Field data, numerical simulations and probability analyses to assess lava flow hazards at Mount Etna

Improving lava flow hazard assessment is one of the most important and challenging fields of volcanology, and has an immediate and practical impact on society. Here, we present a methodology for the quantitative assessment of lava flow hazards based on a combination of field data, numerical simulations and probability analyses. With the extensive data available on historic eruptions of Mt. Etna, going back over 2000 years, it has been possible to construct two hazard maps, one for flank and the other for summit eruptions, allowing a quantitative analysis of the most likely future courses of lava flows. The effective use of hazard maps of Etna may help in minimizing the damage from volcanic eruptions through correct land use in densely urbanized area with a population of almost one million people. Although this study was conducted on Mt. Etna, the approach used is designed to be applicable to other volcanic areas.

Magnetic and petrographic properties of ODP Site 120-747 (Table 1)

Carbonate sediments from the Kerguelen Plateau (ODP Leg 120) of Eocene to Pliocene age were investigated with rock magnetic, petrographic and geochemical methods to determine the carriers of remanent magnetization. Magnetic methods showed that the major magnetic minerals were titanomagnetites slightly larger than single domain particles. Submicrometre to micrometre-size grains of titanomagnetite were identified as inclusions in volcanic glass particles or as crystals in lithic clasts. Volcanic fallout ash particles formed the major fraction of the magnetic extract from each sediment sample. Three groups of volcanic ashes were identified: trachytic ashes, basaltic ashes with sideromelane and tachylite shards, and palagonitic ashes. These three groups could be equally well defined based on their magnetic hysteresis properties and alternating field demagnetization curves. The highest coercivities of all samples were found for the tachylite, due to the submicrometre-size titanomagnetite inclusions in the matrix. Trachytic ashes had intermediate magnetic properties between the single-domain-type tachylites and the palagonitic (altered) basaltic ashes with low coercivities. Samples which contained mixtures of these different volcanic ashes could be distinguished from the three types of ashes based on their magnetic characteristics. There was neither evidence of biogenic magnetofossils in the transmission electron micrographs nor did we find magnetic particles derived from continental Antarctica. The presence of dispersed volcanic fallout ashes between visible ash layers suggests continuous explosive volcanic activity on the Kerguelen Plateau in the South Indian Ocean since the early Eocene. The continuous fallout of volcanic ash from explosive volcanism on the Kerguelen Archipelago is the source of the magnetic particles and thus responsible for the magnetostratigraphy of the nannofossil oozes drilled during Leg 120.

(Table T2) Rock magnetic parameters of ODP Leg 180 sites

Rock magnetic measurements were performed on sediments above 20 meters below seafloor (mbsf) (general) and above 2.5 mbsf (detailed) at Sites 1109, 1110, and 1115 (Ocean Drilling Program Leg 180) in the western Woodlark Basin. Rock magnetic parameters imply the presence of magnetite as a principal magnetic mineral in the sediments. The hysteresis ratios lay in the pseudo-single domain field and generally showed the trend close to that for the mixture of single domain and multidomain magnetite The sediments in the oxidized zones at the top at Sites 1109 and 1115 provided a different trend in the logarithmic plot of the hysteresis ratios, and the oxidized samples were characterized by higher coercivity.

Conventional and 40Ar/39Ar K-Ar ages of volcanic rocks at DSDP Leg 55 Holes

Conventional K-Ar, 40Ar/39Ar total fusion, and 40Ar/39Ar incremental heating data on hawaiite and tholeiitic basalt samples from Ojin (Site 430), alkalic basalt samples from Nintoku (Site 432), and alkalic and tholeiitic basalt samples from Suiko (Site 433) seamounts in the Emperor Seamount chain give the following best ages for these volcanoes: Ojin = 55.2 ± 0.7 m.y., Nintoku = 56.2 ± 0.6 m.y., and Suiko = 64.7 ± 1.1 m.y. These new data bring to 27 the number of dated volcanoes in the Hawaiian-Emperor volcanic chain. The new dates prove that the age progression from Kilauea Volcano on Hawaii (0 m.y.) through the Hawaiian-Emperor bend (- 43 m.y.) to Koko Seamount (48.1 m.y.) in the southernmost Emperor Seamounts continues more than halfway up the Emperor chain to Suiko Seamount. The age versus distance data for the Hawaiian-Emperor chain are consistent with the kinematic hot-spot hypothesis, which predicts that the volcanoes are progressively older west and north away from the active volcanoes of Kilauea and Mauna Loa. The data are consistent with an average volcanic propagation velocity of either 8 cm/year from Suiko to Kilauea or of 6 cm/year from Suiko to Midway followed by a velocity of 9 cm/year from Midway to Kilauea, but it appears that the change in direction that formed the Hawaiian- Emperor bend probably was not accompanied by a major change in velocity.

Geochemical investigations of sediment profiles in the Norwegian-Greenland Sea

High-, i.e. 15-140-yr-resolution climate records from sediment cores 23071, 23074, and PS2644 from the Nordic Seas were used to recon:;truct changes in the surface and deep water circulation during marine isotope stages 1-5.1, i.e. the last 82 000 yr. From this the causal links between the paleoceanographic signals and the Dansgaard-Oeschger events 1-21 revealed in 0180-ice-core records from Greenland were determined. The stratigraphy of the cores is based on the planktic 0180 curves, the minima of which were directly correlated with the GISP2-0180 record, numerous AMS 14C ages, and some ash layers. The planktic d18O and dl3C curves of all three cores reveal numerous meltwater events, the most pronounced of which were assigned to the Heinrich events 1-6. The meltwater events, among other things also accompanied by cold sea surface temperatures and high IRD concentration, correlate with the stadial phases of the Dansgaard-Oeschger cycles and in the western Iceland Sea also to colder periods or abrupt drops in 0180 within a few longer interstadials. Besides being more numerous, the meltwater events also show isotope values lighter in the Iceland Sea than in the central Norwegian Sea, especially if compared to core 23071. This implies a continuous inflow of relative warm Atlantic water into the Norwegian Sea and a cyclonic circulation regime.

Oxygen isotope ratios amd Li concentrations in spilitized basaltic rocks of DSDP Hole 83-504B (Table 5)

Li-delta18O-SiO2 relationships have been examined for suites of spilitized basaltic rocks (DSDP 504B; Xigaze Ophiolite; Blanco Fracture Zone; Greater Caucasus; Rhenohercynian Fold Belt) and intra-plate evolved tholeiites (Northern Hessian Depression and Vogelsberg, W Germany; Mount Falla, Transantarctic Mountains). Relative to unaltered MORB and intra-plate primary olivine tholeiites, both the spilitic rocks and the evolved tholeiites are characterized by Li and 18O enrichment. For the spilitic rocks, Li and 18O enrichment is accompanied by a loss of SiO2 as a result of seawater hydrothermal alteration, whereas the evolved tholeiites have gained SiO2, Li and 18O from fractionation of mafic phases and assimilation of crustal rocks. On Li vs. SiO2 and delta18O vs. SiO2 diagrams, the two rock groups plot largely in distinct fields, suggesting the possibility of so distinguishing between such lithologies in the ancient rock record. Mafic granulite xenoliths from the Northern Hessian Depression have elevated Li and 18O abundances at low SiO2 contents. Even after correction for extraction of felsic components, their Li-delta18O-SiO2 signatures plot within the field of spilitic protoliths, suggesting that the lower crust in this region contains relics of spilitic rocks from a former oceanic crust.