results from weathering of smectite in leached and silica depleted environments halloysite smectite mixed layered clays have been proposed to form from weatherable minerals in volcanic ash soils through simultaneous formation of 1 1 and 2 1 units in silica rich environments here we report a mineralogical study of weathered b horizon material from soils developed on late quaternary fluvio volcanic deposits of basaltic origin at the southern foot of mount kilimanjaro in northern tanzania this area is characterized by a strong seasonality two months of highly humid conditions followed by a 10 month pronounced dry season during which mineral authigenesis takes place the weak leaching conditions are reflected in the high base saturation of the soils and by their high content of amorphous silica the soils contain no allophane the clay fractions contain dioctahedral 1 1 layer silicates trioctahedral mica gibbsite and feldspar as well as a substantial amount of 1 1 2 1 mixed layered clays with predominance of 1 1 layers the latter consist of dehydrated halloysite that only partially expands after formamide intercalation because of its history of drying in field conditions the interstratified phases are high charge halloysite smectite mixed layered clays cec 30 72 cmol kg 1 clay that are predominantly very fine grained

evolution of water reservoirs on mars from d h ratios in the atmosphere and crust ancient fluvial networks on the surface of mars suggest that it was warm and wet over three billion years ago surface features resembling massive outflow channels provide evidence that even more recently the martian crust contained the equivalent of a planet wide reservoir of water several hundred metres deep but arguments based on the isotopic fraction and present day escape rate of hydrogen in the martian atmosphere require only 0 5 metres of crustal water today and about six metres in the past an additional constraint on the evolution of the isotopic composition of martian water has recently been obtained from measurements of the deuterium to hydrogen ratio of hydrous minerals in the snc meteorites meteorites that almost certainly originated on mars here i show that these new data require that the modern crustal reservoirs of martian water must be quite large at least several metres in global equivalent depth the deuterium enrichment of the present martian atmosphere then implies that the reservoir of crustal water on ancient mars was several hundred metres deep consistent with the geological evidence

methods for calculating frechet derivatives and sensitivities for the non linear inverse problem a comparative study1 a fundamental step in the solution of most non linear inverse problems is to establish a relationship between changes in a proposed model and resulting changes in the forward modelled data once this relationship has been established it becomes possible to refine an initial model to obtain an improved fit to the observed data in a linearized analysis the frechet derivative is the connecting link between changes in the model and changes in the data in some simple cases an analytic expression for the frechet derivative may be derived in this paper we present three techniques to accomplish this and illustrate them by computing the frechet derivative for the id resistivity problem for more complicated problems where it is not possible to obtain an expression for the frechet derivative it is necessary to parameterize the model and solve numerically for the sensitivities partial derivatives of the data with respect to model parameters the standard perturbation method for computing first order sensitivities is discussed and compared to the more efficient sensitivity equation and adjoint equation methods extensions to allow for the calculation of higher order directional and objective function sensitivities are also presented finally the application of these various techniques is illustrated for both the 1d and 2d resistivity problems

extraction of martian valley networks from digital topography 1 we have developed a novel method for delineating valley networks on mars the valleys are inferred from digital topography by an autonomous computer algorithm as drainage networks instead of being manually mapped from images individual drainage basins are precisely defined and reconstructed to restore flow continuity disrupted by craters drainage networks are extracted from their underlying basins using the contributing area threshold method we demonstrate that such drainage networks coincide with mapped valley networks verifying that valley networks are indeed drainage systems our procedure is capable of delineating and analyzing valley networks with unparalleled speed and consistency we have applied this method to 28 noachian locations on mars exhibiting prominent valley networks all extracted networks have a planar morphology similar to that of terrestrial river networks they are characterized by a drainage density of 0 1 km 1 low in comparison to the drainage density of terrestrial river networks slopes of streams in martian valley networks decrease downstream at a slower rate than slopes of streams in terrestrial river networks this analysis based on a sizable data set of valley networks reveals that although valley networks have some features pointing to their origin by precipitation fed runoff erosion their quantitative characteristics suggest that precipitation intensity and or longevity of past pluvial climate were inadequate to develop mature drainage basins on mars

morphometric analysis of martian valley network basins using a circularity function 1 this paper employs a circularity function to quantify the internal morphology of martian watershed basins in margaritifer sinus region and to infer the primary erosional processes that led to their current geomorphologic characteristics and possible climatic conditions under which these processes operated the circularity function describes the elongation of a watershed basin at different elevations we have used the circularity functions of terrestrial basins that were interpreted as having been modified by 1 erosion related to primarily groundwater sapping and 2 erosion related to primarily rainfall and surface run off as well as the circularity functions of cratering basins on the moon in order to formulate discriminant functions that are able to separate the three types of landforms the spatial pattern of the classification of martian basins based on discriminant functions shows that basins that look morphologically similar to terrestrial fluvial basins are mostly clustered near the mainstream at low elevation while those that look morphologically similar to terrestrial basins interpreted as groundwater sapping origin are located near the tributaries and at higher elevation there are more of the latter than the former this spatial distribution is inconsistent with a continuous earth like warm and wet climate for early mars instead it is more aligned with an overall early dry climate punctuated with episodic wet periods alternatively the concentrated erosion in the mainstream could also be caused by a change of water source from rainfall to snowfall or erosion cut through a duricrust layer

composition of the drainage network on early mars abstract among the 2208 martian fluvial features plotted in a previous study z geomorphol 37 1 1993 57 the hydrological characteristics of 71 pristine fluvial valley networks located between 18 0 n and 55 0 s were surveyed using viking orbiter photomosaic bases at 1 2 million scale the surveyed networks display 1 systems organized mainly as first order streams 85 of which have lengths not exceeding 1000 km with a large amount of the statistical sample having lengths between 200 and 500 km generally shorter than the degraded valleys studied by baker and partridge j geophys res 91 1986 3561 2 drainage basins with average areas of about 5000 km2 3 a random distribution and 4 headwater tributary drainage densities kd ranging systematically between 0 03 and 0 2 km 1 which are comparable to terrestrial drainage densities in arid climates the compositions of the surveyed pristine valley networks are comparable to the degraded fluvial systems that dissect older martian surface materials thus it appears that no dramatic changes occurred in martian hydrology since the earlier period of formation of the degraded valleys such as described by baker and partridge j geophys res 91 1986 3561 subsurface aquifer drainage may have been a large contributor to drainage basin formation since early in mars history

evidence for extensive denudation of the martian highlands high resolution topographic data from the mars orbiter laser altimeter reveal evidence for widespread denudation from margaritifer sinus to northern arabia terra an area of 1 107 km2 a major resurfacing event is indicated by 1 a heavily degraded landscape hosting numerous inliers 2 truncation or absence of valley networks and 3 a break in slope at the edge of early to middle noachian plateau materials geomorphic mapping was completed on the type locale of denudation 0 30 s 0 30 w superposition relations and crater counts for geomorphic units indicate that large scale resurfacing took place in the late noachian eroding the martian highlands and resulting in transportation and deposition of 4 5 106 km3 of sediment in the northern plains this is equivalent to a 120 m thick uniform layer of sediment on the surface of mars north of 30 n geomorphic mapping and crater counts limit the timing of denudation to the late noachian an interval of 350 500 m y using this limit we estimate a minimum rate of denudation of 2 0 m yr comparable to denudation of typical slopes in a temperate maritime climate on earth the morphology rate of denudation and extensive nature of upland degradation suggest that precipitation fed surface runoff is the most likely geomorphic agent capable of such a process indicative of a warm wet mars during the late noachian epoch

clay minerals and humus complexes in five kenyan soils derived from volcanic ash abstract clay minerals and humus complexes and their effects on soil chemical properties were studied for five profiles around the longonot and susua volcanoes in kenya morphologically all profiles have some resemblance to andepts but there were clear cut differences in clay contents and mineral composition as well as ph between profiles 1 through 4 and profile 5 which occur under semi arid to subhumid and under humid climatic conditions respectively profiles 1 through 4 contained embryonic halloysites with x rays amorphous iron oxide and silica whereas profile 5 contained a kaolin mineral chloritized 2 1 layer silicates gibbsite and hematite these mineral associations probably represent early and advanced stages of weathering of volcanic ash under weak and strong leaching conditions respectively embryonic halloysites consisted of more or less poorly ordered halloysite and 1 0 and 0 7 1 0 nm minerals the carbon contents of a horizons ranged from 100 to 112 g kg in profiles 2 3 and 5 humus complexes increased in the order fehumus al humus ca humus in profiles 2 and 3 whereas al and fe humus were found exclusively in profile 5 the ph naf phosphate retention and acid oxalate extractable al qualify only profile 5 as an andept or andisol

origin of the valley networks on mars a hydrological perspective abstract the geomorphology of the martian valley networks is examined from a hydrological perspective for the compatibility with an origin by rainfall globally higher heat flow and localized hydrothermal systems comparison of morphology and spatial distribution of valleys on geologic surfaces with terrestrial fluvial valleys suggests that most martian valleys are probably not indicative of a rainfall origin nor are they indicative of formation by an early global uniformly higher heat flow in general valleys are not uniformly distributed within geologic surface materials as are terrestrial fluvial valleys valleys tend to form either as isolated systems or in clusters on a geologic surface unit leaving large expanses of the unit virtually untouched by erosion with the exception of fluvial valleys on some volcanoes most martian valleys exhibit a sapping morphology and do not appear to have formed along with those that exhibit runoff morphology in contrast terrestrial sapping valleys form from and along with runoff valleys the isolated or clustered distribution of valleys suggests localized water sources were important in drainage development persistent groundwater outflow driven by localized but vigorous hydrothermal circulation associated with magmatism volcanism impacts or tectonism is however consistent with valley morphology and distribution snowfall from sublimating ice covered lakes or seas may have provided an atmospheric source of water for the formation of some valleys in regions where the surface is easily eroded and where localized geothermal hydrothermal activity is sufficient to melt accumulated snowpacks

scaling relations for large martian valleys 1 the dendritic morphology of martian valley networks particularly in the noachian highlands has long been argued to imply a warmer wetter early martian climate but the character and extent of this period remains controversial we analyzed scaling relations for the 10 large valley systems incised in terrain of various ages resolvable using the mars orbiter laser altimeter mola and the thermal emission imaging system themis four of the valleys originate in point sources with negligible contributions from tributaries three are very poorly dissected with a few large tributaries separated by long uninterrupted trunks and three exhibit the dendritic branching morphology typical of terrestrial channel networks we generated width area and slope area relationships for each because these relations are identified as either theoretically predicted or robust terrestrial empiricisms for graded precipitation fed perennial channels we also generated distance area relationships hack s law because they similarly represent robust characteristics of terrestrial channels whether perennial or ephemeral we find that the studied martian valleys even the dendritic ones do not satisfy those empiricisms on mars the width area scaling exponent b of 0 7 4 7 contrasts with values of 0 3 0 6 typical of terrestrial channels the slope area scaling exponent ranges from 25 6 5 5 whereas values of 0 3 0 5 are typical on earth the length area or hack s exponent n ranges from 0 47 to 19 2 while values of 0 5 0 6 are found on earth none of the valleys analyzed satisfy all three relations typical of terrestrial perennial channels as such our analysis supports the hypotheses that ephemeral and or immature channel morphologies provide the closest terrestrial analogs to the dendritic networks on mars and point source discharges provide terrestrial analogs best suited to describe the other large martian valleys

oxygen isotope composition of natural phosphates from volcanic ash soils of the great rift valley of africa and east java indonesia abstract volcanic ash soils of the great rift valley of africa and east java indonesia are highly fertile due to an ample supply of available phosphorus the origin of the natural phosphates has been determined from oxygen isotope analyses 18o which reflect the formation temperature of the p o bond the 18o values of phosphates extracted from fourteen surface or near surface soil samples ranges from 10 1 to 24 8 the values are higher than those of recent volcanic ashes from oldoinyo lengai tanzania and merapi indonesia 18o 5 3 to 6 2 and those of igneous apatites from carbonatites geodes and hydrothermal deposits 18o 0 2 to 12 2 n 10 the soils with 18o values at the lower end of the range are from ngorongoro crater highlands and the footslope of mt meru northern tanzania 10 4 to 15 9 and east java indonesia 10 1 to 16 9 respectively where the soil surfaces have both been rejuvenated by frequent deposition of volcanic phosphates in recent ashes higher 18o values 16 7 to 24 8 which are comparable with those of wild mammal s skeletons 18o 18 6 to 24 0 are observed for soils in advanced stages of pedogenesis oxygen isotope fractionation between phosphate and associated calcite has been evaluated for selected soil samples the resulting isotopic temperatures are unreasonable however and indicate that the soil phosphates are not in isotopic equilibrium with the fluids responsible for authigenic calcite available phosphorus in the soils studied is derived from both of biogenic plants and mammal bones and volcanic sources

3d morphometry of valley networks on mars from hrsc mex dems implications for climatic evolution through time 1 martian valley networks have been identified mainly in the noachian heavily cratered uplands eight dense branching valley networks were studied in noachian terrains of huygens newcomb and kepler craters south tyrrhena terra and thaumasia in hesperian terrains of echus plateau and west eberswalde craters and in amazonian terrains of alba patera using images and digital elevation models from the mars express high resolution stereo camera to determine 2d and 3d morphometric parameters extracted geomorphic parameters show similar geometry to terrestrial valleys drainage densities organization from bifurcation ratios and lengths ratios hack exponent consistent with terrestrial values of 0 6 and progressive deepening of valleys with increasing strahler order in addition statistics on valley depths indicate a deeper incision of noachian valleys compared to younger post noachian valleys 100 m for noachian ones showing a strong difference in fluvial erosion these characteristics show that dense martian valley networks formed by overland flows in relation to a global atmospheric water cycle in noachian epoch and confirm that the later stages of activity may be related to shorter duration of activity distinct climatic conditions and or regional processes or conditions

scale dependence of hypsometric integrals an analysis of southeast african basins abstract previous studies have shown that the hypsometry of individual drainage basins is sensitive to both tectonic uplift rates and variations in erosional resistance of different lithological units however basin hypsometry has also been found to be related to the size the shape and relief of the sampled area as well as factors such as the type of dominant erosional process this study extends the evaluation of the controls on a basin s hypsometry by assessing factors that might influence the spatial distribution of hypsometric integrals at different scales the method is applied to catchments draining the southeast margin of southern africa kwazulu natal region because of the region s rather uniform runoff a rather well constrained denudational history and a relatively simple coastward sequence of bedrock geology several sets of basins were extracted from an srtm derived 90 m resolution dem one set of main basins those that have outlets at sea level and six sets of sub basins of different size based on strahler order the mean area of the sub basins sampled ranged from 9 km2 for strahler order 2 through to 3215 km2 for strahler order 6 in contrast to previous studies data from this study fail to show a correspondence between hypsometric integral and indices of basin dimension such as basin area and basin relief rather basin hypsometry in se africa varies spatially and with scale in particular a mountain range scale positive hypsometric integral anomaly situated between 10 and 100 km of the coast line was observed but only in basins of strahler order 5 and less this anomaly is compatible with moderate crustal displacement focussed midway between the coast and the drakensburg escarpment some intermediate scale positive hypsometric integral anomalies in basins of strahler order 4 and less was also observed in some cases these anomalies correspond to differences in erosional resistance among major lithological groups finally numerous local basin scale positive hypsometric integral anomalies in basins of strahler order 3 and less were also observed in many cases these latter anomalies are related to local differences in lithological resistance e g the presence of dolerite sills and dikes the analysis of the spatial variation of hypsometric integrals in basins of different size ranges is therefore a useful first step in assessing factors that control landscape development

polar basal melting on mars if ice is present throughout the cryosphere anywhere on mars thermodynamic considerations suggest that it is most likely at the poles given this condition the deposition of dust and h2o at the polar surface will ultimately result in a situation where the equilibrium depth to the melting isotherm has been exceeded melting ice at the base of the cryosphere until thermal equilibrium is once again established should deposition persist the polar deposits will ultimately reach a thickness where melting will occur at their actual base at this point the cap may reach a state of equilibrium where the deposition of any additional ice is balanced by geothermal melting thermal calculations yield basal melting thicknesses that are consistent with the inferred 4 6 km thickness of the present north polar cap however in the south the deposits appear sufficiently thin 1 2 km that geothermal melting is likely to be relegated to a depth that lies well below the regolith polar cap interface similar conclusions are reached from consideration of the polar caps theoretical equilibrium profiles in the north a basal yield stress characteristic of ice at or near the melting point is indicated while in the south it appears the cap has yet to achieve the necessary height for significant deformation to occur at its base the potential importance of basal melting is illustrated through the discussion of four examples 1 the origin of the major polar reentrants 2 the removal and storage of an ancient martian ice sheet 3 the mass balance of the polar terrains and 4 the possibility of basal melting at temperate latitudes this analysis suggests that the process of basal melting may play a key role in understanding the evolution of the martian polar terrains and the long term climatic behavior of water on mars

effect of drainage area on hypsometry from an analysis of small scale drainage basins in the siwalik hills central nepal hypsometry of drainage basins area elevation analysis has generally been used to infer the stage of geomorphic development and to study the influence of varying forcing factors i e tectonics climate lithology on topography however the scale dependence of hypsometry has generally been neglected in order to assess the scale dependence of hypsometry this study focuses on the sensitivity of hypsometry to different digital elevation model dem resolutions and on the influence of drainage area hypsometry inferred from different dems is shown to be robust against variations of their resolution however hypsometry appears to be dependent on drainage area we propose that this scale dependence may reflect the varying importance of river and hillslope processes with basin area copyright 1999 john wiley sons ltd

minerals formed and mineral formation from volcanic ash by weathering abstract weathering of volcanic ash and pumice is unique regarding minerals formed and mineral formation these minerals include allophane imogolite opaline silica and some halloysites and have distinctive structures and properties studies on the surface and subsurface weathering of various volcanic ashes in different settings are reviewed this review illustrates that relatively rapid weathering of finely comminuted volcanic ash well reflects the effects of climate vegetation and time and produces various combinations of weathering products the moisture regime the nature and amount of organic matter incorporated the deposition of volcanic ash as overburden and the chemical and mineralogical composition of parent ash are important in controlling the mineral formation in weathered volcanic ash

mineralogical and chemical composition of three tuffs from northern israel abstract the mineralogical and chemical composition of three types black yellow and red of tuffs from mt peres in northern israel that differ in terms of degree of weathering were determined in order to understand the weathering sequence under mediterranean or semi arid conditions the black tuff is very slightly weathered and contains 62 volcanic glass 15 primary minerals 12 titano magnetite 5 halloysite and 4 5 hydroxyapatite the yellow tuff considered to be the weathering product of the black tuff contains only 4 volcanic glass and 21 primary minerals 8 fe rich minerals 51 amorphous material identified as halloysite like allophane 15 halloysite and 5 hydroxyapatite a different mineralogical composition from that of red tuff indicates that this material was formed during a different eruption the red tuff consisted of 29 volcanic glass 26 primary minerals different from those of the black tuff 11 iron bearing minerals 10 halloysite 5 hydroxyapatite and 19 amorphous material the specific surface area and cation exchange capacity of the black red and yellow tuff 7 28 174 m2 g 1 and 107 285 601 mmolc kg 1 at ph 7 respectively were in accord with their amorphous material contents

mars a water rich planet abstract mars had outgassed at least 0 5 to 1 km of water 10 to 20 bar of co2 and 0 1 to 0 3 bar of n2 the volatiles that have been retained are mostly in the cratered uplands terrain softening fretted channels debris flows and closed depressions indicate that at least the upper 2 km of the cratered uplands at high latitudes 30 contain ice in amounts that exceed the porosity estimated to be 10 20 theoretical studies and lack of these features in the cratered uplands at low latitudes suggest that the upper 1 km of the uplands at low latitudes is ice poor however valley networks indicate that water was present near the surface early in the planet s history although in amounts smaller than at high latitudes the entire upper 1 km planetwide is estimated to have contained 75 125 m of water at the end of heavy bombardment the largest sink for water is the megaregolith below 1 km episodic eruption of water from the deep megaregolith cut many of the large outflow channels from the volume of water needed to cut the circum chryse channels and assuming uniform planetwide distribution of water the deep megaregolith is estimated to have contained at least 350 m of water at the end of heavy bombardment thereby giving a total minimum inventory of 424 475 m planetwide most of the water lost from the low latitude uplands by diffusion and in cutting the valley networks is now believed to be in the polar layered terrains most of the water involved in cutting the outflow channels is in the low lying northern plains where a variety of features that have been attributed to ground ice is present a large fraction of the planet s surface has been overplated with water poor volcanics of which we have samples in the snc meteorites the younger volcanics have reacted extensively with the old volatile rich basement some of the co2 and n2 outgassed was lost during heavy bombardment by impact erosion of the atmosphere and other processes the remaining was fixed carbonates and folded deep into the megaregolith during heavy bombardment

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

revisiting the hypsometric curve as an indicator of form and process in transport limited catchment hypsometry has historically been used as an indicator of geomorphic form of catchments and landforms yet there has been little work aimed at relating hypsometry to landform process and scale this paper uses the siberia catchment evolution model to explore linkages between catchment process and hypsometry siberia generates results that are qualitatively and quantitatively similar to observed hypsometric curves for physically realistic parameters however we show that not only does the hypsometry reflect landscape runoff and erosion process but it is strongly dependent on channel network and catchment geometry we show that the width to length ratio of the catchment has a significant influence on the shape of the hypsometric curve though little on the hypsometric integral for landforms dominated by fluvial sediment transport the classic strahler mature hypsometric curve is only generated for catchments with roughly equal width and length narrow catchments show a hypsometric curve more similar to strahler s monadnock form for landscapes dominated by diffusive transport the simulated hypsometric curve is concave down everywhere this being consistent with curves reported for some example catchments in france because the transition between diffusive dominance to fluvial is scale dependent with larger catchments exhibiting greater fluvial dominance then the hypsometric curve is a scale dependent descriptor of landforms experimental results for simulated landforms from a small scale rainfall erosion simulator are reported it is shown that siberia yields satisfactory fits to the data confirming its ability to predict the form of the hypsometric curve from a simple model of geomorphic processes 1998 john wiley sons ltd

low potential for large intraslab earthquakes in the central cascadia subduction zone the cascadia subduction zone csz can be divided into three distinct sections based on the characteristics of intraslab seismicity based on a 150 year historical record no moderate to large intraslab earthquakes of moment magnitude m 5 5 or greater have occurred within the subducting juan de fuca plate of the central csz from south of the puget sound in northwestern washington to the oregon california border also very few intraslab earthquakes as small as m 3 have been instrumentally located within the central csz since 1960 and a wadati benioff zone is not apparent in the southern csz beneath northwestern california a wadati benioff zone is present to a depth of about 40 km but no large gorda block earthquakes have been observed in the downgoing slab although large events have occurred near the trench axis in contrast the puget sound region within the northern csz has been repeatedly shaken by large intraslab earthquakes of m 6 5 in the depth range of 40 to 60 km such as the recent 2001 m 6 8 nisqually event a critical question addressed in this article is what is the potential for such large shallow intraslab earthquakes in the central csz beneath western oregon and southwestern washington i have evaluated the available information on the thermal and physical properties geometry and historical and contemporary seismicity of the central csz and performed thermal modeling based on these analyses and comparisons with other subduction zones worldwide the lack of shallow intraslab earthquakes in the central csz is not unusual the hot temperatures 500 c within the juan de fuca plate particularly below a depth of 40 km where large events are expected are not conducive to earthquake generation resulting in either the complete absence of m 6 5 shallow intraslab earthquakes or long recurrence intervals hundreds of years between such events temperatures appear to be sufficiently high in the central csz so that no wadati benioff zone can exist even at shallow depths 40 km the young plate age slower convergence rate and the insulating effect of the siletz terrane above the plate are factors that probably lead to the hot temperatures in this portion of the slab the variability in the maximum depth of the wadati benioff zone along the csz 60 km beneath the puget sound 40 km within the subducting gorda block and essentially zero in the central csz reflect the differing temperature conditions that is the cutoff temperature varies with depth and rock composition and also the potential for large shallow intraslab earthquakes in addition to the effects of temperature the level of tectonic stresses which vary along the length of the csz must also be a factor in controlling the occurrence of large intraslab earthquakes large events can occur in the puget sound region probably because of cooler intraslab temperatures and possibly because of a stress concentration or zone of weakness along the pronounced arch in the juan de fuca plate a previous study has suggested an intraslab subduction zone origin for a m 7 3 earthquake that occurred in 1873 near the town of brookings in southernmost oregon however analysis of its seismotectonic setting and comparison with other historical earthquakes in northernmost california suggest that the event probably had a very shallow origin within the gorda block southern csz and was not a deep intraslab earthquake in the central csz

hypsometric analysis of margaritifer sinus and origin of valley networks 1 the formation of martian valley networks has been debated since their discovery the relative roles of groundwater sapping and fluvial runoff processes have different implications on martian paleoclimate this paper uses a hypsometric analysis technique that has been tested on terrestrial landforms to analyze the hypsometric attributes of watershed basins in the margaritifer sinus region on mars using mars orbiter laser altimeter mola gridded topographic data on the basis of quantitative characteristics of their hypsometric attributes the majority of the basins covering 3 5 of the study area look more like terrestrial basins of sapping origin and a significant number of basins covering 1 5 of the study area are more fluvial like the classification of the rest of the basin is less certain at the presently available resolution of the digital elevation model dem overlay with viking photomosaic indicates that the classification is generally consistent with the morphology shown in viking images although this analysis alone cannot make a sure determination of valley network origin combined with other morphometric analysis the results from this study are consistent with a valley network formation by precipitation recharged groundwater sapping suggesting a warm and wet climate for early mars

small martian valleys pristine and degraded morphology the equatorial heavily cratered uplands of mars are dissected by two classes of small valleys that are intimately associated in compound networks pristine valleys with steep valley walls preferentially occupy downstream portions of compound basins degraded valleys with eroded walls are laterally more extensive and have higher drainage densities than pristine valleys morphometric and crater counting studies indicate that relatively dense drainage networks were emplaced on mars during the heavy bombardment about 4 0 b y ago over a period of approximately 10 sup 8 years these networks were degraded and subsequently invaded by headwardly extending pristine valleys the pristine valleys locally reactivated the compound networks probably through sapping processes dependent upon high water tables fluvial activity in the heavily cratered uplands generally ceased approximately 3 8 3 9 b y ago coincident with the rapid decline in cratering rates the relict compound valleys on mars are morphometrically distinct from most terrestrial drainage systems the differences might be caused by a martian valley formation episode characterized by hyperaridity by inadequate time for network growth by very permeable rock types or by a combination of factors

inversion of induced polarization data we present an algorithm for inverting induced polarization ip data acquired in a 3 d environment the algorithm is based upon the linearized equation for the ip response and the inverse problem is solved by minimizing an objective function of the chargeability model subject to data and bound constraints the minimization is carried out using an interior point method in which the bounds are incorporated by using a logarithmic barrier and the solution of the linear equations is accelerated using wavelet transforms inversion of ip data requires knowledge of the background conductivity we study the effect of different approximations to the background conductivity by comparing ip inversions performed using different conductivity models including a uniform half space and conductivities recovered from one pass 3 d inversions composite 2 d inversions limited aim updates and full 3 d nonlinear inversions of the dc resistivity data we demonstrate that when the background conductivity is simple reasonable ip results are obtainable without using the best conductivity estimate derived from full 3 d inversion of the dc resistivity data as a final area of investigation we study the joint use of surface and borehole data to improve the resolution of the recovered chargeability models we demonstrate that the joint inversion of surface and crosshole data produces chargeability models superior to those obtained from inversions of individual data sets

dissolution of subglacial volcanic glasses from iceland laboratory study and modelling abstract subglacial hyaloclastites from iceland with ages ranging from 2 ka to 2 2 ma have been studied from a mineralogical and geochemical standpoint the chemical composition of palagonite alteration crust formed on the surface of the glass is almost identical with that of the clayey material filling the intergranular spaces of the rock the clayey material is made up of two particle populations the first is si mg and ca rich with a smectite structure while the second is amorphous fe ti and al rich and has a smectite like morphology it is suggested that these two types of particles can be formed simultaneously in the same solution such that it is not necessary to explain their existence by local or temporary equilibria the mineralogical sequences observed in natural samples were reproduced using the geochemical computer code dissol the geochemical mass balances calculated with dissol also fit quite well with those calculated from icelandic samples illustrating the predictive capability of such a calculation code and gives us confidence in applying a similar approach to nuclear waste form glass problems

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

comparative study between rivers in tarim basin in northwest china and evros vallis on mars abstract the morphometric characteristics of the kaidu river and keriya river in the extremely arid tarim basin and the evros vallis on mars were compared to study the formation of the dendritic evros vallis which has great significance for exploring ancient climate of mars the following results were obtained a the average sinuosities of kaidu river keriya river and evros vallis are 1 17 1 35 and 1 32 respectively b the average bifurcation ratios are 3 84 4 73 and 3 43 respectively c the average stream length ratios are 2 21 3 86 and 2 08 respectively d the stream frequencies are 0 017 0 028 and 0 002 respectively e the drainage densities are 0 195 km 1 and 0 217 km 1 and 0 048 km 1 respectively f the stream gradients are 3 74 7 03 and 1 63 respectively g the stream fractal dimensions are 1 70 1 0 and 1 68 respectively paleodischarge estimations at different stream segments of evros vallis support the hypothesis that the v bend area that joints the eastern and western segments possibly has a tectonic origin geomorphological evidence e g tributaries from high resolution images and stream morphometric parameters from a comparative analysis e g concave upward longitudinal profile and stream fractal dimension support previous hypothesis that evros vallis is a mature drainage system formed by precipitation driven surface runoff this drainage process occurred either in a continuously warm wet climate that lasted long enough on early mars or in regional hydrologic cycles consisting of precipitation and occasionally returned runoff in intermittently clement climates

internal structure and conditions of permafrost mounds at umiujaq in nunavik canada inferred from field investigation and electrical resistivity tomography a systematic approach was used for the interpretation of the electrical resistivity tomography carried out on two permafrost mounds at umiujaq in nunavik canada to assess their internal structure and conditions prior information under the form of a geocryologic model of the permafrost mounds was integrated in the inversion of the pseudo section of apparent electrical resistivity the geocryologic model was developed from the synthesis of previous field investigations including shallow and deep sampling temperature and electrical resistivity logging and cone penetration tests performed in the permafrost mounds values of electrical resistivity were ascribed to the different layers making of the geocryologic model to define a synthetic resistivity model of the permafrost mounds used as a reference model to constrain the inversion the constrained resistivity model clearly show the presence of ice rich cores in the permafrost mounds underscored by high resistivity values in excess of 30 000 m while t

comparing morphologies of drainage basins on mars and earth using integral geometry and neural maps 1 we compare morphologies of drainage basins on mars and earth in order to confine the formation process of martian valley networks basins on both planets are computationally extracted from digital topography integral geometry methods are used to represent each basin by a circularity function that encapsulates its internal structure the shape of such a function is an indicator of the style of fluvial erosion we use the self organizing map technique to construct a similarity graph for all basins the graph reveals systematic differences between morphologies of basins on the two planets this dichotomy indicates that terrestrial and martian surfaces were eroded differently we argue that morphologies of martian basins are incompatible with runoff from sustained homogeneous rainfall fluvial environments compatible with observed morphologies are discussed we also construct a similarity graph based on the comparison of basins hypsometric curves to demonstrate that hypsometry is incapable of discriminating between terrestrial and martian basins