geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

pore properties as indicators of breakdown mechanisms in experimentally weathered limestones the results are reported of four experimental weathering tests freeze thaw wetting and drying slake durability and salt weathering on five different types of limestone effective porosity mercury intrusion porosimetry and scanning electron microscopy were used to evaluate changes in pore properties while weight loss and fracture density were used to assess deterioration severity a primary aim was to observe modifications in porosity due to weathering and to draw inferences about the internal rock deterioration mechanisms taking place it is concluded that the five limestones not only show a wide range of resistance to weathering in general but considerable difference in resistance to particular weathering processes consequently when assessing durability it is essential to consider rock properties in the context of the weathering process to which the rock is subject the type of deterioration indicator used is also important in interpretation of durability a variety of pore modification mechanisms operate including changes in pore connectivity pore infilling and the introduction of additional void space there are indications that changes to the internal pore structure of rocks due to weathering may be a precursor to more substantial macrodeterioration copyright 2001 john wiley sons ltd

deformation maps in grain size stress space as a tool to investigate mantle rheology abstract deformation maps have found widespread use in the study of the rheology of earth materials the usual procedure is to construct a map in stress temperature space from which predominant creep mechanisms strain rates and viscosities can be determined for a given grain size the rheology of polycrystals however depends strongly on grain size and consequently a fuller description would entail the construction of three dimensional stress grain size temperature diagrams as these do not display clearly the parameters of interest it is proposed to use deformation maps in stress grain size space at a given temperature in several situations of geodynamic interest grain size is a more critical parameter than temperature furthermore stress grain size maps have the advantages of simplicity and clarity for instance the boundaries between nabarro herring coble and power law creep are straight lines and so are constant strain rate and constant viscosity contours the triple point at which the three boundaries converge is under reasonable assumptions a function of temperature only and the slopes of the boundaries are independent of temperature it is therefore possible to project on a single map data for various temperatures the coordinates of the triple point contain all the necessary information for a synoptic representation of the rheology as an example deformation maps in stress grain size space are presented for olivine under laboratory and upper mantle conditions

mechanisms of uplift preceding rifting abstract mareschal j c 1983 mechanisms of uplift preceding rifting in p morgan and b h baker editors processes of continental rifting tectonophysics 94 51 66 the feasibility of three mechanisms that have been proposed to account for the uplifts and heat flow anomalies which might precede rifting is examined the conductive heating following an increase in the heat flux at the base of the lithosphere could result in large scale uplifts 1000 m for 15 mw m2 change in heat flux on a time scale of 108 years a pulse of additional heat flow could induce a more rapid uplift but not the surface heat flow anomaly which is always delayed the advection of heat by magma intrusion into the lithosphere could also produce the uplift and heat flow anomaly if magmas are injected at a steady rate an uplift of the order of 1000 m can be induced in about 50 106 years but it requires the rate of magma injection to be equivalent to 0 3 of the total volume of the lithosphere per 106 years a short intense episode of magma invasion could explain a rapid uplift and change in surface heat flow but it requires the replacement of about 30 of the total volume of the lithosphere the complete replacement of the lithosphere by the rise of a diapir of lighter and hotter asthenospheric material has been modelled numerically the model indicates that the rise of the asthenospheric diapir can take place in a very short time 3 106 years and produce the surface uplift and the crustal thinning observed in rift systems provided that following heating the lower lithosphere viscosity is reduced to 1021 pa s

a field based classification scheme for gravel beaches a tripartite classification of gravel beaches based upon morphodynamic properties is proposed and demonstrated for 42 new zealand beaches the main advantage of this scheme is that it is based on simple visual classification that can be applied globally in the field and is underpinned by morphodynamic differences between the beach types the three types identified from the results are 1 pure gravel beach 2 mixed sand and gravel beach 3 composite gravel beach pure gravel beaches have steep slopes tan 0 08 0 24 and gravels extending from the storm berm to below mean low water spring tide level mixed sand and gravel beaches have moderate slopes tan 0 04 0 13 with sand and gravel entirely mixed both cross shore and at depth composite gravel beaches have a steep gravel berm fronted by a low angle intertidal terrace with overall beach slopes of tan 0 05 0 14 on composite beaches there is distinct hydrodynamic cross shore sorting of the sand and gravel component these broad types are tested using discriminant analysis and the three classes are shown to be highly significant f 16 24 df 8 p 0 00005 the key discriminating variables are iribarren number beach width average grain size and storm berm height

neogene tectonics in the western mediterranean may have caused the messinian salinity crisis and an associated glacial event the messinian salinity crisis msc was a catastrophic event which led to the deposition of 106 km3 of evaporite in the mediterranean between 6 5 and 5 ma b p stratigraphic investigations have previously suggested that the progressive increase of salinity in the mediterranean leading to the msc may have been caused by tectonic narrowing and closure of seaways between the mediterranean and the atlantic detailed reconstruction of the tectonic history of the arc of gibraltar and adjacent alboran basin independently suggests 1 1 that the early miocene guadalquivir and alboran seaways closed and narrowed respectively near the end of the tortonian 7 ma b p and 2 2 that the tectonic arc of gibraltar progressively emerged above the sea level during the messinian 7 5 ma b p which caused together with a eustatic glacial lowering of the sea level the isolation and subsequent dessication of the mediterranean this is in agreement with a two stage history of the msc previously postulated on the basis of stratigraphical observations 1 1 deep basin deep water and 2 2 deep basin shallow water salt deposition the closure of the seaways between the mediterranean and the atlantic and the associated drop in world wide oceanic surface salinity may even have caused the kapitean optian glacial event about 5 5 ma b p

geotechnical properties of rock masses their control on slope form and mechanisms of change along the napier range western australia abstract slope form and the mechanisms of change which slope profiles exhibit are frequently subject to scrutiny by geomorphologists however the majority of studies do not consider fundamental material properties and rock mass geotechnical characteristics the results presented here highlight the importance of synthesisistandard geomorphological site investigation techniques with quantifiable rock geotechnical parameters in order to understand slope form and development field research has been undertaken along the napier range of the kimberly region western australia the napiers are an extensive upraised devonian limestone reef along which a number of characteristic slope profiles can be identified laboratory studies of yield strength stress strain characteristics elastic properties and discontinuity parameters have been conducted on material sampled at sites representative of each slope profile type the results suggest that highly concave slopes have formed in limestone which exhibits little deformation before yield has a high modulus of elasticity and few irregular fractures convexo concave slopes on the other hand are characteristic of material which displays a greater ability to strain below yield a relatively low modulus of elasticity and a pronounced discontinuity pattern it is the combination of field investigation and laboratory study which most successfully explains variations in slope form

interaction between the controls on fluvial system development tectonics climate base level and river capture rio alias southeast spain fluvial systems in uplifting terrain respond to tectonic climatic eustatic and local base level controls modified by specific local factors such as river capture the rio alias in southeast spain is an ephemeral transverse to structure fluvial system the river drains two interconnected neogene sedimentary basins the sorbas and almeria basins and crosses two major geological structures the sierras de alhamilla cabrera and the carboneras fault zone regional epeirogenic uplift resulted in sustained fluvial incision during the quaternary punctuated by major climatically driven periods of aggradation and dissection which created a suite of five river terraces the river terrace sequence was radically modified in the late pleistocene by a major river capture itself a response to regional tectonics localized tectonic activity and eustatic base level change the rio alias is defined by four reaches within each the climatically generated region wide fluvial response was modified by tectonics base level change or river capture to varying degrees in the upper part of the basin lucainena reach climate was the dominant control on river development with limited modification of the sequence by uplift of the sierra alhamilla and local drainage reorganization by a local river capture downstream of the sierra alhamilla in the polopus reach the climatic signal is dominant but its expression is radically modified by the response to a major river capture whereby the alias system lost up to 70 of its pre capture drainage area in the reach adjacent to the carboneras fault zone argamason reach modification of the terrace sequence by local tectonic activity and a resultant local base level fall led to a major local incisional event propagating c 3 4 km upstream from the area of tectonic disturbance at the seaward end of the system el saltador reach quaternary sea level changes modified the patterns of erosion and incision and have resulted in steep incisional terrace profiles the signals generated by regional tectonics and the quaternary climate change can be identified throughout the basin but those generated by ongoing local tectonics river capture and sea level change are spatially restricted and define the four reaches the connectivity of the system from the headwaters to the coast decreased through time as incision progressed resulting in changes in local coupling characteristics copyright 2012 john wiley sons ltd

a dynamical basis for crustal deformation and seismotectonic block movements in central europe abstract the stress field in the earth s crust as inferred from satellite gravity data causes crustal deformation and seismotectonic block movements in central europe the satellite determined stresses in the crust of central europe are consistent with earthquake focal mechanisms joint orientation and in situ stress measurements

modelling failure mechanisms to explain rock slope change along the isle of purbeck coast uk results are presented of distinct element computer modelling used to examine rates and mechanisms of change in rock slopes and cliffs where material intact properties determine process and form but the most significant controls are the joint pattern and cross joint properties the modelling approach does not appear to have been used before in a geomorphological context and provides an alternative approach for examining cliff development field and laboratory data have been collected for the portland limestone outcrop of the isle of purbeck central southern england the portland limestome is a hard shelly crystalline sediment of the upper jurassic it has a regular discontinuity pattern throughout the outcrop in purbeck while joint orientation remains relatively constant bedding changes from horizontal to vertical a consequence of the purbeck monocline there are resulting implications for spatial variations in rock slope evolution the modelling exercise enhances previous knowledge on rock failure mechanisms and slope development along the purbeck coast and demonstrates its potential in research where landforms are developed in lithified jointed rock masses 1998 john wiley sons ltd

the gravity field in the central pacific from satellite to satellite tracking satellite to satellite doppler tracking between the ats 6 and the geos 3 spacecraft is used to measure the high degree and order gravity field over an 80 area in the central pacific ocean doppler tracking provides velocity measurements of geos 3 as a function of time which are easily converted to line of sight accelerations since the low degree and order gravity field is known well each geos 3 revolution is reduced relative to a twelfth degree and order field model the method is then capable of measuring wavelengths in the range from about 3500 to 1000 km accelerations computed along 40 revolutions roughly half of them descending and the others ascending can be contoured into a map of the gravity field at the geos 3 altitude of 840 km the dominant wavelength of the map is about 2000 km a comparison of this field with an altimeter derived geoid and the gem 10b gravity field shows good agreement since each map is essentially independent of the others this comparison is critical in establishing the validity of any of the maps each map shows virtually the same areas of positive and negative anomalies these areas are essentially the same in the central pacific as those found in our earlier study compared with surface amplitudes these anomalies are only one tenth as large at the geos 3 altitude this observation and the correlation of gravity with residual depth anomalies imply that the cause of some of these anomalies may be due to bumps in the upper surface of the lithosphere that are compensated at depths of about 30 100 km some of the anomalies apparently do not correlate with residual depth anomalies

crustal structure beneath spain from deep seismic sounding experiments major tectonic units of spain have been investigated by deep seismic sounding experiments since 1974 to determine crustal structures and to delineate their differences these areas are the central part of the hercynian meseta and the alpine chains the betic cordillera in the south including the balearic promontory and the alboran sea and the pyrenees in the north the main features of the crust and the upper mantle along a nne ssw cross section from the pyrenees to the alboran sea are described the crust under the meseta is typical of hercynian areas found elsewhere in europe with an average thickness of 31 km whereas the two alpine regions are characterized by very large lateral inhomogeneities such as rapid thickening of the crust to 50 and 40 km under the pyrenees and the betics respectively the deep reaching e w trending north pyrenean fault has a throw of 10 15 km at the base of the crust a pn velocity of 8 1 km s 1 is found under the entire iberian peninsula in the alboran sea strongly varying thicknesses of sediments shallow variable depths to the moho 13 km under the alboran ridge and strong variations of pn velocity between 7 5 and 8 2 km s 1 have been found

vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements 1 theoretical predictions of the vertical structure of wave motion over a sloping seabed are compared with field observations close to the bed in the nearshore zone of particular interest is the effect of the local slope on the magnitude and phase of the vertical velocity field measurements of near bed velocity profiles on a 2 bed slope were obtained using a coherent doppler profiler the surface elevation was measured by a colocated upward looking acoustic sounder results are presented from two intervals of different wave energy levels during a storm event for wave height water depth ratios smaller than 0 3 and for ursell numbers smaller than 0 6 the local comparisons of magnitude and phase between the vertical velocity and surface elevation measurements are in good agreement with linear theory for a sloping bed but differ greatly from that for a horizontal bottom especially in the lower water column the sloping bottom however has little effect on the horizontal velocity linear theory appears to adequately describe the transfer function between the surface elevation and the near bed velocities not only at the peak frequencies but also at their harmonics however in relatively shallow water the local transformations of free and forced waves at the harmonic frequencies are indistinguishable in the lower water column therefore given surface elevation measurements at a particular location which reflect the integrated effects of nonlinearities associated with wave shoaling the vertical structure of the third moments of velocity fields estimated from linear theory is in reasonable agreement with the observations both theory and observations show that the skewness and asymmetry of the vertical velocity are subject to significant bottom slope effects whereas those of horizontal velocity are not index terms 4211 oceanography general benthic boundary layers 4203 oceanography general analytical modeling 4219 oceanography general continental shelf processes 4546 oceanography physical nearshore processes 4560 oceanography physical surface waves and tides 1255 keywords shoaling waves bottom slope vertical structure skewness asymmetry boundary layers citation zou q a e hay and a j bowen vertical structure of surface gravity waves propagating over a sloping seabed theory and field measurements j geophys res 108 c8 3265 doi 10 1029 2002jc001432 2003

fluvial system response to tectonically induced base level change during the late quaternary the rio alias southeast spain abstract the rio alias of southeast spain crosses a major tectonically active structure the carboneras fault zone within the central portion of the drainage basin the fault originated in the mid miocene and has c 40 km of strike slip offset the impact of late quaternary movement along the fault zone on the evolution of the rio alias is addressed geomorphological and sedimentological analysis of the landform assemblage preserved suggests the development of highly sinuous meander loops and laterally incising streams during phases of tectonic activity continued tectonic activity led to the abandonment of the meander loops and a wave of incision that propagated c 2 km upstream the propagation of this incision wave was restricted by the development of a nickpoint itself controlled by an anticlinal structure sub parallel to the fault zone syn sedimentary and post depositional faulting is evident within the late quaternary fluvial sediments and suggests dominantly vertical movement along the fault lines with downthrow to the southeast regional climatic patterns of aggradation and incision resulting in a basinwide terrace sequence were complicated i e an additional terrace was created and meander wavelength was changed through the study reach by tectonic activity this study highlights the importance of tectonically modified sequences when interpreting climatically generated sequences of aggradation and incision

an asymptotic theory for the interaction of waves and currents in coastal waters a multi scale asymptotic theory is derived for the evolution and interaction of currents and surface gravity waves in water of finite depth under conditions typical of coastal shelf waters outside the surf zone the theory provides a practical and useful model with which wave current coupling may be explored without the necessity of resolving features of the flow on space and time scales of the primary gravity wave oscillations the essential nature of the dynamical interaction is currents modulating the slowly evolving phase of the wave field and waves providing both phase averaged forcing of long infra gravity waves and wave averaged vortex and bernoulli head forces and hydrostatic static set up for the low frequency current and sea level evolution equations analogous relations are derived for wave averaged material tracers and density stratification that include advection by horizontal stokes drift and by a vertical stokes pseudo velocity that is the incompressible companion to the horizontal stokes velocity illustrative solutions are analysed for the special case of depth independent currents and tracers associated with an incident surface wave field and a vortex with o 1 rossby number above continental shelf topography

geodynamics of cenozoic deformation in central asia this paper presents a study of the tectonic stresses in central asia based on an interpretation of satellite gravity data for mantle convection and supplemented with published fault plane solutions of earthquakes northwest southeast to north south compressional stresses exist in the tien shan region where reverse faulting dominates the maximum compressive stress is oriented approximately northeast southwest in the regions of altai and southern mongolia farther north compressive stress gives way to tensional stress which causes normal faulting in the baikal rift system it is also shown that all of the tectonic stresses in the tibetan plateau and himalayan frontal thrust are related to the convection generated stress patterns inferred from satellite gravity data these results suggest that the complex crustal deformation in central asia can be convincingly described by the deformation of the lithosphere on top of the up and down welling asthenospheric material beneath it this observational fact may not only upset the simple view of the fluid crustal model of the tibetan plateau but also provide some useful constraints for the future development of deformation theory of continental crust

diffusion creep dislocation creep and mantle rheology abstract viscosity depth profiles in the earth s mantle are estimated on the basis of microrheological equations for ultrabasic silicates the preliminary reference earth model prem and two assumed geotherms one with and one without a lower mantle upper thermal boundary layer the estimation includes assessment of variations of creep parameters with depth both constant strain rate non linear viscosity and newtonian viscosity are in the range 1020 1021 pa s in the upper mantle in the lower mantle there is a moderate increase in viscosity with depth and upper limit estimates are of the order of 1022 and 1023 pa s respectively as uncertainties are one order of magnitude the newtonian viscosity mantle inferred from geophysical observations cannot be rejected on the strength of rheological considerations by the same token convection should be mantle wide as the viscosity layering is not sufficient to prevent it on the other hand if the mantle is chemically stratified and separate convective circulations exist in the upper and lower mantle the thermal boundary layer below the 670 km discontinuity should have a discernible viscosity signature

experimental study on the hydrodynamics of regular breaking waves this paper illustrates the results of experimental research carried out in the wave flume of the water engineering and chemistry department laboratory of bari technical university italy and based on the analysis of three different regular waves breaking on a sloping bottom the investigation refers particularly to the surf zone with the aim to develop two themes the study of velocity and reynolds shear stress distributions in the shoaling zone of a regular wave field and the study of turbulence in the breaking region observing that these two aspects greatly influence many coastal processes such as undertow currents sediment transport and action on maritime structures

the effects of fire on rock weathering some further considerations of laboratory experimental simulation fire in the natural environment is a widespread agent of geomorphological and biological change temperatures can exceed 1000 c there is often a rapid rise from ambient conditions through a steep thermal gradient promoting rock disintegration laboratory simulation studies have established that temperature changes which are representative of natural fires affect rock material properties which can then be related to weathering susceptibility this study extends previous work by more closely replicating the natural environment a through the simulation of rainfall and b by encasing samples to reflect the exposure of a single rock face to a passing fire event rock samples collected on cyprus were prepared and tested following previously reported procedures change in modulus of elasticity was monitored using a non destructive ultrasonic method the data corroborate previous work but with somewhat different degrees of change the new results are more likely to be representative of natural conditions and real world change the rate of rock disintegration and effects such as case hardening appear to be a function of rock thermal characteristics material properties and environmental constraints such as diurnal temperature range copyright 1999 john wiley sons ltd

geodynamics of the baikal stanovoy seismic belt abstract the convection generated tensional stress field in the earth as inferred from satellite gravity data reveals an anomalous lens of upwelling mantle rocks under the baikal rift zone the point of no strain at 56 n 116 e forms a seismic gap along the baikal stanovoy seismic belt east of this point the stress field changes from extension to compression therefore the position of no strain at the eastern termination of the rift accounts for the dying out of the rift zone and for the appearance of a compressive structure in the stanovoy range

palaeocontinental configurations and geoid anomalies reconstructions of past continental configurations help our understanding of the evolution of planetary surface morphology and impose valuable constraints on the models for planetary dynamics the problem is that although well established palaeogeographical maps now exist for mesozoic and later times1 2 thanks to excellent agreement between palaeomagnetic and marine magnetic deductions this is not true for earlier times mainly due to the lack of independent palaeogeophysical control over otherwise longitudinally ambiguous palaeomagnetic data the prospect of relating palaeocontinental configurations to geoid anomalies recently raised by anderson3 has thus given a fresh perspective to this problem here his continental insulation model is shown to be an inadequate explanation of the undulations of subduction compensated geoid instead the geoid highs and lows are shown to correlate well with the overall divergent and convergent plate tectonism since the middle palaeozoic and are thus ascribed respectively to the ascending and descending patterns of lower mantle convection

normal and inverted metamorphic isograds and their relation to syntectonic proterozoic batholiths in the wopmay orogen northwest territories canada discussion

thermal effects on the physical properties of limestones from the yucatan peninsula abstract the effect of thermal degradation on the compression strength ultimate compression strain color and mass loss of four limestones extracted from the yucatan peninsula was studied the samples sets were independently subjected to 25 100 200 300 400 500 and 600 c during one hour for each temperature the thermal degradation of the investigated rocks and their chemical composition microstructure and porosity is also investigated the results show a correlation between the mechanical properties thermal behavior the presence of minerals and porosity in each type of limestone rock the variation of the limestones color with temperature was described in terms of standard space color parameters and their diffuse reflectance

vertical distribution of wave shear stress in variable water depth theory and field observations 1 a generalized analytical model is developed to describe the vertical distribution of wave induced shear stress in the presence of bottom slope bottom friction and depth induced wave breaking in the shoaling region and surf zone the theory is compared to data obtained on an unbarred beach in 3 7 m mean water depth over a 2 bottom slope bottom slope and bottom friction are incorporated in the theory by including the wave energy dissipation by bottom friction in a potential wave theory for variable water depth and coupling the wave theory with a wave bottom boundary layer wbbl theory over a sloping bottom the effect of wave breaking is included through a periodic bore dissipation model previous studies have considered some but not all of these effects each of the three components sloping bottom bottom friction and wave breaking exhibits a different vertical structure the contributions due to bottom slope and bottom friction attain maximum strength in the wbbl and decay with distance above the bed approaching smaller but nonzero values at the surface in contrast the contribution from wave breaking is maximal at the surface and decays linearly with depth becoming zero at the bed the vertical structure of the cross shore u and vertical w components of wave orbital velocity was measured using a coherent doppler acoustic profiler the measured velocity fields were used to obtain the ensemble averaged wave shear stress profiles that extend across the wbbl to a height of 30 cm above the bed close to the seabed the observed and predicted uw profiles are similar confirming the sensitivity of wave stress to frictional and bottom slope effects within the wbbl farther from the bed however the observed profiles fall off more rapidly with height as w approaches quadrature with u faster than predicted wave breaking induced shear stresses were not observed

the global stress field in the lithosphere obtained from the satellite gravitational harmonics abstract in this paper the lithosphere is considered to be a homogeneous elastic spherical shell for the sake of simplicity and the stress equations for the base of the lithosphere are taken as boundary conditions then the stress equations are obtained for use in the computation of the stress field in the lithosphere with the satellite gravitational harmonic coefficients the 5 5 global stress field in the lithosphere is computed from harmonics of 2 30 the directions of principal stresses of this stress field agree favourably with the directions of principal stresses indicated by mid plate earthquake mechanisms in situ stress measurements and sensitive geological features this result indicates that the drag forces exerted on the base of the lithosphere due to gravitational mantle convection may be among the driving forces of plate motion and a major source for the stress field in the lithosphere

developments in a non destructive method of determining rock strength material strength is an important variable for any study of the relationships between rock mass geomechanical characteristics and landform development standard field and laboratory tests for measuring strength present a variety of problems to the geomorphologist recent studies allison 1988 have described a laboratory based non destructive method for indirectly determining material strength by measuring dynamic young s modulus data presented here suggest that the same apparatus can be used as a field technique tests have been conducted on the devonian limestone of the napier range western australia laboratory results obtained using the non destructive ultrasonic apparatus have a high correlation with triaxial hoek cell tests results from on site tests have much greater accuracy than data collected using the schmidt hammer which is currently the most widely used geomorphological field technique for determining rock strength

the structure and tectonic evolution of the aguilon fold nappe sierra alhamilla betic cordilleras se spain abstract detailed structural work in the sierra alhamilla se spain shows that the aguilon nappe comprising triassic and older metasedimentary rocks is a fold nappe the most prominent set of small scale folds changes from dominantly n vergent in the upper right way up limb to s vergent in the greatly thinned lower limb the nappe closes to the north and must have been emplaced in this direction nappe formation was accompanied by small scale folding and extensive solution transfer producing a pronounced differentiated crenulation cleavage these structures overprint an earlier set of folds and cleavage and are overprinted in turn by late n vergent structures the lower limb of the nappe was thinned and disrupted during continued nappe transport pre triassic schist in the core of the nappe was affected by medium grade metamorphism of probable post triassic age the contact with low grade permo triassic sediments above and below the schist coincides with a distinct change in metamorphic grade this contact may be a post metamorphic extensional fault that is now folded around the nappe which suggests that nappe formation was preceded by extensional faulting this is consistent with gravity spreading as the driving process for nappe emplacement

complex weathering in drylands implications of stress history for rock debris breakdown and sediment release abstract weathering studies have often sought to explain features in terms of a prevailing set of environmental conditions however it is clear that in most present day hot desert regions the surface rock debris has been exposed to a range of weathering environments and processes these different weathering conditions can arise in two ways either from the effects of long term climate change acting on debris that remains relatively static within the landscape or through the spatial relocation of debris from high to low altitude consequently each fragment of rock may contain a unique weathering related legacy of damage and alteration a legacy that may greatly influence its response to present day weathering activity experiments are described in which blocks of limestone sandstone granite and basalt are given stress histories by subjecting them to varying numbers of heating and freezing cycles as a form of pre treatment these imposed stress histories act as proxies for a weathering history some blocks were used in a laboratory salt weathering simulation study while others underwent a 2 year field exposure trial at high mid and low altitude sites in death valley california weight loss and ultrasonic pulse velocity measurements suggest that blocks with stress histories deteriorate more rapidly than unstressed samples of the same rock type exposed to the same environmental conditions laboratory data also indicate that the result of imposing a known weathering history on samples by pre stressing them is an increase in the amount of fine sediment released during salt weathering over a given period of time in comparison to unstressed samples

observations and a model of undertow over the inner continental shelf abstract onshore volume transport stokes drift due to surface gravity waves propagating toward the beach can result in a compensating eulerian offshore flow in the surf zone referred to as undertow observed offshore flows indicate that wave driven undertow extends well offshore of the surf zone over the inner shelves of martha s vineyard massachusetts and north carolina theoretical estimates of the wave driven offshore transport from linear wave theory and observed wave characteristics account for 50 or more of the observed offshore transport variance in water depths between 5 and 12 m and reproduce the observed dependence on wave height and water depth during weak winds wave driven cross shelf velocity profiles over the inner shelf have maximum offshore flow 1 6 cm s 1 and vertical shear near the surface and weak flow and shear in the lower half of the water column the observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the su

in search for a relationship between harmonic resolutions of the geoid convective stress patterns and tectonics in the lithosphere a possible explanation for the betic rif orocline abstract convective stress fields implied by the runcorn model have been integrated with geological structures in the overlying lithosphere this is dangerous since small scale convection patterns in the mantle might have remained stationary for at least 50 ma while particular parts of the lithosphere are likely to have passed over distinct convective stress regimes in such periods the mantle component of the stress history of lithospheric structures younger than 32 ma is potentially tractable if a mean plate velocity of 5 cm y 1 is assumed this is because the satellite gravity data used here allow the detection of convection cells with horizontal length scales of the order of 1600 km which the lithosphere may cross in 32 ma for example the sublithospheric stress field might have accounted for the uplift and subsequent subsidence of the alboran sea basin w mediterranean between 25 and 20 ma ago an immature diapiric rise of the mantle due to upwelling is likely to have occurred beneath this region between 25 and 20 ma ago the resulting lithospheric swell caused extensive tectonic unroofing by nappe spreading with or without some sliding the subsidence of the alboran sea after the rise of the dome seems an excellent example of the combined effects of lithospheric cooling connected with ceasing mantle diapirism and mechanical thinning of the lithosphere by nappe translations

experimental salt weathering of limestones in relation to rock properties a total of 21 different types of british and european mesozoic limestones have been subjected to simulated salt weathering using sodium sulphate na2so4 with the following aims assessment of the relative durabilities of different types of limestone assessment of the importance of modulus of elasticity and other factors in affecting durability and assessment of the use of impulse excitation techniques to monitor changes in rock modulus of elasticity the rocks showed a wide spectrum of durabilities while rocks with high values of modulus of elasticity lower water absorption capacities high densities and low salt uptakes tended to be durable there were anomalies the explanation for which probably lies in their pore structures non destructive testing techniques showed that although the more durable rocks failed to lose weight or to show visual signs of disintegration their modulus of elasticity values did tend to decline indicating a loss in strength copyright 1999 john wiley sons ltd

geometry of isograds in metamorphic terrains abstract a simple mathematical relation among the dip of isograd surface dip of isotherm surface temperature gradient t g pressure gradient p g and t gdp of reaction is given by 1 sin ga t p p g 1 t g cos cot p g is taken to be constant at 0 3 kb km four major theoretical models for shapes and orientations of isograds are formulated on the basis of the parameters t g and t p this offers a rational basis for studying the geometry of isograds normal reverse metamorphism and determination of temperature gradient two examples have been studied in the light of these models in one case the domed shape of the isograd is best explained by a downwardly directed t g in the other case reverse metamorphism is best explained as the result of a horizontal t g of 18 c km

mantle convection as a boundary layer phenomenon summary the boundary layer nature of vigorous thermal convection is explored using high resolution numerical solutions to the governing hydrodynamic equations these solutions are obtained for a series of idealized models of the earth s mantle in which the viscosity is assumed to be constant a detailed analysis of the local energy balance within the horizontal and vertical thermal boundary layers is presented in terms of which a test of the fundamental assumptions of boundary layer theory is provided the results of this test have important geophysical consequences since the asymptotic predictions of boundary layer theory have been employed extensively in the context of thermal history modelling although boundary layer theory closely predicts the correct power law behaviour of various quantities it does not determine their absolute values accurately vertical advection is shown to play an important role in the energy balance within horizontal boundary layers at all rayleigh numbers horizontal and vertical advection dominate the energy balance within vertical plumes while horizontal diffusion plays a very minor role when heating is partially from within the fluid vertical advection into the upper thermal boundary layer can produce significant departures in the thermal structure from that found when heating is entirely from below for a free upper boundary this results in a relative flattening of the variations of surface topography and heat flow across the convection cells for a constant velocity upper boundary similar to plate motion the bathymetry flattens but the heat flow does not this result agrees with marine observations rigidity of the thermal boundary layer below the upper surface is not included explicitly in the model and it is not known whether the inclusion of this feature in future models would significantly alter the topographic expression if not the observed departure of the oceanic bathymetry from a 6 dependence at old ocean floor ages could be attributed to a small amount of internal heating in a mantle wide convective circulation

rock resistance to erosion some further considerations rock resistance to erosion is an often described factor in geomorphic studies and is generally considered to strongly influence the shape of erosional landforms however the property of the rock mass that enables it to resist erosion is rarely considered and its measurement is rarely justified and assessed adequately allison 1988 1990 examined the intact strength properties of several types of carbonate rocks and considered that dynamic young s modulus is a good indicator of rock material strength for geomorphic purposes and cast doubts on the reliability of schmidt hammer tests for this purpose alternative approaches to rock characterization from the view point of evaluating rock intact strength are considered

rock hardness and landform development in the gunong mulu national park sarawak e malaysia rock hardness measured by the schmidt test hammer is an important factor in explaining some of the sharp contrasts in relief and wide variety of landforms in the gunong mulu national park it is also useful in consideration of contemporary geomorphological processes such as landsliding

on the forces driving plate tectonics inferences from absolute plate velocities and intraplate stress summary absolute plate motions and intraplate stress both serve as tests of models for the forces acting on plate boundaries plate velocities relative to a presumedly fixed underlying mantle are calculated from the hypothesis that no net torque is exerted on the lithosphere intraplate stress is calculated by solving the equilibrium equations for thin elastic shells in the membrane state of stress the absolute velocity fields predicted from a wide assortment of physical and geological models are all very similar while the global pattern of absolute velocity is probably close to those predicted by such models the absolute motions do not therefore provide a strong test of the driving mechanism comparison of predicted intraplate stress with the long wavelength features of the global stress field however as determined by in situ measurements earthquake mechanisms and stressinduced geological structures does prove to be a powerful test of possible driving forces all absolute velocity models have several interesting properties lithosphere in the equatorial half of the earth is moving significantly faster than lithosphere in the polar half some connection to the earth s rotation is implied since this statement is demonstrably untrue for co ordinate poles much different from the geographic pole subducted slabs are characterized by a slow horizontal translation perpendicular to strike that is independent of the plate convergence rate confounding attempts to explain the dip angles of benioff zones in terms of a uniform vertical sinking and a variable absolute velocity for the overthrust plate ridges must migrate at a wide range of velocities relative to their underlying source of new lithosphere such rapid migration may be a necessary but is not a sufficient condition for ridge jumps force models considered in velocity and stress calculations include driving forces at spreading centres and subduction zones and various parameterizations of drag at the base of the lithosphere from the rms absolute velocities of individual plates there is a weak indication that pull by subducted lithosphere at trenches is an important driving force and that drag may be greater beneath continental than oceanic lithosphere the predicted intraplate deviatoric stress cannot match the well determined stress fields in north america and europe unless the driving force exerted at ridges is at least comparable in magnitude to other forces in the system the mid plate stresses are very sensitive to the nature of drag at the base of the lithosphere and thus measured stresses may ultimately provide a sensitive test of absolute plate velocities

crustal thinning and subsidence in the north sea we present here the results of a detailed study of subsidence and crystal thinning across the central graben of the north sea basin two independent lines of evidence have been used to test how well the uniform extensional model1 2 can account for the evolution of the north sea basin a long range seismic profile was shot perpendicular to the central graben from edinburgh to southern norway and data were analysed from 11 exploration wells situated close to the seismic line fig 1 the estimates of the increase in surface area due to extension from the crustal structure determined using the seismic data and from the well subsidence patterns are both compatible with a simple uniform extensional mechanism for the post palaeozoic evolution of the north sea

rapid salt weathering in the coastal namib desert implications for landscape development data on the rate and style of breakdown on naturally occurring rock types are important to improving geomorphological understanding of landscape development in arid environments two years exposure of rock blocks cut from an english limestone bath stone as well as locally relevant namibian rocks karibib marble and damara granite within four distinctive microenvironments in and around a coastal salt pan environment reveals high rates of breakdown in the bath stone blocks observable breakdown in the marble blocks and weight gains and strength increases in the granite blocks breakdown is associated with high conductivities and large amounts of halite and gypsum within the surface sediments frequency of wetting and drying appears to be a major control on the resultant breakdown rates these findings can be compared with recent data from further inland in the namib desert which suggest very slow rates of breakdown of similar blocks of damara granite and karibib marble even where salts are readily available high rates of rock breakdown within coastal salt pans appear to contribute to dust production and the effective flattening of relief along the coastal strip

rock mass strength and the form of some inselbergs in the central namib desert a rock mass strength classification involving eight parameters has been applied to selected inselbergs in the namib desert the inselbergs are formed of schists gneiss granite and marble their slope inclinations are in a strength equilibrium with their rocks the study suggests that the strength classification is consistent and has a general validity and that rock slopes undergoing uniform weathering retreat to form slopes which are adjusted to their rock mass strength this is a more general statement than the common hypothesis of parallel retreat the favoured hypothesis of slope evolution in the namib is one of retreat rather than downwearing

role of strike slip faults in the betic rifian orogeny abstract a new model for the betic rifian orogeny of the western mediterranean spain and north africa is proposed in which four strike slip faults play an important role the faults are not of the same age two faults the left lateral jebha fault to the south in morocco and principally in the mediterranean sea and the right lateral north betic fault southern spain to the north define the boundaries of the alboran block betic and rifian internal zones final movement along these faults was during the burdigalian time two other faults the left lateral nekor fault north africa to the south of the jebha fault and the right lateral crevillente fault somewhat to the north of the north betic fault define a larger alboran block including part of the betic and rifian external zones that was present during the tortonian the following sequence of events is proposed 1 a during the eocene and oligocene the african and european plates converged in a n s sense causing the breakup and overthrusting of the betic rifian and kabyle internal zones and then the movement towards the wsw of the alboran block by slip along the jebha and north betic faults 2 b by the end of burdigalian time movement along the jebha and north betic faults ceased 3 c with continued n s convergence the nekor and crevillente faults which bound a larger alboran block were formed during the mid and late miocene the arc of gibraltar the zone lying between the four major faults seems to be a result of wsw motion of a crustal block being thrust over external zones the model proposed adds to the earlier idea that tectogenesis proceeds from the interior to the exterior of an erogenic belt in the betic rifian orogeny major strike slip fracture zones shifted to the exterior of the orogenic belt as the orogeny progressed in order to relieve the stress caused by locking of the more internal faults

energy saturation and phase speeds measured on a natural beach field measurements of wave height and speed from 7 m depth shoreward are described the experiment plan consisted of a shore normal transect of closely spaced compared to a dominant wave length velocity pressure and elevation sensors on an almost plane profile having an inshore slope of 1 50 as the waves shoal and begin to break the dominant dissipative mechanism is due to turbulence generated at the crest and wave heights become increasingly depth controlled as they progress across the surf zone wave heights in the inner surf zone are strongly depth independent the envelope of the wave heights is described by h sub rms 0 42 h the depth dependence of the breaking wave height is shown to be related to the kinematic instability criterion celerity spectra were measured by using phase spectra calculated between pairs of adjacent sensors inshore of 4 m depth the celerity was found distant over the energetic region of the spectrum a mean celerity was compared with linear theory and was within 20 and 10 showing good agreement for such a nonlinear dissipative region

the relations between modulus of elasticity and temperature in the context of the experimental simulation of rock weathering by fire fires occur frequently in many biomes and generate high temperatures on the ground surface there are many field examples of fire causing rock disintegration the simulation of fire in the laboratory using a furnace and the monitoring of changes in rock modulus of elasticity with a grindosonic apparatus reveal that different rocks respond differently to heating significant decreases in elasticity occur at temperatures as low as 200 c and granites display particularly marked reductions extended periods of heating are not required for significant reductions to occur it is postulated that the degree of change in elasticity as a result of simulated fire is such that rock outcrops subjected to real fires are likely to be sufficiently modified as to increase their susceptibility to erosion and weathering processes

developments in a non destructive method of determining rock strength a reply in a previous publication allison 1989 a non destructive method for indirectly determining rock strength by measuring dynamic young s modulus was described data were presented to assess the grindosonic apparatus in relation to standard laboratory techniques a further short communication allison 1990 evaluated the non destructive test as a field technique in part achieved by comparing the grindosonic results with data collected using the schmidt hammer the schmidt hammer is a widely used field technique in geomorphology for determining rock strength see for example day and goudie 1977 day 1981 allison 1989 1990 also suggested that the elastic properties of materials are becoming increasingly important in geomorphological studies the opportunity to provide additional information and comments here is appreciated

normal and inverted metamorphic isograds and their relation to syntectonic proterozoic batholiths in the wopmay orogen northwest territories canada abstract three progressive metamorphic suites are developed in pelitic rocks of the northern wopmay orogen two suites are related to the hepburn batholith and one to the wentzel batholith all three suites are cut by post metamorphic wrench faults some of which have significant vertical displacement the structural relief so provided reveals that medium and high grade isograds associated with the hepburn batholith dip inward towards the batholith and are thus hot side up isograds associated with the wentzel batholith dip away from the batholith and are thus hot side down it is concluded that hepburn batholith has the form of the flattened funnel fed from depth and that wentzel batholith is the arched roof of an intrusive complex of unknown shape at depth

magmatic evolution of the alboran region the role of subduction in forming the western mediterranean and causing the messinian salinity crisis the magmatic evolution of the alboran region westernmost mediterranean contains important clues for improving our understanding of the origin of mediterranean style back arc basins and the desiccation of the mediterranean sea in the messinian we use new laser 40ar 39ar age and geochemical major and trace element and o sr nd pb isotope data from igneous rocks from southern spain the alboran sea and northern morocco to reconstruct the magmatic evolution of the westernmost mediterranean since the eocene lower oligocene dikes near malaga 33 6 0 6 ma and middle to upper miocene volcanic rocks from the alboran sea area 6 57 0 04 to 11 8 0 4 ma can be subdivided into two groups 1 lree depleted relative to n morb primarily tholeiitic series and 2 lree enriched primarily calc alkaline series volcanic rocks both groups are generally enriched in fluid mobile elements e g rb th u k and pb relative to fluid immobile elements e g nb ta lree the lree depleted group has 143nd 144nd 0 5128 0 5130 isotope ratios similar to atlantic morb but higher 87sr 86sr 0 7046 0 7100 in contrast the lree enriched group has less radiogenic nd 0 5121 0 5126 and tend to more radiogenic sr 0 7066 0 7205 isotopic composition pb isotope ratios are surprisingly uniform and have compositions similar to marine sediments analyses of mineral separates show that mafic melts with relatively low 18o 5 6 7 2 had high 87sr 86sr 0 7048 0 7088 7 4 10 6 14 1 and 8 4 40 0 49 3 modeling of the trace elements and sr nd pb o isotopic compositions provides compelling evidence for the contamination of the mantle source with hydrous fluids melts which can be explained through subduction of oceanic lithosphere beneath the alboran basin but not through detachment delamination of lithospheric mantle we present a geodynamic model that reconstructs the late eocene to quaternary evolution of the western mediterranean through westward roll back of subducted tethys oceanic lithosphere slab roll back resulted in a large scale reorganization of the western mediterranean paleogeography causing the closure of marine gateways linking the atlantic ocean to the mediterranean sea isolation of the mediterranean sea led to its desiccation causing the messinian salinity crisis

quantification of rock control in geomorphology abstract rock control the influence of rock properties on landform development has for long been a relatively under researched topic but numerous techniques have been developed especially by geotechnical engineers and stone conservationists that are now being applied to geomorphological issues by geomorphologists these techniques range in scale from the quantification of major discontinuities through to analysis of micro pores rock control studies that have taken place over the last few decades have contributed important insights into our understanding of such diverse phenomena as 1 river terraces bedrock channel forms and gradients pot hole development drainage density and gully badland development 2 slope forms and failures especially with respect to rock mass strength 3 the form of glacial troughs and of subglacial erosional landforms 4 weathering controls on rock durability and the association of weathering with porosity 5 classic karst features including various types of karren 6 sandstone landforms 7 inselbergs and tors and 8 cliffs and shore platforms

a non destructive method of determining rock strength rock material strength is an important component of many geomorphological studies current methods for determining this parameter result in sample destruction preventing further analysis a new non destructive technique is described for indirectly determining material strength by measuring dynamic young s modulus tests have been conducted on jurassic portland limestone and upper cretaceous chalk to assess the apparatus young s modulus is becoming an increasingly important rock material property

a revision of the eurasian african plate boundary in the western mediterranean the current picture of the plate configuration in the western mediterranean suggests that africa and europe are separated by a transcurrent fault striking east west through the strait of gibraltar and the alboran sea such a fault has been generally assumed because the azores transform fault approaches the horseshoe seamounts north of madeira and therefore could possibly extend through the strait of gibraltar however detailed geological studies in the arc of gibraltar and the alboran sea reveal no major east west fault transecting the crust there this finding is used here to revise the boundary between the african and eurasian plates it is suggested that the northern boundary of the african plate in the western mediterranean is formed by the hayes atlas fault instead of the azores transform

observations of wave shear stress on a steep beach observations are presented of the wave shear stress u w on a steeply sloping beach above the wave boundary layer wbl positive values of u w were observed and are attributed to a combination of both wave shoaling due to the large scale bed slope and dissipation due to wave breaking in agreement with the wave theory of zou et al 2003 within the wbl observed vertical profiles of u w were also in good agreement with theory in cases where the wave height was small as wave heights increased however the wbl profile of u w generally did not agree with theory near simultaneous rotary sonar observations of the bed suggest the disagreement with theory was due to the presence of orbital scale ripples which the present theory does not accommodate

the impact of a major quaternary river capture on the alluvial sediments of a beheaded river system the rio alias se spain the rio alias is a transverse river system developed within the sorbas and almeria neogene sedimentary basins within the internal zone of the betic cordillera southeast spain headwaters of the rio alias rise in the southern margins of the sorbas basin following a superimposed transverse course across the sierra alhamilla cabrera and its associated boundary faults a major river capture event within the sorbas basin c 70 ka created a situation whereby the rio alias abruptly lost c 70 of its drainage area such an extensive loss of drainage area led to significant modification of the fluvial system in both upstream and downstream zones on the capturing stream and downstream on the beheaded system on the beheaded rio alias a combination of terrace mapping clast identification analysis field descriptions of pedological development and mineral magnetic analysis allows the relative timing of the capture event to be confirmed examination of the fluvial architecture of the quaternary terrace deposits reveals significant changes in bedform geometry involving a reduction in bedform height degree of channelisation and maximum clast size in the post capture sediment assemblage the post capture evolution of the rio alias has been heavily influenced by the river capture event highlighting the need for further analysis of beheaded drainage systems and their influence on developing landform assemblages

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

spatial variability of the wave bottom boundary layer over movable rippled beds observations of the spatially dependent velocity field over movable bed forms subjected to slightly skewed and asymmetric regular wave forcing were collected the dynamics between the ripple elements is dominated by coherent vortices characterized by the swirling strength and evidenced in the temporal and spectral characterization within the boundary layer spectral energy in the second harmonic 3f0 is amplified at the ripple slopes and is consistent with the location of the expected strongest pressure gradients first moment and second moment velocity statistics were used to address the spatial variability of the intra ripple hydrodynamics estimates of displacement and momentum thicknesses and mom are smaller than suggested by the higher harmonics but consistently highlight areas of adverse and favorable pressure gradients shear stress and roughness estimates were inferred by fitting a logarithmic model to first moment and second moment statistics of the velocity field the maximum shields parameter was observed to peak at the stoss slope of asymmetric ripples during the strongest and shorter half wave period onshore first moment roughness estimates are similar in magnitude to bed load parameterizations provided by li et al 1997 and about a factor of 3 larger than second moment estimates assessment of the vertical transfer of horizontal momentum derived using a reynolds decomposition suggests that stresses inferred from the logarithmic law using first moment velocity statistics appropriately reproduce the mean momentum transfer for the longer and weaker offshore half wave period

evolution of the mechanical behaviour of limestone subjected to freeze thaw cycles the frost weathering of three french limestones lens ls migne mi and savonnieres sa with different physico mechanical properties during the freeze thaw cycles was studied the weathering evolution in stone samples undergoing the freeze thaw cycles was monitored by measurement of following properties total porosity p wave velocity static elastic moduli uniaxial compressive strength and toughness the thermo mechanical behaviour of stones was also studied by measurement of the strain and temperature in surface and centre of sample during one freeze thaw cycle these results mainly the weathering observed for sa 73 with a degree of saturation of 73 and a lack of weathering for ls with a degree of saturation of 90 show that it is impossible to define a unique critical degree of saturation for different stones and this varies from stone to stone the shrinkage and or the expansion of samples during the crystallization phase were determined the shrinkage is related to the migration of water away from tiny pores towards larger cavities where ice has already formed the expansion is attributed on the one hand to the rise in pressure that comes from the water which flows towards the ice front and on the other hand to the relatively important quantity of ice formed when thermal contraction and the contraction due to migration dominate the elastic moduli static moduli and dynamic moduli was found to be affected the most by frost weathering and is a real sensor of first micro crack initiation whereas the uniaxial compressive strength and the porosity were found to be affected the least

flow in the mantle inferred from the low degree harmonics of the geopotential summary flow in the earth s mantle is inferred from continental drift its distribution may be obtained from the pattern of zones of compression and tension in the earth s crust and from the low harmonics of the geopotential the origin of the flow is held to be convection the depth to which the flow extends will be discussed the relation of the flow to the earthquake mechanism will be considered