Gezahegn Yirgu

• Addis Ababa University

The Ethiopia Rift System (ERS) is a section of the East African Rift System within Ethio-pia extending from the Afar in the northeast to the Kenya border in the southwest. It is apparent that magmatism and magmatic intrusions influence the crustal shape in the ERS resulting in its thinning and the shallowing of magmatic sources at various locations...

Pumice cones are volcanic landforms that exist worldwide, but whose eruption has never been observed. Interpretations of these eruptions vary significantly in style, intensity, and magnitude, pertinent for volcanic hazard assessment. Aluto volcano (Ethiopia) provides an unprecedented insight into the hazardous nature of these enigmatic eruptions. W...

Aluto volcano (Central Ethiopia) displays a complex, hybrid topography, combining elements typical of caldera systems (e.g., a central, flat caldera floor) and stratovolcanoes (e.g., relatively high and steep, radial flanks, related to eruptions occurring clustered in space). The most recent known eruptions at Aluto have commonly generated column‐c...

The Main Ethiopian Rift (MER) is a well-known continental rift whose axial sector is characterized by the occurrence of regularly spaced silicic caldera complexes and central stratovolcanoes, interspersed with large fields of fissural basalts, small mafic scoria cones and numerous young normal faults and fissures. The Tulu Moye-Bora-Berecha volcani...

The Bora-Baricha-Tullu Moye (BBTM) volcanic complex is located in a transition zone between the central and northern sectors of the Main Ethiopian Rift where tectonic and volcanic features show complex interplays. We mapped and characterized volcanic and tectonic features using high-resolution digital elevation models and performed morphometric and...

Plain Language Summary Continental rifting, the break‐up of continents to form new ocean basins, is a key component in the tectonic cycle that affects Earth's surface environment. The rifting process is aided by magmatic activity in its final stages, which weakens the crust by heating it. This is believed to facilitate present‐day rifting in Ethiop...

Major and trace element data are presented for Quaternary basalts from Butajira-Kibet area, close to the western escarpment of the Central Main Ethiopian Rift to investigate the petrogenetic processes involved and the nature of mantle source compositions. The data indicate that the basalts are mildly alkaline characterized by moderate to high conte...

Significant volumes of magma are intruded into the crust during continental break-up, which can influence rift evolution by altering thermo-mechanical structure of the crust and thereby its response to extensional stresses. Rift magmas additionally feed surface volcanic activity and can be globally significant sources of tectonic CO2 emissions. Und...

The Main Ethiopian Rift (MER) is renowned as a focus of investigations into human origins. It is also the site of many large volcanic calderas, whose eruptions have spanned the timeframe of speciation, cultural innovation, and dispersal of our species. Yet, despite their significance for dating human fossils and cultural materials, the timing and g...

Fluoride-enriched ground and surface waters represent a major health risk for the local population in many areas along the East African Rift. The present study investigates the origin of fluoride and the reason for its accumulation in the rift waters, following two hypotheses: (i) fluid-rock-interactions release fluoride from minerals into the wate...

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...

Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish 1–3 and Herto 4,5 in Ethiopia, have drawn on a variety of chronometric evidence, including ⁴⁰ Ar/ ³⁹ Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I 3,6,7 ,...

The study area is located in the North Wollo zone within the NW Ethiopian volcanic plateau. The area provides a well-preserved volcano-stratigraphic sequence from lower basalt initiation to upper lava flow termination. The main objective of the study is to establish the petrovolcanic stratigraphy of the area and to put the petrographic observations...

Efforts to date the oldest modern human fossils in East Africa, from Omo-Kibish and Herto in Ethiopia, have drawn on a variety of chronometric evidence, including 40Ar/39Ar ages of stratigraphically-associated tuffs. The generally-accepted ages for these fossils are ca. 196 thousand years (ka) for the Kibish Omo I and ca. 160-155 ka for the Herto h...

Aluto volcano, in the Main Ethiopian Rift, is a peralkaline caldera system, which comprises conglomerations of rhyolite (obsidian) lavas and enigmatic pumice cones. Recent work at Aluto has found that pumice cone eruptions are highly unsteady, and form convective eruption plumes that frequently collapse to generate pyroclastic density currents (PDC...

Opals are widespread within Miocene volcanic sequences in the North Shoa province of Central Ethiopia. The opal occurs as cavity fillings in a 5 m thick seam of glassy rhyolitic ignimbrite that is sandwiched between basaltic lava flows. The opals occur over a large area (>25 km2). X-ray diffraction analyses show that they are CT-type. The opals con...

Peralkaline rhyolites are medium to low viscosity, volatile-rich magmas typically associated with rift zones and extensional settings. The dynamics of peralkaline rhyolite eruptions remain elusive with no direct observations recorded, significantly hindering the assessment of hazard and risk. Here we describe uniquely-preserved, fluidal-shaped pyro...

Silicate weathering of basaltic rocks constitutes a non-negligible sink of atmospheric CO 2 but the role it plays in the regulation of past and future global climate is still matter of debate. In this study, silicate weathering rates for various sub-basins of the Ethiopian Traps, emplaced 30 million years ago, and the corresponding atmospheric CO 2...

We report field observation, age, chemical (major and trace elements), and isotope (Sr-Nd-Pb) data for felsic volcanic rocks from Central Afar and adjacent western margin. Investigated volcanic rocks are dominantly rhyolites with minor trachytes, and they are geochemically similar. Their ages range from ~30 Ma (prerift stage), ~20 Ma (early synrift...

For many magmatic systems, crystal compositions preserve a complex and protracted history, which may be largely decoupled from their carrier melts. The crystal cargo may hold clues to the physical distribution of melt and crystals in a magma reservoir and how magmas are assembled prior to eruptions. Here we present a geochemical study of a suite of...

The Boku volcanic complex is a Quaternary center situated on the axial segment of the Main Ethiopian Rift (MER), located 92 km South-east from Addis Ababa. The main objective of this study is to understand the magmatic evolution of the volcanic complex and to develop a model to answer some outstanding questions related to bimodal products of rift r...

The geographic heterogeneities in lava composition observed in continental flood basalt provinces could provide a probe of material upwelling from the deep mantle and their length scales, but their utility is limited by uncertainties in the locus of magmatism. We examine the magma plumbing system for the Oligocene Ethiopian flood basalts. The provi...

The Boku volcanic complex is a Quaternary center situated on the axial segment of the Main Ethiopian Rift (MER), located 92 km South-east from Addis Ababa. The main objective of this study is to understand the magmatic evolution of the volcanic complex and to develop a model to answer some outstanding questions related to bimodal products of rift r...

Within continental rift settings, extensional strain is initially accommodated along the nascent rift margins, subsequently localizing to zones of focused magmatic intrusion. The migration of strain from rift-border faults to diking places an emphasis on constraining the magmatic plumbing system of zones of focused intrusion to resolve how extensio...

Magma plays a vital role in the break-up of continental lithosphere. However, significant uncertainty remains about how magma-crust interactions and melt evolution vary during the development of a rift system. Ethiopia captures the transition from continental rifting to incipient sea-floor spreading and has witnessed the eruption of large volumes o...

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 know...

The fragmentation of peralkaline rhyolites is considered somewhat enigmatic. Peralkaline rhyolitic melts, due to their high Na+, K+ and halogen contents, have low melt viscosities relative to metaluminous melts of equivalent silica content. While typical rhyolite viscosities are around 108 Pa S, the viscosity of volatile free peralkaline rhyolites...

Peridotite constitutes most of the Earth's upper mantle, and it is therefore unsurprising that most mantle-derived magmas exhibit evidence of past equilibrium with an olivine-dominated source. Although there is mounting evidence for the role of pyroxenite in magma generation within upwelling mantle plumes, a less documented non-peridotite source of...

The Main Ethiopian Rift hosts a number of peralkaline volcanic centres, several of which show signs of recent unrest. Due to the low number of historical eruptions recorded in the region and lack of volcanic monitoring, conditions of magma storage in the Main Ethiopian Rift remain poorly constrained. Aluto is one of these restless volcanic centres...

Peridotite constitutes most of the Earth's upper mantle, and it is therefore, unsurprising that most mantle-derived magmas exhibit evidence of past equilibrium with an olivine-dominated source. Although there is mounting evidence for the role of pyroxenite in magma generation within upwelling mantle plumes, a less documented non-peridotite source o...

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth, however, current understanding of the magnitude and timing of large explosive eruptions in this region is poor. Detailed records of volcanism are essential for interpreting the palaeoenvironments occupied by our hominin ancestors; and also for evaluati...

40Ar/39Ar age data table for Aluto (analysis conducted at SUERC).

Supplementary Figures 1-11, Supplementary Tables 1-5 and Supplementary References

40Ar/39Ar age data table for Corbetti (analysis conducted at USGS Menlo Park). a. COI2E - Sanidine. b. Chabbi 7 - Sanidine.

Volumetrically, the lithospheric mantle comprises the bulk of the continental lithosphere, yet the mechanisms by which the lithospheric mantle is deformed during rifting are unresolved. Stretching and thermo-mechanical erosion are often cited mechanisms for facilitating lithospheric deformation during continental rift development; however, the infi...

Magmatic underplates, which are characterized by high seismic velocity and anomalously high density in comparison to normal lower crust, are among the most significant compositional heterogeneities identified in the rift lithosphere. The interaction of a magma with the lithospheric mantle to form pyroxenites is considered a viable mechanism for the...

The silicic peralkaline volcanoes of the East African Rift are some of the least studied volcanoes on Earth. Here we bring together new constraints from fieldwork, remote sensing, geochronology and geochemistry to present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in a densely populated section o...

Restless silicic calderas present major geological hazards, and yet many also host significant untapped geothermal resources. In East Africa this poses a major challenge, although the calderas are largely unmonitored their geothermal resources could provide substantial economic benefits to the region. Understanding what causes unrest at these volca...

In volcanically and seismically active rift systems, preexisting faults may control the rise and eruption of magma, and direct the flow of hydrothermal fluids and gas in the subsurface. Using high-resolution airborne imagery, field observations, and CO2 degassing data on Aluto, a typical young silicic volcano in the Main Ethiopian Rift, we explore...

Unravelling the volcanic history of the Dabbahu/Manda Hararo rift segment in the Afar depression (Ethiopia) using a combination of cosmogenic (36Cl and 3He) surface exposure dating of basaltic lava-flows, field observations, geological mapping and geochemistry, we show in this paper that magmatic activity in this rift segment alternates between two...

Despite their significance for understanding the potential environmental factors involved in hominin evolution in Ethiopia, very few modern volcanologic studies have been carried out on the Quaternary calderas and associated silicic tephra deposits of the Ethiopian Rift. We present here the second of a set of papers reporting the findings of fieldw...

In the tectonically active northern Main Ethiopian Rift (MER), the locus of strain has migrated away from rift border faults towards narrow rift axial zones of focused magma intrusion and short length-scale faulting. However, the observation of rift-marginal magmatic belts in the less mature central MER may indicate the transition from mechanical t...

Investigations of a variety of continental rifts and margins worldwide have revealed that a considerable volume of melt can intrude into the crust during continental breakup, modifying its composition and thermal structure. However, it is unclear whether the cause of voluminous melt production at volcanic rifts is primarily increased mantle tempera...

In the Afar depression (Ethiopia), extension is organised along rift segments that morphologically resemble oceanic rifts. Segmentation results from interactions between dyke injection and volcanism, as observed during the well-documented 2005 rifting event on the Dabbahu rift segment. This tectono-volcanic crisis was observed in detail via remote...

As continental rift zones mature the tectonic and volcanic processes associated with crustal extension become confined to narrow magmatic rift zones, reminiscent of oceanic spreading ridges. The formation of these rift zones and the development of ocean-ridge type topography is a significant milestone in rift evolution as it signifies the localizat...

Dabbahu is a composite volcano at the north end of the active Manda-Hararo segment of the Afar Rift in northern Ethiopia. We present 93 new whole-rock analyses, mineral analyses from 65 samples, and 9 new Ar-40-Ar-39 dates for rocks ranging in composition from mildly alkaline basalt through trachyandesite to peralkaline rhyolite (comendite and pant...

This paper presents the results of an investigation carried out on young volcanic rocks from the Gedemsa and Fanta 'Ale complexes, located in the Main Ethiopian Rift, the site of an intense magmatism since Eocene–Oligocene. The earlier NW–SE direction of extension of the Rift, which generated NE–SW trending faults, rotated around E–W in Quaternary...

In the Afar depression (Ethiopia), extension is already organised along rift segments which morphologically resemble oceanic rifts. Segmentation here results from interactions between dyke injection and volcanism, as observed during the well documented 2005 event on the Dabbahu rift segment. During this tectono-volcanic crisis, a megadyke was injec...

The 3.119 ± 0.010 Ma Chefe Donsa phreatomagmatic deposits on the shoulder of the Ethiopian Rift mark the northern termination of the Silti-Debre Zeyit Fault Zone, a linear zone of focused extension within the modern Ethiopian Rift. These peralkaline pumice fragments and glass shards span a wide range of glass compositions but have a restricted phen...

A variety of methods exist to constrain sub-volcanic storage conditions of magmas. Petrological, seismological and satellite geodetic methods are integrated to determine storage conditions of peralkaline magmas beneath Dabbahu Volcano, Afar, Ethiopia. Secondary ion mass spectrometry (SIMS) analysis of volatile contents in melt inclusions trapped wi...

The Afar depression (Ethiopia) is the junction of two oceanic ridges (the Red Sea and the Aden Ridges) with the Main Ethiopian Rift, which leads the crust close to the Continent-Ocean Transition. The extension of the Red Sea Ridge in Afar is organised along rift segments which morphologically resemble oceanic rifts. Segmentation here seems to be th...

The Afar region is a large, triangular low-lying (-120-500 m elevation) area stretching from Eritrea in the north to Djibouti in the east and Ethiopia in the south. It is bordered by the Ethiopian plateau to the west (~2000-3000 m), the Somali plateau to the southeast, and the Danakil block to the northeast (Fig. 14.1). For the most part Afar is sp...

The East African Rift System (EARS) is particularly famous because sediments trapped in some of the rift depressions have recorded a major piece of the late Cenozoic mammalian and hominin evolution, as well as associated proxies of climate and environmental changes. The present day landscape along the EARS is spectacular and characterized by axial...

Quaternary volcanism in the northern Main Ethiopian Rift is characterized by rift-axis eruptive centres with complicated collapse structures. Despite their association with major explosive eruptions, few modern studies have been carried out on them. We present the results of fieldwork and laboratory analyses of one of the largest of these centres,...

Variations in the Fe/Mn ratio and Osmium isotopes in magnesium-rich mafic rocks from plume-related volcanic provinces have been exploited to imply the entrainment of core material in mantle plumes and the involvement of ancient recycled oceanic lithosphere. Here we present new major and trace element, 187Os/188Os ratios and precise Fe/Mn ratios on...

Although fault and magmatic processes have achieved plate spreading at mid-ocean ridges throughout Earth's history, discrete rifting episodes have rarely been observed. This paper synthesizes ongoing seismic, structural, space-based geodetic, and petrologic studies from the subaerial Red Sea rift in Ethiopia where a major rifting episode commenced...

Rift zones are the most common magmatic environment on Earth. However opportunities to observe active rifting are rare, and consequently the volcanological characteristics of rift systems are not well understood. An ongoing phase of magmatic rifting along a section of the Red Sea system in Afar, Ethiopia, presents an exceptional opportunity to cons...

The western Afar margin represents the southern end of the Red Sea rift system. It developed in the heart of the Afar plume related volcanic province which lies at the famous triple junction connecting the East African, the Gulf of Aden and the Red Sea rifted systems. This margin is presently separating the Afar depression from the Ethiopian Highla...

The Afar Rift in Ethiopia is one of the only subaerial locations in the world where the transition from continental break-up to oceanic-spreading can be observed. Extension and volcanism in the Afar is concentrated in tectono-magmatic segments (TMS), similar in size and morphology to those that characterize mid-ocean ridge systems. However, unlike...

Opportunities to observe active magma-mediated rifting episodes are rare, and consequently the volcanic characteristics of dynamic rift systems are not well known. The currently ongoing phase of magmatic rifting along a section of the Red Sea system in Afar, Ethiopia, presents an exceptional opportunity to provide constraints on the volcanic compon...

A 60-km-long dyke intruded the Dabbahu segment of the Nubia–Arabia Plate boundary (Afar, Ethiopia) in 2005 September, marking the beginning of an ongoing rifting episode. We have monitored the continuing activity using Satellite Radar Interferometry (InSAR) and with data from Global Positioning System (GPS) instruments and seismometers deployed aro...

Thin-section observations and electron probe analyses, and trace element data are reported from a new mantle xenolith hosted in Miocene alkali basalt from the western flank of Simien shield volcano, Ethiopia. The spinel lherzolite enclaves contain variable proportions of olivine, orthopyroxene, green clinopyroxene and brown spinel, and have undergo...

Here we report measurements of the chemical composition and flux of gas emitted from the central lava lake at Erta 'Ale volcano (Ethiopia) made on 15 October 2005. We determined an average SO2 flux of ∼ 0.69 ± 0.17 kg s− 1 using zenith sky ultraviolet spectroscopy of the plume, and molar proportions of magmatic H2O, CO2, SO2, CO, HCl and HF gases t...

In September 2005, a 60-km-long dike, up to 8 meters thick, was intruded into the Dabbahu rift segment, a nascent seafloor spreading center on the Nubia-Arabia plate boundary in the Afar Depression of Northern Ethiopia. Localized subsidence of 2-3 meters at Dabbahu and Gabho, measured by InSAR, indicated that some of the intrusion was fed from shal...

The Afar Rift in Ethiopia is one of the only subaerial locations in the world where the transition from continental break-up to oceanic-spreading can be observed. Extension and volcanism in the Afar is concentrated in tectono-magmatic segments (TMS), similar in size and morphology to those that characterise spreading ridges. The Dabbahu TMS is the...

Dabbahu is situated in the western region of Afar, Ethiopia, at the northern end of the Manda Hararo rift segment. This volcano came back to life in 2005 with a small rhyolitic eruption from the Da'Ure vent, the first such eruption in Africa for a century. This coincided with the start of a major rifting event which has been modelled as a basalt dy...

Accurate determination of rifting chronology and associateduplift is crucial to understanding the evolution of the EastAfrican Rift System (EARS) and for identifying the significanceof mantle plumes during continental breakup. This investigationof rift-related cooling along a major fault scarp in southernEthiopia, using (U-Th)/He thermochronometry,...

The 60-km-long Dabbahu segment of the Nubia-Arabia plate boundary lies in the Northern Ethiopian region of Afar. In September 2005 a major rifting episode resulted in the injection of a 60-km-long dyke with a maximum thickness of ~8m (Wright et al., 2006). Subsidence observed at Dabbahu and Gabho volcanoes implied that some of the magma was sourced...

The 2005 seismo-volcanic crisis in a remote area of Ethiopia graphically illustrated the problems faced by research scientists in East Africa, as well as the need for regional hazard mitigation programs. Over a 3-week period in 2005, 163 mb > 3.9 earthquakes and a silicic eruption occurred as a 60 km-long dike was intruded along a previously identi...

1] Quaternary lavas erupted in zones of tectonomagmatic extension within the Main Ethiopian Rift (MER) preserve details of lithospheric structure in the East African Rift System. Despite observed source heterogeneity, basalts, trachybasalts, and basaltic trachyandesites erupted in the Wonjii Fault Belt (WFB) and the Silti-Debre Zeyit Fault Zone (SD...

Major, trace element and isotopic data for mafic to peralkaline silicic volcanic rocks from the northern sector of the main Ethiopian rift are discussed with the aim of placing constraints on processes of magma genesis and evolution and to present models for magma plumbing systems of rift volcanoes. Basalts straddle the subalkaline–alkaline boundar...

The September 2005 Afar extension episode generated many fractures in the Da'ure' area. On September 26, a volcanic eruption began along one of these fractures and, according to local accounts, lasted 3 days. The fracture, trending around N10W, was 400 m long. A detailed geological survey of the area, carried out during the following month of Octob...

Rifting is a common though rarely observed process on Earth. As a consequence, our understanding of the related processes is far from complete. The 2005 rifting event in Ethiopia was the largest subaerial event since more than 2 decades and was accompanied by a small volume volcanic eruption. The pyroclast distribution was very restricted and allow...

The rifting episode in northern Afar, Ethiopia, which began in late 2005 was accompanied by a brief eruption of silicic magma and tephra, from a vent at Da'Ure, just south of the stratovolcano of Dabbahu (or Boina). This serendipitous event affords a remarkable opportunity to investigate the coupled relationships between magmatism and tectonics in...

The recent volcano-tectonic activity in Afar started on September 4th while the major eruption occurred on 26 September 2005. The chief of the Dabbahu district, Mr. Mohammed Kello said that it was common to feel earthquakes in that locality previously but the rumbling noise, vibration and explosion in this recent crisis in September 2005 was distur...

Rifting is a common though rarely observed process on Earth. As a consequence, our understanding of the related processes is far from complete. The 2005 rifting event in Ethiopia was the largest subaerial event since more than 2 decades and was accompanied by a small volume volcanic eruption. The pyroclast distribution was very restricted and allow...

The September 2005 Afar extension episode generated many fractures in the Da'ure' area. On September 26, a volcanic eruption began along one of these fractures and, according to local accounts, lasted 3 days. The fracture, trending around N10W, was 400 m long. A detailed geological survey of the area, carried out during the following month of Octob...

From September 4 to October 4, 2005, a tectono-magmatic event of unprecedented scale and intensity occurred along the Dabbahu segment of the Afar rift, Ethiopia, with a 60 km-long dike intrusion, 162 3.9 < mb < 5.6 earthquakes, and the emplacement of about 2.5 km3 of magma. It is the largest single rifting event known on land since the Laki (Icelan...

Seafloor spreading centres show a regular along-axis segmentation thought to be produced by a segmented magma supply in the passively upwelling mantle. On the other hand, continental rifts are segmented by large offset normal faults, and many lack magmatism. It is unclear how, when and where the ubiquitous segmented melt zones are emplaced during t...

Continental rifting processes continually reshape the Earth's surface, producing sediment-filled rift basins, or rupturing the tectonic plates to form new ocean basins. Rift architecture and tectonics focus volcanic and seismic hazards, as well as geothermal energy resources, while rift systems in Africa have controlled faunal dispersal patterns an...

Primitive recent mafic lavas from the Main Ethiopian Rift provide insight into the structure, composition and long-term history of the Afar plume. Modern rift basalts are mildly alkalic in composition, and were derived by moderate degrees of melting of fertile peridotite at depths corresponding to the base of the modern lithosphere (c. 100 km). The...

New structural and geochronological analyses indicate that the felsic volcanism at the top of the Oligocene flood basalt sequences along the western margin of the Afar Depression marks the onset of rifting in the southern Red Sea. Geochronological studies show a pattern of riftward migration of the locus of magmatism and faulting from 28 Ma to pres...

Mineral chemistry, major and trace elements and Sr-Nd isotopes are presented for basalts and trachybasalts from the Quaternary alkaline Tepi shield from southwest Ethiopia. The lavas are variably porphyritic with phenocrysts of olivine (Fo(67-87)), clinopyroxene (Wo(45-47)En(38-40)Fs(13-16)), plagioclase (An(57-68)) and Ti-magnetite set in a microc...

A 60‐kilometer‐long rift segment ruptured in north central Afar, Ethiopia, in September 2005. This rupture followed a short but intensive period of volcanic and tectonic activity during which time more than 162 earthquakes (magnitudes 4.1—5.2) occurred and a 400‐meter‐long and 80‐meter‐wide volcanic vent opened (Figure l ). For its spatial extent a...

The morpho-tectonic evolution of the Afar triple junction has been debated for long, especially concerning the timing of rift development and basement uplift. Based on a low-T (U-Th)/He study, we have proposed recently that the stability of the Blue Nile river (on the main Ethiopian flood-basalts plateau) could last since the emplacement of the lav...