the significance of phenocryst diversity in tephra from recent eruptions at popocatepetl volcano central mexico tephra lapilli from six explosive eruptions between april 1996 and february 1998 at popocatepetl volcano popo in central mexico have been studied to investigate the causes of magma diversification in thick crusted volcanic arcs the tephra particles are sparsely porphyritic 5 vol magnesian andesites sio2 58 65 wt mgo 2 6 5 9 wt that contain phenocrysts of nio rich up to 0 67 wt nio magnesian olivine fo89 91 cores with inclusions of cr spinel cr 59 70 orthopyroxene mg 63 76 clinopyroxene mg 68 86 intermediate to sodic plagioclase an33 66 and traces of amphibole major and trace element systematics indicate magma mixing the liquid mg melt ratios inferred from the ferromagnesian phenocrysts suggest the existence of a mafic mg melt 72 76 and an evolved component magma mg melt 35 40 these component magmas form a hybrid magnesian andesite with an intermediate range of mg melt 50 72 the mafic end member mg melt 72 75 is saturated with olivine and spinel and crystallizes at temperatures 1170 1085 c with oxygen fugacities close to the fayalite magnetite quartz buffer and elevated water contents of several wt h2o a likely location of crystallization is at lower crustal levels possibly at the moho olivine is followed by high mg clinopyroxene which could start to crystallize during magma ascent at depths of 4 to 13 km the mafic magma mixes with an evolved composition containing low mg clino and orthopyroxene and plagioclase at a temperature of 950 c the repetitive ascent of batches of mafic magmas spaced days to weeks apart implies multiple episodes of crystallization and magma mixing the tephra is similar to the popo magnesian andesites suggesting similar generic processes for the common lavas of the volcano the advantage of the tephra is that it can be used to reconstruct the composition of the mafic magma building on the elemental systematics of the tephra and a comparison to the near primary basalts from the surrounding monogenetic fields we infer that the popo mafic end member is a magnesian andesite with variable but high sio2 contents of 55 62 wt and near primary characteristics such as high mg melt of 72 75 feo mgo ratios 1 if extrapolated to an mg melt of 72 75 and high ni contents 200 ppm ni this model implies that the typical elemental signature of the popo andesites such as the low cao al2o3 feo high na2o contents and the depletion in high field strength elements e g p zr ti are mantle source phenomena thus determining the elemental budget of the magnesian andesite as it is prior to the modifications by crustal differentiation is central to quantifying the subcrustal mass fluxes beneath popo

igneous or metamorphic hornblende phenocrysts as greenschist facies reaction cells in the half dome granodiorite california the half dome granodiorite yosemite national park california is recognized in the field by euhedral fresh looking black hornblende phenocrysts up to 2 cm in length this variety of granodiorite typifies intermediate age hornblende phyric units of cretaceous nested plutonic suites in the sierra nevada batholith although only inclusions of feldspar are evident in hand samples the phenocrysts are riddled with up to 50 inclusions of every major mineral found in the host granodiorite plus metamorphic minerals formed during cooling amphibole compositions within single phenocrysts vary from actinolite with less than 1 wt al 2 o 3 to magnesiohornblende with over 8 wt elemental zoning within the amphibole is highly irregular on the micrometer scale showing patches and polygonal zones with dramatically different compositions separated by sharp to gradual transitions the chemical compositions of entire phenocrysts are equivalent to hornblende plus a small proportion of biotite suggesting that the non biotite inclusions are the result of metamorphism of the phenocrysts backscattered electron imaging shows evidence of brecciation that may have been the result of volume changes as hornblende was converted to actinolite pressure calculations using the al in hornblende barometer show unreasonably wide variations on the micrometer scale that cannot have been produced by temperature or pressure variations during crystallization these hornblende phenocrysts would thus be unsuitable for geobarometry and caution must be used to avoid similarly zoned phenocrysts in the application of the al in hornblende geobarometer

intermittent mixing processes occurring before plinian eruptions of popocatepetl volcano mexico insights from textural compositional variations in plagioclase and sr nd pb isotopes volcan popocatepetl has explosively erupted in plinian style at least five times in the last 23 000 years extreme deviations in composition and the occurrence of dissolution features in plagioclase and pyroxene and the occasional presence of xenocrysts of cr rich fe ti oxides and mg rich olivines and pyroxenes indicate that magma mixing has been a major process affecting the magmatic system the nearly invariant composition of the erupted products andesitic dacitic suggests however that mixing is not acting alone and must be balanced by assimilation and or crystallization to investigate the magmatic processes that have modified the plinian magmas textural and compositional variations and growth rates in plagioclase were used to approximate the frequency of mixing events affecting each magma systematic analysis of sr nd and pb isotopes was carried out on plagioclase pyroxene and pumice matrix glass to constrain the extent of assimilation of upper crustal rocks additionally a series of phase equilibrium experiments were carried out to constrain the depth where such mixing and assimilation occurred we find that magma was stored at one of two different depths beneath popocatepetl with magma mixing acting in both reservoirs mixing frequency and the relative impact on mineral compositions and textures has varied with time assimilation of calcareous rocks underneath popocatepetl has not been pervasive and does not contribute significantly to the evolution of the plinian magmas the similar compositions of magmas with diverse mixing histories suggest that fractional crystallization and possibly assimilation of deep crust takes place at depth and that intermediate magmas ascend into the upper crust already differentiated

el ventorrillo a paleostructure of popocatepetl volcano insights from geochronology and geochemistry volcan popocatepetl mexico was constructed over the remains of a volcanic paleostructure based on fieldwork 40ar 39ar dating u pb dating and geochemistry we have determined the age chemistry and location of this paleostructure and named it el ventorrillo most remnants of el ventorrillo are covered by deposits from subsequent activity of popocatepetl except for the el abanico scarp and the barranca de nexpayantla where the stratigraphy of el ventorrillo eruptive products can be investigated inception of volcanism at el ventorrillo occurred at 331 10 ka with emission of the nexpayantla andesitic lavas and continued with extrusion of the yoloxochitl 267 31 ka and microwave 227 6 ka domes intrusion of dikes occurred at 298 94 and 230 3 ka activity at el ventorrillo continued with the emission of lavas that built the el abanico scarp 193 29 to 96 8 ka and continued until the tutti frutti eruption destroyed the cone 14 1 kyr ago el ventorrillo magmas produced rocks divided into two mineralogical groups the first group contains biotite amphibole rich rocks and the second group consists of biotite amphibole free lavas the rocks that contain biotite and amphibole are older than 198 13 ka whereas the rocks with no hydrous phases are younger than 227 6 ka and contain skarn and granodiorite xenoliths we interpret the change to an anhydrous mineral assemblage and the occurrence of skarn and granodiorite xenoliths as evidence for the formation of a new shallower reservoir a granodiorite xenolith was chosen for 40ar 39ar dating and u pb zircon analyses the u pb method yielded an age of 540 110 ka and the 40ar 39ar an age of 109 24 ka these ages are interpreted to indicate granodiorite crystallization 540 110 ka which metamorphosed the calcareous basement beneath popocatepetl into skarn and an influx of magma 109 24 ka that reheated the granodiorite major and trace elements sr nd and pb isotopic compositions and textural analyses of plagioclase show that el ventorrillo magmas were moderately modified by mixing with more mafic magmas and that assimilation of the calcareous basement was negligible

the 23 500 y 14 c bp white pumice plinian eruption and associated debris avalanche and tochimilco lava flow of popocatepetl volcano mexico abstract the white pumice wp is one of the thickest and most voluminous plinian fallouts produced by popocatepetl volcano in central mexico during the late pleistocene holocene its eruption 23 500 14 c y bp 27 800 cal bp was triggered by the catastrophic failure of the sw flank of the volcano the resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction l h of 0 06 the deposit covers an area of 1200 km 2 and has a volume of 10 4 km 3 this gigantic landslide characterized by exceptionally large proximal hummocks 400 m provoked the sudden decompression of the hydrothermal and magmatic systems which produced an initial blast followed by the rise of a plinian column that reached an altitude of 33 km the isopach map allows the recognition of a dispersal axis pointing toward the south where an area of 2490 km 2 was covered by 10 cm of pumice and ash the total volume of the pumice fallout was estimated at 1 9 km 3 dre dense rock equivalent pumice clasts are dacitic 62 66 wt sio 2 anhydrous basis highly vesicular 55 88 vol and display a seriate texture with phenocrysts of plagioclase hornblende augite hypersthene oxides ti magnetite and ilmenite apatite as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by rain induced lahars that reached great distances from the volcano at the same time more degassed andesitic dacitic 61 65 wt sio 2 magma was erupted effusively 4 4 km 3 dre in the new horseshoe shaped 5 km wide crater from which the tochimilco lava flow descended toward the sse where it inundated an area of 68 km 2 and reached as far as 22 km from its source since then multiple eruptions have reconstructed the summit cone almost completely obliterating the horseshoe shaped crater during the course of this catastrophic eruption vei 5 a total volume of 6 3 km 3 dre of juvenile magma pumice and lava were emitted and at least an additional 10 km 3 of pre existing rocks debris avalanche mobilized it surpasses in magnitude most other known plinian eruptions from popocatepetl and can be envisaged as an example of a worst case scenario for hazard evaluation purposes it dramatically changed the morphology of the volcano and had profound and far reaching effects beyond its immediate vicinity along rivers draining surrounding plains as well as on the lacustrine basins e g chalco to the ne a repeat of such an eruption in this densely populated area would certainly cause a major calamity of unprecedented dimensions

timing magma ascent at popocatepetl volcano mexico 2000 2001 abstract magnetic anomalies may be used to constrain magma ascent and are useful as precursors to eruptions especially when correlated with other geophysical and geochemical data in this paper we present multiparameter data on the magnetics dome morphology geochemistry and seismicity associated with the december 2000 january 2001 eruptions the largest of the recent eruptions at popocatepetl volcano a 6 month data period was studied in order to evaluate the precursors and post eruption processes several cycles of dome construction and destruction occurred from september 2000 through february 2001 in december large amplitude tremor associated with a higher effusion rate resulted in the formation of a large dome which filled the crater to within about 50 m of the lowest part of the crater rim seismic activity in december was marked by many volcanotectonic earthquakes and both high frequency and harmonic tremor on december 12 and 13 an increase in the tremor amplitude was followed by ash eruptions with 1 7 5 km high columns tremor amplitude increased again on december 15 and oscillated for the next four days activity remained high until the end of the month on january 22 an 18 km high plume produced ash and pumice fall to the east as well as pyroclastic flows and mudflows which reached 6 km from the crater the eruption left three concentric explosion pits partially destroying the december dome mixing of a mafic olivine bearing melt with a more evolved magma triggered the larger eruption on january 22 as can be seen from the higher mgo concentrations in some of the ejecta and the presence of a dark andesitic scoria with lower silica content and a white andesitic pumice with higher silica content precursory negative magnetic anomalies up to 5 nt 3 2 nt 5 nt 2 9 nt were associated with the ascent of the larger batches of magma which preceded the increases in seismicity before the december 2000 january 22 vei 3 4 eruptions no significant increases in seismicity were observed prior to the january 22 eruption except for a magnitude 2 4 earthquake on the day of the eruption there was however a 0 8 nt magnetic anomaly which lasted from january 10 to 12 and possibly to january 17 most of the magma ascended in three large batches and several smaller ones from october 22 through december 10 short lived crater domes with small volumes were formed at popocatepetl in september october and november 2000 and in march 2001 even the smaller negative anomalies from september to february were associated with the ascent of several batches of magma they preceded the increases observed in the seismicity and growth of a dome by several days

dynamics of the ca 4965 yr 14c bp ochre pumice plinian eruption of popocatepetl volcano mexico abstract the ochre pumice op plinian fallout was produced by popocatepetl volcano in central mexico during a major plinian eruption that occurred 4965 65 14 c yr bp 3700 bc the op is part of the ochre pumice sequence ops that consists of surge fall and pyroclastic flow deposits the op plinian fallout shows a bimodal grain size distribution with poor to moderate sorting that improves progressively towards the upper beds the juvenile component is mainly pumice 83 wt whereas the accidental components consist of igneous sedimentary and metamorphic clasts from the walls of the magma chamber and or conduit the vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal and glass contents increase this suggests increasing magma degassing prior and during the eruption the chemical composition of the pumice varies insignificantly at the base it is less evolved sio 2 61 wt and it becomes slightly more silicic towards the top sio 2 63 wt pumice clasts have a crystallinity index that ranges between 10 and 25 vol and display a seriate texture with phenocrysts of euhedral plagioclase pl clinopyroxene cpx orthopyroxene opx olivine ol oxide ox apatite ap the size of the maximum lithic 2 5 cm at a horizontal distance of 19 km indicates an eruption column height of 37 41 km the isopach map allows the recognition of a dispersal axis that points towards the nne where an area of 300 km 2 was covered by 6 cm of pumice and ash a minimum volume for the op plinian fallout deposit was calculated using a minimum thickness of 6 cm found at distal outcrops and was estimated at 4 9 km 3 which corresponds to 2 km 3 of dense rock equivalent dre stratigraphic relations indicate that the entire ops was emplaced during a short time interval of a few days to weeks and consisted of three main different phases phreato magmatic plinian and vulcanian it started violently with the emplacement of surges and then culminated with the eruption of the op fallout deposit as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by the growth of domes in the crater and the emplacement of block and ash flows generated by vulcanian explosions

characterization of the recent ash emissions at popocatepetl volcano mexico abstract nine representative ash emissions from 1994 1997 were studied to characterize the recent activity and the eruptive process at popocatepetl a series of tephra eruptions began on december 21 1994 and intermittent activity continues to present the first eruptions were phreatomagmatic but in mid march 1996 they turned magmatic cumulative volumes 529 1810 10 3 m 3 were determined for the first eruptions however when eruptions grew larger more widely spaced and magmatic the volumes were then calculated individually 22 1107 10 3 m 3 both using the simpson rule and based on 244 sampling sites this numerical integration method is more precise than other methods especially since sub mm isopachs are neglected in most cases dominant winds carried ash mainly to the east january through april 1995 and april 1996 except for the summer months when ash fell on mexico city to the northwest october 28 1996 and june 30 1997 in march 1996 changing wind direction produced ash fall to the southwest as well during the first year volume calculations indicated that emission rate was higher at the beginning of the eruptions and then declined and stopped activity resumed the following year with a similar pattern until larger amounts of magma ascended detailed studies of the ashfall provided constraints on the dynamics of the volcanic plumbing system tephra emission was related with clearing december 1994 to march 1995 and clogging of the vent may 1995 to february 1996 until a larger new ascending batch was able to clear its way to the surface march 1996 after april 1996 dome formation and explosive destruction were related to individual small ascending magma batches tephra from december 1994 to early march 1996 was made up mostly of andesitic lithic clasts and plagioclase and pyroxene crystals with minor amounts of accidental and accessory minerals in march 1996 prior to dome formation glass was also detected afterwards ash components were mostly dome lithics and scoria with minor amounts of plagioclase pyroxene and olivine crystals from the incoming magma batches

a simplified equation of state for the density of silicate hydrous magmas an application to the popocatepetl buoyancy driven dome growth process abstract we present a simplified equation of state eos for calculating the density of hydrous siliceous magmas in a range of pressures temperatures and dissolved water content of interest to study several magma conduit processes a simpler linear form and a more precise non linear yet simple form of the equation both valid in the range 0 to 0 25 gpa 800 to 1000 k and 0 to 7 wt h2o are proposed for the dacitic and andesitic popocatepetl magma melt compositions we apply these equations to explain some aspects of the dome forming effusive activity that has been observed at popocatepetl volcano since 1996 this model poses a density reduction dependent mainly on the volatile contents of the magma filling the volcano conduit system as the driving buoyancy force causing magma extrusions and dome growth

applications of a simplified equation of state for the density of silicate hydrous magmas the volcan de colima mexico buoyancy driven dome growth process similarities and differences with the popocatepetl volcano domes abstract colima and popocatepetl volcanoes began erupting during the second half of the twentieth century after periods or relatively long quiescence both eruptive episodes show similarities persistent dome growth and destruction episodes over periods of decades and differences higher rates of magma and gas production at popocatepetl with similar magmas popocatepetl s slightly more acidic we use a simplified equation of state eos for calculating the density of the hydrous andesitic magmas of volcan de colima in a realistic range of pressures temperatures and dissolved water content to model the density contrast with the host rock causing buoyancy of the magmatic column we use this model to explain some aspects of the dome forming effusive activity of colima and compare the results with a similar study made in a previous work on popocatepetl this dome height isostatic model explains well the observed mean heights around 50 m of the colima lava domes with the buoyant force resulting from a 2 5 wt h 2 o content in the melt a value consistent with recently published measurements of rock inclusions the slightly higher h 2 o contents required for the observed dome heights at popocatepetl is explained in terms of the different depths of the isostatic compensation levels the compositional differences between the magmas and the structural differences between the volcanic edifices

temporal evolution of magmatism in the northern volcanic zone of the andes the geology and petrology of cayambe volcanic complex ecuador in the northern volcanic zone of the andes the cayambe volcanic complex consists of 1 a basal mostly effusive volcano the viejo cayambe whose lavas andesites and subordinate dacites and rhyolites are typically calc alkaline and 2 a younger essentially dacitic composite edifice the nevado cayambe characterized by lavas with adakitic signatures and explosive eruptive styles the construction of viejo cayambe began 1 1 myr ago and ended at 1 0 ma the young and still active nevado cayambe grew after a period of quiescence of about 0 6 myr from 0 4 ma to holocene its complex history is divided into at least three large construction phases angureal cone main summit cone and secondary summit cone and comprises large pyroclastic events debris avalanches as well as periods of dome activity geochemical data indicate that fractional crystallization and crustal assimilation processes have a limited role in the genesis of each suite on the contrary field observations and mineralogical and geochemical data show the increasing importance of magma mixing during the evolution of the volcanic complex the adakitic signature of nevado cayambe magmas is related to partial melting of a basaltic source which could be the lower crust or the subducted slab however reliable geophysical and geochemical evidence indicates that the source of adakitic component is the subducted slab thus the viejo cayambe magmas are inferred to come from a mantle wedge source metasomatized by slab derived melts adakites whereas the nevado cayambe magmas indicate a greater involvement of adakitic melts in their petrogenesis this temporal evolution can be related to the presence of the subducted carnegie ridge modifying the geothermal gradient along the wadati benioff zone and favouring slab partial melting

source and behavior of pyroclastic density currents generated by vulcanian style explosions of popocatepetl volcano mexico on 22 january 2001 abstract since 1994 popocatepetl volcano has extruded 85 lava domes each of which has been destroyed by vulcanian style explosions the paroxysmal vulcanian explosion of 22 january 2001 has been unique by generating multiple pyroclastic density currents pdcs scientists and civil protection authorities have used those pdcs to remap the high risk hazard zone of the volcano although little study has been carried out to understand the generation and evolution of those pdcs here we examine 38 stratigraphic sections and analyze the granulometry componentry vesicularity and petrology glass melt inclusions in plagioclase of collected samples to interpret the origins of the vulcanian explosions and the pdc behavior the 22 january event generated two series of dense pdcs that detached from the base of the eruption column the first set of pdcs traveled northwest across a glacier on the volcano partially scouring and melting the ice that hours later generated a lahar two pulses of these pdcs were confined within a large ravine surpassed the slope break and traveled up to 3 km away from the vent the deposits are matrix supported throughout their extent the second set of pdcs traveled to the northeast mainly as unconfined currents that split into two lobes prior to the slope break the farthest traveled current followed a western ravine and reached the forest 3 5 km from the summit the eastern lobe buried a local hiking hut and reached 2 1 km the deposits from these northeastern currents are massive and block supported all deposits volume of 5 71 105 m3 have finger like morphology with levees and frontal snouts all pdcs flowed as a dense basal granular current with turbulent upper clouds at minimum speeds of 7 10 m s in terms of hazards pdcs that interact with glaciers on the volcano are expected to travel farther and potentially generate extensive lahars at present small intermittent patches of glacier occur on the northern upper slopes of the volcano the components of the deposits are in order of abundance black scoria 53 62 wt sio2 banded scoria pumice 63 wt sio2 dome lithics 60 61 wt sio2 accidental lithics and free crystals juvenile pumice and scoria contain phenocrysts of plagioclase an47 10 clinopyroxene en48 3 orthopyroxene en64 1 ilmenite and titanomagnetite set in a rhyolitic glass pumice clast 74 39 wt sio2 or microlite rich matrix scoria clast the dome lithics also contain these phenocrysts as well as rare olivine phenocrysts fe2 fe2 mg 0 1 dissolved h2o co2 contents in melt inclusions hosted by pumice plagioclase phenocrysts suggest the felsic magma was stored at depths of 2 4 km thus the 2001 event was triggered by the injection of mafic magmas into a small volume of felsic magma probably forming dikes left from the previous eruptive episode we propose that the vulcanian explosions tap a column of magma 2 km depth equivalent to the volume that contained the felsic dikes this mechanism has been acting during the destruction of all summit domes of the ongoing eruption of the volcano

mineralogical and geochemical constraints for the origin and evolution of magmas in sierra chichinautzin central mexican volcanic belt abstract the sierra chichinautzin volcanic field is a key area for understanding the origin of the controversial mexican volcanic belt mvb this is due to its recent volcanic activity which is located at the front of the central mvb although a direct genetic relationship between the volcanism of the mvb and the subduction of the cocos plate is accepted by most authors geological geophysical and geochemical key features of the mvb depart from those of typical magmatic arcs this fact has promoted a debate on the nature of the complex mantle beneath the mvb 1 slab induced convection in the mantle wedge that causes advection of asthenospheric mantle and 2 anomalously hot mantle related to the eastward channeling of plume related material this is a petrological study of the sierra chichinautzin volcanism using mineralogical data from selected representative samples together with their geochemistry to refine the existing models of magmatic processes the integrated petrological analyses have been used to define four main groups of rocks in sierra chichinautzin 1 ol mafic rocks 2 opx intermediate rocks 3 opx felsic rocks and 4 qtz intermediate felsic rocks moreover two different types of mantle derived primitive mafic magmas have been described based on their mineralogical and geochemical features 1 oib like mafic magmas presence of olivine plagioclase phenocrysts higher incompatible element contents with no hfse lile negative anomalies and 2 mafic magmas derived from a metasomatized mantle no plagioclase phenocrysts and more forsteritic olivine hfse lile negative anomalies we prove that the diversity of magmas basalts to dacites in sierra chichinautzin is un related to fractional crystallization processes from the mafic magmas rather magma mixing phenomena between mafic magmas and two different crustal derived felsic magma types opx dacite and qtz bt amp pl cpx opx dacite explain the textural mineralogical and geochemical signatures of most of the sierra chichinautzin rocks there is a strong genetic relationship between the mafic and felsic end members of each mixing trend the relatively anhydrous oib like mafic magmas promote partial melting of a basaltic lower crust under low water fugacity conditions generating opx bearing felsic rocks on the contrary hydrous mafic magmas derived from a metasomatized mantle promote basaltic crustal partial melting under high water fugacities yielding magmas with a complex hydrous phenocryst assemblage several important geodynamical implications for the origin of the mvb magmatism can be extracted from this petrological study 1 the existence of two different primitive mafic magmas implies the presence of an heterogeneous mantle source beneath sierra chichinautzin 2 present data do not offer enough evidence to constrain the nature of the metasomatizing fluids beneath sierra chichinautzin and 3 the negative nb anomaly of most of the sierra chichinautzin rocks andesites and dacites is due to magma mixing and therefore is not a signature of the role of fluids from the subducting cocos plate these geochemical features together with the geophysical and tectonic scenario of the sierra chichinautzin indicate that volcanism in this area is mainly related to the upwelling of an anomalously hot oib like mantle and cast further doubts on a significant role of the subducting cocos plate in the origin of this magmatism

mafic magma recharge supplies high co2 and so2 gas fluxes from popocatepetl volcano mexico since late 1994 open vent eruptive activity and degassing at popocatepetl volcano mexico have released large masses of co2 and so2 tephra and lava produced by these eruptions show evidence for mixing of mafic and silicic magmas shortly before eruption we present the first measurements of dissolved co2 in the mafic magma end member based on analyses of olivine hosted melt inclusions that were trapped at pressures as high as 400 mpa 15 km depth beneath the volcano we combine our data with thermodynamic models to show that degassing of mafic magma at 150 350 mpa pressure can explain the co2 so2 mass ratios 1 8 of volcanic gases released from the volcano during 1995 1997 our results demonstrate that mafic magma recharge was responsible for the high measured fluxes of co2 and so2 from 1995 to 1997 the total so2 emission of 9 mt during this period requires intrusion and degassing of a minimum of 0 8 km3 of mafic magma only 0 3 of this new mafic magma has been erupted in the form of mixed hybrid lava and tephra our results suggest that the ongoing eruption of popocatepetl is essentially an intrusive event more generally we suggest that intrusion and deep degassing may explain the high gas fluxes at some other open vent volcanoes rather than convection of magma in the uppermost parts of subvolcanic conduits

the history of geoconservation an introduction in many parts of the world the regeneration econ omic growth and social changes that took place inthe two decades that followed the second worldwar led to increased leisure time and tourismand a greater awareness of the world around us in addition the realization of our ability todestroy both ourselves and the environment inwhich we live clearly evident during the coldwar years led to a greater appreciation of thefragile nature of the natural environment by thelate 1960s increasing loss of countryside to devel opment and the ability to see our planet fromspace led to an enhanced regard of the fragilityof the environment in which we live by the1970s an environmental revolution with conserva tion at its core was in full swing highlighted bythe pioneering 1972 united nations conferenceon the human environment held in stockholm by the 1990s the earth summit held in rio in1992 had placed the environment through itsrole in achieving sustainable development on theglobal political and social agenda today it isclimate change that reminds us that we have thepower to do irreparable damage to the naturalenvironment that supports us this book provides the rst collection of paperstoaddressthehistoryofgeoconservation itseekstoexplore the origins of the subject and the conceptsthat helped to de ne it it describes the history ofgeoconservation in the uk looks more widely tothe republic of ireland mainland europe and aus tralia and explores the evolution and impact ofglobal conservation initiatives including worldheritage sites and geoparks in doing this it high lights the invaluable contributions to geoconserva tion made by academics geological societies governments conservationists volunteers andlocal communities the papers demonstrate thatthe origin and development of this subject is inter esting and informative in itself but more impor tantly through revealing the history ofgeoconservation successes and failures theyprovide us with an increased understanding ofhow we got to where we are now invaluableknowledge in helping geoconservation meet thechallenges that lie in the future geoconservation is now a growing and wide spread activity that is well established in the uk europe and many other parts of the world priorto the conference held in dudley england innovember 2006 there had been little thought ormaterial published on the history of geoconserva tion there are a number of reasons for this the rst is that geoconservation is a relatively new dis cipline that has had a low pro le until the lastcouple of decades during which it has grownrapidly anotheris thatthisexpansionhasbeensus tained bya forward lookingapproach rather thanonlooking back at the history of the subject thispattern of slow steady growth with more recentrapid expansion is well illustrated in the uk here a few early but isolated examples of geocon servation can be identi ed prior to the twentiethcentury conservation legislation and a nationallycoordinated and structured approach to geoconser vation was in place by 1950 and the rise of thevoluntary sector in the form of regionally impor tant geological geomorphological sites rigs groups regionally important geodiversity sitesin wales boosted activity levels and participationingeoconservationbythe1990s bythetwenty rstcentury the appearance of european geoparks hasled to another step up in geoconservation activitylevel in many other parts of the world activitylevels have risen even more rapidly jumping fromrelatively low levels to relatively high levels asgeoparks have opened up new opportunities andenthusiasm for geoconservation geoconservation is undoubtedly an expandingand dynamic activity it is happening today andthrough geoparks is growing a strong internationalcommunity involving more countries than everbefore it is an exciting time for those interestedin geoconservation it is possible to demonstratehow geoconservation can inform an enlightenedpublic and how geological and geomorphologicalfeatures processes sites and specimens can con tribute to the environmental social and economic

characterization of open and closed volcanic systems in indonesia and mexico using insar time series 1 we use 2007 2011 advanced land observing satellite alos data to perform an arc wide interferometric synthetic aperture radar insar time series survey of the trans mexican volcanic belt tmvb and to study time dependent ground deformation of four indonesian volcanoes selected following the 2007 2009 study of chaussard and amelung 2012 our objectives are to examine whether arc volcanoes exhibit long term edifice wide cyclic deformation patterns that can be used to characterize open and closed volcanic systems and to better constrain in which cases precursory inflation is expected we reveal deformation cycles at both regularly active and previously inactive indonesian volcanoes but we do not detect deformation in the tmvb reflecting a lower activity level we identify three types of relationships between deformation and activity inflation prior to eruption and associated with or followed by deflation kerinci and sinabung inflation without eruption and followed by slow deflation agung and eruption without precursory deformation merapi colima and popocatepetl at merapi no significant deformation is detected even during eruption the first two cases correspond to closed volcanic systems and suggest that the traditional model of magmatic systems and eruptive cycles do apply to andesitic volcanoes i e inflation and deflation episodes associated with magma accumulation or volatile exsolution in a crustal reservoir followed by eruptions or in situ cooling in contrast the last case corresponds to open volcanic systems where no significant pressurization of the magmatic reservoirs is taking place prior to eruptions and thus no long term edifice wide ground deformation can be detected we discuss these results in terms of insar s potential for forecasting volcanic unrest

evolution of the lunar crust sims study of plagioclase from ferroan anorthosites abstract the lunar crust down to a depth of 65 km is composed of older 4 5 ga ferroan anorthosites and younger 4 43 4 17 ga mg suite lithologies which include dunites troctolites and norites the anorthosites are generally inferred to represent floating cumulates in a lunar magma ocean possible depth 800 km moon s radius 1 738 km the cumulates that are inferred to be located near the base of the magma ocean are dominantly olivine and pyroxene the last dregs of the magma ocean are enriched in incompatible elements and have been named kreep k rare earth elements p kreep formed in this manner is probably concentrated near the crust mantle boundary at 70 km depth we are attempting to characterize melts parental to ferroan anorthosites and mg suite norites by analyzing rees la ce nd sm eu dy er yb and ba sr and y in their cumulus plagioclase if the cumulus grains have not been compromised by postcrystallization effects and if we know the relevant mineral melt partition coefficients ds we can invert the trace element data for plagioclase to parental melt compositions melts parental to ferroan anorthosites are estimated to contain ree at concentrations ten to fifty times chondrites melts parental to the earlier crystallizing anorthosites lower ree have virtually no eu anomaly while melts parental to later crystallizing anorthosites higher ree have small negative eu anomalies this is qualitatively consistent with the fractionation of eu relative to other ree by crystallization of plagioclase with large positive eu anomalies melts parental to the mg suite have much higher total ree and very large negative eu anomalies the characteristics of mg suite norite parental magmas may have been derived by the assimilation of kreep near the crust mantle boundary by mg rich basaltic melts formed deeper in the cumulate pile or near the contact between the lower cumulate horizons of the magma ocean and primitive unprocessed lunar mantle 800 km

broadband seismic measurements of degassing activity associated with lava effusion at popocatepetl volcano mexico abstract from november 1999 through july 2000 a broadband seismic experiment was carried out at popocatepetl volcano to record seismic activity over a wide period range 0 04 100 s we present an overview of the seismicity recorded during this experiment and discuss results of analyses of long period lp and very long period vlp seismic signals recorded at stations nearest to the crater over a four month interval december 1999 march 2000 three families of lp signals types i ii and iii are identified based on distinctive waveform features observed periods shorter than 1 s periods longer than 15 s and within the period range 0 5 2 5 s type i lp events have impulsive first arrivals and exhibit a characteristic harmonic wave train with dominant periods in the 1 4 1 9 s range during the first 10 s of signal these events are also associated with a remarkable vlp wavelet with period near 30 s type ii lp events represent pairs of events occurring in rapid succession and whose signatures are superimposed these are typically marked by slowly emergent first arrivals and by a characteristic vlp wave train with dominant period near 30 s made of two successive wavelets whose shapes are quasi identical to those of the vlp wavelets associated with type i events type iii lp events represent the most energetic signals observed during our experiment these have an emergent first arrival and display a harmonic signature with dominant period near 1 1 s they are dominated by periods in the 0 25 0 35 s band and contain no significant energy at periods longer than 15 s hypocentral locations of the three types of lp events obtained from phase picks point to shallow seismic sources clustered at depths shallower than 2 km below the crater floor observed variations in volcanic eruptive activity correlate with defined lp families most of the observed seismicity consists of type i events that occur in association with 1 3 min long degassing bursts exhalations eruptive activity increased in intensity in february coinciding with an increasing occurrence of type ii lp events type iii events were first observed at the end of february and during march in coincidence with the formation of a new lava dome vulcanian eruptions occurred in april and may these events typically exhibit broadband signatures extending over the full period range of the sensors and lasting 30 80 min

influence of volcanic activity on spring water chemistry at popocatepetl volcano mexico abstract the results of the 7 years 1994 2000 of monthly monitoring of spring water before and during eruptions show response to volcanic activity low salinity and temperature characterize most of the springs which are located on the flanks of popocatepetl volcano the ph ranges from 5 8 to 7 8 and temperature from 3 to 36 c oxygen and hydrogen isotopic data show that the water is of meteoric origin but so 4 2 cl f hco 3 b and so 4 2 cl variations precede main eruptive activity which is considered linked to influx of magmatic gases and acid fluids that react with sublimates and host rock and mix with the large water system na ca 2 sio 2 and mg 2 concentrations in the water also increased before eruptive activity the computed partial pressure of co 2 in equilibrium with spring waters shows values higher than air saturated water asw with the highest values up to 0 73 bar of pco 2 boron is detected in the water only preceding the larger eruptions when present boron concentration is normally under health standard limits but in two cases the concentration was slightly above other components are within health standard limits except for f in one spring

magnetic signatures associated with magma ascent and stagnation at popocatepetl volcano mexico during 2006 monitoring of real time magnetic signals at popocatepetl during 2006 has allowed discrimination of magma injection and dome growth magnetic signals correlated with seismic volcanotectonic events and harmonic tremor as well as number of small emissions spring water ph ash components and dome evolution helped define upward magma transport and yield a better understanding of the volcanic plumbing system magma ascent occurs mostly in periods of 7 3 days associated with harmonic tremor and decreasing magnetic signals between 21 1 and 215 nt followed by increasing signals linked to cooling of the domes and increased seismicity over periods of 1 to more than 3 months the dome clogs the vent after the negative magnetic anomaly harmonic tremor period associated with magma ascent and forces an explosive crater reopening explosion larger negative changes in the magnetic signals occurred in april 26 nt august 23 to 26 nt and october to december 25 to 215 nt associated with dome formation and growth negative magnetic anomalies preceded eruptions