combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

broadband recording of strombolian explosions and associated very long period seismic signals on mount erebus volcano ross island antarctica in december 1996 and january 1997 broadband seismometers were deployed on the summit plateau of mount erebus at radial distances of 0 7 1 4 and 1 9 km from the central crater and lava lake strombolian explosions at erebus previously have been observed to produce seismic and acoustic energy between 1 and 6 hz new observations document significant energy with spectral peaks as grave as 20 s nearly identical very long period vlp signals begin 1 5 s prior to explosions have dilatational onsets and persist for up to 150 s similar vlp waveforms were recorded at all three stations indicating that the seismograms are essentially source dominated particle motions suggest an initial depth for the vlp source of up to several hundred meters migrating deeper in the course of 15 s such explosion associated vlp signals may indicate a nondestructive lossy resonance or nonlinear fluid flow excitation within the shallow magmatic system

behavior of rare earth elements in a paleoweathering profile on granodiorite in the front range colorado usa abstract a paleoweathering profile on the boulder granodiorite in northern colorado provides an opportunity to trace the behavior of rees from parent rock through a weathering profile into unconformably overlying permian sediments with progressive upward weathering of the granodiorite na2o cao sio2 ta hf co th cr sc cr th zr hf la sc zr y and la th decrease al2o3 and fe2o3t increase and tio2 mgo k2o p2o5 rb zr sc cr co hf nb ta y th u ree ti nb and zr nb increase to maximum values and then either level off or decrease lree enrichment is less in the weathering profile than in the parent granodiorite and although the parent does not have an eu anomaly or only a slight positive anomaly all samples from the weathering profile and overlying sediments have significant negative eu anomalies this observation is especially important in that it shows conclusively that a negative eu anomaly can be produced during chemical weathering of granitoids we suggest these eu anomalies are due to relative enrichment of the other rees and partial loss of eu during the breakdown of plagioclase the boulder weathering profile also has a very minor negative ce anomaly that is within error of a ce anomaly in the parent in the unweathered parent 50 of the ree are contained in sphene and in the case of la also in allanite from 10 20 of the ree are contained in apatite and biotite hornblende and from 7 10 of the hrees are in zircon with exception of eu for which feldspars contribute about 8 negligible amounts of rees occur in the feldspars in weathered samples 75 of the rees are contained in clay minerals the crossover between sphene and clay control of rees occurs over a distance of 1 m near the contact with fresh rock except for their small negative eu anomalies the clay minerals have ree patterns very similar to those of the parent rock isocon plots suggest apparent enrichments of many elements in the boulder weathering profile result from losses of na ca and si during plagioclase weathering in addition variable amounts of sr eu ta nb p and ba were lost during weathering although th u zr y th sc zr hf lu hf and ti zr may have been transferred relatively unchanged from granodiorite parent to the bulk weathering profile most other element ratios and ree distributions were significantly changed during weathering this observation implies that caution needs to be exercised when using ree patterns and element ratios to trace sediment provenance the fact that most element ratios and ree distributions also differ between fountain sediments and the bulk weathering profile may be related to one or a combination of four factors listed in order of probable decreasing importance contribution of other sources to the fountain sediments sorting of minerals during sediment deposition remobilization of elements during diagenesis and leaching of elements by water flow through the upper meter of the weathering profile

geochemical characteristics of the eolian deposits in southern china and their implications for provenance and weathering intensity abstract the loess paleosol sequences in the middle lower reaches of the yantgze river are valuable geological records of quaternary environments that bear information about climate change for the subtropical zone of southern china type sections containing eolian deposits in this region mostly include the upper loess soil sequence referred to as xiashu loess formation the middle vermiculated red soil vrs and the underlying fluvial deposits or bedrock in this study xiashu loess paleosol formed in the xiashu loess and the vrs samples from xuancheng xc and jiujiang jj sections were analyzed for their elemental major and trace elements and isotopic sm nd geochemistry and compared with pleistocene loess and paleosol samples from the chinese loess plateau clp in northern china the results show an overall similarity in geochemical characteristics between the southern china loess and the average ucc indicating that the dust materials were derived from well mixed sedimentary protoliths which had undergone numerous upper crustal recycling processes in comparison with the loess of northern china the eolian deposits in southern china have higher tio2 zr hf and lower ba concentrations higher tio2 al2o3 u pb th pb and lower ba rb zr hf eu eu ce yb eu yb ratios and lower end 0 values with relatively greater range these features coincide with the complicated source rock compositions in the middle lower yangtze river which suggests local sources for the eolian deposits in this region the eolian deposits in southern china have experienced the intermediate k removal weathering stage ca sr na mg and k are the main mobile elements in the weathering process in comparison with the xiashu loess formation the vrs has greater depletion of na mg k and mn indicating a stronger weathering intensity or perhaps a longer period of weathering

geochemical facies analysis of fine grained siliciclastics using th u zr rb and zr rb sr ratios abstract abundance of the trace elements zr rb sr th and u may provide insight into the sedimentological origin of fine grained siliciclastic sediments provided that the units are derived from similar source areas as demonstrated here with suites of the fine grained jurassic and cretaceous rocks from the barents sea and svalbard zr rb ratios can be interpreted to indicate grain size variations while zr rb sr values reflect variations in the siliciclastic versus carbonate contents the th u ratio can be applied as an indicator of the redox conditions in 3d plots such as presented here the interplay between these geochemical factors can be interpreted in terms of the sedimentological evolution of the depositional basin the geochemical facies analyses show that similar depositional conditions existed on the jurassic shelf in the two studied localities the succeeding prodeltaic cretaceous beds were generally coarser grained and deposited in ventilated depositional conditions

spatial distribution of landslides triggered by the 2008 ms 8 0 wenchuan earthquake china abstract the ms 8 0 wenchuan earthquake of may 12 2008 is one of the most disastrous earthquakes in china the earthquake triggered tens of thousands of landslides over a broad area including shallow disrupted landslides rock falls deep seated landslides and rock avalanches some of which buried large sections of some towns and dammed the rivers the purpose of this study is to investigate correlations between the occurrence of landslides with geologic and geomorphologic conditions and seismic parameters over 56 000 earthquake triggered landslides with a total area of 811 km 2 are interpreted using aerial photographs and remote sensing images taken following the earthquake the spatial distribution of these landslides is analyzed statistically using both landslide point density lpd defined as the number of landslides per square kilometer and landslide area density lad the percentage of the area affected by landslides to determine how the occurrence of landslides correlates with distance from the epicenter distance from the major surface rupture seismic intensity and peak ground acceleration pga slope angle slope aspect elevation and lithology it is found that both lad and lpd have strong positive correlations with slope steepness distance from the major surface rupture and seismic intensity and that pre sinian schist and cambrian sandstone and siltstone intercalated with slate have the most concentrated landslide activities followed by the permian limestone intercalated with shale and devonian limestone statistical analyses also indicate that the major surface rupture has influence on the spatial distribution of landslides because lad and lpd are relatively higher on the hanging wall than on the footwall however the correlation between the occurrence of landslides with distance from the epicenter of the earthquake is complicated rather than a relatively simple negative correlation as found from other reported cases of earthquakes this is possibly due to complicated rupture processes of the earthquake

strombolian explosions 1 a large bubble breaking at the surface of a lava column as a source of sound strombolian activity consists of a series of explosions caused by the breaking of large overpressurized bubbles at the surface of the magma column acoustic pressure has been measured for 36 explosions at stromboli we propose that sound is generated by the vibration of the bubble before it bursts oscillations are driven by an initial overpressure inside the bubble assumed to be initially at rest just below the magma air interface inertia effects cause the bubble to overshoot its equilibrium radius then the bubble becomes underpressurized and contracts because of gas compressibility these oscillations are only slightly damped by viscous effects in the magma layer above the bubble the bubble cannot complete more than one cycle of vibration because of instabilities developing on the magma layer that lead to its breaking near the minimum radius assuming a simple geometry we model this vibration and constrain the radius and length of the bubble and the initial overpressure by fitting a synthetic waveform to the measured acoustic pressure the fit between synthetic and observed waveforms is very good both for frequency 60 rad s 1 and amplitude the initial bubble radius is 1 m and the length varies between several and a few tens of meters from the initial overpressure approximately 105 pa we calculate the maximum radial velocity of ejecta 30 m s 1 the generally good agreement between data and predictions of our model leads us to suggest that acoustic measurements are a powerful tool for the understanding of eruption dynamics

ash plume dynamics and eruption source parameters by infrasound and thermal imagery the 2010 eyjafjallajokull eruption during operational ash cloud forecasting prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate mer which is typically inferred from plume height uncertainties for plume heights are large especially for bent over plumes in which the ascent dynamics are strongly affected by the surrounding wind field here we show how uncertainties can be reduced if mer is derived directly from geophysical observations of source dynamics the combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained a dipole in this case and for the plume exit velocity to be calculated 54 142 m s based on the acoustic signal recorded during the 2010 eyjafjallajokull eruption from 4 to 21 may exit velocities are converted into mer using additional information on vent diameter 50 10 m and mixture density 5 4 1 1 kg m3 resulting in an average 9 105 kg s mer during the considered period of the eruption we validate our acoustic derived mer by using independent measurements of plume heights icelandic meteorological office radar observations acoustically derived mer are converted into plume heights using field based relationships and a 1d radially averaged buoyant plume theory model using a reconstructed total grain size distribution we conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real time determination of eruption source parameters this could improve substantially the forecasting of volcano related hazards with important implications for civil aviation safety

new insights into the 1999 eruption of shishaldin volcano alaska based on acoustic data data collected by a pressure sensor provide new insights into the 1999 eruption of shishaldin volcano unimak island alaska on 19 april 1999 after 3 months of unrest and an extended period of low level strombolian activity shishaldin experienced a subplinian eruption ash plume to 16 km followed by several episodes of strong strombolian explosions acoustic data from the pressure sensor allow us to investigate the details of an eruption which was instrumentally well recorded but with few visual observations in the 12 h prior to the subplinian phase the pressure sensor detected a series of small repeated pulses with a constant spectral peak at 2 3 hz the amplitude and occurrence rate of the pulses both grew such that the signal became a nearly continuous hum just before the subplinian eruption this humming signal may represent gas release from rising magma the main subplinian phase was heralded by 1 the abrupt end of the humming signal 2 several pulses of low frequency sound interpreted as ash bursts and 3 a dramatic increase in seismic tremor amplitude the change in acoustic signature at this time allows us to precisely time the start of the subplinian eruption previously approximated as the time of strongest tremor increase the 50 min subplinian phase actually contained several bursts of signal each of which may represent a discrete volume of magma passing through the system following the subplinian event the pressure sensor recorded four discrete episodes of strombolian gas explosions on 19 20 april and another on 22 23 april four of the five episodes were accompanied by strong seismic tremor the fifth has not been previously recog nized and was not associated with anomalous tremor amplitudes in time series these events are similar to explosions recorded at other volcanoes but in general they are much larger with maximum amplitudes of 65 pa at 6 5 km from the vent and they have low 0 7 1 5 hz peak frequencies these large explosions occurred at rates of 3 20 per minute for 1 5 h in each episode the explosions were accompanied by a small 5 km above sea level ash plume and only minor amounts of ejecta were produced thus the explosion activity was domi nated by gas release

infrasonic waves and volcanic tremor at stromboli the origin of the volcanic tremor is still under debate many theories have been proposed in the last years but none has yet been completely accepted in 1993 highly sensitive pressure sensors 2 175 pa volt used to monitor the explosive activity at stromboli have revealed unexpected correlation between small spike shaped pressure signals 1 2 pa and volcanic tremor these pressure pulses repeat regularly in time with a recurrent period of ca 1 s video camera images allowed us to correlate the pressure pulses with small gas bursts occurring at one of the active vents the striking correlation 0 971 between infrasonic and seismic energy fluctuations is particularly meaningful in the frequency domain infrasonic and seismic signal share the same spectral content 3 hz for every station within a range of 700 m around the craters correlations in time and frequency domain remained unaltered during the 1994 field experiments moreover during 1994 the increased degassing activity has been followed by an increase in pressure release 7 8 pa and by a shift towards higher frequencies 8 hz both in the infrasonic and seismic records infrasonic waves and volcanic tremor show similar energy fluctuations and frequency contents appearing therefore to be produced by the same dynamical process on this basis we claim that volcanic tremor at stromboli originates by continuous outbursting of small gas bubbles in the upper part of the magmatic column

analysis of tec data from the topex poseidon mission 1 topex poseidon mission has provided an extensive database of vertical tec over the ocean since august 1992 data from nearly 10 years of topex tec observations were analyzed to study the tec climatology first tec data were binned by season geomagnetic activity and solar activity to create longitudinally averaged tec maps in magnetic latitude and local time these maps show the annual and semiannual anomalies well known from climatological studies of nmf2 but lack the seasonal anomaly because of the longitudinally averaged binning the equatorial anomaly is the most prominent feature in the maps and they show strong tec variations with solar activity but relatively weak variations with geomagnetic activity in our three kp bins compared with the low solar activity conditions f10 7 120 the tec values for f10 7 120 are much larger and the equatorial anomaly lasts longer into the night up to midnight during geomagnetically active periods the tec maps generally show a noticeable increase at low latitudes for f10 7 120 but this effect is barely detectable for f10 7 120 finally three longitudinal bins indian pacific and atlantic were added in order to see how the tec morphology varies with longitude the tec measurements display strong longitudinal variations that closely follow the longitudinal variation of the magnetic declination in the southern pacific where the declination is positive and large the diurnal tec variations significantly differ from those in the other longitude sectors where the magnetic declination is negative in the southern hemisphere also at noon the phase of the longitudinal tec variation is typically opposite to that at midnight

geochemistry of the pliocene red clay formation in the chinese loess plateau and implications for its origin source provenance and paleoclimate change abstract recent field observations and sedimentological studies suggest the eolian origin of the late tertiary red clay formation underlying the pleistocene loess soil sequence in the loess plateau thereby extending the wind blown record from 2 6 ma down to 7 0 ma in north central china to address the source provenance of the red clay major and trace element concentrations were analyzed on the samples from a north south loess transect of the loess plateau and a red clay section at jiaxian results show that there is a good agreement of both major and trace element compositions between the last glacial interglacial loess soil units and the jiaxian red clay record the ree distribution patterns of the loess soil and red clay samples are remarkably similar in shape with enriched lree and fairly flat hree profiles and clear negative eu anomaly the geochemical features of the red clay are also identical to those of upper continental crust these chemical characteristics provide further evidence for eolian sedimentation of the red clay from the relations both between na2o al2o3 and k2o al2o3 ratios and between u pb and th pb ratios the eolian loess and red clay materials must have been subject to thorough sedimentary differentiation and moderate chemical weathering in the source area the chemical similarity between soil unit s1 and the red clay implies that such an environment as occurred in the last interglacial period may have already formed in northwestern china during the late tertiary comparison of down section variations in elemental ratios with field observations of pedogenic development of the red clay suggests that cao al2o3 sr rb and sr ba are more sensitive to climate changes than magnetic susceptibility and can be used to reconstruct the climate history of the late cenozoic

an evaluation of geochemical weathering indices in loess paleosol studies abstract applying geochemical proxies as measure for the weathering intensity of paleosols and sediments such as loess the quaternary scientist is confronted with various element ratios that have been proposed in literature this paper gives an overview on the principle of geochemical weathering indices different types of indices are evaluated with respect to the suitability for loess paleosol sequences regarding the special characteristics of this type of sediments and paleosols case examples in this study are key sections in southeastern and eastern europe the loess paleosol sequences batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine which represent archives of the late and mid pleistocene climate change of the region considering element behavior during weathering or diagenesis the chemical proxy of alteration cpa i e the molar ratio al2o3 al2o3 na2o 100 is proposed as the most appropriate index for silicate weathering the cpa was evaluated against commonly used weathering indices including the chemical index of alteration cia the chemical index of weathering ciw the plagioclase index of alteration pia the index b of kronberg and nesbitt and the ba sr and rb sr ratio depth profiles of sr type indices e g ba sr rb sr are likely to be influenced by the dynamics of secondary carbonate on the other hand common na type indices e g cia pia ciw may suffer from uncertainties in separating carbonate ca from silicate ca or from biases due to k fixation illitization the cpa is insensitive against such effects additionally using the cpa as with other na type indices provides the possibility to evaluate the homogeneity of the parent material regarding the relevant host minerals via the a cn k diagram

geochemical composition of the last deglacial lacustrine sediments in east tibet and implications for provenance weathering and earthquake events abstract identifying and understanding the respective influence of climate and tectonic processes becomes a frontier topic in tectonically active mountain ranges in the eastern tibetan plateau earthquake occurred frequently and usually led to formation of many dammed lakes in this study a last deglacial section of lacustrine sediments at xinmocun in eastern tibet is selected for conventional x ray fluorescence xrf and scanning xrf sxrf elemental analysis the high correlation of major and trace element abundances between the xinmocun lacustrine samples and the loess soil samples from the chinese loess plateau clp supports the previous view of the eolian origin of the xinmocun lacustrine sediments analysis of major element abundances ratios and trace element ratios indicates that the dust provenance of the xinmocun lacustrine sediments is different from that of the clp and is similar to that of the loess at ganzi and hongyuan nearby the study area the significant variations of most geochemical elements and their close coupling with grain size variations cannot be reasonably explained by the changes in transport dynamics of eolian dust and is possibly caused by the intermittent changes in available dust provenance frequent earthquakes triggered abundant landslides and provided large amounts of dust for the study area accordingly in the 16 m fraction of the xinmocun grain size record many element abundances and their ratios such as sio2 al2o3 tio2 al2o3 cao al2o3 sr al2o3 rb sr and na2o al2o3 can be regarded as sensitive indicators of earthquake events in the tectonically active regions sxrf measurements at the u channel surface can provide some cost effective indicators of seismic events such as si al ti al ca al sr al zr rb and rb sr significant variations in most element abundances and their ratios of the xinmocun lacustrine sediments correlate closely with those of its grain size record they all show no increasing or decreasing trends with time these suggest that tectonic activities characterized by seismic events possibly had a major role on the landscape erosion in the eastern tibetan plateau while the climatic influence seems minor

landslides associated with the may 12 2008 wenchuan earthquake implications for the erosion and tectonic evolution of the longmen shan abstract satellite images and aerial photography following the wenchuan earthquake show that a broad area experienced severe landsliding in association with the main earthquake and aftershocks a zone of high density landsliding 10 landslide surface area affected stretches for 240 km along the earthquake region in proximity to the yingxiu beichuan and pennguan faults which ruptured during the earthquake the width of this severe landsliding zone varies along the strike from 25 30 km wide in the southwestern section of the earthquake region to 3 5 in the northeastern section these variations coincide with differences in hillslope gradients bedrock lithologies co seismic slip and ground shaking observed in these sections of the earthquake region in general there is good correlation between the magnitude and distribution of ground shaking experienced during the earthquake and mapped landslide density though limited data and varying fault models prevent any in depth comparison with high resolution maps of ground shaking experienced landslides associated with wenchuan earthquake highlight interesting aspects of erosion and tectonic evolution of the longmen shan short term erosion rates in the longmen shan region measured from cosmogenic nuclides prior to the earthquake were 0 2 0 3 mm yr reflecting the last 2000 3000 years a time period shorter than the estimated recurrence interval of large earthquakes along the fault that ruptured while long term erosion rates measured by low temperature thermochronology were higher 0 5 0 7 mm yr for the last 8 10 ma integrating the total amount of erosion associated the earthquake into the short term erosion rate estimates pushes the rate much higher this suggests that the earthquake and associated landslide erosion was necessary for the landscape to catch up and balance the long term tectonic growth of the longmen shan particularly in the southwestern section of the earthquake region taken together the earthquake and associated landslide erosion can be seen as the most recent expression of the rapid deformation uplift and erosion that previous geomorphic evidence and geodynamic models had argued for along longmen shan front

beyond threshold hillslopes channel adjustment to base level fall in tectonically active mountain ranges numerous empirical and model based studies argue that in general hillslopes and river channels increase their gradients to accommodate high rates of base level fall to date however few data sets show the dynamic range of both these relationships needed to test theoretical models of hillslope evolution and river incision here we utilize concentrations of 10 be in quartz extracted from river sand on the eastern margin of the tibetan plateau to explore relationships among short term 10 2 10 5 a erosion rate hillslope gradient and channel steepness our data illustrate nonlinear behavior and a threshold in the relationship between erosion rate and mean hillslope gradient confi rming the generalization that hillslopes around the world are limited by slope stability and cease to provide a metric for erosion at high rates 0 2 mm a the relationship between channel steepness index and erosion rate is also nonlinear but channels continue to steepen beyond the point where threshold hillslopes emerge up to at least 0 6 mm a demonstrating that channel steepness is a more reliable topographic metric than mean hillslope gradient for erosion rate and that channels ultimately drive landscape adjustment to increasing rates of base level fall in tectonically active settings

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

on the relation between infrasound seismicity and small pyroclastic explosions at karymsky volcano 1 ground and atmospheric propagating elastic waves are integrated with digitized video to reconstruct important parameters during the onset of eruptions at karymsky volcano in 1999 muzzle velocities which range from 10 to 55 m s for 34 analyzed explosive events are found to be very well correlated with eruption velocities synthesized from infrasonic trace data acoustic modeling proposed here invokes a linear acoustic source consistent with a 3 m piston that accelerates upwards timing of acoustic arrivals relative to video records of material emission is used to constrain fragmentation sources depths which are assumed to be coincident with infrasound generation these sources are generally shallow with an observed vertical range of about 15 m systematic changes in source depth are observed during two nights of data collection and are attributed to variations in the depth of the magma free surface relative timing of acoustic and seismic arrivals is used to identify the presence of seismicity prior to fragmentation this seismicity is emergent and low intensity but significant because it precedes the presumed fragmentation events by variable amounts up to 4 s the primary short period seismic phases appear coincident with the initiation of fragmentation and infrasound generation because of the complexity of the seismic green s function it is not possible to correlate amplitude from a specific seismic pulse with observed eruption intensity

chronology for terraces of the nalinggele river in the north qinghai tibet plateau and implications for salt lake resource formation in the qaidam basin abstract the nalinggele river located in the northern qinghai tibetan plateau is the largest river originating from the northern slope of the eastern kunlun mountains and flowing into the enclosed qaidam basin controversy exists whether the formation of its terraces reflects the history of the plateau uplift or climate changes or both the salt lakes in the enclosed qaidam basin fed by this river bear an unusual world class enrichment of lithium and boron elements which are critical resources for regional economy the concentration of lithium is one of the highest found in brine resource in the world and sourced from the upstream water of the river the chronology of the river terraces is essential to understand the plateau uplift history the regional climate change the evolution of the terminal salt lakes and the process of enrichment of the valuable elements however the age constraint for the terraces of the rivers in the east kunlun mountains is still limited and debated and no dating work has been reported yet for terraces of the nalinggele river five terraces were identified in this river in this study the terraces were dated using quartz optically stimulated luminescence osl dating the results indicate that the osl ages 7 5 ka 9 9 ka 11 3 ka and 13 1 ka of the four terraces t1 t2 t3 and t4 are consistent with geomorphic relationship and that they formed since 13 1 ka and were probably triggered by climatic change rather than by the plateau uplift the sediment of t5 is too coarse to collect osl samples and not dated based on our dating we confirm the previous view that the lithium concentration in the terminal salt lakes should have initiated since 15 13 ka we further propose that the formation of salt lakes and the enrichment of their resources in the qaidam basin should have occurred mainly in interglacial periods e g the holocene a warm and humid period not as previously thought to be in the glacial periods a dry and cold period and that during the glacial periods the basin was mainly under wind erosion

magnetostratigraphy and grain size record of the xijiadian fluviolacustrine sediments in east china and its implied stepwise enhancement of the westerly circulation during the eocene period in order to reveal the eocene westerlies evolution history 1053 paleomagnetic samples were collected and thermally demagnetized for the fluviolacustrine sediments at xijiadian hubei province east china fourteen normal and 14 reversed polarity zones are recognized for the section correlation of the resultant magnetic polarity column to the geomagnetic polarity time scale suggests that the section was generally continuous and spanned 56 4 37 1 ma with respect to the stable eurasian continent variations in magnetic declination of the section indicate no significant rotations supporting the earlier view that the south china block has experienced no significant rotation relative to eurasia since the late cretaceous provenance analysis suggests that the dominant fine sediments red beds of the xijiadian section were transported by wind into the study area grain size measurements indicate that the 20 m fraction and clay in the study area decreased from 56 4 to 50 7 ma and stepwise increased during 50 7 37 3 ma implying that the westerly circulation in the northern hemisphere weakened during 56 4 50 7 ma and stepwise strengthened during 50 7 37 3 ma in contrast the 20 63 m fraction mainly from nearby dust sources of the study area generally increased during 56 4 50 7 ma and stepwise decreased from 50 7 to 37 3 ma implying aridity in the study area strengthened during 56 4 50 7 ma and stepwise mitigated from 50 7 to 37 3 ma changes in global temperature during the eocene period probably played the primary role on evolutions of the westerly circulation in the northern hemisphere and of the arid conditions in the study area

basaltic thermals and subplinian plumes constraints from acoustic measurements at shishaldin volcano alaska the 1999 basaltic eruption of shishaldin vol cano alaska usa included both strombolian and sub plinian activity as well as a pre subplinian phase inter preted as the local coalescence within a long foam in the conduit although few visual observations were made of the eruption a great deal of information regarding gas ve locity gas flux at the vent and plume height may be inferred by using acoustic recordings of the eruption by relating acoustic power to gas velocity a time series of gas velocity is calculated for the subplinian and pre subplinian phases these time series show trends in gas velocity that are inter preted as plumes or for those signals lasting only a short time thermals the subplinian phase is shown to be com posed of a thermal followed by five plumes with a total expelled gas volume of 1 5 10 7 m 3 the initiation of the subplinian activity is probably related to the arrival of a large overpressurised bubble close to the top of the magma column a gradual increase in low frequency 0 01 0 5 hz signal prior to this trigger bubble may be due to the rise of the bubble in the conduit this delay corresponds to a reservoir located at 3 9 km below the surface in good agreement with studies on other volcanoes the presence of two thermal phases is also identified in the middle of the pre subplinian phase with a total gas release of 4 3 10 6 m 3 and 3 6 10 6 m 3 gas veloc ity at the vent is found to be 82 m s 1 and 90 m s 1 for the subplinian plumes and the pre subplinian thermals respectively the agreement is very good between estimates of the gas flux from modelling the plume height and those obtained from acoustic measurements leading to a new method by which eruption physical parameters may be quantified fur thermore direct measurements of gas velocity can be used for better estimates of the so2 flux released during the eruption

geochemical mineralogical and sedimentological studies on the taklimakan desert sands major element composition mineral composition and grain size distribution have been studied for quaternary aeolian sediments from the taklimakan desert north western china together with the variation of chemical and mineralogical compositions of different grain size fractions aeolian sediments from the taklimakan desert have higher ratios of feldspar quartz and calcite quartz finer grain size poorer roundness of quartz and feldspar grains and lower abundances of frosted quartz than found in aeolian sediments from other deserts such as the saudi arabian desert in spite of these immature mineralogical and sedimentological features the aeolian sediments from the taklimakan desert show low regional variations in major element and mineral compositions and are homogenized these observations confirm that two processes glacial activity within surrounding mountains and aeolian activity at the tarim basin are important in the homogenization of the taklimakan desert sands taklimakan desert sediments are constantly and effectively supplied from basement rocks in the surrounding mountains by glacial erosion the supplied sediments are further homogenized by aeolian activity in the desert and are partly blown away serving as the source of chinese aeolian loess compositional differences are observed between loess mainly 10 40 m particles and the 45 m fraction of the taklimakan desert sediments as well as between loess and whole rock of the taklimakan desert sediments these observations provide constraints for precise modelling of loess formation and for assessment of the chemical composition of the upper continental crust based on the chemical composition of aeolian loess

nonlinear characteristics of paleoseismicity in china detailed studies of historical seismicity and paleoseismological data for major late quaternary faults in china reveal spatial and temporal patterns in paleoseismic activity associated with these faults analysis of space time distributions of late quaternary faults and consideration of new models for deformation of the asian continent provide a basis for proposing a division of china and surrounding areas into five active tectonic provinces slip rates for active faults are highest in the himalayan collision zone between the indian and eurasian plates and gradually decrease away from the collision zone into the adjacent active tectonic provinces paleoearthquake recurrence intervals in the active tectonic provinces of china reflect seismogenic properties that are closely related to the position of these provinces relative to the converging indian and eurasian plates average recurrence intervals are 2000 years to as little as 310 900 years for active faults in the qinghai tibetan active tectonic province whereas recurrence intervals are 2000 4500 years in the xinjiang active tectonic province and longer than 2000 years to as much as 7250 years in the north china active tectonic province although average recurrence intervals are closely related to the slip rates of late quaternary faults no simple linear relationship exists between recurrence interval and slip rate further analysis of paleoseismicity on major active faults shows that there are temporal variations in recurrence intervals the case studies also indicate that for some provinces faults or fault segments there are three paleoseismic patterns linear logarithmic and stepped in the logarithmic and stepped patterns the earthquake temporal sequence is characterized by active periods earthquake clusters with relatively short recurrence intervals and quiet periods lack of clustering and relatively long recurrence intervals

repeating coupled earthquakes at shishaldin volcano alaska since it last erupted in 1999 shishaldin volcano aleutian islands alaska has produced hundreds to thousands of longperiod 1 2 hz lp earthquakes every day with no other sign of volcanic unrest in 2002 the earthquakes also exhibited a short period 4 7 hz sp signal occurring between 3 and 15 s before the lp phase although the sp phase contains higher frequencies than the lp phase its spectral content is still well below that expected of brittle failure events the sp phase was never observed without the lp phase although lp events continued to occur in the absence of the precursory signal the twophased events are termed bcoupled eventsq reflecting a triggered relationship between two discrete event types both phases are highly repetitive in time series suggestive of stable non destructive sources waveform cross correlation and spectral coherence are used to extract waveforms from the continuous record and determine precise p wave arrivals for the sp phase although depths are poorly constrained the sp phase is believed to lie at shallow b4 km depths just west of shishaldin s summit the variable timing between the sp and lp arrivals indicates that the trigger mechanism between the phases itself moves at variable speeds a model is proposed in which the sp phase results from fluid moving within the conduit possibly around an obstruction and the lp phase results from the coalescence of a shallow gas bubble the variable timing is attributed to changes in gas content within the conduit the destruction of the conduit obstacle on november 21 2002 resulted in the abrupt disappearance of the sp phase published by elsevier b v

weathering histories of chinese loess deposits based on uranium and thorium series nuclides and cosmogenic 10be the long continuous deposition of dust in the chinese loess plateau liu et al 1985 kukla and an 1989 ding et al 1991a offers an unique opportunity to study the nature of soil weathering in a wide range of climatic conditions in this paper we report on measurements of concentrations of u and th series nuclides and of major cations in 150 loess and paleosol samples from five sites going back 2 5 ma using the results for 10be concentrations in these soils gu et al 1996 we determined the absolute amounts of water added to several soil units and obtained 1 first order leaching constants for u and several cations and 2 the compositions of the soils contributing to the dust source regions and of the dust at deposition further based on analyses of 230th in soils deposited in the past ca 140 ka we determined when the soils weathered in the source regions we conclude that most of the weathering in the dust source regions may have occurred during the interglacials

a case study of ionospheric storm effects during long lasting southward imf bz driven geomagnetic storm multiple instrumental observations including gps total electron content tec fof2 and hmf2 from ionosondes vertical ion drift measurements from communication navigation outage forecasting system magnetometer data and far ultraviolet airglow measured by thermosphere ionosphere mesosphere energetics and dynamics global ultraviolet imager timed guvi are used to investigate the profound ionospheric disturbances at midlatitude and low latitude during the 14 17 july 2012 geomagnetic storm event which was featured by prolonged southward interplanetary geomagnetic field component for about 30 h below 10 nt in the east asian australian sector latitudinal profile of tec variations in the main phase were characterized by three bands of increments and separated by weak depressions in the equatorial ionospheric anomaly eia crest regions which were caused by the combined effects of disturbance dynamo electric fields ddef and equatorward neutral winds in the recovery phase strong inhibition of eia occurred and the summer crest of eia disappeared on 16 july due to the combined effects of intrusion of neutral composition disturbance zone as shown by the timed guvi o n2 measurements and long lasting daytime westward ddef inferred from the equatorial electrojet observations the transit time of ddef over the dip equator from westward to eastward is around 2200 lt in the american longitude the salient ionospheric disturbances in the summer hemisphere were characterized by daytime periodical intrusion of negative phase for three consecutive days in the recovery phase preceded by storm enhanced density plume in the initial phase in addition multiple short lived prompt penetration electric fields appeared during stable southward interplanetary magnetic field imf bz in the recovery phase and were responsible for enhanced the eia and equatorial ionospheric uplift around sunset

ionosphere disturbances observed throughout southeast asia of the superstorm of 20 22 november 2003 1 ionospheric disturbances in the southeast asian region during the super magnetic storm of 20 22 november 2003 were investigated through an ionosonde chain and a gps network assisted by the space borne instruments at early stage of the storm in the postsunset sector large enhancements in the critical frequency of f2 layer and total electron content were observed at northern crest region of the equatorial ionization anomaly eia which might be produced by both the storm meridional wind superimposed with traveling atmospheric disturbances and prompt penetration electric field ppe during the main phase of the storm when interplanetary magnetic field started a 12 h southward turning equatorial ionosphere was elevated to a very high level which should be most probably caused by a long duration ppe event meanwhile at mid low latitudes ionosphere witnessed an initial simultaneous decrease then followed by drastic increases which is very different from the past observations in this region reddy and nishida 1992 combined analysis of the data from the ionosonde and other space based measurement shows that for the present case the penetration efficiency of the interplanetary electric field ief to the equatorial ionosphere was larger at night than in the daytime which agrees with the results of fejer et al 2007 showing the ratios of ppe and ief changes were highly variable with the local time during the recovery phase eia was severely inhibited owing to a wind convergence and possibly because of the westward disturbance dynamo electric field

an experimental study of the flow structure and acoustics of jets implications for volcano infrasound abstract aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operating parameters based on empirical aeroacoustic relationships a link between peak frequency and amplitude and jet diameter and velocity has been used by volcano acousticians to return the operating parameters of column generating volcanic eruptions there are however significant differences between the nozzle geometries and structures of flows studied in the aeroacoustic literature and flows emitted from volcanic vents these differences raise questions as to the validity of applying engineering relationships to volcanic eruptions combining particle image velocimetry and acoustic data we investigated the flow structures acoustic signals and dominant source locations of jet flows emitted from three simple nozzle geometries convergent straight and divergent flows from the straight and divergent nozzles exited in a more developed flow regime than those emitted from convergent nozzles while for the convergent nozzles dominant sound sources were located within the jet flow the dominant signals from the straight and divergent nozzles were located in the region of the nozzle exit consequently for the straight and divergent nozzles it was not possible to differentiate between signals generated by the jet flow and those generated by internal sound sources without beamforming analysis in order to better replicate the volcanic case and in contrast to studies for industrial applications our experimental test section was not engineered to minimise internal noise without acoustic treatment such as screens choke plates and paddles jet noise signals were contaminated by signals generated within the test rig and so even for the convergent nozzles the aeroacoustic relationships derived from engineering studies could not be used to retrieve the jet operating parameters our results indicate that in the volcanic case the raw acoustic spectra will contain signals generated by both in conduit and above vent processes therefore inversions for volcanic jet parameters such as mass eruption rate from standard aeroacoustic relationships may be unreliable

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

geology and petrology of ejecta from the 1999 eruption of shishaldin volcano alaska shishaldin volcano erupted repeatedly during april and may 1999 with major eruptive events on 19 april and 23 april tephra deposits 20 cm thick were distributed across the southern flanks and hyperconcentrated debris flows ran down the northern slope all analyzed clasts were basaltic in composition with abundant 29 vol phenocrysts of plagioclase olivine and magnetite glass inclusion analyses indicate low volatile contents 900 to 58 ppm respectively comparisons of sulfur contents in glass inclusions and groundmass glasses suggest significant degassing occurred even prior to eruption trace element studies suggest that the magma reservoir below shishaldin may not be a closed long lived chamber and u th ra isotopic analyses indicate short crustal residence times on the order of at most a few thousand years for the 1999 products comparison of the deposits from this eruption with other similarly sized eruptions suggests the 19 april explosive event should be classified as a sub plinian basaltic eruption such eruptions are rare the 19 april explosive event was the largest at shishaldin during the last 175 years however the petrology chemistry and deposit thickness and distribution resemble those of at least 11 scoria deposits in the last 9 000 years suggesting that this type of eruption is common for shishaldin

degassing explosions at karymsky volcano kamchatka during the summer of 1997 karymsky vol cano produced summit explosions about six times each hour typical explosive episodes lasted between 30 seconds and three minutes produced gas and ash columns several hun dred meters high and ejected some incandescent material to better understand the physical source mechanisms re sponsible we recorded hundreds of explosions with a three component broad band seismometer and microphone lo cated 1650 meters from the active vent nearly every explo sion is recorded as an emergent yet identical seismic wavelet which is followed 4 15 s later by an impulsive acoustic ar rival we interpret the signals as a near surface gas volume burst which fractures the vent plug lowers the lithostatic pressure within the magma column and often induces fur ther degassing when degassing continues it is generally manifested as either a series of regular one second chug ging 1 explosions steady higher frequency jetting or a hy brid combination we believe that the seismic signature for chugs short duration harmonic tremor with integer over tones is the result of repeated gas volume bursts at the vent in contrast seismograms for jetting are non harmonic and contain higher frequencies we believe that the competing degassing behaviors are influenced by the gas flux as well as the plug conduit characteristics we propose that a plug exists due to a viscosity gradient caused by volatile depletion in the upper conduit

eolian grain size signature of the sikouzi lacustrine sediments chinese loess plateau implications for neogene evolution of the east asian winter monsoon in order to explore the neogene evolution of east asian winter monsoon circulation grain size analysis was conducted on the neogene sikouzi section guyuan ningxia china a relatively monsoon sensitive region the results show that most of the particles are fine the sand bearing samples median grain size md 63 m are less than 6 4 and that all the grain size distribution curves of representative samples have a similar pattern to those of eolian dust sediments on the chinese loess plateau rare earth element ree patterns of eight samples from the sikouzi section are all characterized by light l ree enrichments relatively flat heavy h ree patterns and slight negative eu anomalies similar to those of loess and the average upper continental crust these lines of evidence point to a windblown origin of the sikouzi fine sediments based on previous studies the 10 70 m fraction of the sikouzi sediments is mainly transported by the east asian winter monsoon and an increase in content of the 10 70 m fraction reflects strengthening of the winter monsoon in contrast sand grains in samples of md 63 m are probably brought into the study area by rivers and streams linked with precipitation enhancement according to stratigraphic variations in content of various fractions of the sikouzi grain size record the neogene evolution of the east asian monsoon circulation can be divided into three stages during the period 20 1 12 0 ma the 10 70 m fraction holds the lowest values whereas sand content usually shows high percentages denoting a weak winter monsoon and a strong summer monsoon after 12 0 ma the 10 70 m fraction increased substantially and remained at high values while sand content showed a marked decline indicating that the winter monsoon strengthened dramatically and the summer monsoon declined significantly from 4 3 to 0 07 ma the winter monsoon strengthened further as evidenced by the gradual increase in content of the 10 70 m fraction this inference agrees well with the timing of glaciation development in the northern hemisphere during the early to middle miocene the high values of both md and sand content are mainly distribute in five intervals 19 8 18 8 ma 18 0 17 5 ma 16 7 15 6 ma 14 3 13 7 ma and 13 0 12 0 ma corresponding to five periods of intense precipitation the interval from 16 7 to 15 6 ma is well correlated with the middle miocene climatic optimum determined by the well known miocene shanwang biota from eastern china as for the other four periods it is speculated that episodic growth of the east antarctic ice sheet possibly shifted atmospheric fronts such as the intertropical convergence zone itcz and thus carried water vapor further northward leading to increases in regional precipitation on the northern midlatitude continent including north china

thermal observations of gas pistoning at kilauea volcano 1 data acquired by three continuously recording thermal infrared thermometers situated on the north rim of pu u o o crater at kilauea volcano during 2002 revealed episodes of periodic thermal pulses originating from a degassing vent on the crater floor these thermal pulses are interpreted as gas release jetting events associated with gas pistoning a mechanism observed previously at both mauna ulu and pu u o o during a 35 day long period spanning june and july 2002 gas pistoning was frequently the dominant mode of gas release with as many as several hundred pulses occurring in uninterrupted series on other days degassing alternated between periods of quasi continuous gas jetting and intervals of gas pistoning that contained a few to a few dozen pulses characteristic time intervals between pistoning events ranged from 2 up to 7 min we identify three types of pistoning type 1 involves emission of lava followed by gas jetting and drain back type 2 is the same but the elevated position of the vent does not allow postjet drain back and type 3 involves gas jetting only with no precursory lava flow to explain gas pistoning we apply a model whereby a stagnant cap of degassed magma develops in the conduit below the vent gas bubbles rise through the magma column and collect under the cap the collective buoyancy of these bubbles pushes the cap upward when the cap reaches the surface it erupts from the vent as a lava flow unloading of the conduit magma in this way results in an abrupt pressure drop i e the overburden felt by the bubbles is reduced causing explosive gas expansion in the form of gas jetting from the vent this terminates the event and lava drains back into the conduit to start the cycle anew in the case where there is no surface lava emission or drain back the cap instead pushes into and spreads out within a subsurface cavity again this unloads the conduit magma and terminates in explosive gas release once gas is expelled lava in the cavity is free to drain back we hypothesize that pistoning is a stable mode of degassing for low viscosity basaltic magmas with appropriate conduit geometries and volatile supply rates

reconstruction of the sibinal pumice an andesitic plinian eruption at tacana volcanic complex mexico guatemala abstract the tacana volcanic complex located on the mexico guatemala border has had numerous small historical explosions the latest being a phreatic explosion in 1986 the stratigraphic record however suggests that much more voluminous eruptions have occurred in the past here we document one such eruption the sibinal pumice deposit which occurred ca 23 540 years b p the deposit consists of two pumice rich units 1 a lower stratified member sm that consists of at least seven normally graded fall layers interbedded with pyroclastic wet surge layers and 2 an upper massive member mm made up of a single fall deposit both members can reach up to 2 5 m in thickness and are separated by a single massive indurated yellowish pumice rich reworked layer sm was dispersed to the northeast n70 e with its 6 cm isopach covering an area of 275 km2 whereas mm was dispersed to the north n22 e with its 70 cm isopach covering an area of ca 330 km2 yellow vesicular pumice fragments light gray lithics and hydrothermally altered red and black dense lithics are abundant in both members although altered lithics are more abundant at the base of each reaching 15 vol pumice compositions range from basaltic to andesitic 48 61 wt sio2 anhydrous basis but are highly altered they contain plagioclase andesine labradorite augite hypersthene fe ti oxides and rare amphibole no compositional or mineralogical differences occur between the units indicating a common magma source during the same eruption the sibinal pumice eruption started with a weak pulsating column that reached at most 19 km in height ejecting 2 9 km3 of tephra 1 1 km3 dre at an average mass discharge rate of 4 7 107 kg s with repeated hydromagmatic explosions that generated wet surges down the slopes of the volcano the eruption ceased for a while during which rainfall generated a widespread lahar that eroded the top of sm the eruption began anew with a sustained and stable plinian column that ejected 4 6 km3 1 9 km3 dre of tephra at a mass discharge rate of 8 1 107 kg s the lack of any compositional differences in the magma suggests that the change in eruptive style was driven by influxes of external water provoking hydromagmatic explosions that cleared the conduit then the system changed to dry system and the eruption style changed from pulsating to stable plinian as the conduit became wider the mass discharge rate also increased

total electron content behavior over japan during geomagnetic storms 1 the total electron content tec obtained from gps signals is used to study ionospheric dynamics over japan during geomagnetically disturbed conditions the numerous tec measurements are averaged in cells with a size 1 5 1 5 geographic scale and formatted as time series within the years 2000 2002 to extract the storm time changes of tec the diurnal and 27 day periodicities are subsequently removed diurnal variations are removed by replacing absolute tec values in each cell with their relative deviations rtec from medians the hourly rtec values from all cells within the central 4 wide band over japan area are then approximated by a plane surface this surface is represented by two parameters its value at the center rt and the slope b along the main axis taken as constants of the linear regression the 27 day periodicity was approximated by fourier waves with main period of 640 hours and two harmonics separately for rt and b and subtracted from them the analysis of rt and b behavior during a number of geomagnetic storms allowed us to reveal several repeatable features of average tec behavior it was found that tec behavior during the storms is similar to that of fof2 at the f region and was local time dependent a marked poleward expansion of the equatorial ionosphere crest region at the end of recovery phase is persistently observed feature produced probably by intensified eastward zonal winds such an expansion of equatorial ionosphere is observed also during isolated substorms outside main geomagnetic storms an oscillation like change of positive and negative disturbances with period of 24 hours is observed during a 4 day period following a moderate storm in the absence of geomagnetic activity driver that effect is probably caused by the alternative expansion and contraction of equatorial ionosphere

geochemical evolution of archean shales from south africa i the swaziland and pongola supergroups abstract the fig tree group and moodies group part of the swaziland supergroup are exposed in the barberton mountain land and are 3 3 3 5 ga old shales from the fig tree group are characterized by variable rare earth element ree patterns with lan ybn 5 5 1 8 95 confidence and eu eu 0 97 0 18 shales from the moodies group have more fractionated ree patterns lan ybn 8 7 2 0 and less variable eu anomalies eu eu 0 92 0 02 both groups are characterized by very high abundances of cr and ni modelling of those trace elements which are relatively unfractionated during sedimentary processes ree th sc is consistent with the derivation of these sedimentary rocks from a mixture of the archean bimodal igneous suite mafic volcanics tonalites trondhjemites felsic volcanics with the moodies group requiring a larger percentage of the felsic end member the data for shales from the swaziland supergroup support models suggesting that the archean exposed crust was of more mafic composition than the post archean upper crust and that intracrustal melting was relatively unimportant in differentiating the archean crust the pongola supergroup is younger than the swaziland supergroup but older than 2 9 ga shales and mudstones from the nsuze and mozaan groups show ree characteristics intermediate between the older shales of the swaziland supergroup and typical post archean shales one quartzite sample from the witwatersrand supergroup ca 2 6 ga has a ree pattern virtually parallel to average post archean shales but with much lower abundances the change from typical archean to post archean sedimentary trace element patterns has been documented in early proterozoic successions from canada and australia this change has been related to a short interval of intense growth and chemical differentiation of the continental crust during the late archean 2 7 2 5 ga in southern africa this change appears to have taken place much earlier 3 2 2 9 ga but can be related to similar processes thus the period of crustal evolution related to the archean proterozoic boundary while virtually episodic regionally occurred over a protracted period world wide during the period ca 3 2 2 5 ga

seismo acoustic signals associated with degassing explosions recorded at shishaldin volcano alaska 2003 2004 in summer 2003 a chaparral model 2 microphone was deployed at shishaldin volcano aleutian islands alaska the pressure sensor was co located with a short period seismometer on the volcano s north flank at a distance of 6 62 km from the active summit vent the seismo acoustic data exhibit a correlation between impulsive acoustic signals 1 2 pa and long period lp 1 2 hz earthquakes since it last erupted in 1999 shishaldin has been characterized by sustained seismicity consisting of many hundreds to two thousand lp events per day the activity is accompanied by up to 200 m high discrete gas puffs exiting the small summit vent but no significant eruptive activity has been confirmed the acoustic waveforms possess similarity throughout the data set july 2003 november 2004 indicating a repetitive source mechanism the simplicity of the acoustic waveforms the impulsive onsets with relatively short 10 20 s gradually decaying codas and the waveform similarities suggest that the acoustic pulses are generated at the fluid air interface within an open vent system so2 measurements have revealed a low so2 flux suggesting a hydrothermal system with magmatic gases leaking through this hypothesis is supported by the steady state nature of shishaldin s volcanic system since 1999 time delays between the seismic lp and infrasound onsets were acquired from a representative day of seismo acoustic data a simple model was used to estimate source depths the short seismo acoustic delay times have revealed that the seismic and acoustic sources are co located at a depth of 240 200 m below the crater rim this shallow depth is confirmed by resonance of the upper portion of the open conduit which produces standing waves with f 0 3 hz in the acoustic waveform codas the infrasound data has allowed us to relate shishaldin s lp earthquakes to degassing explosions created by gas volume ruptures from a fluid air interface

soft sediment deformation structures from the diexi paleo dammed lakes in the upper reaches of the minjiang river east tibet abstract the north south trending upper reaches of the minjiang river run along the longmen shan min shan fault zone a zone of abrupt topographic change along the eastern margin of the tibetan plateau multiple levels of well preserved soft sediment deformation structures seismites occur in sediments deposited in paleo dammed lakes in the upper part of the minjiang river valley these deformation structures include liquefied convolute deformation water escape structures flame structures pseudonodules ball and pillow structures sedimentary dykes mud lenses and large scale folds several kilometers from the barrier bar of the diexi paleo dammed lakes seven deformed structural layers were identified at different heights in late quaternary stratigraphic sequences near shawan village maoxian county analyses of the deformation structures landforms and the structural environment indicate that these deformation structures were caused by earthquakes slumps and landslides osl optical stimulated luminescence and 14c dating of soft sediment layers from the shawan site indicate that intense earthquakes occurred during the period 25 20 ka b p therefore accurate geological dating of deformed features in dammed lake deposits in high mountains and canyons enables the record of moderate to large magnitude earthquakes to be extended to the late pleistocene holocene upon the eastern tibetan plateau

variability of the 14c reservoir effects in lake tangra yumco central tibet china determined from recent sedimentation rates and dating of plant fossils abstract sediments from lakes provide one of the most important archives for past environmental changes on the tibetan plateau the recent sedimentation rate of modern lakes is widely used as an independent method to calibrate 14 c derived chronologies because 14 c values are often affected by a reservoir effect terrestrial plant residues in lake sediments are believed to be the ideal material for 14 c dating because they normally provide the true ages of the sediments in this study we present the spatial and temporal variations in modern sedimentation rates over the past 150 years and evaluate the reservoir effects of 14 c ages determined from bulk sediments and plant residues from lake tangra yumco on the central tibetan plateau the results show that ages determined from plant residues are systematically younger than those of the bulk sediments however the reservoir effects associated with the bulk sediments are much more constant than those of the plant residues highlighting the complicated composition of these macro remains and the fact that they might not be the best dating materials in tangra yumco especially in southern part a similar reservoir effect of 2200 years is observed in the southern and northern parts of tangra yumco based on the dating of modern surface sediments and aquatic plants this study demonstrates the complexity of the reservoir effect in a closed lake on the tibetan plateau and careful consideration must be paid to the use of different approaches to date different materials in order to establish a reliable chronology

infrasonic component of volcano seismic eruption tremor air ground and ground air elastic wave coupling are key processes in the rapidly developing field of seismoacoustics and are particularly relevant for volcanoes during a sustained explosive volcanic eruption it is typical to record a sustained broadband signal on seismometers termed eruption tremor eruption tremor is usually attributed to a subsurface seismic source process such as the upward migration of magma and gases through the shallow conduit and vent however it is now known that sustained explosive volcanic eruptions also generate powerful tremor signals in the atmosphere termed infrasonic tremor we investigate infrasonic tremor coupling down into the ground and its contribution to the observed seismic tremor our methodology builds on that proposed by ichihara et al 2012 and involves cross correlation coherence and cross phase spectra between waveforms from nearly collocated seismic and infrasonic sensors we apply it to datasets from mount st helens tungurahua and redoubt volcanoes

modeling the f layer during specific geomagnetic storms important progress has been made recently in developing an understanding of the effects of geomagnetic storms in the thermosphere and ionosphere numerical simulations of theoretical storms with the coupled thermosphere ionosphere model ctim have provided a better understanding of the dynamics of the upper atmosphere and have also permitted the identification of the processes responsible for global storm effects at highlatitude and midlatitude the theory developed based on the model simulations can explain most of the apparent coherence of local time and seasonal dependencies and the apparent randomness in the longitudinal response of the global ionosphere uncovered through statistical analysis of storm observations a true test of the model and the theory is their ability to predict the large scale distribution of storm effects for specific storms in this paper ctim simulation results for the december 7 9 1982 period are presented we compare model results with de 2 temperature and plasma density data we also compare modeled electron densities with ionosonde data from several sectors in both hemispheres the global characteristics of the response are reproduced by the model and we are able to explain the pronounced longitude differences in the summer hemisphere the australian sector passes through midnight during the main driven phase of the storm and experiences the largest energy input and the largest neutral composition changes the deepest ionospheric negative phase seen in ionosonde data is over australia and is consistent with this interpretation given the large uncertainties in our knowledge of the magnitude and spatial distribution of energy input during a particular storm predicting local changes is still a challenge

origin of the sound generated by strombolian explosions during strombolian eruptions large bubbles break at the surface of the lava column and produce sound acoustic pressure recorded during several explosions on the eastern vent of stromboli volcano shows a pattern consistent between explosions the well marked oscillation contains only very low frequencies around 7 hz and is followed by a signal containing now both higher frequencies and lower frequency less than 4 hz the generation of sound is explained by the vibration 7 hz and bursting higher frequencies of large bubbles followed by the drainage of magma down in the conduit less than 4 hz the interpretation suggests that 1 the bubble vibrates before bursting and 2 the vibration prior to bursting yields more energy than the bursting itself the radius of bubbles responsible for explosions is determined to be close to 1 meter in agreement with observations of a few conduit sizes

late cenozoic evolution of the eastern margin of the tibetan plateau inferences from 40ar 39ar and u th he thermochronology high topography in central asia is perhaps the most fundamental expression of the cenozoic indo asian collision yet an understanding of the timing and rates of development of the tibetan plateau remains elusive here we investigate the cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the sichuan basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed temperature time paths inferred from 40 ar 39 ar thermochronology of biotite multiple diffusion domain modeling of alkali feldspar 40 ar release spectra and u th he thermochronology of zircon and apatite imply that rocks at the present day topographic front of the plateau underwent slow cooling 30 50 c m y coincident with exhumation from inferred depths of 8 10 km at denudation rates of 1 2 mm yr samples from the interior of the plateau continued to cool relatively slowly during the same time period 3 c m y suggesting limited exhumation 1 2 km however these samples record a slight increase in cooling rate from 1 to 3 c m y at some time during the middle tertiary the tectonic significance of this change remains uncertain regardless late cenozoic denudation in this region appears to have been markedly heterogeneous with the highest rates of exhumation focused at the topographic front of the plateau margin we infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable sichuan basin and thus marks the onset of deformation related to the development of the tibetan plateau in this region the present margin of the plateau adjacent to and north of the sichuan basin is apparently no older than the late miocene or early pliocene 5 12 ma

frequency based satellite monitoring of small scale explosive activity at remote north pacific volcanoes abstract monitoring of volcanoes in the north pacific can be an expensive and sometimes dangerous task specifically for those located in alaska usa and kamchatka russia an active frequency detection method previously used at stromboli italy uses the thermal and mid infrared wavelength bands from the moderate resolution imaging spectroradiometer modis satellite data to detect anomalies at a volcano this method focuses on small scale explosive activity often referred to as strombolian activity which can produce small spatter fields near a volcano s active vent in the north pacific there are a number of volcanoes which exhibit small scale explosive activity and three are the focus of this study chuginadak mt cleveland and shishaldin in alaska and karymsky volcano in kamchatka satellite images from the advanced very high resolution radiometer avhrr were used to monitor the frequency of thermal features as well as the occurrence of ash plumes at each volcano this data was then used to produce a time series spanning 2005 2010 for all three volcanoes during this time period each volcano underwent a series of eruptive cycles including background levels of activity heightened frequency of small explosions identified as precursory activity and heightened activity typified by ash plume producing eruptions each location has a unique precursory signal both in timing and magnitude the use of a previously developed method on a new sample set of volcanoes has proved the validity of this method as a monitoring tool for volcanoes with small scale explosive activity this method should be applied to a larger set of volcanoes to continue the development and database production for its use as a volcano monitoring tool

a 700 year macrophyte productivity record inferred from isotopes of macrophyte remains and bulk carbonates in lake koucha northeast qinghai tibetan plateau abstract the isotopic composition of total organic carbon toc in lakes has been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments however the main factors that affect the carbon isotopes of toc may vary in different lake sediment records limiting the ability of organic carbon isotopes to explain biogeochemical and environmental changes especially in lakes with a large number of aquatic plants in this study the 13c values of macrophyte remains and bulk carbonate in a sedimentary core from lake koucha were investigated to evaluate their paleoenvironmental implications we found that the bulk carbonate was dominated by authigenic carbonates formed in the lake and that their 18o and 13c values can be used to reconstruct environmental changes in the lake koucha area the macrophyte productivity derived from the carbon isotopic offset between the macrophyte remains and the bulk carbonate eremains bc in the lake koucha area agree well with total solar irradiance tsi records inferred from 10be and temperature records based on tree rings from the qinghai tibetan plateau although the distribution of macrophytes is related to water depth according past studies and our observations in the field our findings suggest that changes in macrophyte productivity may be primarily driven by temperature changes in the lake koucha area

vegetation evolution and human expansion on the qinghai tibet plateau since the last deglaciation abstract the spatial patterns and changes of vegetation on the qinghai tibet plateau qtp since the last deglaciation 16 5 cal ka bp are reconstructed by fossil pollen records from 36 sampling sites the modern analogues technique and isochrones of 15 of arboreal pollen are used the results show that the plateau vegetation pattern has been meadow steppe since 14 cal ka bp which replaced desert dominated pattern during the last glacial maximum lgm vegetation zones of qtp have moved and expanded from the southeast to the northwest the edge to the hinterland and low altitude to high altitude the most significant expansion occurred during 14 11 cal ka bp and 8 6 cal ka bp reached the westernmost extent at 6 cal ka bp and then began to retreat to the east in the meantime human activities began to flourish in the northeastern margin of the plateau at 14 cal ka bp the age of the earliest human remains of the plateau the vegetation expansion during 8 6 cal ka bp drove humans further to the hinterland and the western regions such as kekexili and the qiangtang plateau moreover the archaeological chronology of human remains in the eastern region is earlier than those from the hinterland these all indicate that human activities have been greatly affected by changes and expansion of vegetation on the qtp

geochemical characterization of the luochuan loess paleosol sequence china and paleoclimatic implications abstract chemical major and trace element and isotopic sr nd analyses of the luochuan loess paleosol sequence in china were performed in order to examine the following problems 1 potential source heterogeneity 2 element behavior during pedogenesis 3 paleoclimatic implications and 4 the use of loess data to determine the average composition of the upper continental crust new results clearly indicate that rb sr u and ce abundances are severely depleted in paleosols relative to their parental loess the behavior of these elements is strongly controlled by the breakdown of primary minerals such as carbonate sr or by alteration processes in highly oxidizing environments ce and u the pattern of element variations through the upper section of the luochuan sequence mimics the magnetic susceptibility signal both in position and in intensity thus reinforcing the pedogenesic origin of the enhanced magnetic susceptibility in paleosols all loess samples display highly uniform ree patterns except for ce characterized by the upper continental crust ucc ratios la yb n 10 and eu eu 0 66 the paleosol ree patterns are similar to those of the loess with the same lree hree fractionation but they also show distinct and variable negative ce anomalies nd and sr isotopic compositions are rather uniform in both loess and paleosols and do not vary with stratigraphic position nd 10 5 to 9 2 87 sr 86 sr 0 715 to 0 719 the isotopic homogeneity in the luochuan sequence strongly suggests a uniform source region during the entire period of deposition since 800 ka ago to the present several conclusions may be drawn from the present study 1 1 no geochemical distinction can be made between loess layers l1 to l7 the sources and the dust storm trajectories must have been essendally the same for the last 800 ka 2 2 some elements e g ca rb sr u ce are strongly fractionated by pedogenesis between loess and paleosols ce mobility in soils is clearly demonstrated but the process responsible for this leaching is still poorly understood 3 3 systematic variations of element abundances and ratios between loess and paleosols can be used as chemical indicators for pedogenesic intensity and so for paleoclimatic change these chemical indicators serve a function similar to that of oxygen isotopes in deep sea sediments pelagic foraminifera or that of magnetic susceptibility in loess sequences they are different recorders of paleoclimatic change 4 4 the striking uniformity of ree patterns and la th ratios in the luochuan loess and paleosols as well as in loess worldwide is an excellent starting point for estimating the average composition of the upper continental crust

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

refractory element mobility in volcanic soils refractory trace element concentrations in strongly weathered hawaiian soils ranging in age from 20 to 4100 ka are highly elevated over parent rock values due to extensive mass loss of more soluble major elements during pedogenesis nb and ta exhibit virtually no mobility soil nb ta ratios are within the range of fresh bedrock even when soil nb concentrations are residually enriched by a factor of 10 in contrast al zr and hf are depleted relative to nb in surface soil horizons but are enriched at depth clearly indicating mobility of these elements variations in th nb ratios in soil profiles indicate significant th mobility within the soil column however mass balance calculations require that accretion of th enriched asian dust has resulted in a net increase in th in some soils soils developed on a 150 ka rainfall gradient show that the mobility and loss of zr increase with mean annual precipitation

plinian airfall deposits of basaltic composition two widespread scoria fall deposits locally known as the fontana lapilli and san judas formation are demonstrated to have issued from masaya caldera complex nicaragua and to be the first documented plinian airfall deposit of basaltic composition data from maps of median grain size average maximum pyroclast diameter and average maximum diameter of lithic fragments provide conclusive evidence of the plinian nature of both deposits the volume within the 1 mm isopach of the fontana lapilli is 12 km3 3 4 km3 dense rock equivalent and within the san judas formation it is 1 2 km3 0 35 km3 dre theoretical eruption parameters calculated for the fontana lapilli and san judas formation respectively include muzzle velocity 170 m s and 150 m s column height 50 km and 18 km volume eruption rate 2 105 m3 s and 1 104 m3 s and duration 2 h and 10 h these are all similar to the calculated parameters for silicic plinian eruptions basaltic magmas are generally considered incapable of erupting in the manner characteristic of plinian eruptions recognition of them argues that factors other than high viscosity may be of fundamental importance

interpretation of umbrella cloud growth and morphology implications for flow regimes of short lived and long lived eruptions new numerical and analytical modeling shows that the growth of a volcanic umbrella cloud expressed as the increase of radius with time proceeds through regimes dominated by different force balances four regimes are identified regime ia is the long time behavior of continuously supplied intrusions in the buoyancy inertial regime regime iia is the long time behavior of continuously supplied turbulent drag dominated intrusions regime ib is the long time behavior of buoyancy inertial intrusions of constant volume and regime iib that of turbulent drag dominated intrusions of constant volume power law exponents for spreading time in each regime are 3 4 ia 5 9 iia 1 3 ib and 2 9 iib both numerical modeling and observations indicate that transition periods between the regimes can be long lasting and during these transitions the spreading rate does not follow a simple power law predictions of the new model are consistent with satellite data from seven eruptions and together with observations of umbrella cloud structure and morphological evolution support the existence of multiple spreading regimes

infrasonic precursors to a vulcanian eruption at sakurajima volcano japan the may 1998 eruption sequence of sakurajima volcano was monitored by ten infrasonic stations ten seismometers and a video camera during this seismo acoustic experiment we recorded hundreds of infrasonic tremor and long period events associated with seismic signals and observed a progression from relative quiescence to a vulcanian eruption the number of infrasonic events increased with escalating volcanic activity and the dominant character of the infrasonic signals changed from impulsive to emergent at 22 17 of may 19 sakurajima released ash and gases to a height of 2 km above the vent an event that was recorded continuously by one infrasonic and two seismic stations we present the experimental setup as well as a procedure through which infrasonic signals may be incorporated into future eruption monitoring and forecasting algorithms for open vent volcanic systems in addition our recordings suggest that infrasonic signals are more representative of processes occurring within the volcanic interior than are seismic signals which are strongly altered by diffraction and scattering in the volcanic edifice

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

osl and pollen concentrate 14c dating of dammed lake sediments at maoxian east tibet and implications for two historical earthquakes in ad 638 and 952 abstract formation of dammed lakes provides exceptionally important information of continental geological processes responding to tectonic and climatic influences establishing accurate geochronological frameworks within lake strata is challenging because the stratigraphy is often bereft of biostratigraphy and directly dateable material optically stimulated luminescence osl and ams 14 c dating of pollen concentrates are well established tools for dating lake sediments whether they are suitable for lake sediments in high alpine settings remains uncertain in this study osl and ams 14 c dating of pollen concentrate were conducted on the diaolin section in a high alpine setting in the eastern tibetan plateau good match of both dating results suggests that they are fit for dating lake sediments in high alpine settings more than 300 g of sediment is required for preparation of pollen concentrates during the pretreatment 3 naoh solution should be added to the sample and then heated until just boiling 5 min because naoh treatment easily destroys pollen grains applying the heavy liquid flotation with specific gravity of 1 74 1 76 is useful to isolate relatively pure pollen grains sieving with a 20 m and 63 m mesh can concentrate pollen grains substantially the osl and ams 14 c dating yielded the basal age of the diaolin section 650 ad this indicates that the dammed lake formed around 650 ad probably caused by the earthquake occurring in the study area in 638 ad the seismites characterized by soft sediment deformation and phyllite layer happened at 780 980 ad probably corresponding to the earthquake occurring on november 20 952 ad in the study area

seismic and infrasonic evidences for an impulsive source of the shallow volcanic tremor at mt etna italy during a seismo acoustic experiment we recorded volcanic tremor around the summit craters of mt etna volcano tremor shows amplitude modulation which disappear 900 m from the crater area the infrasonic wavefield is coherent even at distances of 750 m time delay between infrasonic transient is stable around 1 3 s and is consistent with the position of the source in the voragine crater amplitude modulation of tremor is well correlated 0 72 with infrasound amplitude with a time lag of 0 37 s coherent with a shallow position of the source amplitude of volcanic tremor decays over increasing distances according to geometrical spreading of body waves tremor wavefield shows a linear polarization following the same time occourrence as the infrasonic pulses polarization azimuth indicates that wavefield rectilinearity is mostly due to p waves we infer that most of the volcanic tremor we recorded at mt etna is generated by superimposition of small impulsive sources acting at 1 2 s rate caused by pressure instability during magma degassing

soil moisture balance and magnetic enhancement in loess paleosol sequences from the tibetan plateau and chinese loess plateau abstract we present a first combined environmental magnetic and geochemical investigation of a loess paleosol sequence

sandy beach ridges from xingkai lake ne asia timing and response to palaeoclimate abstract lake beach ridges and their sediments have been investigated as palaeoenvironmental records robust chronology is crucial to utilize this archive for palaeoenvironmental reconstruction and interpretation this study investigates the optically stimulated luminescence osl dating of quartz in two beach ridges of aeolian origin from xingkai lake ne asia the applicability of the selected measurement procedure is validated by a set of internal tests on luminescence characteristics such as preheat plateau test and dose recovery test and the reliability of the resulting 24 osl ages are also confirmed by agreement with four 14c ages as well as two k feldspar luminescence dates the constructed chronologies are thought to be robust in the stratigraphic and geomorphologic context the two aeolian beach ridges b1 and b2 are dated to 32 15 ka and 1 2 0 5 ka respectively which are interpreted as two distinct periods of lake lowstand that could have caused beach exposure and provided a more extended sand source for foredune formation around xingkai lake these two lowstands could be correlated to the dry cold regional climate including the time span from late mis3 to late glacial and the most recent one at the late holocene

natural vs anthropogenic sources supply aeolian dust to the miaoergou glacier evidence from sr pb isotopes in the eastern tienshan ice core abstract the compositions of sr and pb isotopes in the soluble and insoluble dust in six samples from the miaoergou ice core in eastern tienshan china were measured the six samples were dated from top to bottom as follows 2000 ad 1991 ad 1983 ad 1977 ad 1962 ad and 1958 ad the 87sr 86sr ratios in the soluble fraction ranged from 0 709984 to 0 711031 the isotopic ratios of pb in the soluble and insoluble dust were between 17 962 18 182 and 18 198 18 409 for 206pb 207pb 15 540 15 606 and 15 560 15 581 for 208pb 207pb and 37 994 38 173 and 38 179 38 384 for 208pb 204pb respectively these isotopic results for insoluble dust allowed us to document the origins of the dust in the miaoergou glacier in eastern tienshan the major sources of the natural aeolian deposits were the taklamakan and gobi deserts natural and anthropogenic pb sources were assessed using a simple ternary model in which deserts lead ore and coal served as the primary sources of insoluble dust lead ore coal combustion and the use of leaded gasoline in the surrounding area may represent additional anthropogenic sources of soluble dust thus anthropogenic sources could be further investigated by using the dust free soluble fractions the pb concentration and pb isotopic compositions from the high asia ice cores provided distinct evidence of the positive influences of anthropogenic factors associated with industrial development and the prevailing atmospheric circulation patterns in these regions

estimates of eruption velocity and plume height from infrasonic recordings of the 2006 eruption of augustine volcano alaska abstract the 2006 eruption of augustine volcano alaska began with an explosive phase comprising 13 discrete vulcanian blasts these events generated ash plumes reaching heights of 3 14 km the eruption was recorded by a dense geophysical network including a pressure sensor located 3 2 km from the vent infrasonic signals recorded in association with the eruptions have maximum pressures ranging from 13 111 pa eruption durations are estimated to range from 55 350 s neither of these parameters however correlates with eruption plume height the pressure record however can be used to estimate the velocity and flux of material erupting from the vent assuming that the sound is generated as a dipole source eruptive flux in turn is used to estimate plume height assuming that the plume rises as a buoyant thermal plume heights estimated in this way correlate well with observations events that exhibit strongly impulsive waveforms are underestimated by the model suggesting that flow may have been supersonic

geochemistry of the xining xifeng and jixian sections loess plateau of china eolian dust provenance and paleosol evolution during the last 140 ka abstract loess and paleosol samples from three distant sections xining xifeng jixian of the chinese loess plateau were analyzed for chemical and nd sr isotopic compositions in order to obtain information about the paleoclimatic variation during the last 140 ka these three sections represent three different climatic conditions from arid in the west xining to more humid in the east jixian across the loess plateau isotopic analyses show that all the three sections display a restricted range of 143 nd 144 nd ratios or e nd 10 0 5 indicating the dominance of relatively young and uniform upper crustal sources for the eolian dust the loess and paleosol samples have typical upper crustal 87 sr 86 sr ratios 0 714 0 718 and their variation can partly be attributed to different carbonate silicate ratios in the samples ree data from the three sections are indistinguishable from each other they show typical upper crust patterns characterized by la yb n 10 and eu eu 0 65 the high degree of chemical and isotopic homogeneity suggests that the dust source region must have undergone multiple recycling and thorough sedimentary mixing processes various chemical indicators have been used to monitor the pedogenetic intensity in these sections although results for the jixian section agree reasonably well with the known climatic conditions on the loess plateau the other two sections yield results not in agreement with some well accepted proxies like magnetic susceptibility or grain size distribution some chemical proxy indicators established in our previous work on the luochuan section such as the systematic u depletion and negative ce anomalies in ree patterns in soils are not clearly recorded in the present case the discrepancy between different climatic proxies could be related to the effective soil water budget temperature as well as the rate of development of each proxy

geochemical and isotopic characterization of the bodele depression dust source and implications for transatlantic dust transport to the amazon basin the bodele depression chad in the central sahara sahel region of northern africa is the most important source of mineral dust to the atmosphere globally the bodele depression is purportedly the largest source of saharan dust reaching the amazon basin by transatlantic transport here we have undertaken a comprehensive study of surface sediments from the bodele depression and dust deposits chad niger in order to characterize geochemically and isotopically sr nd and pb isotopes this dust source and evaluate its importance in present and past african dust records we similarly analyzed sedimentary deposits from the amazonian lowlands in order to assess postulated accumulation of african mineral dust in the amazon basin as well as its possible impact in fertilizing the amazon rainforest our results identify distinct sources of different ages and provenance in the bodele depression versus the amazon basin effectively ruling out an origin for the amazonian deposits such as the belterra clay layer by long term deposition of bodele depression material similarly no evidence for contributions from other potential source areas is provided by existing isotope data sr nd on saharan dusts instead the composition of these amazonian deposits is entirely consistent with derivation from in situ weathering and erosion of the precambrian amazonian craton with little if any andean contribution in the amazon basin the mass accumulation rate of eolian dust is only around one third of the vertical erosion rate in shield areas suggesting that saharan dust is consumed by tropical weathering contributing nutrients and stimulating plant growth but never accumulates as such in the amazon basin the chemical and isotope compositions found in the bodele depression are varied at the local scale and have contrasting signatures in the silica rich dry lake bed sediments and in the calcium rich mixed diatomites and surrounding sand material this unexpected finding implies that the bodele depression material is not pre mixed at the source to provide a homogeneous source of dust rather different isotope signatures can be emitted depending on subtle vagaries of dust producing events our characterization of the bodele depression components indicate that the bodele calcium rich component identified here is most likely released via eolian processes of sand grain saltation and abrasion and may be significant in the overall global budget of dusts carried out by the harmattan low level jet during the winter

on the absence of insar detected volcano deformation spanning the 1995 1996 and 1999 eruptions of shishaldin volcano alaska shishaldin volcano a large frequently active basaltic andesite volcano located on unimak island in the aleutian arc of alaska had a minor eruption in 1995 1996 and a vei 3 sub plinian basaltic eruption in 1999 we used 21 synthetic aperture radar images acquired by ers 1 ers 2 jers 1 and radarsat 1 satellites to construct 12 coherent interferograms that span most of the 1993 2003 time interval all interferograms lack coherence within 5 km of the summit primarily due to persistent snow and ice cover on the edifice remarkably in the 5 15 km distance range where interferograms are coherent the insar images show no intrusion or withdrawal related deformation at shishaldin during this entire time period however several insar images do show deformation associated with a shallow ml 5 2 earthquake located 14 km west of shishaldin that occurred 6 weeks before the 1999 eruption we use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from c band ers 1 2 and radarsat 1 synthetic aperture radar images we also find that insar images cannot resolve relatively shallow deformation sources 1 2 km below sea level due to spatial gaps in the insar images caused by lost coherence the lack of any deformation particularly for the 1999 eruption leads us to speculate that magma feeding eruptions at the summit moves rapidly at least 80m day from n10 km depth and that the intrusion eruption cycle at shishaldin does not produce significant permanent deformation at the surface published by elsevier b v

geochemical and isotopic studies of aeolian sediments in china the sr and nd isotopic rare earth element ree and major element compositions together with mineral and grain size proportions are reported for aeolian loess deposits and desert sands from several chinese localities the study was carried out in order to examine regional variations in the isotopic and geochemical features of these aeolian sediments and to constrain the provenance of chinese loess samples include loesses from the tarim and junggar basins and desert sands from the taklimakan desert in north west china loess from the ordos area and desert sands from the tengger and mu us deserts in north central china as well as loess and desert sands from the naiman area north east china ree distributions show minimal variation among the chinese loess deposits whereas those for the desert sands show regional variations new isotopic data document a latitudinal variation in sr and nd isotopic features for the loesses and desert sands the naiman and junggar loesses have distinctly lower 87sr 86sr ratios and higher end 0 values than the loesses from the tarim basin the ordos area and the loess plateau among the desert sands the naiman samples have higher end 0 values than the taklimakan tengger and mu us samples isotopic data suggest that loesses of the loess plateau were supplied from the tarim basin loesses and taklimakan desert sand and that the naiman loesses were supplied from the junggar basin loesses the latitudinal variation in the loesses and desert sands may be partly explained by isotopic variations reported previously for moraines from the tianshan and west kunlun mountains which are possible sources for the loesses and desert sands these inferences on the provenance of the loesses and desert sands are consistent with the dust transport pattern over east asia

acoustic measurements of the 1999 basaltic eruption of shishaldin volcano alaska 1 origin of strombolian activity the 1999 basaltic eruption of shishaldin volcano alaska usa displayed both classical strombolian activity and an explosive subplinian plume strombolian activity at shishaldin occurred in two major phases following the subplinian activity in this paper we use acoustic measurements to interpret the strombolian activity acoustic measurements of the two strombolian phases show a series of explosions that are modeled by the vibration of a large overpressurised cylindrical bubble at the top of the magma column results show that the bubble does not burst at its maximum radius as expected if the liquid film is stretched beyond its elasticity but bursting occurs after one cycle of vibration as a consequence of an instability of the air magma interface close to the bubble minimum radius during each strombolian period estimates of bubble length and overpressure are calculated using an alternate method based on acoustic power we estimate gas velocity to be 30 60 m s in very good agreement with synthetic waveforms although there is some variation within these parameters bubble length and overpressure for the first strombolian phase are found to be c82f11 m and 0 083 mpa for the second strombolian phase bubble length and overpressure are estimated at 24f12 m and 0 15 mpa for the first 17 h after which bubble overpressure shows a constant increase reaching a peak of 1 4 mpa just prior to the end of the second strombolian phase this peak suggests that at the time the magma in the conduit may contain a relatively large concentration of small bubbles maximum total gas volume and gas fluxes at the surface are estimated to be 3 3 10 7 and 2 9 10 3 m 3 s for the first phase and 1 0 10 8 and 2 2 10 3 m 3 s for the second phase this gives a mass flux of 1 2 10 3 and 8 7 10 2 kg s respectively for the first and the second strombolian phases

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

volcanic eruptions observed with infrasound 1 infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes here we present new results from erebus fuego and villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters such as eruption duration source mechanism and explosive gas flux

damping of large scale traveling ionospheric disturbances detected with gps networks during the geomagnetic storm 1 large scale traveling ionospheric disturbances lstids during the geomagnetic storm on 22 september 1999 were studied using total electron content tec data from the gps earth observation network geonet in japan international gps service igs and continuously operating reference stations cors in the united states the damping rates of the lstids were precisely derived in several local time sectors and were found to depend on values of the background tec this indicates that the dominant physical mechanism of the lstids damping is the ion drag effect by the background ionosphere the high resolution tec data from geonet revealed that two successive lstids were damped significantly as they traveled equatorward in the dawn sector the ratio of the perturbation component of tec to the background component i i0 decreased exponentially with the damping rate of 0 89 1000 km and 0 77 1000 km we studied also the amplitude of i i0 at high latitudes using igs data and found that the damping rates of lstids at high latitudes tended to be smaller than those at midlatitudes global tec observations during this geomagnetic storm by the igs and cors networks detected that several lstids propagated also equatorward in the afternoon sector and in the night sector the lstids in the afternoon sector were most damped with the damping rate of 1 04 1000 km which corresponds to the e folding length of 961 km the damping rate of lstids in the night sector was found to be small the lstids had a tendency to be damped rapidly in the regions where background tec was large this dependence of the damping rate on latitude and local time indicates that this intense damping of lstids was caused mainly by the ion drag effect that is proportional to the ion collision frequency the relation between the damping rates and the background tec derived from the observation are consistent with those estimated with a theoretical calculation of the gravity wave damping by the ion drag effect the worldwide distribution of gps receivers enabled us to estimate the longitudinal extent of these lstids the zonal width of lstids in the dawn sector was narrower than 45 in longitude 2 900 km around 55 n and wider than 20 in longitude 1 800 km around 40 n these widths were narrower than those reported in previous studies

tarawera 1886 new zealand a basaltic plinian fissure eruption abstract new zealand s biggest and most destructive volcanic eruption of historical times was that of tarawera in 1886 the resulting scoria fall has a dispersal very similar in extent to that of the vesuvius a d 79 pumice fall and is one of the few known examples of a basaltic deposit of plinian type a new estimate of the volume 2 km 3 is significantly greater than previous estimates the basalt came mainly from a 7 km length of fissure and emission and exit velocity were fairly uniform along at least 4 km of it this is one of the few documented examples of a plinian eruption from a fissure vent primary welding of the scoria fall resulted where the accumulation rate exceeded about 250 mm min 1 a model of the eruption dynamics is proposed which leads to an estimate of 28 km for the height of the eruption cloud and implies a magma volatile fraction of 1 5 3 violent phreatic explosions occurred in the southwestern extension of the fissure across the rotomahana geothermal field and it is thought that some of the water responsible for the power of the plinian eruption came from this source though its amount was not sufficient to turn the eruption into a phreatoplinian one

geochemical evidence for the provenance of middle pleistocene loess deposits in southern china the provenance of middle pleistocene loess in the middle and lower reaches of the yangtze river the most intensively investigated loess deposits outside the loess plateau region in china remains controversial identification of the provenance will provide crucial insight into the environmental implications of this valuable sedimentary archive and into the potential role of the east asian winter monsoon in transporting the dust from deserts in the asian interior in this study geochemistry was used to compare the provenance of loess in the lower reaches of the yangtze river in southern china with that inferred for loess deposits on the loess plateau in northern china compared with samples from the loess plateau the 20 mm fraction in the loess deposits of southern china has higher tio2 al2o3 zr nb zr al zr ti zr hf y al and lan smn ratios and lower eu eu th nb y nb and al nb ratios the clear distinction in immobile element ratios between samples from the two regions indicates that the loess deposits in the two regions have different provenances the inferred difference in source area is also supported by variations in the major element composition of bulk samples obtained in this study and collected from published data these lines of evidence indicate that the deserts in the asian interior are not the primary provenance for the southern loess it is suggested that the adjacent floodplains to the north of yangtze river are the dominant dust sources and the occurrence of sustained loess deposits in the lower reaches of the yangtze river currently an area of northern subtropical climate is an indication of local aridification and strengthened winter monsoon activity during glacial periods as a regional response to the middle pleistocene climate transition around 0 8 ma the role of the east asian winter monsoon in transporting the dust from northern deserts to southern china has been overestimated in previous studies

burst conditions of explosive volcanic eruptions recorded on microbarographs explosive volcanic eruptions generate pressure disturbances in the atmosphere that propagate away either as acoustic or as shock waves depending on the explosivity of the eruption both types of waves are recorded on microbarographs as 1 to 0 1 hertz n shaped signals followed by a longer period coda these waveforms can be used to estimate burst pressures and gas concentrations in explosive volcanic eruptions and provide estimates of eruption magnitudes

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

provenance and earthquake signature of the last deglacial xinmocun lacustrine sediments at diexi east tibet abstract well preserved lacustrine sediments are found in some areas in east tibet this region is characterized by a windy and semi arid climate alpine valleys and frequent earthquakes measurements of rare earth elements observations from a scanning electron microscope and a high resolution record of grain size measurements allowed us to compare fine sediments from the xinmocun section in the diexi lake with loess from the chinese loess plateau and south china results indicate that fine grains of the xinmocun lacustrine sediments were transported by wind and trapped in the lake whereas the 16 m fraction was likely from local sources the grain size changes within the section repeatedly show abrupt coarsening and upward fining probably due to palaeoearthquake events large earthquakes in the study area often caused rockfalls and landslides exposing fine sediments that had accumulated on mountains slopes the fine grains were then retransported by wind to the diexi lake optically stimulated luminescence dating of the xinmocun section indicates continuous deposition from 18 65 to 10 63 ka these results indicate that palaeoearthquakes in the study area had a mean recurrence interval of 0 32 ka therefore we propose that lacustrine sediments in a tectonically active region have the potential to record a continuous history of palaeoearthquakes palaeoearthquakes probably produced numerous rockfalls and landslides in alpine valleys and provided significant sources of regional eolian dust

acoustic measurements of the 1999 basaltic eruption of shishaldin volcano alaska 2 precursor to the subplinian phase the 1999 eruption of shishaldin volcano alaska usa displayed both strombolian and subplinian basaltic activity the subplinian phase was preceded by a signal of low amplitude and constant frequency c2 hz lasting 13 h this bhumming signalq is interpreted as the coalescence of the very shallow part of a foam building up in the conduit which produces large gas bubbles before bursting the acoustic waveform of the hum event is modelled by a helmholtz resonator gas is trapped into a rigid cavity and can only escape through a tiny upper hole producing sound waves at shishaldin the radius of the hole c 5m is close to that of the conduit c6 m the cavity has a length of c60 m and gas presents only a small overpressure between c1 2 10 3 and 4 5 10 3 mpa such an overpressure is obtained by the partial coalescence of a foam formed by bubbles with a diameter from c2 3 mm at the beginning of the episode towards c0 64 mm very close to the end of the phase the intermittency between hum events is explained by the ripening of the foam induced by the h2o diffusion through the liquid films the two extreme values from 600 to 10 s correspond to a bubble diameter from 2 2 to 0 3 mm at the beginning and end of the pre subplinian phase respectively the extremely good agreement between two independent estimates of bubble diameters in the shallow foam reinforces the validity of such an interpretation the total gas volume lost at the surface during the humming events is at most 5 9 10 6 m 3 at the very end of the presubplinian phase there is a single large bubble with an overpressure of c0 42 mpa the large overpressure suggests that it comes from significant depth unlike other bubbles in the pre subplinian phase this deep bubble may be responsible for the entire foam collapse resulting in the subplinian phase d 2004 elsevier b v all rights reserved

variation of gypsum morphology along deep core sg 1 western qaidam basin northeastern tibetan plateau and its implication to depositional environments abstract the qaidam basin is an arid closed intermontane basin located on the northern margins of the tibetan plateau in china a 938 5 m long core sg 1 dated between 2 8 ma 0 1 ma was obtained from the western qaidam basin gypsum is one of major evaporative minerals in the core a total of 201 gypsum samples were selected and their crystal morphologies were carefully investigated the crystal habits are lenticular prismatic tabular twinned stubby and aggregate prismatic crystals occur in the upper 723 m while lenticular crystals exist almost entirely in the upper 523 m tabular crystals are the most common morphology the total abundance of gypsum crystal including tabular lenticular and prismatic forms tends to increase with decreasing depth the relationship between crystal habits and depositional environments is complex because same morphology can appear in different environments and different morphologies can also occur in the same depositional environment however the occurrence of different morphologies can be attributed to the variable growth rates caused by the inhibition effect of additional cations e g mg 2 na k and sr 2 on particular lattice parameters and the variation in precipitation experiments the lattice parameters of the unit cell of gypsum measured by x ray diffraction method are a 5 854 12 57 a b 9 654 16 231 a and c 5 163 14 024 a 113 54 119 88 volume 601 55 712 65 a 3 the substitution of k na and mg 2 for ca 2 can reduce c axis while sr 2 can reduce a and b axes a c b c a b tend to increase with k na and mg 2 and decrease with sr 2 the mg 2 na k and sr 2 contents in gypsum show significant variability with k ca molar ratios varying from 1 03 10 4 to 32 08 10 4 mg ca molar ratios from 0 0023 to 0 1629 na ca molar ratios from 0 031 to 0 575 and sr ca molar ratios from 5 59 10 4 to 19 67 10 4 sr 2 mg 2 na and k concentrations in gypsum mainly depend on growth rate and brine concentration

three distinct regimes of volcanic tremor associated with the eruption of shishaldin volcano alaska 1999 tremor signals associated with the eruption of shishaldin volcano on 19 and 23 april 1999 were the strongest recorded anywhere in the aleutian arc by the alaska volcano observatory avo in its 10 year history reduced displacements dr reached 23 cm2 on 19 april and 43 cm2 on 23 april during the activity dr and spectral data with a frequency resolution of 0 1 hz were computed and put on the world wide web every 10 min these data are analyzed here the general temporal patterns of seismicity of these eruption events were similar but the eruptions and their effects quite different the 19 april event is known to have culminated in a sub plinian phase which ejected ash to an altitude of 16 km despite higher amplitudes and the largest hotspot from satellite data the 23 april event produced little ash reaching only 6 km altitude for several hours prior to the sub plinian phase on 19 april tremor with a peak frequency of 1 3 hz intensified during the sub plinian phase the peak frequency increased to 4 8 hz however in 15 h after the eruption three episodes of stronger tremor occurred with a lower 1 0 hz peak alternating with weaker tremor with a 1 3 hz peak these transitions correspond to dr 8 cm2 although these strong tremor episodes produced higher dr levels than the sub plinian phase data from a pressure sensor show that only strong strombolian explosions occurred the suite of observations suggests three distinct tremor regimes that may correspond to slug flow bubbly flow and sustained strong eruptions or a cyclic change in source parameters e g geometry sound speed or ascent rate this behavior occurred at shishaldin only during the april 1999 sequence and we are not aware of similar behavior at other volcanoes