Obsidian Lava Research Articles

Stratigraphy and eruptive history of Corbetti Caldera in the Main Ethiopian Rift

The East African Rift (EAR) hosts the highest density of peralkaline volcanoes of any region globally, making it an ideal location to study the subaerial and magmatic processes of peralkaline volcanism. Corbetti Caldera is one such peralkaline centre found within the southern part of the Main Ethiopian Rift (MER), a segment of the EAR. Corbetti is actively deforming and has previously undergone large-scale Plinian eruptions. However, our broader understanding of Corbetti's evolution is limited. Here we present a detailed study of the pre-, syn-and post-caldera eruptive deposits and compile them into a composite stratigraphy of the volcanic sequence. We find evidence for multiple previously undocumented large-scale eruptions, including the deposition of two pre-caldera lithic lag breccias, and we identify three additional post-caldera obsidian lavas. We constrain the age of a young Tuff Cone, Biftu, which sits outside the caldera walls, to <7375 ± 54 cal BP through 14C dating of shells within an associated PDC deposit. The Wendo Koshe Cone, the most recent cone within the complex, is interpreted as the remains of two cones that opened in close proximity to each other and formed the vents for two pyroclastic eruptions: Bedded Pumice and Wendo Koshe Younger Pumice (WKYP). There is abundant evidence for the occurrence of pyroclastic density currents (PDC) within the caldera, usually associated with pumice cone-forming eruptions. These flow deposits rarely extend beyond the caldera walls. From our compiled stratigraphy, we estimate a recurrence rate of one eruption per 300–400 years over the last 2.3 ky.These findings are especially significant as Corbetti is earmarked for potential geothermal exploration, and an understanding of eruptive frequency and style provides vital context to assess the potential hazards associated with this future infrastructure.

Hybrid rhyolitic eruption at Big Glass Mountain, CA, USA

Eruptive dynamics of the 1060 CE rhyolitic eruption of Big Glass Mountain (BGM), USA, are investigated with field observations, hydrogen isotope and H2O content analysis of pyroclastic obsidian chips and lavas. Field relations at BGM reveal evidence for hybrid eruption, defined as synchronous explosive venting and effusive emplacement of vast obsidian lava flows. This activity is particularly well manifested by extensive breccia zones implanted within the BGM obsidian lavas, which may represent rafted tephra cones, in addition to remnants of airfall tephra on the lava. Rhyolitic obsidians collected from a 2.5-m-thick fall deposit and co-eruptive lava flow were studied by FTIR and TCEA methods to elucidate the eruption’s degassing history. The data, along with VolcDeGas program simulations, demonstrate a correlation between H2O content and H-isotopic composition (δD) that likely reflects ever-increasing amounts of volatile loss via repetitive close-system steps, best described as batched degassing.

Chrono-stratigraphy of the youngest (last 1500 years) rhyolitic eruptions of Lipari (Aeolian Islands, Southern Italy) and implications for distal tephra correlations

The youngest (last 1500 years) volcanic eruptions of Lipari, within the Aeolian Archipelago, produced the prominent pumice cone of Monte Pilato and the obsidian lava flows of Rocche Rosse and Forgia Vecchia, concentrated in the north-eastern sector of the island as well as highly dispersed white-coloured, fine-grained tephra layers of rhyolitic composition in terrestrial and marine settings on the regional scale. Here we describe in detail the stratigraphy of pyroclastic successions and lava flows erupted by different vents - Monte Pilato, Forgia Vecchia, Lami, and Rocche Rosse - combining field observations, sedimentological characteristics of the tephra deposits, and major and trace element compositions of the volcanic glass. All the pyroclastic materials consist of aphyric pumice lapilli and ash with a largely homogeneous rhyolitic composition. The Monte Pilato and Forgia Vecchia deposits primarily consist of highly vesicular pumice fragments and subordinate obsidian clasts, whilst Rocche Rosse and Lami are characterized by moderately vesicular juvenile fragments with a more significant fraction of obsidian. The Lami tephra also contains peculiar pumice clasts with a fibrous texture and breadcrust bombs.Stratigraphic relationships, and paleomagnetic and 14C ages of the lava and pyroclastic deposits are combined with the archaeological information and historical reports, enabling us to provide an accurate chrono-stratigraphic framework for the youngest eruptions of Lipari. Following the 8th century CE eruption of Monte Pilato, which produced a pumice cone and a obsidian lava flow, activity resumed in the second half of 13th century CE with the explosive eruption of Forgia Vecchia that culminated in the emission of a bilobate obsidian lava flow. This eruption was shortly followed by the explosive eruptions of Lami and Rocche Rosse, the latter concluded with the emission of the widely renowned obsidian lava flow.By integrating stratigraphy and geochemistry of tephra deposits with a new chronological scheme, our work facilitates the refinement of proximal-to-distal correlation of Lipari's rhyolitic tephra in continental marine environments of the central Mediterranean area in the last 1500 years. A fine-grained, rhyolitic ash found on Stromboli (~40 km NE from Lipari) has an origin from the Monte Pilato and thus, constrains tephra dispersion towards the NE. Very similar ash beds dispersed southwards and interlayered within the near-source deposits of La Fossa, Vulcano island (~10 km from Lipari) exhibit features that are consistent with the younger activities of the Rocche Rosse eruption. A possible link between previously identified rhyolitic ash layers identified in marine cores of the Ionian Sea and the Forgia Vecchia eruption are postulated, although the age and textural characteristics of these distal tephra are not univocal in indicating a correlation to either Monte Pilato or Forgia Vecchia.

Faster geospeedometry: A Monte Carlo approach to relaxational geospeedometry for determining cooling rates of volcanic glasses

The thermal history of natural glasses is critical to understanding a wide range of geologic processes. Relaxation geospeedometry has been used to infer the cooling rates of naturally formed glasses across a wide range of compositions and geologic settings. However, using the Tool-Narayanaswamy (TN) geospeedometer is time consuming, requiring multiple isobaric heat capacity (CP) measurements to constrain four sample-specific model parameters, before quantifying natural cooling history of a sample. Here we present a Monte Carlo-inspired numerical solver called CoolMonte, which automates the fitting procedure of experimental CP measurements, and is capable of determining an unknown cooling rate using a single CP measurement. We compare quantitative cooling rates of four naturally cooled obsidian lava samples determined using the traditional approach with multiple CP measurements, to cooling rates determined using a single CP measurement without sample-specific model calibration. Cooling rates calculated using a single CP measurement are within 0.1 to 1.3 log10 K s−1 of cooling rates determined using multiple CP measurements. We also assessed CoolMonte using 50 synthetic datasets with known cooling rates (≳0.1 K per year) and 10 previously published natural cooling rates which were reproduced within 0.8 log10 K s−1. CoolMonte reduces the time necessary to determine cooling rates of natural samples, improves the reproducibility of cooling rate estimates, and makes relaxational geospeedometry a more accessible method for the study of thermal histories of geologic systems.

Eruption dynamics and explosive-effusive transitions during the 1400 cal BP eruption of Opala volcano, Kamchatka, Russia

Deposits and pumice from the 1400 cal BP eruption of Opala volcano record activity that occurred at the explosive-effusive transition, resulting in intermittent, or stop-start, behavior, where explosive activity resumed following a pause. The eruption deposited distinctive, biotite-bearing rhyolite tephra across much of Kamchatka, and its stratigraphy consists of a lithic-rich pumice fall, overlain by pumice falls and pyroclastic density deposits, with the proportion of the latter increasing with height. This sequence repeats such that the middle of the total deposit is marked by a lithic-rich fall with abundant obsidian clasts. Notably, the eruptive pumice are poorly vesiculated, with vesicle textures that record fragmentation of a partially collapsed magmatic foam. The eruption vent, Baranii Amphitheater is filled with obsidian lavas of the same composition as the rhyolite tephra. Based upon the stratigraphic and compositional relations, we divide the eruption into four phases. Phase I initiated with eruption of a lithic-rich pumice fall, followed by eruption of Plinian falls and pyroclastic density currents. During Phase II, the eruption paused for at least 5–6h; in this time, microlites nucleated and began to grow in the magma. Phase III essentially repeated the Phase I sequence. Obsidian lavas were emplaced during Phase IV. The pumice textures suggest that the magma ascended very near the threshold decompression rate for the transition between explosive (fast) and effusive (slow) behavior. The pause during Phase II likely occurred as decompression slowed enough for the magma to develop sufficient permeability for gas to escape resulting in collapse of the magmatic foam, stopping the eruption and temporarily sealing the conduit. After about 5–6h, eruption resumed with, once again, magma decompressing very near the explosive-effusive transition. Phase III ended when the decompression rate slowed and lava dome emplacement began. Distributions of pumice and lithic clasts, and inclusion of data from previous workers, indicate minimum deposit volumes of ~0.75 and ~0.75–1.15km3 (DRE) and eruption column heights of ~18 and ~20km for Phases I and III, respectively. Phases I-III had a likely total duration of ~60–80h, including a pause in activity of 5–6h during Phase II. This study demonstrates that analysis of vesicle textures from numerous pumice combined with stratigraphic data can reveal syn-eruptive changes in and links between magma permeability, decompression rate, and eruption style.

Contrasting styles of post-caldera volcanism along the Main Ethiopian Rift: Implications for contemporary volcanic hazards

The Main Ethiopian Rift (MER, ~7–9°N) is the type example of a magma-assisted continental rift. The rift axis is populated with regularly spaced silicic caldera complexes and central stratovolcanoes, interspersed with large fields of small mafic scoria cones. The recent (latest Pleistocene to Holocene) history of volcanism in the MER is poorly known, and no eruptions have occurred in the living memory of the local population. Assessment of contemporary volcanic hazards and associated risk is primarily based on the study of the most recent eruptive products, typically those emplaced within the last 10–20ky. We integrate new and published field observations and geochemical data on tephra deposits from the main Late Quaternary volcanic centres in the central MER to assess contemporary volcanic hazards.Most central volcanoes in the MER host large mid-Pleistocene calderas, with typical diameters of 5–15km, and associated ignimbrites of trachyte and peralkaline rhyolite composition. In contrast, post-caldera activity at most centres comprises eruptions of peralkaline rhyolitic magmas as obsidian flows, domes and pumice cones. The frequency and magnitude of events varies between individual volcanoes. Some volcanoes have predominantly erupted obsidian lava flows in their most recent post-caldera stage (Fentale), whereas other have had up to 3 moderate-scale (VEI 3–4) explosive eruptions per millennium (Aluto). At some volcanoes we find evidence for multiple large explosive eruptions (Corbetti, Bora-Baricha, Boset-Bericha) which have deposited several centimetres to metres of pumice and ash in currently densely populated regions. This new overview has important implications when assessing the present-day volcanic hazard in this rapidly developing region.

Measuring effusion rates of obsidian lava flows by means of satellite thermal data

Space-based thermal data are increasingly used for monitoring effusive eruptions, especially for calculating lava discharge rates and forecasting hazards related to basaltic lava flows. The application of this methodology to silicic, more viscous lava bodies (such as obsidian lava flows) is much less frequent, with only few examples documented in the last decades. The 2011–2012 eruption of Cordón Caulle volcano (Chile) produced a voluminous obsidian lava flow (~0.6km3) and offers an exceptional opportunity to analyze the relationship between heat and volumetric flux for such type of viscous lava bodies. Based on a retrospective analysis of MODIS infrared data (MIROVA system), we found that the energy radiated by the active lava flow is robustly correlated with the erupted lava volume, measured independently. We found that after a transient time of about 15days, the coefficient of proportionality between radiant and volumetric flux becomes almost steady, and stabilizes around a value of ~5×106Jm−3. This coefficient (i.e. radiant density) is much lower than those found for basalts (~1×108Jm−3) and likely reflects the appropriate spreading and cooling properties of the highly-insulated, viscous flows. The effusion rates trend inferred from MODIS data correlates well with the tremor amplitude and with the plume elevation recorded throughout the eruption, thus suggesting a link between the effusive and the coeval explosive activity. Modelling of the eruptive trend indicates that the Cordón Caulle eruption occurred in two stages, either incompletely draining a single magma reservoir or more probably tapping multiple interconnected magmatic compartments.

Spherulite formation in obsidian lavas in the Aeolian Islands, Italy

The authors wish to gratefully acknowledge Andy Tindle (The Open University) for assistance with EMP analyses, and Richard Darton and David Evans (Keele University) for assistance with XRD and Prof Alun Vaughan and Nicola Freebody (University of Southampton) with Raman analyses. LAB is grateful to Sophie Blanchard for support with MATLAB. The authors acknowledge support from Keele University, and grants from the Mineralogical Society (UK and Ireland) and Volcanic and Magmatic Studies Group. The authors thank Silvio Mollo and Francesca Forni for their detailed and helpful comments.

北海道,白滝ジオパークの黒曜石溶岩の内部構造(＜特集＞火山噴火史解明のための露頭データベース構築の検討(2))

北海道,白滝ジオパークの黒曜石溶岩の内部構造(＜特集＞火山噴火史解明のための露頭データベース構築の検討(2))

B1-05 微細組織観察から推定される白滝十勝石沢黒曜石溶岩の噴出過程(火山の岩石学,口頭発表)

B1-05 微細組織観察から推定される白滝十勝石沢黒曜石溶岩の噴出過程(火山の岩石学,口頭発表)

Nucleation rates of spherulites in natural rhyolitic lava

The rates of nucleation and crystal growth from silicate melt are difficult to measure because the temperature–time path of magma is often unknown. We use geochemical gradients around spherulites in obsidian glass to estimate the temperature–time interval of spherulite crystallization. This information is used in conjunction with new high-resolution X-ray computed tomography (HRXCT) data on the size distributions of spherulites in six samples of rhyolite obsidian lava to infer spherulite nucleation rates. A large data set of geochemical profiles indicate that the lavas cooled at rates of 10 −2.2 to 10 −1.2 °C/h, and that the spherulites grew at rates that decreased exponentially with time, with values of 10 −0.70 to 10 0.30 μm/h at 600 °C. Spherulites are estimated to have begun nucleating when undercooling [Δ T , = liquidus T (≈800 °C) minus nucleation T ] reached 100–277 °C, and stopped when Δ T = 203–365 °C, with exact values dependent on assumed cooling and growth rates. Regardless of rates, we find that spherulites nucleated within a ~88–113 °C temperature interval and, hence, began when Δ T ≈ 0.65–0.88 × T L , peaking when Δ T ≈ 0.59–0.80 × T L . A peak rate of nucleation of 0.072 ± 0.049 cm −3 h −1 occurred at 533 ± 14 °C, using cooling and growth rates that best fit the data set of geochemical profiles. While our inferred values for Δ T overlap those from experimental studies, our nucleation rates are much lower. That difference likely results from experimental studies using hydrous melts; the natural spherulites grew in nearly anhydrous glass.

Identification and characterization of two new obsidian sub-sources in the Nemrut volcano (Eastern Anatolia, Turkey): The Sıcaksu and Kayacık obsidian

In the framework of the GeObs project (http://geobs.univ-rouen.fr), we performed an exhaustive field study of obsidian lava outcropping of the Nemrut volcano (Eastern Anatolia, Turkey). The macroscopic facies and the chemical characteristics of all sub-sources are presented and compared to each other. The Nemrut sub-sources are distinguishable using microscopic facies and geochemistry (LA-ICP-MS) data. We identify and characterize two previously unknown outcrops (Sıcaksu and Kayacık) both located in the western part of the volcano. Only one of these two sub-sources, which is located near the Sıcaksu village, provides good quality obsidian for knapping. 40Ar/39Ar dating of this sub-source reveals an age of 203±18ka. It thus belongs to the early pre-caldera stage of the Nemrut volcano. Chemical analyses and comparison of datasets composed of results from (i) all Nemrut sub-sources sampled, and (ii) various artefacts presented in Khalidi et al. (this volume) and attributed to the Nemrut volcano, clearly match these artefacts to the Sıcaksu outcrop.The data obtained from a combination of fieldwork and geochemical analyses demonstrates that the Sıcaksu obsidian outcrop was exceptionally important as a source of obsidian raw material for the production of tools and artefacts by prehistoric populations across the Near East.

Ascent and emplacement dynamics of obsidian lavas inferred from microlite textures

To assess the eruption and emplacement of volumetrically diverse rhyolite lavas, we measured microlite number densities and orientations from samples collected from nine lavas in Yellowstone Caldera and two from Mono Craters, USA. Microlite populations are composed of Fe-Ti oxides ± alkali feldspar ± clinopyroxene. Number densities range from 108.11 ± 0.03 to 109.45 ± 0.15 cm−3 and do not correlate with distance from the vent across individual flows and are remarkably similar between large- and small-volume lavas. Together, those observations suggest that number densities are unmodified during emplacement and that ascent rates in the conduit are similar between small domes and large lava flows. Microtextures produced by continuous decompression experiments best replicate natural textures at decompression rates of 1–2 MPa hr−1. Acicular microlites have a preferred orientation in all natural samples. Because the standard deviation of microlite orientation does not become better aligned with distance travelled, we conclude that microlites exit the conduit aligned and that strain during subaerial flow was insufficient to further align microlites. The orientations of microlite trend and plunge in near-vent samples indicate that pure shear was the dominant style of deformation in the conduit. We speculate that collapsing permeable foam(s) provides a mechanism to concurrently allow microlite formation and alignment in response to the combination of degassing and flattening by pure shear.

Rates of water exsolution and magma ascent inferred from microstructures and chemical analyses of the Tokachi–Ishizawa obsidian lava, Shirataki, northern Hokkaido, Japan

Very few quantitative textural data exist for viscous obsidian lava eruptions, and it is still unclear from the mechanical behavior of ascending magmas if outgassing is controlled dominantly by brittle or ductile deformation. In order to obtain insights into how degassing and ascent proceed in such highly viscous magmas, we conducted textural and chemical analyses of the Tokachi–Ishizawa (TI) obsidian lava, in the Shirataki rhyolite volcanic area, northern Hokkaido, Japan, and estimated the water exsolution rate and ascent rate. The storage conditions of the TI lava are estimated from the Rhyolite-MELTS program as T=840–860°C and P=50MPa using the mineral assemblages and the chemical compositions of plagioclase phenocrysts and glass. To estimate the magma ascent rate, we measured the length, width, and number of oxide microlites using three-dimensional techniques. Textural analysis indicates that the microlite number densities (Nv [number/m3]) of oxide microlites in TI lava samples are 2.1×1013 to 1.4×1014, which correspond to water exsolution rates of 3.5×10−9 to 1.7×10−8wt.%/s and ascent rates of 1.7×10−6 to 1.1×10−5m/s. Together with an estimate of viscosity, the inferred ascent velocities allow us to examine the mechanical behavior of the magma in the conduit. We conclude that the development of permeability leading to outgassing is controlled by ductile deformation rather than brittle fracturing.

B2-28 黒曜石溶岩中のマイクロライトの形態から推定されるマグマ上昇過程(浅部マグマ上昇過程,口頭発表)

B2-28 黒曜石溶岩中のマイクロライトの形態から推定されるマグマ上昇過程(浅部マグマ上昇過程,口頭発表)

P2-03 神津島砂糠山,黒曜石溶岩の内部構造(ポスターセッション)

P2-03 神津島砂糠山,黒曜石溶岩の内部構造(ポスターセッション)

Explosive origin of silicic lava: Textural and [formula omitted]–H2O evidence for pyroclastic degassing during rhyolite effusion

A long-standing challenge in volcanology is to explain why explosive eruptions of silicic magma give way to lava. A widely cited idea is that the explosive-to-effusive transition manifests a two-stage degassing history whereby lava is the product of non-explosive, open-system gas release following initial explosive, closed-system degassing. Direct observations of rhyolite eruptions indicate that effusive rhyolites are in fact highly explosive, as they erupt simultaneously with violent volcanic blasts and pyroclastic fountains for months from a common vent. This explosive and effusive overlap suggests that pyroclastic processes play a key role in rendering silicic magma sufficiently degassed to generate lava. Here we use precise H-isotope and magmatic H2O measurements and textural evidence to demonstrate that effusion results from explosion(s)—lavas are the direct product of brittle deformation that fosters batched degassing into transient pyroclastic channels (tuffisites) that repetitively and explosively vent from effusing lava. Our measurements show, specifically that D/H ratios and H2O contents of a broad suite of explosive and effusive samples from Chaitén volcano (hydrous bombs, Plinian pyroclasts, tuffisite veins, and lava) define a single and continuous degassing trend that links wet explosive pyroclasts (∼1.6 wt.% H2O, δD=−76.4‰) to dry obsidian lavas (∼0.13 wt.% H2O, δD=−145.7‰). This geochemical pattern is best fit with batched degassing model that comprises small repeated closed-system degassing steps followed by pulses of vapour extraction. This degassing mechanism is made possible by the action of tuffisite veins, which, by tapping already vesicular or brecciated magma, allow batches of exsolved gas to rapidly and explosively escape from relatively isolated closed-system domains and large tracts of conduit magma by giving them long-range connectivity. Even though tuffisite veins render magma degassed and capable of effusing, they are nonetheless the avenues of violent gas and particle transport and thus have the potential to drive explosions when they become blocked or welded shut. Thus the effusion of silicic lava, traditionally thought to be relatively benign process, presents a particularly hazardous form of explosive volcanism.

Exceptional mobility of an advancing rhyolitic obsidian flow at Cordón Caulle volcano in Chile

The emplacement mechanisms of rhyolitic lava flows are enigmatic and, despite high lava viscosities and low inferred effusion rates, can result in remarkably, laterally extensive (>30 km) flow fields. Here we present the first observations of an active, extensive rhyolitic lava flow field from the 2011-2012 eruption at Cordón Caulle, Chile. We combine high-resolution four-dimensional flow front models, created using automated photo reconstruction techniques, with sequential satellite imagery. Late-stage evolution greatly extended the compound lava flow field, with localized extrusion from stalled, ~35 m-thick flow margins creating >80 breakout lobes. In January 2013, flow front advance continued ~3.6 km from the vent, despite detectable lava supply ceasing 6-8 months earlier. This illustrates how efficient thermal insulation by the lava carapace promotes prolonged within-flow horizontal lava transport, boosting the extent of the flow. The unexpected similarities with compound basaltic lava flow fields point towards a unifying model of lava emplacement.

Shallow vent architecture during hybrid explosive–effusive activity at Cordón Caulle (Chile, 2011–12): Evidence from direct observations and pyroclast textures

In June 2011, an eruption of rhyolite magma began at the Puyehue–Cordón Caulle volcanic complex, southern Chile. By January 2012, explosive activity had declined from sustained pyroclastic (Plinian to sub-Plinian) fountaining to mixed gas and ash jetting punctuated by Vulcanian blasts. This explosive activity was accompanied by synchronous effusion of obsidian lava in a hybrid explosive–effusive eruption. Fortuitous climatic conditions permitted ground-based observation and video recording of transient vent dynamics as well as real-time collection of proximal juvenile ash as it sedimented from the active plume. The main eruptive vent complex and site of lava effusion were represented by two loci of Vulcanian blasts within a single tephra cone containing a pancake-shaped proto-lava dome. These blast loci each consisted of clusters of sub-vents that expressed correlated shifts in eruption intensity, indicating the presence of partially connected and/or branching zones of high permeability within the upper conduit. Pyroclast textures were examined by X-ray computed microtomography and their permeability was modelled by lattice Boltzmann simulations. The porosity (39 to 67%) and Darcian permeability (3.1×10−15m2 perpendicular to fabric to 3.8×10−11m2 parallel to fabric) of fine ash emitted during ash jetting indicate that the permeable zones comprised highly sheared, tube-like bubbly magma, and contrast with the low porosity (~17%) and nul permeability of bombs ejected to hundreds of metres from the vent in Vulcanian blasts. Residual H2O content of ash (0.14wt.%) and two bombs (0.2–0.25wt.%), determined by Karl–Fischer titration indicate degassing of this pyroclastic material to near-atmospheric pressures. Ash textures and simple degassing/vesiculation models indicate the onset of permeability by ductile processes of shear-enhanced bubble coalescence in the upper 1 to 1.5km of the conduit. Repeated ash jetting and Vulcanian blasts indicate that such ductile processes were not sufficiently effective to accommodate all degassing requirements, and additional brittle (e.g., fragmentation) events transiently assisted in maintaining an open-system degassing regime that permitted long-lived, hybrid explosive–effusive activity. The eruption at Cordón Caulle has provided an excellent opportunity to closely observe key processes of silicic volcanism.

New investigations of the Göllüdağ obsidian lava flows system: a multi-disciplinary approach

The Göllüdağ obsidian lava flow system is relatively complex. More than ten different obsidian outcrops and knapping workshops have been identified around this volcano. Their importance for long and short distances obsidian supply has already been demonstrated. One of the main problem encountered when studying the Göllüdağ obsidian flows, is the great chemical similarity of some of them. The use of the geochemical approach to solve the problems of obsidian trade around the Göllüdağ is therefore insufficient. A multi-disciplinary program joining archaeology, geochemistry and geomorphology, was thus started to understand the relationships between the different obsidian flows and to draw the pattern of the Göllüdağ obsidian trade. Our archaeological and geomorphologic approach will help us to understand which obsidian outcrops were available during the Palaeolithic and Neolithic periods. Also our geomorphologic approach, linked to intensive geochemical analyses, will help us to understand the spatial variability of the geochemistry of the obsidian outcrops. Lithic technology will also give information about the different knapping methods used at the workshops.