Abstract Onshore exposures of the North Atlantic Igneous Province have been studied in detail for over 200 years, whereas the more extensive offshore volcanic stratigraphy is significantly less well constrained with the exception of a small number of boreholes. Within this study we integrate seismic and well data across the northern Faroe–Shetland Basin and Møre Marginal High to improve understanding of the volcanic stratigraphy and its relationship to rifting in the NE Atlantic. Volcanic seismic facies, including compound and tabular lavas and hyaloclastites (representing subaerial and subaqueous emplacement), are interpreted across the study area, calibrated by the Lagavulin borehole. The volcanic sequence was erupted between c. 56.1 and 55.2 Ma, when subaerial conditions dominated in the region, but extensive lava deltas developed in a seaway east of the main lava field. Geochemical and thickness variations within the volcanic pile have important implications for the regional rifting history. MORB-like lavas at the base of Lagavulin, which thicken substantially northward, support an early onset of rifting near the Møre Marginal High prior to major thinning associated with continental breakup to the south and north. Following a period of erosion, smaller-degree melting caused the eruption of higher-TiO 2 /Zr lavas, marking the final ‘pre-breakup’ volcanism before emplacement of seaward-dipping reflectors.

ABSTRACT Intralava geochemical variations resulting from subtle changes in magma composition are used here to provide insights into the spatial-temporal development of large basalt lava flow fields. Recognition that flood basalt lavas are emplaced by inflation processes, akin to modern pāhoehoe lava, provides a spatial and temporal frame-work, both vertically at single locations and laterally between locations, in which to examine lava flow emplacement and lava flow field development. Assuming the lava inflation model, we combined detailed field mapping with analysis of compositional profiles across a single flow field to determine the internal spatio-temporal development of the Palouse Falls flow field, a lava produced by an individual Columbia River flood basalt eruption. Geochemical analyses of samples from constituent lobes of the Palouse Falls lava field demonstrate that systematic compositional whole-rock variations can be traced throughout the flow field from the area of the vent to the distal limits. Chemical heterogeneity within individual lava lobes (and outcrops) shows an increase from lava crusts to cores, e.g., MgO = 3.24–4.23 wt%, Fe 2 O 3 = 14.71–16.05 wt%, Cr = 29–52 ppm, and TiO 2 = 2.83–3.14 wt%. This is accompanied by a decrease in incompatible elements, e.g., Y = 46.1–43.4 ppm, Zr = 207–172 ppm, and V = 397–367 ppm. Systematic compositional variations from the source to distal areas are observed through constituent lobes of the Palouse Falls flow field. However, compositional heterogeneity in any one lobe appears less variable in the middle of the flow field as compared to more proximal and distal margins. Excursions from the general progressive trend from vent to distal limits are also observed and may reflect lateral spread of the flow field during emplacement, resulting in the juxtaposition of lobes of different composition. Transport of magma through connected sheet lobe cores, acting as internal flow pathways to reach the flow front, is interpreted as the method of lava transport. Additionally, this can explain the general paucity of lava tubes within flood basalt provinces. In general, flow field development by a network of lava lobes may account for the occurrence of compositionally similar glasses noted at the proximal and distal ends of some flood basalt lavas.

Abstract DOWNFLOW is a probabilistic code for the simulation of the area covered by lava flows. This code has been used extensively for several basaltic volcanoes in the last decade, and a review of some applications is presented. DOWNFLOW is based on the simple principle that a lava flow tends to follow the steepest descent path downhill from the vent. DOWNFLOW computes the area possibly inundated by lava flows by deriving a number, N , of steepest descent paths, each path being calculated over a randomly perturbed topography. The perturbation is applied at each point of the topography, and ranges within the interval ±Δ h . N and Δ h are the two basic parameters of the code. The expected flow length is constrained by statistical weighting based on the past activity of the volcano. The strength of the code is that: (i) only limited volcanological knowledge is necessary to apply the code at a given volcano; (ii) there are only two (easily tunable) input parameters; and (iii) computational requirements are very low. However, DOWNFLOW does not provide the progression of the lava emplacement over time. The use of DOWNFLOW is ideal when a large number of simulations are necessary: for example, to compile maps for hazard and risk-assessment purposes.

Abstract Using two hypothetical effusive events in the Chaîne des Puys (Auvergne, France), we tested two geographical information systems (GISs) set up to allow loss assessment during an effusive crisis. The first was a local system that drew on all immediately available data for population, land use, communications, utility and building type. The second was an experimental add-on to the Global Disaster Alert and Coordination System (GDACS) global warning system maintained by the Joint Research Centre (JRC) that draws information from open-access global data. After defining lava-flow model source terms (vent location, effusion rate, lava chemistry, temperature, crystallinity and vesicularity), we ran all available lava-flow emplacement models to produce a projection for the likelihood of impact for all pixels within the GIS. Next, inundation maps and damage reports for impacted zones were produced, with those produced by both the local system and by GDACS being in good agreement. The exercise identified several shortcomings of the systems, but also indicated that the generation of a GDACS-type global response system for effusive crises that uses rapid-response model projections for lava inundation driven by real-time satellite hotspot detection – and open-access datasets – is within the current capabilities of the community.

Continental flood basalt provinces are the subaerial expression of large igneous province volcanism. The emplacement of a continental flood basalt is an exceptional volcanic event in the geological history of our planet with the potential to directly impact Earth's atmosphere and environment. Large igneous province volcanism appears to have occurred episodically every 10–30 m.y. through most of Earth history. Most continental flood basalt provinces appear to have formed within 1–3 m.y., and within this period, one or more pulses of great magma production and lava eruption took place. These pulses may have lasted from 1 m.y. to as little as a few hundred thousand years. Within these pulses, tens to hundreds of volumetrically large eruptions took place, each producing 10 3 –10 4 km 3 of predominantly p3hoehoe lava and releasing unprecedented amounts of volcanic gases and ash into the atmosphere. The majority of magmatic gas species released had the potential to alter climate and/or atmospheric composition, in particular during violent explosive phases at the eruptive vents when volcanic gases were lofted into the stratosphere. Aside from the direct release of magmatic gases, magma-sediment interactions featured in some continental flood basalt provinces could have released additional carbon, sulfur, and halogen-bearing species into the atmosphere. Despite their potential importance, given the different nature of the country rock associated with each continental flood basalt province, it is difficult to make generalizations about these emissions from one province to another. The coincidence of continental flood basalt volcanism with periods of major biotic change is well substantiated, but the actual mechanisms by which the volcanic gases might have perturbed the environment to this extent are currently not well understood, and have been little studied by means of atmospheric modeling. We summarize current, albeit rudimentary, knowledge of continental flood basalt eruption source and emplacement characteristics to define a set of eruption source parameters in terms of magmatic gases that could be used as inputs for Earth system modeling studies. We identify our limited knowledge of the number and length of non-eruptive phases (hiatuses) during continental flood basalt volcanism as a key unknown parameter critical for better constraining the severity and duration of any potential environmental effects caused by continental flood basalt eruptions.

Monogenetic volcanism is commonly represented by evolution of clusters of individual volcanoes. Whereas the eruption duration of an individual volcano of a volcanic field is generally short, the life of the entire volcanic field is longer than that of a composite volcano (e.g., stratovolcano). The magmatic output of an individual center in a volcanic field is 1–3 orders of magnitude less than that of a composite volcano, although the total field may be of the same volume as a composite volcano in any composition. These features suggest that the magma source feeding both monogenetic volcanic fields and composite volcanoes are in the same range. Monogenetic volcanic fields therefore are an important and enigmatic manifestation of magmatism at the Earth's surface. The long eruption duration for an entire volcanic field makes this type of volcanism important for understanding sedimentary basin evolution. Accumulated eruptive products may not be significant from a single volcano, but the collective field may contribute significant sediment to a basin. The eruptive history of volcanic fields may span millions of years, during which dramatic climatic and paleoenvironmental changes can take place. Through systematic study of individual volcanoes in a field, detailed paleoenvironmental reconstructions can be made as well as paleogeographic evaluations and erosion-rate estimates. Monogenetic volcanoes are typically considered to erupt only once and to be short-lived; recent studies, however, demonstrate that the general architecture of a monogenetic volcano can be very complex and exhibit longer eruption durations than expected. In this way, monogenetic volcanic fields should be viewed as a complex, long-lasting volcanism that in many respects carries the basic characteristics similar to those known from composite volcanoes.

The southern Tyrrhenian region represents a rare case of an active backarc basin where island-arc basalt (IAB)–type and ocean-island basalt (OIB)–type magmas coexist. IAB-type magmatism is the most common, whereas OIB-type magmas are restricted to a few areas. Geochemical and isotopic characteristics of southern Tyrrhenian submarine volcanic samples are summarized herein, with special attention to samples recovered during recent seafloor sampling. Samples derived from Marsili volcano, the biggest seamount in the Tyrrhenian Sea, together with those of the Prometeo submarine lava field and Palinuro seamount, give a comprehensive picture of the mantle sources of southern Tyrrhenian magmatism. Most of these samples are relatively high-magnesian basalts that approximate primary magma compositions, thus providing insight into petrogenesis of IAB- and OIB-type magmas of this area. Petrological data, integrated with new bathymetric data, allow the geodynamic evolution of the southern Tyrrhenian backarc basin to be reconstructed. We suggest that the transition from IAB- to OIB-type magmas recorded in the southern Tyrrhenian backarc basin is related to the propagation of asthenospheric mantle from beneath Africa around the edges of the Ionian slab. The data suggest that the inflow of asthenosphere from beneath Africa has been important since the early Neogene evolution of the southern Tyrrhenian region.