mississippi river subaqueous delta is entering a stage of retrogradation abstract the subaqueous delta of the mississippi river the largest river system in the conterminous u s has entered a stage of retrogradation caused by multiple natural and anthropogenic activities since the 1950s the suspended sediment load of the mississippi river has decreased by 50 due primarily to the construction of 50 000 dams in the mississippi basin the impact of this decreased sediment load has been observed in subaerial environments but the impact on sedimentation and geomorphology of the subaqueous delta front has yet to be examined to identify historic trends in sedimentation patterns we compiled bathymetric datasets including historical charts industry and academic surveys and national oceanic and atmospheric administration hydrographic data collected between 1764 and 2009 the progradation rate measured at the 10 m depth contour of southwest pass which receives 69 of the suspended sediment load reaching head of passes has decreased from 67 m yr between 1874 and 1940 to 26 m yr between 1940 and 1979 with evidence of further deceleration from 1979 to 2009 at south pass and pass a loutre the delta front has entered the destructive phase with the 10 m contour retreating at rates 20 m yr at both passes since 1979 advancement of the delta front also decelerated in deeper water in some areas out to 180 m depth except locally where mudflow lobes are advancing deeper contours show a pattern of decreasing progradation rate between 1874 1940 and 1979 2005 time periods furthermore based on differences measured between available bathymetric datasets the sediment accumulation rate across the delta front decreased by 73 for the same period the retention rate of mississippi river sediment on the delta front ranged from 67 to 81 for the time periods assessed with total sediment load stored on the delta front equal to 317 54 mt yr from 1874 to 1940 145 25 mt yr from 1940 to 1979 and 87 15 mt yr from 1979 to 2005 we document for the first time that the mississippi river delta front has entered a phase of retrogradation which will likely be accelerated by future upstream activities that divert a portion of the sediment load to the upper delta for coastal protection and restoration projects the decline of the subaqueous mississippi river delta has critical implications for biogeochemical cycling subaqueous mass wasting and sediment dispersal to the coastal ocean

deformation and stress in hydrothermal regions the case of a disk shaped inclusion in a half space abstract hydrothermal regions are affected by a wide variety of phenomena including ground inflation and deflation episodes among them calderas offer the opportunity to study the complex interactions between magmatic processes at depth and permeable rocks saturated with fluids in the upper sedimentary layers one of such regions is the campi flegrei caldera in southern italy where several source models have been applied over the years to reproduce the ground displacement and seismicity observed during the most recent phase of major unrest 1982 1984 the present work aims at introducing a new source model consisting of a thermo poro elastic inclusion embedded in a homogeneous poroelastic half space the inclusion is meant to represent a permeable rock layer stressed and strained by hot and pressurized volatiles released upward by an underlying magmatic reservoir and is modeled as a thin horizontal disk inside which a sudden change of temperature and pore pressure occurs we provide semi analytical solutions for the displacement and stress fields both within and outside the source and check them by comparison with those obtained through a fully numerical approach results provided by our model are compared with two other deformation source models often used to describe volcanic environments in terms of pressurized cavities describing a spherical magma chamber mogi source or a sill like magma intrusion fialko source for the campi flegrei 1982 84 unrest our model provides a better reproduction of ground deformation data and manages to explain the widespread presence of compressive focal mechanisms since the stress field promoted both inside and outside the thermo poro elastic inclusion is very different from pressurized cavities

retrieving the stress field within the campi flegrei caldera southern italy through an integrated geodetical and seismological approach we investigated the campi flegrei caldera using a quantitative approach to retrieve the spatial and temporal variations of the stress field for this aim we applied a joint inversion of geodetic and seismological data to a dataset of 1 100 optical levelling measurements and 222 focal mechanisms recorded during the bradyseismic crisis of 1982 1984 the inversion of the geodetic dataset alone shows that the observed ground deformation is compatible with a source consisting of a planar crack located at the centre of the caldera at a depth of about 2 56 km and a size of about 4 4 km inversion of focal mechanisms using both analytical and graphical approaches has shown that the key features of the stress field in the area are a nearly subvertical 1 and a sub horizontal roughly nne ssw trending 3 unfortunately the modelling of the stress fields based only upon the retrieved ground deformation source is not able to fully account for the stress pattern delineated by focal mechanism inversion the introduction of an additional regional background field has been necessary this field has been determined by minimizing the difference between observed slip vectors for each focal mechanism and the theoretical maximum shear stress deriving from both the volcanic time varying and the regional constant field the latter is responsible for a weak nne ssw extension which is consistent with the field determined for the nearby mt vesuvius volcano the proposed approach accurately models observations and provides interesting hints to better understand the dynamics of the volcanic unrest and seismogenic processes at campi flegrei caldera this procedure could be applied to other volcanoes experiencing active ground deformation and seismicity

understanding fine grained river sediment dispersal on continental margins studies of fine grained sediment dispersal in the marine environment have documented diversity in the behavior of depositional systems on continental margins with different oceanographic conditions and morphologies based on the pattern and nature of sediment accumulation for twenty three case studies we propose there are five basic types of dispersal systems and these are related to river wave tide and margin characteristics data suggest that the type of dispersal system on any margin can be predicted with knowledge of sediment load mean significant wave height tidal range and continental shelf width at a river mouth and from these a hierarchical decision tree is developed analysis of the dispersal system type of more than 100 river mouths reveals that proximal accumulation dominated pad and marine dispersal dominated mdd systems are most abundant but estuarine accumulation dominated ead systems also are anticipated to be numerous globally research quantifying marine sediment dynamics in these system types is needed although less common the size and nature of subaqueous delta clinoform sdc and canyon captured cc systems also warrant future attention to their study strong correlations between physical characteristics i e significant wave height and tidal range and the depth and distance to the nearest maximum shelf depocenter provide evidence that in reality a continuum exists between the system types the process related partitioning of sediment in the five different types of marine dispersal systems has important implications for understanding the stratigraphic record and the cycling of carbon

deltaic morphodynamics and stratigraphic evolution of middle barataria bay and middle breton sound regions louisiana usa implications for river sediment diversions abstract river sediment diversions have been recognized as a key strategy for offsetting land loss in coastal louisiana recently much attention has been focused on sediment capture from the main stem river and conveyance of that material through diversion outflows yet the performance and long term feasibility of diversions as land building agents also hinges upon the subsurface stratigraphic architecture of receiving basins a concept that has largely been unexplored a major core collection and analysis program was undertaken to study the geological properties of substrates in the middle barataria bay and middle breton sound diversion receiving basins louisiana usa over a region of 200 square kilometers in both basins 50 vibracores up to 5 5 m in length were collected in spring and summer of 2015 cores were logged for bulk density and imaged with a geotek multi sensor core logger split cores were then subsampled for granulometry organic content and 14c dating both receiving basins are characterized by 1 2 m of organic rich surficial strata underlain by 2 m of mineral rich sand and silt beds that display a greater bulk density additionally some cores contain deeper peaty strata intercalated within muds and sands 14c dates of these buried peats range between 1910 and 3203 calendar years before present demonstrating that relatively old deltaic strata exist at shallow depths age comparisons of stratigraphically similar peat beds from this study and previous delta lobe chronological models indicate that the st bernard lobe prograded eastward at a time averaged rate of 75 m yr from a geotechnical standpoint the surficial uncompacted

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

deformation regime and long term precursors to eruption at large calderas rabaul papua new guinea eruptions at large calderas are normally preceded by variable rates of unrest that continue for decades or more a classic example is the 1994 eruption of rabaul caldera in papua new guinea which began after 23 years of surface uplift and volcano tectonic vt seismicity at rates that changed unevenly with time by an order of magnitude although the vt event rate and uplift rate peaked in 1983 1985 eruptions only began a decade later and followed just 27 hours of anomalous changes in precursory signal here we argue that the entire 23 years of unrest belongs to a single sequence of damage accumulation in the crust and that in 1991 1992 the crust s response to applied stress changed from quasi elastic elastic deformation with minor fault movement to inelastic deformation predominantly by fault movement alone the change in behaviour yields limiting trends in the variation of vt event rate with deformation and can be quantified with a mean field model for an elastic crust that contains a dispersed population of small faults the results show that identifying the deformation regime for elastic brittle crust provides new criteria for using precursory time series to evaluate the potential for eruption they suggest that in the quasi elastic regime short term increases in rates of deformation and vt events are unreliable indicators of an imminent eruption but that in the inelastic regime the precursory rates may follow hyperbolic increases with time and offer the promise of developing forecasts of eruption as much as months beforehand

sub decadal submarine landslides are important drivers of deltaic sediment flux insights from the mississippi river delta front submarine mass failures triggered by energetic forcing events such as hurricanes and earthquakes are relatively well studied due to the potential for infrastructure damage and tsunami generation such failures are common on heavily sedimented margins where underconsolidated deposits are preconditioned to fail however studies of seafloor sediment movement between large events remain scarce using repeat bathymetric surveys of the mississippi river delta front mrdf we document substantial seafloor movement in absence of major hurricanes about 1 m yr of deepening was observed within preexisting failures with downslope sediment transport on the order of 10 5 m 3 yr outside failure features seafloor depths remained stable or showed minor 20 cm yr accretion mrdf volumetric sediment flux during hurricane driven mass failures is an order of magnitude greater than the annual flux during a quiescent interval when normalized by time however sediment flux during the quiescent interval 5 5 10 5 m 3 yr was half that of hurricane driven mass failures 1 1 10 6 m 3 yr these observations corroborate our wave modeling results which infer that even waves of 1 yr recurrence interval can generate differential seafloor pressures sufficient to trigger submarine landslides this does not exclude the possibility of river floods also being agents of failure these findings indicate that sub decadal submarine landslides are important to mrdf dynamics comparable to the role of major hurricanes and observation during seemingly quiescent periods is necessary to holistically assess sediment flux the periodicity and prevalence of moderate scale mass transport documented here corroborates similar recent studies offshore other deltas globally indicating that highstand mass and time budgets of shelf to deep sea sediment flux in addition to organic carbon and bioreactive particles may need to be revised

an insight into the unrest phenomena at the campi flegrei caldera from vp and vp vs tomography high resolution vp and vp vs tomography of the campi flegrei caldera is obtained using active and passive seismic data we find a continuous ring of high vp anomaly that defines the caldera rim associated to the last collapse a sharp vp vs decrease is observed between 2 and 4 km depth suggesting the absence of magmatic fluids and the presence of rock volumes with over pressured gas within the source region of uplift atmospheric water penetrating within the caldera and deep co2 fluids are presumably heated by a magmatic body located at depth greater than 4 km nested within the limestone layer along the fractures bordering the shallow high vp rim deep gas and co2 fluids up raise and are released in the pozzuoli solfatara we hypothesize that the past unrest episode is more likely due to pressure changes within the shallow geothermal reservoir located at the top of the magma intrusion

the campi flegrei deep drilling project cfddp new insight on caldera structure evolution and hazard implications for the naples area southern italy the 501 m deep hole of the campi flegrei deep drilling project located west of the naples metropolitan area and inside the campi flegrei caldera gives new insight to reconstruct the volcano tectonic evolution of this highly populated volcano it is one of the highest risk volcanic areas in the world but its tectonic structure eruptive history and size of the largest eruptions are intensely debated in the literature new stratigraphic and 40ar 39ar geochronological dating allow us to determine for the first time the age of intracaldera deposits belonging to the two highest magnitude caldera forming eruptions i e campanian ignimbrite ci 39 ka and neapolitan yellow tuff nyt 14 9 ka and to estimate the amount of collapse tuffs from 439 m of depth yield the first 40ar 39ar age of ca 39 ka within the caldera consistent with the ci volcanic rocks from the nyt were moreover detected between 250 and 160 m our findings highlight i a reduction of the area affected by caldera collapse which appears to not include the city of naples ii a small volume of the infilling caldera deposits particularly for the ci and iii the need for reassessment of the collapse amounts and mechanisms related to larger eruptions our results also imply a revaluation of volcanic risk for the eastern caldera area including the city of naples the results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics whose understanding needs more robust constraints which can be obtained from scientific drilling

stratigraphic evolution of the nakdong river valley in response to late quaternary sea level changes abstract sequence analysis using borehole samples and high resolution seismic data in the nakdong river valley yielded a good example of a river valley sequence influenced by the complex interplay between the bottom morphology of the steep paleo valley varying sediment supply and holocene sea level change associated with coastal currents the late quaternary stratigraphic sequence in the nakdong river estuary approximately 60 70 m thick forms a high frequency sequence consisting of a set of lowstand transgressive and highstand systems tracts that corresponds to a fifth order 20 ka sea level cycle four main depositional systems including ten sedimentary facies constitute these systems tracts fluvial estuarine coastal shoreface and deltaic the lowstand systems tract lst consisting of gravelly sand forms a fluvial depositional system unit i which fills the thalweg of river valley mainly developed before 12 ka the transgressive systems tract tst showing a succession of retrograding or backstepping depositional arrangements can be divided into two depositional systems unit ii and iii the riverine sediments were trapped within the paleo estuary forming an estuarine depositional system unit ii developed between 12 and 7 ka as the transgression continued the coarse sediments were deposited and redistributed by coastal processes resulting in coastal shoreface depositional system unit iii it is characterized by an isolated sand body and thin sand veneer the hst is composed of deltaic depositional system including delta plain delta front and prodelta unit iv during the delta progradation most coarse grained sands derived from the river were deposited in the lower delta plain and delta front forming sand bars and shoals less than 15 m deep the remaining fine grained sediments were transported further offshore in a suspension mode and deposited in the inner shelf off the present river mouth forming a subaqueous prodelta radiocarbon and optically stimulated luminescence osl dating suggest that the holocene deltaic system was initiated by aggradational and progradational stacking patterns at approximately 8 ka during the last stage of decelerated sea level rise and was then followed by a prograding clinoform after the highest sea level at approximately 7 ka

analytical models of deformation and residual gravity changes due to a mogi source in a viscoelastic medium abstract the popular mogi model describing deformation due to a small pressurized spherical cavity embedded in a homogeneous elastic half space is shortly reviewed similarities and differences with other isotropic deformation models are discussed and the interpretation of the different volume changes accompanying source inflation is provided the model is then generalized to viscoelastic rheology the overpressure needed within the source to reproduce the large deformation sometimes observed in volcanic regions is found to be strongly dependent on rheological parameters so that reasonably low values may be obtained if the relaxation time of the medium surrounding the source is short months instead of the extremely high values inferred from the elastic theory if the inflation of the source is due to the input of new magma from remote distance the resulting residual gravity change g may be easily computed thanks to the spherical geometry of the source and the density of the newly emplaced material may be inferred from the ratio of g w between the gravity change and the uplift this ratio is independent of the overpressure and the radius of the source which are generally ill defined parameters and is slightly dependent on the relaxation time in the transient phase explicit solutions are shown for a step like overpressure history and for a constant magma supply rate a more realistic model is also proposed in which the viscoelastic properties are restricted to a small spherical volume around the source surrounded by an elastic medium even if an accurate interpretation of deformation and gravity changes in volcanic areas generally requires taking into account topography elastic layering and the triaxial geometry of the inflation source values computed according to the generalized mogi model are compared with observations made during the 1982 84 uplift episode at campi flegrei caldera italy for the sake of illustration

a revised chronology for mississippi river subdeltas radiocarbon measurements by accelerator mass spectrometry relating to three of the four late holocene mississippi river subdeltas yielded consistent results and were found to differ by up to 2000 carbon 14 years from previously inferred ages these geological dataare in agreement with archaeological carbon 14 data and stratigraphic ages based on ceramic seriation and were used to develop a revised chronologic framework which has implications for prehistoric human settlement patterns coastal evolution and wetland loss and sequence stratigraphic interpretations

drowning of the mississippi delta due to insufficient sediment supply and global sea level rise global sea level rise reduced sediment supply and subsidence threaten the stability of the mississippi delta calculations of riverine sediment load and storage indicate that 10 000 13 500 km2 of the delta could be submerged by ad 2100

coastal barriers northern gulf last eustatic cycle genetic categories and development contrasts a review abstract a large body of chronologically well constrained and detailed quaternary data accumulated in the last decades from the coastal shelf region of the northern gulf of mexico consequently a preliminary synthesis of major aspects of the late quaternary barrier and mainland coastal development on the northern gulf of mexico is timely several major factors account for the striking differences between barrier size and development styles in the three northern gulf coast regions barriers are nearly continuous in the nw where they dominate by the greatest dimensions and continuity sand supply from shelf and mainland sources continued at variable rates throughout six stages of the last eustatic cycle lec differences in antecedent topography in fluvial runoff volumes and relative sea level rise including rapid overstepping flooding events were critical in the regional distinctions leaving fewer and smaller relict fluvial delta behind drowned shore and nearshore landforms on the shelf only two large fluvial systems impacted the ne the nw shelf and nearshore received abundant sediment supply from the mississippi and lesser streams indirectly by ravinement erosion of relict landforms and landward directed cross shelf sediment transfer sands originated mainly in relict deltas fluvial tidal channel and inlet fill as well as from submerged shore ridge remnants on the continental shelf shelf margin deltas represented major secondary sources barrier formation categories and their respective importance in specific areas represent critical aspects of coastal development the authorship of various formation concepts e g penck gilbert mcgee haage ganong and keilhack often is still miscredited or remains unrecognized in the literature recognition of the stratigraphic and sedimentological diagnostic characteristics of the basic genetic barrier categories plays a key role in testing the validity of barrier evolution models closely knit process form relationships prevail between hydrodynamic sea level change storm tidal current overwash sedimentary shoal and island aggradation rollover and eolian accumulation processes and the resulting landform morphology the most detailed accounts that deal with the development of the alabama louisiana and apalachicola barrier chains are particularly instructive almost all modern gulf barriers with identifiable genetic background formed by shoal aggradation between 5 5 and 2 0 ka during a marked deceleration in sea level rise concurrently a sizable mainland strand plain complex extended the ne coastal plain tide and storm driven sediment transport to the large mobile bay ebb delta the focal role of composite east dauphin island in establishing the ms la island chain and the island blocking role of mississippi delta advance were prime factors in a complex barrier history migration paradoxically may also occur by transgressive rollover concurrently with regressive landward progradation of island strand plains stream discharge and sand reworked from relict lithosomes on the shelf were insufficient in compensating for wave and tide related sediment loss gulf levels stayed below the present throughout the mid and late holocene

evidence of thermal driven processes triggering the 2005 2014 unrest at campi flegrei caldera abstract an accelerating process of ground deformation that began 10 years ago is currently affecting the campi flegrei caldera the deformation pattern is here explained with the overlapping of two processes short time pulses that are caused by injection of magmatic fluids into the hydrothermal system and a long time process of heating of the rock the short pulses are highlighted by comparison of the residuals of ground deformation fitted with an accelerating polynomial function with the fumarolic co 2 ch 4 and he ch 4 ratios which are good geochemical indicators of the arrival of magmatic gases the two independent datasets show the same sequence of five peaks with a delay of 200 days of the geochemical signal with respect to the geodetic signal the heating of the hydrothermal system which parallels the long period accelerating curve is inferred by temperature pressure gas geoindicators referring to a recent interpretation that relates variations in the fumarolic inert gas species to open system magma degassing we infer that the heating is caused by enrichment in water of the magmatic fluids and by an increment in their flux heating of the rock caused by magmatic fluids can be a central factor in triggering unrest at calderas

an evaluation of mobile mud dynamics in the mississippi river deltaic region abstract large rivers are the primary interface between terrestrial and ocean environments a relatively small number of rivers account for a disproportionate amount of the freshwater and suspended materials that are delivered to the coastal ocean sediment delivery to these coastal systems plays a key role in the global carbon cycle since deltas and continental shelves are considered to be the main repositories of organic carbon in marine sediments particulate material in these environments are typically deposited and resuspended several times before permanent accumulation or transport off the shelf this sediment cycling is an important component influencing biogeochemical processes that occur in coastal environments during two cruises in april and october 2000 on the shelf adjacent to the mississippi river water and sediment samples were collected for analysis of suspended solids and particle reactive radionuclides 210 pb 137 cs 7 be and 234 th to evaluate the transport and fate of terrestrial and marine material a comparison of the distribution of these tracers provides insight about the pathways and residence times of particulate materials on the shelf inventories of these short lived radiotracers showed variations of more than two orders of magnitude indicating dramatic variations in sediment deposition between sampling events short lived radiotracers indicate that river borne materials are transported less than 30 km from the river mouth before initial deposition however seasonal variations in 7 be and 137 cs indicate significant remobilization of sediment and potential export of sediment out of the study area during the high energy e g wind wave winter months in addition depth profiles of 7 be and excess 234 th indicate sediment deposition rates between 0 8 and 3 9 cm month 1 0 4 2 1 g cm 2 month 1 at two shelf locations near river and open shelf environments these rates are much greater than those observed on decadal time scales 1 3 2 0 cm year 1 or 0 6 1 5 g cm 2 year 1 via 210 pb at the same sites this further substantiates active sediment reworking and potential export off the shelf as has been observed in other river dominated ocean margins

mass wasting on the mississippi river subaqueous delta abstract the mississippi river delta front mrdf is an excellent natural laboratory for studying seafloor instability and evaluating the preconditioning factors and triggering mechanisms that lead to seafloor failures the occurrence of seafloor landslides on the mrdf has been recognized since the 1950s but the bulk of research on the topic was conducted in the 1970s 80s after seafloor landslides triggered by hurricane camille damaged offshore infrastructure through these efforts it was recognized that seafloor instability features are present across the entire delta front that rapid sediment delivery from the mississippi river is a primary preconditioning factor for failures and that cyclic loading from hurricane waves is the main triggering mechanism for deep seated catastrophic events however mounting evidence shows that mrdf seafloor motion occurs even during periods of no hurricane activity which could be attributed to creep like motion of underconsolidated sediment or smaller episodic flows triggered by winter storms or mississippi river floods given the extensive spatial distribution of instabilities on the mrdf the multiple mechanisms of failure and variety of resulting morphology and the range of potential triggering mechanisms with short recurrence the mrdf is an exceptional location to assess the complex problem of seafloor landslides an improved understanding of seafloor landslides is crucial for understanding global sediment budgets and associated biogeochemical cycling as they can evacuate large volumes of sediment into deep water over short time periods additionally seafloor landslides pose a hazard to offshore infrastructure and to coastal communities through possible tsunami inundation and advancing research on preconditioning factors and triggering mechanisms would improve hazard assessments this paper presents a review and synthesis of geological and geotechnical research on the mrdf particularly with respect to seafloor landslides their occurrence geological and geotechnical controls triggering mechanisms and knowledge gaps related thereto this synthesis is conducted at times of rapidly developing technologies for studying seafloor instability and as the mrdf enters a stage of degradation characterized by reduced sediment delivery and accumulation

magma and fluid migration at yellowstone caldera in the last three decades inferred from insar leveling and gravity measurements we studied the yellowstone caldera geological unrest between 1977 and 2010 by investigating temporal changes in differential interferometric synthetic aperture radar insar precise spirit leveling and gravity measurements the analysis of the 1992 2010 displacement time series retrieved by applying the sbas insar technique allowed the identification of three areas of deformation i the mallard lake ml and sour creek sc resurgent domes ii a region close to the northern caldera rim ncr and iii the eastern snake river plain srp while the eastern srp shows a signal related to tectonic deformation the other two regions are influenced by the caldera unrest we removed the tectonic signal from the insar displacements and we modeled the insar leveling and gravity measurements to retrieve the best fitting source parameters our findings confirmed the existence of different distinct sources beneath the brittle ductile transition zone which have been intermittently active during the last three decades moreover we interpreted our results in the light of existing seismic tomography studies concerning the sc dome we highlighted the role of hydrothermal fluids as the driving force behind the 1977 1983 uplift since 1983 1993 the deformation source transformed into a deeper one with a higher magmatic component furthermore our results support the magmatic nature of the deformation source beneath ml dome for the overall investigated period finally the uplift at ncr is interpreted as magma accumulation while its subsidence could either be the result of fluids migration outside the caldera or the gravitational adjustment of the source from a spherical to a sill like geometry

recent ground movement and seismic activity in campi flegrei southern italy episodic growth of a resurgent dome leveling surveys in campi flegrei an active volcanic caldera in southern italy show that this caldera has undergone both subsidence and uplift of a few meters during the past 85 years a single source located at a depth of about 3 km beneath the center of the caldera can account for almost all elevation changes recorded in campi flegrei since the first leveling survey conducted in 1905 1907 this includes leveling surveys that span periods of subsidence such as between 1905 1907 and 1919 and between january 1985 and october 1986 and periods of rapid uplift between march 1970 and october 1971 and between january 1981 and december 1984 a possible geometry for the source of uplift and subsidence beneath campi flegrei is a rectangular horizontal sheet located at a depth of about 3 km and centered a few hundred meters east of the city of pozzuoli the horizontal dimensions of this sheet are about 1 5 km by 3 0 km the long axis is oriented n70 w this sheet lies adjacent to the most intense area of seismicity that occurred from mid 1983 to december 1984 during an uplift episode this sheet may represent the top of a magma body undergoing internal pressure changes possibly by intrusion of additional magma subsidence is caused by groundwater removal from the water saturated deposits that fill this caldera to a depth of a few kilometers a temporary increase in subsidence rate after an uplift episode is caused by increased rate of groundwater removal from newly fractured regions that lie immediately above the magma body the close proximity of this water saturated region and the magma body makes it impossible to separate the depth to these two sources from the results of leveling surveys two observations indicate that uplift has occurred in the center of campi flegrei for at least the past several thousand years first marine deposits in the center of campi flegrei were uplifted at least 40 m between 4000 and 8000 years ago second continuous seismic profiles of the undersea portion of campi flegrei have identified only one region where rocks are fractured and faulted adjacent to the uplifted marine deposits that surround the point of maximum uplift indicated by recent leveling surveys on the basis of these observations and the historical record of activity we suggest that campi flegrei caldera is in a stage of growing a resurgent dome the present diameter of the resurgent dome is about 4 km and the maximum amount of vertical uplift during the past 10 000 years has probably not exceeded 100 m the episodes of rapid uplift and shallow earthquake swarms during the past 20 years are probably related to the growth of this resurgent dome

a physical appraisal of a new aspect of bradyseism the miniuplifts 1 the campi flegrei caldera is characterized by well known episodes of fast uplift called bradyseism the last of which produced 1 8 m of maximum vertical displacement in the period 1982 1984 less known is a particular aspect of campi flegrei unrests detected only in the last 20 years namely the occurrence of miniuplift episodes characterized by relatively small positive vertical displacements in the range 0 03 0 11 m miniuplift episodes occurred in 1989 1994 and 2000 and probably one or two times in the period 1972 1982 these small ground uplifts were also accompanied by moderate seismicity each of them was followed by a short phase of relatively quick subsidence after which the previous rate of subsidence of the period was resumed an order of magnitude analysis of the forces energy and power that can cause the onset and determine the evolution of these events is derived on the basis of a thermal fluid dynamical approach it allows the quantitative correlation of the power input from the energy source with the rate of energy dissipation in the geologic system during the miniuplifts in order to assess the likelihood of our fluid dynamical model for these episodes theoretical ground displacements have been computed these displacements result from the changes in pressure as a function of depth predicted by the fluid dynamical model for reasonable perturbations of the geothermal system described as changes of the peclet number theoretical results agree extremely well with the observed amounts of the miniuplifts

fluid evolution in a volcanic hosted epithermal carbonate base metal gold vein system alto de la blenda farallon negro argentina alto de la blenda is a 6 6 ma intermediate sulphidation epithermal vein system in the farallon negro volcanic complex which also hosts the 7 1 ma porphyry cu au deposit of bajo de la alumbrera the epithermal vein system is characterised by a large extent and continuity 2 km 400 m open to depth 6 m maximum width and an average gold grade of 8 g t the vein is best developed within an intrusion of a fine grained equigranular monzonite interpreted as the central conduit of a stratovolcano whose extrusive activity ended prior to porphyry cu au emplacement at bajo de la alumbrera which is in turn cut by minor epithermal veins the alto de la blenda vein consists predominantly of variably mn rich carbonates and quartz with a few percent of pyrite sphalerite galena and other sulphide and sulphosalt minerals four phases of vein opening hydrothermal mineralisation and repeated brecciation can be correlated between different vein segments stages 2 and 3 contain the greatest fraction of sulphide and gold they are separated by the emplacement of a polymictic breccia containing clasts of quartz feldspar porphyry as well as basement rocks fluid inclusions in quartz related to stages 2 to 4 are liquid rich with 2 4 wt nacl eq they homogenise between 160 and 300 c with very consistent values within each assemblage vapour inclusions are practically absent in the epithermal vein quartz fragments in the polymictic breccia contain inclusions of intermediate to vapour like density and similar low salinity 3 wt nacl eq besides rare brine inclusions containing halite laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of epithermal inclusions indicate high concentrations of k fe as sb cs and pb that significantly vary within and through subsequent vein stages careful consideration of detection limits for individual inclusions shows high gold concentrations of 0 5 to 3 ppm dissolved in the ore fluid which contains variably high sulphur concentrations in excess over fe and other chalcophile metals compositional variations are interpreted to reflect cooling and contraction of lower density magmatic fluids at depth like those preserved in porphyry clasts that were mechanically transported up by the polymictic breccia ore mineral precipitation from the magmatic fluid occurred by further cooling and possibly minor mixing with surface derived water leading to sulphide saturation de sulphidation of the magmatic fluid and consequent gold precipitation the absence of flash boiling and or reduction by carbonaceous host rocks has led to relatively modest but constant gold grades in the carbonate base metal gold veins of alto de la blenda

causes of river avulsion insights from the late holocene avulsion history of the mississippi river u s a abstract the emphasis on gradient advantages in studies of avulsion is misleading while gradient advantages are necessary for an avulsion to occur the late holocene avulsion history of the mississippi river in louisiana suggests that factors such as substrate composition and floodplain channel distributions are more important cross valley to down valley slope ratios of the modern floodplain range from 16 to 110 and are typically 30 the slope ratio is 35 at the location of the mississippi atchafalaya diversion old river yet slope ratios are 83 to 110 immediately upvalley of old river all values of mississippi river floodplain slope ratios are significantly larger than values of avulsion threshold calculated by numerical models shallow floodplain cores 14c dating of organic remains and geologic mapping show that the mississippi river has avulsed only four times over the past 5 ky in the southern lower mississippi valley lmv gradient advantages are widespread yet avulsions are rare these observations indicate that factors other than gradient advantage control mississippi river avulsion several examples of mississippi and red river avulsion by channel reoccupation support the idea that channel distributions and substrate compositions are primary influences on avulsion incipient mississippi river avulsion and development of the atchafalaya river involved reoccupation of abandoned mississippi river channels and a red river crevasse splay complex the modern atchafalaya river also incises buried mississippi river channel belt sands abandoned channel belts and crevasse splay complexes consist of sandy substrates that facilitate scour and the development of channels capable of capturing the mississippi river abandoned channels provide ready made conduits for mississippi river flow that can efficiently develop into avulsive channels multi storied sheet sandstones in ancient fluvial deposits may provide additional support for the idea that erodible substrates and floodplain channel distributions are critical influences on avulsion these features record episodic reoccupation of channel belts which at least in some cases may simply reflect successive avulsions rather than major changes in aggradation rate or extrabasinal factors such as climate

mississippi delta subsidence primarily caused by compaction of holocene strata coastal subsidence causes sea level rise shoreline erosion and wetland loss which poses a threat to coastal populations this is especially evident in the mississippi delta in the southern united states which was devastated by hurricane katrina in 2005 the loss of protective wetlands is considered a critical factor in the extensive flood damage the causes of subsidence in coastal louisiana attributed to factors as diverse as shallow compaction and deep crustal processes remain controversial current estimates of subsidence rates vary by several orders of magnitude here we use a series of radiocarbon dated sediment cores from the mississippi delta to analyse late holocene deposits and assess compaction rates we find that millennial scale compaction rates primarily associated with peat can reach 5mm per year values that exceed recent model predictions locally and on timescales of decades to centuries rates are likely to be 10 mm or more per year we conclude that compaction of holocene strata contributes significantly to the exceptionally high rates of relative sea level rise and coastal wetland loss in the mississippi delta and is likely to cause subsidence in other organic rich and often densely populated coastal plains

the bay of naples southern italy constraints on the volcanic structures inferred from a dense seismic survey 1 the bays of naples and pozzuoli host volcanic areas that have been active within recent history in addition the vicinities areas around the vesuvius volcano and the campi flegrei caldera are extremely densely inhabited over the past decade this situation has prompted several active seismic experiments focused on the vesuvius volcano more recently the serapis active seismic survey covered the entire bay of naples with particular attention to pozzuoli bay the processed serapis p wave travel time collection extended with a previously acquired data set has allowed the computation of the most comprehensive three dimensional p wave velocity distribution for the bay of naples which includes a small scale high resolution model of the campi flegrei caldera the joint interpretation of the velocity distribution together with both the available gravity measurements and models and the geothermal drilling information has allowed us to locate and map lithological units at depths we propose a model of the campi flegrei caldera in relation to the underlying mesozoic limestone unit in this model no magma chamber exists in the upper 6 km beneath the bay of naples the feeding system of the campi flegrei caldera is directly controlled by the tectonic structures affecting the limestone unit beneath the bay of naples two ne sw normal faults run beneath the vesuvius volcano and campi flegrei which are related to the pre pleistocene apenninic tectonics

magma degassing as a source of long term seismicity at volcanoes the ischia island italy case transient seismicity at active volcanoes poses a significant risk in addition to eruptive activity this risk is powered by the common belief that volcanic seismicity cannot be forecast even on a long term here we investigate the nature of volcanic seismicity to try to improve our forecasting capacity to this aim we consider ischia volcano italy which suffered similar earthquakes along its uplifted resurgent block we show that this seismicity marks an acceleration of decades long subsidence of the resurgent block driven by degassing of magma that previously produced the uplift a process not observed at other volcanoes degassing will continue for hundreds to thousands of years causing protracted seismicity and will likely be accompanied by moderate and damaging earthquakes the possibility to constrain the future duration of seismicity at ischia indicates that our capacity to forecast earthquakes might be enhanced when seismic activity results from long term magmatic processes such as degassing

phosphorus distribution c n p ratios and δ13coc in arctic temperate and tropical coastal sediments tools for characterizing bulk sedimentary organic matter abstract onshore offshore trends in phosphorus p organic carbon oc and total nitrogen tn concentration p distribution elemental organic c n p ratios and stable carbon isotopic composition of oc 13 c oc of surficial sediments are presented from three river dominated coastal regimes the mackenzie river beaufort shelf in the canadian arctic the mississippi delta and louisiana shelf in the temperate gulf of mexico and the tropical amazon shelf these parameters measured in surficial sediments from the three sites are used to assess changes in the importance of terrestrial and marine organic matter sources to sediments as a function of distance from the locus of riverine discharge trends in elemental ratio data from the arctic transect and a portion of the gulf of mexico transects can be explained in terms of a two end member mixture of terrestrial and marine phytodetritus in the arctic transect covariation of organic c p ratios with 13 c oc is consistent with a two end member mixture of terrestrial and marine organic matter a similar relationship between c p ratios and 13 c oc is not evident in gulf of mexico or amazon shelf sediments at these sites the two end member model fails to explain the data adequately the most striking feature of the onshore offshore trends in elemental oc op and oc tn ratios is the occurrence of low ratios in sediments from deep water stations in the gulf of mexico and all stations on the amazon shelf resulting from p and n enrichments exceeding the redfield ratio for marine plankton three explanations are discussed to account for these low ratios 1 the dominance of refractory op and on compounds in the residuum of degraded organic matter 2 differential sorption of op and n compounds regardless of lability on the surfaces of the fine grained sediments characteristic of these sites and 3 a dominance of bacterial biomass or components derived from bacterial biomass elemental ratios and 13 c oc signatures indicate that differential sorption may be most important in the deep water gulf of mexico sites in contrast elemental ratios and 13 c oc on the amazon shelf are most consistent with a sedimentary organic matter pool dominated by bacterial biomass or derivative substances

impact of river discharge on hydrodynamics and sedimentary processes at yellow river delta abstract during the anthropocene regulating river discharge by high dams may have met the need for water demands in river basins but resulted in carrying less freshwater and sediment to the sea inducing land degradation and shoreline retreat in worldwide mega river deltas in land ocean interaction tide response to water discharge changes plays an important role and is crucial for the river laden sediment transfer and dispersal affecting both nearshore and estuarine deposits the yellow river delta yrd which is under an increasing pressure of the new discharge regime of the yellow river has undergone drastic changes in terms of sediment dynamics and morphologic evolution to gain a better understanding of the overall fluvial and marine hydrodynamics and morphodynamic processes in the yrd in this study a full scale numerical model is built to investigate the interaction and impacts of changing environmental forcing and dynamics on flow and sediment transport in the estuary of yrd and its adjacent coasts the results show that the river discharge strongly affects the tidal dynamics and morphology of the delta particularly in the close vicinity of the outlet and the intertidal zone tidal constituents m2 and k1 which are the most significant ones in the yrd are found to be noticeably affected with a decreasing trend when the river discharge increases the model results also indicate that river discharge affects the location and intensity of the shear front that occurs in the nearshore areas of the yrd increasing the river discharge can induce a seaward movement of the shear front reduce its width and concentrate its shear intensity it is found that the reverse of the flow direction at each side of the shear front and strong longshore tidal current can act as a barrier for the sediment dispersal process by keeping suspended sediment in the inner zone thus to form a particular sediment deposition zone and the depo center

gravity changes and passive so2 degassing at the masaya caldera complex nicaragua an understanding of the mechanisms responsible for persistent volcanism can be acquired through the integration of geophysical and geochemical data sets by interpreting data on micro gravity ground deformation and so2 flux collected at masaya volcano since 1993 it is now clear that the characteristically cyclical nature of the activity is not driven by intrusion of additional magma into the system rather it may be due in large part to the blocking and accumulation of gas by restrictions in the volcano substructure the history of crater collapse and formation of caverns beneath the crater floor would greatly facilitate the trapping and storage of gas in a zone immediately beneath san pedro and the other craters another mechanism that may explain the observed gravity and gas flux variations is the convective overturn of shallow pre existing degassed cooled dense magma that is replaced periodically by lower density hot gas rich magma from depth buoyant gas rich magma rises from depth and is emplaced near the surface resulting in the formation and fluctuation of a low density gas rich layer centred beneath nindiri and santiago craters as this magma vigorously degasses it must cool increase in density and eventually sink five stages of activity have been identified at masaya since 1853 and the most recent data suggest that the system may have been entering another period of reduced degassing in 2000 this type of analysis has important implications for hazard mitigation because periods of intense degassing are associated with poor agricultural yields and reduced quality of life a better understanding of persistent cyclically active volcanoes will allow for more effective planning of urban development and agricultural land use

a review of sediment diversion in the mississippi river deltaic plain abstract one of the proposed methods for restoring the disappearing mississippi delta is sediment diversion which uses channels and structures to divert water and sediment from the mississippi and atchafalaya rivers into adjacent basins this study presents a comprehensive review of geological and physical aspects of sediment dynamics in the mississippi river deltaic plain mrdp with special reference to diversion studies over the past two decades we synthesize these studies present the current understanding of sediment diversions in the context of sediment dynamics identify multiple key knowledge gaps and make recommendations for future studies to maximize net land building in the mrdp management strategies should be focused on a enhancing river sediment delivery both mud and sand b increasing sediment retention in receiving basins and c minimizing erosion in bays and estuaries compared with extensive studies of land building there have been relatively fewer studies of erosional processes a heterogeneous coastal geological framework cohesive sediment erodibility and subsidence together play complicated yet critical roles in future sediment dynamics in bays and estuaries of the mrdp sediment retention rates are highly sensitive to spatial and temporal scales types of sediments and delivery season sediment diversions to seaward receiving basins provide more surge protection but tend to have lower sediment retention due to active coastal processes structures and devices that improve sediment retention trap sediments dissipate waves and build living shorelines should be explored and cost to benefit analysis is needed long term planning should consider more landward diversions strategic community relocation and nonlinear response of the complex sedimentary system of the mrdp

stress heterogeneities and failure mechanisms induced by temperature and pore pressure increase in volcanic regions abstract we study the strain and stress fields produced by temperature and pore pressure increases within and outside a thermo poro elastic tpe inclusion the source region embedded within a medium the matrix in isothermal drained conditions this model is suitable to describe a crustal region in a volcanic environment pervaded by hot pressurized fluids released by an underlying magma chamber after introducing the pertinent constitutive relations a formal solution for the displacement field is provided in terms of the green s function for an elastic medium with drained isothermal elastic moduli employing a generalization of eshelby 1961 procedure if an unbounded medium is considered a displacement potential can be introduced obeying the laplace equation within the source region and the poisson equation within the matrix if a spherically symmetric source region is considered simple analytical solutions are obtained for the displacement the strain and the stress fields showing that thrust faulting mechanisms are promoted within the source region while normal faulting mechanisms prevail in the embedding matrix employing reasonable numerical values for the thermo poro elastic parameters suitable to describe highly porous sedimentary rock strain and stress variations are found to be significant even for moderate changes of temperature and pore pressure variations of the coulomb failure function are high in the tpe region and are strongly dependent on the friction coefficient and pore pressure application of these results to the 1982 84 and 2011 13 unrest episodes at campi flegrei caldera italy suggests that an oblique dike intrusion across a previously unfaulted tpe region took place with a mixed tensile thrust dislocation mechanism in both events as previously inferred from accurate inversion of geodetic data

display and quantitative assessment of distributions of earthquake focal mechanisms summary this paper describes quantitative methods for evaluating the distribution of focal mechanism orientations of groups of earthquakes and shows how to display this distribution on a triangle diagram we present a 2 based statistical test for determining whether two sets of focal mechanisms are drawn from distinct populations we apply these methods to 3625 better determined mechanisms for shallow earthquakes in the harvard centroid moment tensor cmt catalogue we describe the distributions of mechanisms in the whole catalogue and for catalogue subsets in some specific tectonic environments in addition we explore the geographical locations of mechanisms with orientations that occur relatively infrequently that is mechanisms that are unlike thrust normal or strike slip mechanisms such mechanisms are relatively rare along mid ocean ridges and in oceanic subduction zones the majority of these unusual mechanisms occur along plate boundaries where crustal thickness is highly variable and in regions where the plate convergence direction becomes oblique and thus relative motion changes from convergence to transform motion

anatomy and growth of a holocene clinothem in the gulf of papua 1 high resolution seismic profiles and sedimentological data from grab samples and long cores provide an unprecedented picture of the structure sedimentology and late quaternary development of two gulf of papua gop clinothems one probably stage 3 and 4 in age and one holocene in age the older was partially eroded during stage 2 and partially covered by the younger clinothem during stage 1 the younger clinothem consists of three stratigraphic units separated by two surfaces of erosion bypass or correlative surfaces of lap the surfaces were formed by changes in accommodation and sediment supply the underlying physiography of the older clinothem also appears to play an important role in governing the shape of the younger clinothem in the northern gulf oblique clinoforms of the younger clinothem suggest that the rate of sediment supply from the northern rivers outstripped the formation of new accommodation whereas in the south sigmoidal clinoforms indicate that accommodation increased faster than sediment supply the origin of the new accommodation remains uncertain because of limited age constraints on the basis of sediment thickness stratal geometry and acoustic character off shelf transport appears to be the dominant sediment transport direction with preferential accumulation on the promontories and bypass in the valleys presently observed and computed modern flows and complex gyres in shallow water coupled with wave and current supported gravity flows or river floods can explain the form internal clinoform shapes and mineralogy of the younger gulf of papua clinothem

geodetic constraints to the source mechanism of the 2011 2013 unrest at campi flegrei italy caldera campi flegrei caldera italy was affected by a new unrest phase during 2011 2013 we exploit two cosmo skymed data sets to map the deformation field obtaining displacement rates reaching 9 cm yr in 2012 in the caldera center the resulting data set is fitted in a geophysical inversion framework using finite element forward models to account for the 3 d heterogeneous medium the best fit model is a north dipping mixed mode dislocation source lying at 5 km depth the driving mechanism is ascribable to magma input into the source of the large 1982 1984 unrest since similar source characteristics were inferred that generates initial inflation followed by additional shear slip accompanying the extension of crack tips the history and the current state of the system indicate that campi flegrei is able to erupt again and the advanced techniques adopted provide useful information for short term forecasting

sill intrusion as a source mechanism of unrest at volcanic calderas the interpretation of dynamic processes that occur in volcanic calderas is not simple the ground deformations and the local seismicity which in other volcanic contexts are usually regarded as precursors to eruption in caldera environment in many cases are not followed by any eruption we formulate a general hypothesis that can explain these behaviors our hypothesis is that the intrusion of a sill can be responsible for the dynamics observed during unrest at calderas in order to investigate the reliability of this hypothesis we developed a dynamic model of sill intrusion in a shallow volcanic environment in our model the sill fed by a deeper magma reservoir intrudes below a horizontal elastic plate representing the overlying rocks and expands with axisymmetric geometry the model is based on the numerical solution of the equation for the elastic plate coupled with a navier stokes equation for simulating the dynamics of the sill intrusion we performed a number of simulations with the objective of showing the main features of the model in the experiments when the feeding process stops the vertical movement reverses its trend and the area of maximum uplift undergoes subsidence under certain conditions the subsidence can occur even during the intrusion of the sill the stress field produced by the intrusion is mainly concentrated in a circular zone that follows the sill intrusion front the features predicted by the model are consistent with many observations carried out on different calderas as reported in the scientific literature

the mississippi delta region past present and future the mississippi delta region of south louisiana houses a wealth of resources within a dynamic subsiding landscape foundations for the delta region reflect neogene evolution of the depocenter whereas details of the modern landscape reflect late pleistocene to holocene evolution of the alluvial deltaic plain the holocene delta plain was constructed by cyclical growth of deltaic headlands followed by avulsion and relocation of the fluvial sediment source abandoned headlands were then submerged and reworked while a new headland was created at the site of active fluvial sediment input historic period levees have decoupled the delta plain from its fluvial sediment source at the same time global sea level rise was accelerating which has accelerated delta plain submergence diversions of mississippi river water and sediment are necessary to achieve delta plain sustainability but upstream dams trap 50 of the total sediment load and there is not enough supply to keep pace with subsidence and accelerated

apatite fission track thermochronology of the sierras pampeanas central western argentina implications for the mechanism of plateau uplift in the andes over much of its length the andean orogen is characterized by a generally east vergent geometry and a progressive eastward cratonward migration of individual arc orogenic elements a departure from this model occurs in the sierras pampeanas region of central western argentina where a terrane of active basement uplifts is currently developing to the east of the main cordillera apatite fission track data from uplifted precambrian and phanerozoic basement rocks of the sierras pampeanas constrain the tectonic development of this terrane and indicate that deformation associated with exhumation may have propagated broadly westward since the late miocene two pre andean cooling events during the carboniferous permian ca 300 280 ma and the early jurassic middle jurassic ca 200 174 ma have been identified the onset of andean deformation is represented by a cooling event during the late paleocene middle eocene this cooling was followed by a period of middle miocene late miocene reheating during foreland basin style sedimentation exhumation and possible westward migration of the exhumation front in the sierras pampeanas commenced during the late miocene pliocene to the east of the dominantly east vergent precordillera fold and thrust belt the apparent convergence of deformation in these two terranes and the progressive closure of miocene pliocene intermontane basins in the sierras pampeanas may reflect the early stages of andean plateau uplift the relative timing of plateau development along strike suggests that lateral thickening of the orogen is progressing southward at least from the latitude of central bolivia ca 20 s furthermore the time space coincidence between basement uplift and flattening of the subducted slab beneath the sierras pampeanas suggests that a relationship exists between westward displacement of the terrane and the dynamics of plate interaction

decadal link between longitudinal morphological changes in branching channels of yangtze estuary and movement of the offshore depo center in estuaries the morphology of inland and offshore areas usually evolves synergistically this study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo center where sediment deposition rate is maximum of the yangtze river estuary under intense human interference integrated data analysis is provided on morphology runoff discharge and ebb partition ratio from 1950 to 2017 channel volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects ebb partition ratio and duration of discharge 60 000 m3 s 1 act as proxies for the water excavating force in branching channels and runoff intensity it is found that deposition occurs in the lower upper sub reaches or further downstream upstream channels of the inland north south branching channels and the offshore depo center moves southward or southeastward as runoff intensity grows the reverse occurs as runoff intensity declines this is because the horizontal circumfluence in the yangtze estuary rotates clockwise as ebb partition ratios of the north south branching channels increase decrease for increasing runoff and conversely rotates anticlockwise for decreasing runoff land reclamation activities the deepwater channel project and the qingcaosha reservoir have impacted greatly on longitudinal changes of morphology in the north branch and the south passage and on ebb partition ratio variations in the north south channel and the north south passage dam induced runoff flattening has enhanced deposition in the upper lower sub reaches of the north south branching channels and caused northward movement of the offshore depo center except in areas affected by estuarine engineering projects dam induced longitudinal evolution of branching channel morphology and offshore depo center movement will likely persist in the future given the ongoing construction of large cascade dams in the upper yangtze and the completion of major projects in the yangtze estuary

paired deformation sources of the campi flegrei caldera italy required by recent 1980 2010 deformation history we analyze 1980 2010 ground displacements to discern similarities or differences between campi flegrei cf inflations and deflations and highlight possible anomalies in particular areas we show that the deformation pattern can be decomposed into two stationary constant over time except for a mere scaling factor parts both of them are satisfied by simple deformation sources a quasi horizontal elongated crack oriented nw to se and embedded in an elastic layered half space at a depth of about 3600 m satisfies large scale deformation all source parameters but potency volume change are constant over time residual deformation is confined to the area of the solfatara fumarolic field and satisfied by a small spheroid located at about 1900 m in depth again all source parameters but potency are constant over time the histories of the two sources are somewhat similar but not equal supporting the existence of a genuine local deformation source at solfatara against the emergence of a mere distortion of large scale deformation although reality is probably much more complex our simple model explains 1980 2010 cf deformation within ground displacement data errors and is consistent with solfatara geochemical conceptual models fumarolic geochemical data and seismic attenuation imaging of cf the observation that the cf deformation pattern can be decomposed into two stationary parts is hardly compatible with several recent works which proposed multiple sources with different features acting in different periods fluid injections implying ample changes of large scale deformation pattern over time complex spatio temporal patterns of distributions of volumetric sources