spine growth and seismogenic faulting at mt unzen japan the concluding episode of activity during the recent eruption of mt unzen october 1994 to february 1995 was characterized by incremental spine extrusion accompanied by seismicity analysis of the seismic record reveals the occurrence of two dominant long period event families associated with a repeating nondestructive source mechanism which we attribute to magma failure and fault controlled ascent we obtain constraints on the slip rate and distance of faulting events within these families that analysis is complemented by an experimental thermomechanical investigation of fault friction in mt unzen dacitic dome rock using a rotary shear apparatus at variable slip rates and normal stresses a power density threshold is found at 0 3 mw m 2 above which frictional melt forms and controls the shear resistance to slip inducing a deviation from byerlee s frictional law homogenized experimentally generated pseudotachylytes have a similar final chemistry thickness and crystal content facilitating the construction of a rheological model for particle suspensions this is compared to the viscosity constrained from the experimental data to assess the viscous control on fault dynamics the onset of frictional melt formation during spine growth is constrained to depths below 300 m for an average slip event this combination of experimental data viscosity modeling and seismic analysis offers a new description of material response during conduit plug flow and spine growth showing that volcanic pseudotachylyte may commonly form and modify fault friction during faulting of dome rock this model furthers our understanding of faulting and seismicity during lava dome formation and is applicable to other eruption modes

neoproterozoic snowball earth simulations with a coupled climate ice sheet model ice sheets may have reached the equator in the late proterozoic era 600 800 myr ago according to geological and palaeomagnetic studies possibly resulting in a snowball earth but this period was a critical time in the evolution of multicellular animals posing the question of how early life survived under such environmental stress here we present computer simulations of this unusual climate stage with a coupled climate ice sheet model to simulate a snowball earth we use only a reduction in the solar constant compared to present day conditions and we keep atmospheric co2 concentrations near present levels we find rapid transitions into and out of full glaciation that are consistent with the geological evidence when we combine these results with a general circulation model some of the simulations result in an equatorial belt of open water that may have provided a refugium for multicellular animals

the role of alluvial fans in the mountain fluvial systems of southeast spain implications of climatic change the mountain fluvial systems of southeast spain involve sediment supply from steep mountain slopes into headwater channels alluvial fans often occur where these headwater channels emerge from the mountain areas and may influence the connectivity of the sediment transport system from the mountain source areas to the main lowland drainages critical in this role is whether the alluvial fans are aggrading or dissecting and whether there is a break or continuity in the channel through the fan environment previous work has identified some of the factors influencing the behaviour of the alluvial fans in southeast spain this paper deals with the mountain front alluvial fans in the semi arid areas of murcia and almeria provinces it attempts by mapping the location of alluvial fans then their classification into aggrading or dissecting fans to identify the extent to which the mountain fluvial systems are buffered by aggrading alluvial fans or exhibit channel continuity through the mountain front environment it further considers the implications of climatically induced changes between aggradational and dissectional behaviour on alluvial fans

structures and facies associated with the flow of subaerial basaltic lava into a deep freshwater lake the sulphur creek lava flow north cascades washington abstract the ca 8800 14c yrs bp sulphur creek lava flowed eastward 12 km from the schriebers meadow cinder cone into the baker river valley on the southeast flank of mount baker volcano the compositionally zoned basaltic to basaltic andesite lava entered crossed and partially filled the 2 km wide and 100 m deep early holocene remnant of glacial lake baker the valley is now submerged beneath a reservoir but seasonal drawdown permits study of the distal entrant lava as a lava volume that may have been as much as 180 106 m3 entered the lake the flow invaded the lacustrine sequence and extended to the opposite east side of the drowned baker river valley the volume and mobility of the lava can be attributed to a high flux rate a prolonged eruption or both basalt exposed below the former level of the remnant glacial lake is glassy or microcrystalline and sparsely vesicular with pervasive hackly or blocky fractures together with pseudopillow fractures these features reflect fracturing normal to penetrative thermal fronts and quenching by water a fine grained hyaloclastite facies was probably formed during quench fragmentation or isolated magma water explosions although the structures closely resemble those developed in lava ice contact environments establishing the depositional environment for lava exhibiting similar intense fracturing should be confirmed by geologic evidence rather than by internal structure alone the lava also invaded the lacustrine sequence forming varieties of peperite including sills that are conformable within the invaded strata and resemble volcaniclastic breccias the peperite is generally fragmental and clast or matrix supported fine grained and rounded fluidal margins occur locally the lava formed a thickened subaqueous plug that as the lake drained in the mid holocene was exposed to erosion the baker river then cut a 52 m deep gorge through the shattered highly erodible basalt

volcanic deformation at unzen japan visualized by a time differential stereoscopy abstract using a pair of old and new photographs taken at the same location a method named as a time differential stereoscopy is successfully applied to detect visually the deformation at unzen volcano japan on september 6 1992 gradual movement of a lava lobe was visible in a stereo image as relief surrounded by immobile areas in this case accelerated movement of a lava block was detected immediately before the time of its collapse which resulted in the occurrence of a pyroclastic flow in november 1994 growth of a lava spine was also measured with time differential stereoscopy a possible fluctuation of the growth rate might have correlated with an abnormal oscillation of tilt with a period of about 40 h this convenient photographic method is recommended for various occasions to detect volcanic and any other deformations as a supplement to precise instrumental measurements

owyhee river intracanyon lava flows does the river give a dam rivers carved into uplifted plateaus are commonly disrupted by discrete events from the surrounding landscape such as lava flows or large mass movements these disruptions are independent of slope basin area or channel discharge and can dominate aspects of valley morphology and channel behavior for many kilometers we document and assess the effects of one type of disruptive event lava dams on river valley morphology and incision rates at a variety of time scales using examples from the owyhee river in southeastern oregon six sets of basaltic lava flows entered and dammed the river canyon during two periods in the late cenozoic ca 2 ma 780 ka and 250 70 ka the dams are strongly asymmetric with steep blunt escarpments facing up valley and long low slopes down valley none of the dams shows evidence of catastrophic failure all blocked the river and diverted water over or around the dam crest the net effect of the dams was therefore to inhibit rather than promote incision once incision resumed most of the intracanyon flows were incised relatively rapidly and therefore did not exert a lasting impact on the river valley profile over time scales 10 6 yr the net long term incision rate from the time of the oldest documented lava dam the bogus rim lava dam 1 7 ma to present was 0 18 mm yr but incision rates through or around individual lava dams were up to an order of magnitude greater at least three lava dams bogus rim saddle butte and west crater show evidence that incision initiated only after the impounded lakes filled completely with sediment and there was gravel transport across the dams the most recent lava dam formed by the west crater lava flow around 70 ka persisted for at least 25 k y before incision began and the dam was largely removed within another 35 k y the time scale over which the lava dams inhibit incision is therefore directly affected by both the volume of lava forming the dam and the time required for sediment to fill the blocked valley variations in this primary process of incision through the lava dams could be influenced by additional independent factors such as regional uplift drainage integration or climate that affect the relative base level discharge and sediment yield within the watershed by redirecting the river tributaries and subsequent lava flows to different parts of the canyon lava dams create a distinct valley morphology of flat broad basalt shelves capping steep cliffs of tertiary sediment this stratigraphy is conducive to landsliding and extends the effects of intracanyon lava flows on channel geomorphology beyond the lifetime of the dams

monitoring lava dome growth during the 2004 2008 mount st helens washington eruption using oblique terrestrial photography abstract we present an analysis of lava dome growth during the 2004 2008 eruption of mount st helens using oblique terrestrial images from a network of remotely placed cameras this underutilized monitoring tool augmented more traditional monitoring techniques and was used to provide a robust assessment of the nature pace and state of the eruption and to quantify the kinematics of dome growth eruption monitoring using terrestrial photography began with a single camera deployed at the mouth of the volcano s crater during the first year of activity analysis of those images indicates that the average lineal extrusion rate decayed approximately logarithmically from about 8 m d to about 2 m d 2 m d from november 2004 through december 2005 and suggests that the extrusion rate fluctuated on time scales of days to weeks from may 2006 through september 2007 imagery from multiple cameras deployed around the volcano allowed determination of 3 dimensional motion across the dome complex analysis of the multi camera imagery shows spatially differential but remarkably steady to gradually slowing motion from about 1 2 m d from may through october 2006 to about 0 2 1 0 m d from may through september 2007 in contrast to the fluctuations in lineal extrusion rate documented during the first year of eruption dome motion from may 2006 through september 2007 was monotonic 0 10 m d to gradually slowing on time scales of weeks to months the ability to measure spatial and temporal rates of motion of the effusing lava dome from oblique terrestrial photographs provided a significant and sometimes the sole means of identifying and quantifying dome growth during the eruption and it demonstrates the utility of using frequent long term terrestrial photography to monitor and study volcanic eruptions

coupled subdaily and multiweek cycles during the lava dome eruption of soufriere hills volcano montserrat 1 observations of volcanoes extruding andesitic lava to produce lava domes often reveal cyclic behavior at soufriere hills volcano montserrat cycles with subdaily and multiweek periods have been recognized on many occasions observations clearly show that the period of subdaily cycles is modulated by the multiweek cycle the subdaily and multiweek cycles have been modeled separately as stick slip magma flow at the junction between a dyke and an overlying cylindrical conduit and as the filling and discharge of magma through the elastic walled dyke respectively here we couple these two models to describe the behavior over a period of well observed multiweek cycles with accompanying subdaily cycles from 13 may to 21 september 1997 the coupled model captures well the asymmetrical first order behavior the first 40 of the multiweek cycle consists of high rates of lava extrusion during short period high amplitude subdaily cycles as the dyke reservoir discharges itself the remainder of the cycle involves increasing pressurization as more magma is stored and extrusion rate falls followed by a gradual increase in the period of the subdaily cycles

climatic and tectonic controls on fluvial incision and aggradation in the spanish pyrenees the influences of tectonic and climatic changes on upland river systems are investigated using data from plio pleistocene terraces of the rio cinca river in the southern pyrenees this river runs transverse to the main thrust fault structures and is a major conduit for sediment delivery to the ebro basin detailed field mapping combined with long profile and palaeohydraulic reconstructions yields a comprehensive picture of changes in palaeoriver character during the plio pleistocene as the area is over 150 km from the basin outlet in the mediterranean sea changes in base level are unlikely to have influenced terrace development although tectonic activity has exerted a strong control on the position of the river the main period of thrust propagation pre dates the terraces and activity has waned from the pliocene through to the present it is concluded that the main control on incision in this area is climate through its influence on sediment supply rivers which are starved of sediment by climate change will have the power to incise whereas aggradational phases are linked to periods of increased sediment flux

strath terraces of jinshaan canyon yellow river and quaternary tectonic movements of the ordos plateau north china studies of the strath terraces in jinshaan canyon where the yellow river cuts through the ordos plateau in the continental interior of china provide an opportunity to solve some of the critical problems associated with quaternary tectonic movement of the plateau six strath terraces indicate that five episodes of regional epeirogenic uplift affected the ordos plateau during the quaternary the local tectonic deformation is superimposed on the regional epeirogenic uplift expressed either as faulting or as non uniform uplift induced by local arching the results have important implications for understanding the relationship between the regional epeirogenic uplift of the ordos plateau and the uplift of the qingzang plateau time lines of climate change in the regional epeirogenic uplift landscape and the genesis of strath terraces associated with the through flowing plateau drainage in the continental interior

valley incision and the uplift of mountain peaks simple end member models describe the effect of isostatically compensated valley incision on the elevation of mountain peaks these models allow calculation of the maximum portion of mountain peak elevations attributable to the development of observed relief and predict general downstream patterns of ridgetop uplift in response to erosion by fluvial processes analyses of topographic profiles across major drainages of the central sierra nevada and the tibetan plateau indicate that isostatically compensated valley incision could account for at most 5 10 of the present elevation of mountain peaks in contrast analyses of topographic profiles across the himalaya show that as much as 20 30 of the present elevation of himalayan peaks could be explained by isostatically compensated valley incision the degree to which valley incision is compensated locally however depends on the flexural rigidity of the lithosphere the size of the range and its tectonic boundary conditions these results show that while a tectonic control is required for late cenozoic surface uplift of the sierra nevada a significant portion of the elevation of himalayan peaks may reflect late cenozoic valley incision on the margin of the tibetan plateau

river response to high frequency climate oscillations in southern europe over the past 200 k y a 200 k y chronology of river response to climate related environmental change has been established for northeast spain using newly developed luminescence dating techniques this constitutes the best documented record of late quaternary river behavior currently available for the north atlantic region and enables fluvial stratigraphies to be compared with high resolution ice core and marine oxygen isotope climate series pleistocene and holocene river aggradational episodes coincide with stadial or neoglacial events while phases of river incision occur during interstadial or interglacial periods alluviation and erosion cycles would appear to track variations in sediment supply controlled by vegetation cover and winter storm frequency

ground deformation cycles in a magma effusive stage and sub plinian and vulcanian eruptions at kirishima volcanoes japan 1 the dynamics of explosive eruptions such as plinian sub plinian vulcanian and strombolian ones is one of the most fascinating subjects in volcano physics during the early period of volcanic activity at the shinmoe dake volcano in 2011 various kinds of activities such as sub plinian eruptions a magma effusion and vulcanian eruptions occurred sequentially a different kind of tilt motion accompanied each activity here we clarify the characteristics of the tilt motions and their time sequences presenting a new explanation of the triggering mechanism of a vulcanian eruption the sub plinian and the vulcanian eruptions at the shinmoe dake volcano were preceded by inflations at shallow depths near the summit the inflation deflation cycles were also recorded during the magma effusive stage with a typical period of 1 h synchronized with volcanic tremors or long period events almost all vulcanian eruptions were preceded by trapezoidal inflations whose durations systematically lengthened as time progressed and were followed by various time sequences of tilt motions which became increasingly more complicated throughout the frequent vulcanian eruptions we have found clear linearity with a constant gradient of 0 45 between the logarithm of the preceding duration versus elapsed time for each substage these observations can be consistently explained based on the assumption that a vulcanian eruption is induced by a catastrophic rupture of the strongest closed solid magma frame due to magma degassing overpressure and the degassing from magma declines exponentially with time

rates of stream incision in the middle part of the arkansas river basin based on late tertiary to mid pleistocene volcanic ash abstract ages and elevations of ash layers correlated with late tertiary and pleistocene eruptions in the western us and present stream elevations are used to calculate net rates of incision by streams in the middle reaches of the arkansas river basin in the south central us the mean of the 23 measurements of rate of stream incision in the study area is 4 2 2 7 cm ky with a range of 0 6 to 9 7 cm ky major influences on rate of stream incision in the study area include the arid to semi arid climate of the region the type of material being incised by streams stream captures and salt dissolution in the bedrock that underlies the region rates of incision exceeded rates of basin filling but significant deposits of unconsolidated late cenozoic sediments occur in the study area basins of streams that have incised the slowest since the late tertiary contain the thickest and most extensive amounts of unconsolidated quaternary sediments rates of incision by streams in the study area are similar to or slower than rates reported for streams elsewhere in the us and the world streams in mountainous regions and areas affected by rapid uplift have incised at rates orders of magnitude faster than streams in the study area

first radiocarbon dating of a holocene eruption of the datong volcanic field eastern china abstract the accurate dating of prehistoric eruptions is essential for reconstructing volcanic sequences and for preparing volcanic hazard assessments the chronology of the eruptions of the datong volcanic field dvf in eastern china has been debated for several decades especially the start and end of volcanism loess sediments incorporated in explosive volcanic products have been described from the dongpingshan scoria cone in the dvf we conducted radiocarbon dating of the loess sediments which produced an age of 7300 cal yr bp for the dongpingshan volcanic eruption this result confirms the eruption of the dvf during the holocene and it provides important evidence for assessing volcanic hazards in this densely populated region the holocene age of the eruption indicates that dvf is dormant contrary to previous studies which concluded that the dvf is extinct and that its volcanic eruptions ended at 100 ka in addition this study documents a new method of dating late pleistocene to holocene volcanic eruptions in and around the dvf where loess sediments are widespread and may be preserved within volcanic products

stream incision and terrace development in frijoles canyon bandelier national monument new mexico and the influence of lithology and climate abstract the record of stream incision and terrace development in frijoles canyon nm was investigated to examine the controls on channel evolution in this region frijoles canyon developed after deposition of the voluminous ignimbrites of the tshirege member of the bandelier tuff at ca 1 22 ma which provides excellent temporal constraints on canyon evolution base level fall along the rio grande the master drainage in the region contributed to initial incision of the stream development of a major knickpoint in basalt near the rio grande however has effectively isolated most of the stream channel from direct effects of this base level change since the early or middle pleistocene late quaternary evolution of the channel has included development of strath and fill terraces that record the effects of climatic variations and local lithologic variations within the tuff on channel processes a fill terrace underlain by up to 13 m of coarse gravelly alluvium records significant aggradation in the early to middle holocene following a major regional climate change aggradation probably resulted from large increases in sediment supply in the holocene relative to the late pleistocene which was perhaps related to variations in intense summer rains rapid incision in the middle to late holocene has stranded the underlying strath up to 21 m above the modern channel and local rates of incision of up to 4 m ka are more than 10 times the average rates since 1 22 ma holocene incision displays great spatial variability associated with local lithologic variations and results in a stream profile that has evolved rapidly in the last 10 000 years the high rates of incision occur where easily eroded nonwelded tuff is exposed in the canyon bottom whereas a more resistant vapor phase altered tuff unit upstream has impeded incision incision may also have been affected by migration of knickpoints within the tuff paired strath terraces record periods of local base level stability and lateral erosion that were terminated by episodes of downcutting the downcutting was probably controlled by rare high magnitude floods capable of stripping the pervasive gravel armor and exposing nonwelded tuff beneath the stream bed no tectonic influence on late quaternary terrace development or stream incision has been recognized despite frijoles canyon being crossed by the pajarito fault zone a major bounding structure of the rio grande rift instead climatic influences on sediment supply and flood characteristics mediated by lithologic variations in the canyon bottom have controlled late quaternary stream profile evolution

differentiating pleistocene tectonically driven and climate related fluvial incision the sanggan river datong basin north china the sanggan river is an alluvial river flowing through a graben basin system of the northern shanxi rift zone north china during pleistocene times the river reach in the datong basin was affected successively by various external variables such as invasion by basaltic flow along valley faulting and climatic change therefore it provides excellent constraints for differentiating tectonically driven and climate related fluvial incision in the context of tectonic subsidence based on equilibrium profile analysis k ar dating of basalts 0 74 0 41 ma studies of the river terrace and of stream action history we present a conceptual model for differentiating fault driven and climate related fluvial incision by the river the results show that fluvial incision induced by tectonic lowering of the base level due to along valley movement on the sanggan river fault is equal to fault displacement the amount of post basalt fluvial incision of the reach upstream from the lava dam is 23 to 25 m of which the fault driven and climate related incisions are 15 m and 8 to 10 m respectively the former predominating over the latter the total amount of incision in the lava dam reach is 40 to 47 m of which the fault driven and climate related incisions are 10 m and 30 37 m respectively here the latter is predominant over the former since 0 41 0 10 ma the rate of fluvial incision of the lava dam reach of the river has reached 98 115 m ma which is 1 5 2 times as great as those of the reaches upstream and downstream from the lava dam the higher rate of fluvial incision can be attributed to high water levels supplied by the onset and maintenance of backwater conditions in the reach upstream from the lava dam due to the long period of warm and humid climate in this region plucking abrasion and knickpoint migration appear to be the primary erosional processes in the lava dam reach

is high obliquity a plausible cause for neoproterozoic glaciations 1 the main features of the low latitude neoproterozoic glaciations remain the subject of controversial debates concerning possible triggers here we use an agcm coupled with a slab ocean to test one of the earliest and simplest explanation for tropical glaciations a higher obliquity of the earth s rotation axis we show that high obliquity may result in an extensive glaciation during the sturtian episode 750 ma due to the location of continental masses in the tropical areas but cannot produce a large glaciation in the case of mid to high latitude paleogeographies such as those thought to typify the varangian vendian episodes 620 580 ma

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

late glacial sedimentological and morphological changes in a lowland river in response to climatic change the maas southern netherlands the late pleniglacial and late glacial maas valley south of nijmegen contains four terraces three river systems are described based on the morphology of channel scars on these terrace surfaces and by sediment characteristics the river maas reacted to climatic warming at the start of the weichselian late glacial by changing its river system slowly from a braided system to a transitional phase between braiding and meandering and finally to a highly sinuous meandering system the maas reacted rapidly to the younger dryas climate deterioration by again establishing a braiding system at the onset of the holocene the river changed abruptly to a meandering river without a transitional phase the triggering factor for change in the maas river pattern is almost certainly the changing climate in the late glacial gradient lines on the terrace surfaces show that tectonic activity did not modify the morphology of the channels a division of the terraces is shown the morphological sedimentological and petrographical characteristics are presented and the linking of changing fluvial patterns with climatic changes or tectonic movements is discussed 1997 john wiley sons ltd

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

climate driven bedrock incision in an active mountain belt measurements of fluvial bedrock incision were made with submillimeter precision in the east central range of taiwan where long term exhumation rates and precipitation driven river discharge are independently known they indicate that valley lowering is driven by relatively frequent flows of moderate intensity abrasion by suspended sediment is an important fluvial wear process and channel bed geometry and the presence of widely spaced planes of weakness in the rock mass influence erosion rate and style

evidence of possible tectonic upwarping along the south carolina coastal plain from an examination of river morphology and elevation data although the fault s responsible for the 1886 charleston south carolina earthquake have not yet been identified primarily because of the lack of surface rupture evaluation of landsat imagery aerial photography and topographic maps have revealed an 200 km long 15 km wide north northeast trending zone composed of subtle topographic highs and morphologic changes in rivers that may be associated with tectonic activity river anomalies observed within this zone include river bends that are convex toward the north northeast incised channels changes in river patterns and convex upward longitudinal profiles analyses of geologic and geophysical data further indicate that these surface features may be the result of ongoing tectonic uplift along a north northeast trending fault zone possibly associated with recent seismicity near charleston

river incision or diversion in response to bedrock uplift introductionmany researchers have examined the long term behavior of alluvialrivers i e schumm et al 1987 snow and slingerland 1990 paola et al 1992 on long time scales alluvial rivers act as sediment transport systemsthat broadly deposit sediment over low areas in their basins i e tucker andslingerland 1996 the behavior of bedrock rivers is less well understood although most workers agree that bedrock erosion is some function of streampower howard and kerby 1983 seidl and dietrich 1992 howard et al 1994 accordingly researchers addressing a river s response to bedrock up lift equate incision with relatively high stream power and diversion with rela tively low stream power e g burbank et al 1996 however these studiesassume that the erosion rate of the bedrock channel across the mountainrange controls the eventual outcome they have not examined the behavior ofthe alluvial river upstream and downstream of the uplift we propose to lookat the entire erosional and depositional river system and examine the long term response of a coupled alluvial bedrock river system to tectonic uplift our motivation is general and aims at a greater understanding offluvial and tectonic interactions but our model is necessarily both specificand simplified the tectonic uplift of a bedrock massif into the path of a later ally unconstrained alluvial river such a scenario has two possible out comes either the river maintains its original course and incises through theuplift or the river diverts and forms a new course around the uplift a sig nificant complication in the analysis of this scenario is that the evolvingriver system is partial alluvial and partial bedrock channeled because thebehaviors of these two river types are different modeling requires couplingdiverse systems we construct an analytical model to perform a first orderanalysis of this coupled system our objective is to identify the specific fac tors that determine the final outcome of river diversion or incision our model focuses on long time scales 10

imaging the 2013 explosive crater excavation and new dome formation at volcan de colima with terrasar x time lapse cameras and modelling abstract the summit region of steep volcanoes hosting lava domes often displays rapid geomorphologic and structural changes which are important for monitoring the source region of hazards explosive crater excavation is often followed by new lava dome growth which is one of the most dynamic morphometric changes that may occur at volcanoes however details of these crater formations and the ensuing new dome growth remain poorly studied a common problem is the lack of observational data due to hazardous field access and the limited resolution of satellite remote sensing techniques this paper describes the destructive constructive crater activity at volcan de colima mexico which occurred between january and march 2013 the crater geometry and early dome formation were observed through a combination of high resolution terrasar x spotmode satellite radar images and permanently installed monitoring cameras this combined time lapse imagery was used to identify ring shaped gas emissions prior to the explosion and to distinguish between the sequential explosion and crater excavation stages which were followed by dome growth by means of particle image velocimetry the digital flow field is computed from consecutive camera images showing that vertical dome growth is dominant at the beginning the upward growth is found to grade into spreading and a lateral growth domain after approximately two months of gradually filling the excavated craters with new magma the dome overflows the western margin of the crater and develops into a flow that produces block and ash flow hazards we discuss and compare the observations to discrete element models allowing us to mimic the vertical and lateral growth history of the dome and to estimate the maximum strength of the bulk rock mass moreover our results allow a discussion on the controls of a critical dome height that may be reached prior to its gravitational spreading

crustal uplift in southern england evidence from the river terrace records abstract much of the past work on the quaternary rivers of northwest europe has been concerned with river terraces which characterise almost every valley while these terraces are undoubtedly striking features of the landscape the incision achieved by quaternary rivers is equally significant in terms of river behaviour and for an understanding of the factors affecting landform development during the quaternary this paper examines the incision achieved during the quaternary by the thames in both its upper and lower catchments and by the hampshire avon in southern england valley incision rates of ca 0 07 0 10 m ka 1 have been identified although in the lower catchment of the thames these have been enhanced by additional incision in response to glacio isostasy and valley shortening a model is proposed in which regional uplift is recognized as the primary cause of incision by these quaternary rivers possible mechanisms for regional uplift are considered

seismicity associated with the 1991 1995 dome growth at unzen volcano japan abstract from may 1991 until february 1995 seismicity in the crater area of unzen volcano southwest japan intensified in conjunction with the growth of a dacite lava dome we used data from seismic stations located near the crater to identify approximately 580 000 summit earthquakes with maximum amplitudes equal to or greater than 1 10 3 cm s the temporal characteristics of the seismicity level were different for exogenous and endogenous periods of dome growth periods of solely exogenous growth were accompanied by several days or weeks of increased seismicity and levels of seismicity were notably reduced between successive seismically active periods in contrast levels of seismicity were generally high during periods when the dome grew endogenously with repeated cycles of increasing and decreasing seismicity of one to two months duration we classified the waveforms of summit earthquakes into high frequency hf medium frequency mf and low frequency lf types on the basis of spectral analysis dominant waveform types varied significantly over time hf was dominant in may 1991 lf from june 1991 until august 1993 mf during september and october 1993 and hf and mf from november 1993 hf and mf events are mainly distributed at depths of 500 1100 m above sea level asl just below the lava dome while lf events are widely distributed at depths from 500 m asl to the interior of the dome itself to efficiently detect earthquake families we conducted a cross correlation analysis of waveforms using the events one by one as reference events we calculated peak correlation coefficients between each reference event and events that occurred within 24 h either side of the reference event the results show that many earthquake families of all waveform types occurred throughout the growth period of the dome the durations of most families were less than two weeks and were not related to the intensity of seismic activity the incidence rate of events within each family reached a peak in the middle of the respective activity period the results also suggest that the waveforms in several analyzed families gradually evolved over time during periods when hf events intensified several families appeared contemporaneously in contrast during periods when lf events intensified the occurrence pattern of earthquake families was relatively simple a new family became active only once the activity of the previous family had declined or ceased completely a possible source mechanism for families of hf events is stick slip within the stiff rocks surrounding the conduit however several different types of source mechanisms should be considered for families of lf events

differentiating the roles of lithology and uplift in the steepening of bedrock river long profiles an example from southeastern australia hack determined that the equilibrium river long profile on a single lithology is a straight line when plotted semi logarithmically deviation from this straight line may be an equilibrium response to lithological variation or disequilibrium following base level change the amount of deviation d ast at any point downstream of the point of departure from the semi log straight line can be measured by projection of the upstream equilibrium profile and subtraction of the actual stream elevation from the projected elevation comparisons between the values of d ast for a trunk and a tributary at their junction can be used to differentiate steepening as a result of base level change from lithologically induced steepening in the former case d ast represents the incision induced by the base level change and will be equal for the trunk and the tributary it is very unlikely that values of d ast will be equal in the case of lithologically induced steepening because d ast in an

stream incision tectonics uplift and evolution of topography of the sierra nevada california abstract stream incision faulting thermochronologic and geobarometric data suggest that sierra nevada topography is a consequence of two periods of uplift stream incision of up to 1 km has occurred since 5 ma maximum eocene miocene incision was 150 m uplift of the sierra nevada westward tilting stream incision and east down normal and dextral faulting along the present eastern escarpment of the range began at 5 ma estimates of late cenozoic crestal rock uplift for different areas in the sierra nevada range from 1440 to 2150 m low summit erosion rates suggest that the rock uplift approximates the surface uplift of crestal summits tertiary stream gradients were lower than modern ones suggesting that the bottoms of the canyons have been uplifted in the late cenozoic and that the mean elevation of the sierra nevada has increased the elevation of pre cenozoic basement rocks above the base of tertiary paleochannels ranges from 1000 m in the south and

adjustments by the charwell river new zealand to uplift and climatic changes major climatic changes and rapid local and regional tectonic movements were common in new zealand during the late quaternary and caused a diversity of adjustments in the drainage basin and piedmont reaches of the charwell river which are separated by the hope fault the onset of semi arid frigid climates during the latest pleistocene probably greatly increased hillslope sediment yields in a periglacial environment and the piedmont reach aggraded as much as 42 m on top of a broad strath with the return of humid mesic climates in the holocene sediment yields decreased as dense forests again mantled the slopes and the piedmont reach degraded as mush as 81 m dating of eleven cut and strath terraces by radiocarbon calibrated weathering rind measurements on greyawake cobbles shows the degradation rates varied greatly during the last 14 ka 1 ka 1000 yr initial degradation rates of 4 m ka 1 increased to 30 m ka 1 by 6 ka ago during a mid holocene climatic optimum since 4 ka ago degradation rates have been only 1 2 m ka 1 comparable to uplift rates in the piedmont reach inferred from marine terrace studies and the river is again cutting a broad strath each broad strath represents equilibrium conditions attained by this powerful stream during interglacial times despite episodes of being overwhelmed by climatically induced sediment yield increases during full glacial climates and having to maintain a long term degradation rate equal to the uplift rate the 75 81 m of degradation since formation of the latest pleistocene fill terrace tread is the sum of the amount of late pleistocene valley floor aggradation and the amount of regional uplift that occurred between the estimated times of major strath formation at about 30 and 0 ka the 39 m of tectonically induced degradation below the pre aggradation strath is sufficiently large that post 30 ka uplift may have doubled holocene degradation rates each of the eleven degradation terraces represents pauses of a few centuries in holocene downcutting brief equilibrium conditions were attained by streambed armoring and concurrent growth of riparian plants both processes progressively increased hydraulic roughness and the shear stresses needed to entrain streambed materials occasional floods possibly from rare cyclones derived from tropical moisture sources destroyed streambed armor and channel downcutting was renewed thus the formation of eleven equilibrium terraces can be accounted for without postulating additional tectonic perturbations or secular climatic changes

river terrace formation modelling and 3 d graphical simulation a model on river terrace formation is presented written in pascal and run on a vax 8600 the model calculates the influence of a fluvial system on the relief of an area with macroscopical dimensions 10kmx20kmx0 5km over a period of 2 5 million years model input relies on uplift and alternations in discharge and sediment load as a function of climatic changes the output of the model are 3 dimensional grid drawings which visualize the impact of uplift discharge and sediment load on a landscape model formulation is based on empirical information on fluvial systems which was incorporated in the model by means of a slightly adapted way of finite state modelling in which decisions act as thresholds the model is organized using two entities river and landscape with attributes that have values within a specific realistic domain the model produces plausible x y z and x y t plots in the light of existing geomorphological theories the described modelling procedure shows that it is possible to simulate river terrace formation threedimensionally with the use of empirical information

long term fluvial archives in nw france response of the seine and somme rivers to tectonic movements climatic variations and sea level changes the seine and the somme are the two main rivers flowing from northwestern france into the channel during the pleistocene cold stages both rivers were tributaries of the river manche which was exporting sediments into the central deeps of the channel the river seine has a very well developed terrace system recording incision that began at around 1 ma the same age is proposed for the beginning of the main incision in the somme valley on the basis of morphostratigraphy pedostratigraphy palaeontology palaeomagnetism and esr datings the uplift rate deduced from analysis of the seine and somme terrace systems is of 55 to 60 m ma since the end of the lower pleistocene the response of the two rivers to climatic variations uplift and sea level changes is complex and variable in the different parts of the river courses for example the evolution of the lower seine system is influenced by uplift and climate changes but dominated by sea level changes in the middle seine the system is beyond the impact of sea level variations and shows a very detailed response to climatic variations during the middle and upper pleistocene in a context of uplift the somme valley response appears to be more homogeneous especially in the middle valley where the terrace system shows a regular pattern in which incision occurs at the beginning of each glacial period against a general background of uplift nevertheless the lower somme valley and the palaeo somme in the channel area indicate some strong differences compared with the middle valley influence of sea level variations and probably differences in rates of tectonic uplift between the channel and the present continent the differences in the responses of the two river valleys during the pleistocene are related to differences in the size of the fluvial basins to the local tectonic characteristics to the geometry of the platform connected to the lower parts of the valleys and to the hydrodynamic characteristics of each river finally it is shown from these examples that the multidisciplinary study of pleistocene rivers is a very efficient tool for the investigation of neotectonic activity

uplift driven valley incision and river terrace formation in southern england outside the limits of middle pleistocene glaciation the river basins of southern england contain long cenozoic terrestrial sedimentary records of greatest importance are the river terrace sequences which contain biostratigraphical and sedimentary evidence that testifies to the high amplitude climatic changes of the quaternary however trends in valley development cannot easily be accommodated within the framework of quaternary climatic change it is argued in this paper that episodic incision and terrace development result from uplift a consequence of the interplay between continuing alpine orogenic movements and erosion driven isostasy using a simple linear model height age an uplift rate of ca 7 cm ka 1 is estimated for the terrace sequence in the upper thames valley this preliminary model is evaluated using the records of adjacent basins 1997 john wiley sons ltd

simulating the amplification of orbital forcing by ocean feedbacks in the last glaciation according to milankovitch theory the lower summer insolation at high latitudes about 115 000 years ago allowed winter snow to persist throughout summer leading to ice sheet build up and glaciation1 but attempts to simulate the last glaciation using global atmospheric models have failed to produce this outcome when forced by insolation changes only2 3 4 5 these results point towards the importance of feedback effects for example through changes in vegetation or the ocean circulation for the amplification of solar forcing6 7 8 9 here we present a fully coupled ocean atmosphere model of the last glaciation that produces a build up of perennial snow cover at known locations of ice sheets during this period we show that ocean feedbacks lead to a cooling of the high northern latitudes along with an increase in atmospheric moisture transport from the equator to the poles these changes agree with available geological data10 11 12 13 14 15 and together they lead to an increased delivery of snow to high northern latitudes the mechanism we present explains the onset of glaciation which would be amplified by changes in vegetation in response to weak orbital forcing

petrological architecture of a magmatic shear zone a multidisciplinary investigation of strain localisation during magma ascent at unzen volcano japan shearing of magma during ascent can promote strain localisation near the conduit margins anymechanical and thermal discontinuities associated with such events may alter the chemical physicaland rheological stability of the magma and thus its propensity to erupt lava spines can record suchprocesses preserving a range of macroscopic and microscopic deformation textures attributed toshearing and friction as magma ascends through the viscous brittle transition here we use a multi disciplinary approach combining petrology microstructures crystallography magnetics and experi mentation to assess the evidence role and extent of shearing across a marginal shear zone of the1994 1995 lava spine at unzen volcano japan our results show that crystals can effectively moni tor stress conditions during magma ascent with viscous remobilisation crystal plasticity and com minution all systematically increasing towards the spine margin accompanying this we find anincrease in mineral destabilisation in the form of pargasitic amphibole breakdown displaying tex tural variations across the shear zone from symplectitic to granular rims towards the spine margin in addition the compaction of pores chemical and textural alteration of interstitial glass and mag netic variations all change systematically with shear intensity the strong correlation between thedegree of shearing crystal deformation and disequilibrium features together with distinct magneticproperties implies a localised thermal input due to shear and frictional processes near the conduitmargin during magma ascent this was accompanied by late stage or post emplacement fluid andgas induced alteration of the gouge as well as oxidation and glass devitrification understandingand recognising evidence for strain localisation during magma ascent may therefore be vital whenassessing factors that regulate the style of volcanic eruptions which may provide insights into thecryptic shifts from effusive to explosive activity as observed at many active lava domes

digital photogrammetry as a tool in analogue modelling applications to volcano instability abstract three techniques of digital photogrammetry have been applied successfully to laboratory analogue models to study surface displacements caused by various volcano deformation types firstly side perspective videos are used to differentiate profile displacements between cryptodome intrusion models and models deforming by ductile inner core viscous flow both models show similar morphologic features including a bulged flank and an asymmetric upper graben however differences in displacement trajectories of the bulge crest reflect upward intrusion push contrasting with essentially downward displacement vectors of weak core models the other two techniques use vertical views correlated automatically either as time sequence monoscopic views or as coeval stereoscopic pairs this exploits to a maximum the method s potential by imaging surface displacements over the whole model successive monoscopic photograms because they suffer only moderate numerical processing for topographic effect removal can detect very small displacements occurring early in deformation processes as illustrated by analysis of intrusion models the monoscopic method allows prediction of fault locations and main displacement locations it can also anticipate the principal strain directions and separate different deformation stages on the other hand the stereo photogrammetry technique although more complicated provides topography and volume changes as well as pictures of surface displacements in three dimensions results are presented for the spreading of volcano models on a ductile substratum and viscous cored cones we have found digital photogrammetry to be a useful tool for analogue modelling because it provides quantitative data on surface displacements including movement invisible to the eye as well as topographic changes it is a good method for investigating and comparing different deformation mechanisms it is especially useful for interpretation of displacement patterns obtained from monitoring of natural active volcanoes in fact results of the methods used in the laboratory can be directly compared with field data from geodetic or photogrammetric surveys as at mount st helens in 1980

stream terrace genesis implications for soil development genesis of three distinct types of stream terraces can be understood through application of the concepts of tectonically induced downcutting base level of erosion complex response threshold of critical power diachronous and synchronous response times and static and dynamic equilibrium climatic and tectonic stream terraces are major terraces below which flights of minor complex response degradation terraces can form these three types of terraces can be summarized by describing a downcutting aggradation renewed downcutting sequence for streams with gravell bedload by tectonically induced downcutting streams degrade to achieve and maintain a dynamic equilibrium longitudinal profile at the base level of erosion lateral erosion bevels bedrock beneath active channels to create major straths that are the fundamental tectonic stream terrace landform aggradation events record brief reversals of long term tectonically induced downcutting because they raise active channels they may be considered as major the result of climatic perturbations or minor the result of complex response model types of perturbations climatically controlled aggradation followed by degradation leaves an aggradation surface this type of fill terrace tread is the fundamental climatic stream terrace landform aggradation surfaces may be buried by subsequent episodes of deposition unless intervening tectonically induced downcutting is sufficient for younger aggradation surfaces to form below older surfaces raising of the active channel by either tectonic uplift or by climatically induced aggradation provides the vertical space for degradation terraces to form first in alluvial fill and then in underlying bedrock along tectonically active streams these are complex response terraces because they result from interactions of dependent variables within a given fluvial system pauses in degradation to a new base level of erosion and or minor episodes of backfilling lead to formation of complex response fill cut and strath or of fill terraces fill cut terraces are formed in alluvium they are complex response terraces because they are higher than the base level of erosion good exposures and dating are needed to distinguish static equilibrium complex response minor strath terraces from dynamic equilibrium tectonic major straths strath terraces may be regarded as complex response terraces where degradation rates between times terrace tread formation exceed the long term uplift rate for the reach based on ages and positions of tectonic terraces late quaternary global climatic changes control aggradation events and even the times of cutting of major tectonic straths because the base level of erosion can not be attained during times of climatically driven aggradation degradation events most terrace soils form on treads of climatic and complex response terraces aggradation surfaces may provide an ideal flight of terraces on which to study a soils chronosequence each aggradation event is recorded by a single relict soil where tectonically induced downcutting is sufficient to provide clear altitudinal separation of the terrace treads multiple paleosols are typical of tectonically stable regions where younger aggradation events spread alluvium over treads of older climatic terraces pedons on a climatic terrace in a small fluvial system commonly are roughly synchronous variations of soil properties that can be attributed to temporal differences will be minor compared to altitudinally controlled climatic factors climatic terraces of adjacent watersheds also should be roughly synchronous correlatable variations of soil properties that can be attributed to temporal differences will be minor compared to lithologic and climatic factors between different watersheds such generalizations may not apply to basins with sufficient relief that geomorphic responses to climatic changes occur at different and overlapping times and to large rivers whose widely separated reaches are characterized by different response times to climatic perturbations soils on climatic terraces of distant watershedswill not be synchronous if their respective aggradation events occur during full glacial times and interglacial times soils on some complex response terraces may be diachronous within a given fluvial system and typically are diachronous between watersheds

global climate model high obliquity solutions to the ancient climate puzzles of the faint young sun paradox and low altitude proterozoic glaciation there is a general consensus that warm temperatures throughout precambrian were caused by very high co2 or ch4 atmospheric concentrations episodes of glaciation in the early and late proterozoic were caused by a reduction in these greenhouse gases through intensive weathering or large reduction in the methane producing bacteria population there are suggestions that these episodes were global because the continents occupied low latitudes at or near the time of glaciation here it is reported that high obliquity throughout the precambrian serves as a mechanism for producing warm temperatures throughout the archean and glaciation in the late proterozoic in this paper global climate model simulations using high obliquity values that range from 54 to 70 are undertaken these simulations use a simple 50 m slab ocean a faster rotation rate corresponding to an 18 hour day an idealized supercontinent located in the tropics which has a north south mountain chain and co2 concentrations which range from 170 to 3400 ppmv further four simulations under global ocean conditions faster rotation rate and reduced solar constant 15 and 20 using present day and high obliquity values have been undertaken the simulations show warm conditions with high obliquity but snowball earth conditions for the present day obliquity in the global ocean simulations near snowball earth conditions also occur for the tropical supercontinent simulation for an obliquity of 70 and co2 concentrations less than 1020 ppmv together these simulations show that for high obliquity the ocean remains relatively warm while land areas are cooled because of their lower heat capacity large fluxes of latent heat from the ocean balance the longwave energy lost at the top of the atmosphere thereby keeping high latitudes warm during winter seasons it is suggested from this results that lower and upper limits of 65 70 for obliquity serve as a solution for the faint young sun paradox and low latitude proterozoic finally the high obliquity climate relationship sheds some insight on the carbon isotope 13c excursions during the late proterozoic

holocene alluvial geology and geoarchaeology of the san xavier reach of the santa cruz river arizona the 15 km segment of the santa cruz river traversing the san xavier indian reservation near tucson arizona has undergone major environmental changes during the past 8 000 yr the holocene alluvial sequence for this segment called the san xavier reach of the santa cruz river shows three major episodes aggradation until 8000 yr b p by a braided stream channel erosion from 8000 to 5500 yr b p and subsequent vertical aggradation of the flood plain punctuated by short periods of arroyo cutting the major changes in the fluvial regime were probably the result of climatic changes but cycles of arroyo cutting and filling during the past 2 500 yr were probably the result of unstable internal geomorphic conditions flooding and human impacts on the flood plain the alluvial history of the san xavier reach had a pronounced effect on the preservation of archaeological remains environmental changes on the flood plain including arroyo cutting and filling cienega formation and destruction and sand dune development led to the disruption and reorganization of hohokam settlement and subsistence patterns between 1150 and 500 yr b p

quaternary uplift astride the aseismic cocos ridge pacific coast costa rica the pacific coast of costa rica lies within the central american forearc and magmatic arc region that was created by northeastward subduction of the cocos plate beneath the caribbean plate at the middle america trench from the peninsula de nicoya south eastward toward the peninsula de osa and the peninsula de burica on the panamanian border the middle america trench loses its physiographic expression where it intersects the aseismic cocos ridge interaction between subduction of the buoyant aseismic cocos ridge and the overriding caribbean plate is invoked to explain the variation in rates of vertical crustal uplift along a coastal transect from nicoya to burica the pliocene and pleistocene stratigraphic record and holocene marine terraces and beach ridge complexes indicate that maximum rates of crustal uplift have occurred on the peninsula de osa immediately landward of the aseismic cocos ridge crustal uplift rates decrease northwest toward the peninsula de nicoya and to a lesser extent southwest toward the peninsula de burica the late quaternary stratigraphy on the peninsula de osa is subdivided into two major chronostratigraphic sequences from groupings of radiocarbon dates crustal uplift rates calculated from these sequences systematically decrease from 6 5 to 2 1 m ka north east across the peninsula deformation of the peninsula is modeled as uplifted and down to the northeast tilted fault blocks with an angular rotation rate of 0 03 to 0 06 per thousand years although less well constrained crustal uplift rates on the peninsula de nicoya 200 km to the northwest of the peninsula de osa vary from 1 m ka for pliocene and pleistocene sediments to 2 5 m ka for holocene marine terraces in the quepos region 100 km to the northwest of the peninsula de osa calculated uplift rates derived from incision of late quaternary fluvial terraces range from 0 5 to 3 0 m ka on the peninsula de burica only 60 km to the southwest of the peninsula de osa calculated uplift rates range from 4 7 m ka for a late holocene marine terrace to 1 2 m ka for post late pliocene deep sea sediments the variations in calculated uplift rates on the peninsula de osa constrain a dynamic model for subduction of the cocos ridge and the resulting uplift of the overriding caribbean plate deflection of the caribbean plate is modeled using various effective elastic thicknesses as the response of an elastic plate to the buoyant force of the subducted cocos ridge because the shape of the subducted end of the cocos ridge is unknown two scenarios are evaluated 1 a radially symmetric ridge with a slope similar to the slope of the flanks of the ridge and 2 a ridge where the subducted end was truncated by the panama fracture zone the best fit model utilizes a truncated ridge that has been subducted during the past 0 5 m y 50 km beneath the overriding caribbean plate which has an effective elastic thickness of 5 km the model predicts that the highest uplift rate should be 3 7 m ka and occur on the southwest coast of the peninsula de osa the rate of uplift slows considerably to the northeast and indicates that the peninsula de osa is tilting to the northeast which agrees with observations in that region the predicted uplift rate attributed to aseismic ridge subduction also decreases along the coast both north and south of the peninsula de osa resulting in little uplift that can be attributed to cocos ridge subduction in the northwestern portions of the peninsula de nicoya

implications of deflation inflation event models on kīlauea volcano hawaiʻi abstract surface deformation of volcanic areas can reveal information about subsurface magma reservoirs and how magma is transported between them which is an important part of volcano monitoring for hazard mitigation one prominent style of deformation observed at k lauea volcano hawai i is episodic deflation inflation di events which are recorded in surface deformation data and characterized by deflation of the summit region over hours to days followed by rapid re inflation the exact cause of di events is unknown however a commonly proposed explanation is that a temporary blockage occurs in the conduit connecting the south caldera magma reservoir to the shallower halema uma u reservoir thus interrupting the influx of magma this model is investigated by testing the hypothesis that during the deflationary phase of a di event the volume of magma blocked from reaching the halema uma u reservoir is added to the south caldera reservoir using a mass balance approach and deformation modeling the expected deformation tilt pattern was predicted for the reservoirs and compared to tilt observations from 16 large 4 rad magnitude di events between 2010 and 2012 while the predicted tilts due to inflation from the south caldera reservoir are strong enough to be detected this signal is not seen in the tilt observations we also explore the possibility that the blockage occurs below the south caldera reservoir as well as alternative configurations that include a direct connection between the south caldera reservoir and the eruption site none of the simple two reservoir models we test are able to adequately satisfy the observations selected di events show that tilt vectors change in both magnitude and azimuthal direction over the course of deflation we conclude that the portion of the summit storage and plumbing system active during these di events is more complicated than two connected chambers and that it is more likely that these summit reservoirs have their own source conduits connecting in some complex way to the deep magma source

timescales climate and river development abstract in the long term glacial interglacial sequences river development follows general climatic evolution however at the scale of one cold warm cycle it appears that the geomorphological effect of river activity is best expressed at times of climatic change such periods of pronounced fluvial action last only a short time in more detail the internal evolution in a drainage basin after a climatic event results in a delayed response of the morphology and sedimentation pattern finally on the shortest timescale local thresholds may play a decisive role in the reactions of river systems it is concluded that the relation between fluvial development and climate is not a simple one but is fundamentally dependant on the timescale

a stability analysis of a conduit flow model for lava dome eruptions abstract periodic variations in magma discharge rate and ground deformation have been commonly observed during lava dome eruptions we performed a stability analysis of a conduit flow model by barmin et al barmin a melnik o sparks r s j 2002 periodic behavior in lava dome eruptions earth and planetary science letters 199 1 2 173 184 in which the periodic variations in magma flow rate and chamber pressure are reproduced as a result of the temporal and spatial changes of the magma viscosity controlled by the kinetics of crystallization the model is reduced to a dynamical system where the time derivatives of the magma flow rate dq dt and the chamber pressure dp dt are functions of q and p evaluated at a shifted time t t here the time delay t represents the time for the viscosity of fluid particle to increase in a conduit the dynamical system with time delay is approximated by a simple two dimensional dynamical system of q and p where t is given as a parameter the results of our linear stability analyses for these dynamical systems indicate that the transition from steady to periodic flow depends on nonlinearities in the steady state relation between q and p the steady state relation shows a sigmoidal curve in q p phase plane its slope has negative values at intermediate flow rates the steady state solutions become unstable and hence p and q oscillate periodically when the negative slope of the steady state relation dp dq s exceeds a critical value that is dp dq s

climate forcings and the initiation of low latitude ice sheets during the neoproterozoic varanger glacial interval the giss gcm was used to determine if a diverse set of climate forcings alone or in combination could have initiated the low latitude ice sheets of the varanger 600 ma glacial interval the simulations use a realistic reconstruction of the paleocontinental distribution and test the following forcings alone and in combination 6 solar luminosity decrease four atmospheric co2 scenarios 1260 315 140 and 40 ppm a 50 increase and a 50 decrease in ocean heat transports and a change in obliquity to 60 none of the forcings individually produced year round snow accumulation on low latitude continents although the solar insolation decrease and 40 ppm co2 scenarios allowed snow and ice to accumulate at high and middle latitudes combining forcings further cools the climate when solar luminosity co2 and ocean heat transports were all decreased annual mean freezing and snow accumulation extended across tropical continents no simulation would have initiated low latitude glaciation without contemporaneous glaciation at higher latitudes a finding that matches the distribution of glacial deposits but which argues against high obliquity as a cause of the varanger ice age low level clouds increased in most scenarios as did surface albedo while atmospheric water vapor amounts declined all are positive feedbacks that drive temperatures lower in the most severe scenario global snow and ice cover increased to 68 compared to 12 under modern conditions and water vapor dropped by 90 these results do not necessarily preclude a snowball earth climate scenario for the varanger glacial interval however either more severe forcings existed or radical changes occurred in the ocean atmosphere system which are unaccounted for by the gcm also as sea ice extent increased in these experiments snow accumulation began to decline because of an increasingly dry atmosphere under snowball earth conditions glaciation would be impossible since the hydrological cycle would all but cease if the atmosphere s primary moisture source were cut off

multi protocol palaeointensity determination from middle brunhes chron volcanics datong volcanic province china a full vector palaeomagnetic analysis of basalts from the datong volcanic province china has been carried out to constrain the orientation and magnitude of the geomagnetic field during the mid brunhes chron at approximately 0 41 ma palaeomagnetic directions were determined using thermal demagnetization palaeointensity information was determined using a multi protocol approach 1 a thellier type protocol 2 the multi specimen parallel differential partial thermoremanence method and 3 the wilson method the most consistent data set was obtained with the wilson method whilst similar average values with wider data scatter were obtained with the thellier method higher values were obtained with the multi specimen method we suggest that consistency of results from the different protocols which access different sections of the blocking unblocking spectra provide a useful test of the robustness of palaeointensity estimates a mean virtual dipole moment of 5 4 0 6 1022 am2 was determined which agrees well with coeval values from the pint database and with the higher average palaeointensities for the mid brunhes chron indicated by more continuous sedimentary relative palaeointensity records

late quaternary stream incision and uplift in the forearc of the cascadia subduction zone western oregon documentation of a latest pleistocene earliest holocene episode of strath formation and fluvial aggradation in the oregon coast range provides a datum from which long term bedrock stream incision rates are determined variations in long term incision rates probably reflect cumulative differential uplift in the forearc of the cascadia subduction zone although factors such as bedrock and climatic controls and isostatic adjustments to erosion obscure the precise relationship between surface uplift and stream incision patterns of differential incision are most striking near the latitude of newport where a steep gradient divides a region of higher rates 0 6 0 9 mm yr in the northern coast range from a region of lower rates 0 1 0 3 mm yr in the central coast range the steep incision gradient is nearly coincident with abrupt changes in marine terrace 80 125 kyr uplift rates the locations of quaternary faults and the southern flank of a saddle of low historic 40 70 years uplift the exact causes of these variable patterns of incision uplift are unknown analogies with uplift patterns in other subduction zones and comparisons with other neotectonic data in the region indicate that patterns of differential incision probably are caused by variations in permanent strain accumulation along the cascadia subduction zone such variations may be related to differences in seismic moment release during individual earthquakes to changes in plate geometry or rates of wedge accretion to segmentation of earthquake ruptures and or to deformation on active structures in the north american plate and accretionary wedge

geomorphic response of coastal streams to low intermediate and high rates of uplift medocino triple junction region northern california analysis of three dimensional morphological properties of 24 coastal drainage basins that have evolved in areas of low 3 m 1 000 yr rates of uplift near the mendocino triple junction mtj coastal northern california identified channel gradients as the best indicator of tectonism in the landscape lower order tributaries best reflect tectonically controlled differences the largest streams examined of third order are able to adjust to most base level change and maintain their profile form whereas lower order streams farther upstream tend to accumulate the effects of net base level fall and have steepest profiles in the areas of highest uplift rates variations in steepness of first order channel gradients indicate that 1 high uplift rates in the wake of the mtj have existed for at least 73 000 yr and 2 differential tilt of the region to the north and south of the current locus of highest uplift rate is occurring in association with regional uplift although first order streams are excellent indicators of areas of both high uplift rates and regional differential tilting they are less useful in distinguishing between areas of low and intermediate uplift rate analysis of the longitudinal profile of the main trunk stream of ten of the 24 drainage basins using the stream gradient index was more useful to categorize broadly the uplift rates and to distinguish between streams in low and intermediate uplift rate areas although the hypotheses tested herein do not identify the exact mechanism off uplift in the mtj region they do indicate that the nature of deformation is most likely regional tilt rather than crustal shortening with localized compressional folding and thrust faulting they also indicate that geomorphic responses trail in the wake of the uplift rate response caused by development of a slab window beneath the north american plate 1 maximum uplift rates occur 9 km south of the northern boundary of the slab window 2 maximum mean first order channel gradient occurs 16 km south of the northern edge of the slab window and 3 maximum drainage basin relief occurs 20 km south of the northern edge of the slab window associated lag times between passage of the southern edge of the subducted gorda plate slab and geomorphic responses are 160 000 yr for maximum uplift rates 290 000 yr for maximum channel gradients and 370 000 yr for maximum relief