1. Wochenbericht M80/3

FS Meteor Reise M80/3 (Dakar, Senegal – Gran Canaria, Spanien) 1. Wochenbericht, 27. Dezember 2009 bis 3. Januar, 201

4. Wochenbericht M80/3

FS Meteor Reise M80/3 (Dakar, Senegal – Gran Canaria, Spanien) 4. Wochenbericht, 18. bis 24. Januar 201

3. Wochenbericht M80/3

FS Meteor Reise M80/3 (Dakar, Senegal – Gran Canaria, Spanien) 3. Wochenbericht, 11. bis 17. Januar 201

Synchronous degassing patterns of the neighbouring volcanoes Llaima and Villarrica in south-central Chile: the influence of tidal forces

The neighbouring volcanoes Villarrica and Llaima are two of the most active volcanoes in Chile and both currently degas continuously. We present a semi-continuous time series of SO2 fluxes for Villarrica and Llaima volcanoes. The time series was obtained using five scanning Mini-Differential Optical Absorption Spectrometers (Mini-DOAS, UV spectrometers) over 6 months (13 February to 31 July 2010) and is based on 6,829 scans for Villarrica and 7,165 scans for Llaima. Statistical analyses of the SO2 flux time series reveal a periodicity of degassing maxima about every 7 days, and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes. Intra-day variations in SO2 fluxes also show a striking correlation between Villarrica and Llaima. All these patterns correlate well with the trend of the modelled solid Earth tide curves, where the 7-day degassing maxima correspond with both the fortnightly tidal maxima and minima. The intra-day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle, and further with semidiurnal minima in atmospheric pressure, a phenomenon we refer to as “the tidal pump”. As there is little time lag between the tidal action and the changes in degassing rates, we infer that degassing at both volcanoes is controlled by conduit convection, involving physical separation between gas and magma at comparatively shallow levels. Variations in daily degassing rates were up to a factor of ca. 12 and 10 for Villarrica and Llaima, respectively, without any noticeable changes in the periodicity. We thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation

Cruise Report Poseidon Cruise POS270 : Exploring and sampling submarine volcanoes and collapse deposits off the western Canary Islands (El Hierro and La Palma), 02.03. - 15.03.2001, Las Palmas de Gran Canaria - Las Palmas de Gran Canaria

Project: "Beprobung und Untersuchung von submarinen Vulkaniten und Kollapsablagerungen im Bereich der westlichen Kanaren" (DFG: Ha 2100/6-1, Kl 1313/3-1

The Boson peak in supercooled water

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line $T_W$. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.Comment: 25 pages, 9 figure

Naticid Gastropod Prey Selectivity Through Time and the Hypothesis of Escalation

The hypothesis of escalation posits that biologic hazards such as predation have increased during the Phanerozoic. Previously, a survey of drilling frequencies in the Cretaceous and Paleogene of the North American Coastal Plain suggested an episodic pattern of escalation within the naticid gastropod predator-prey system. This study examines escalation from the perspective of naticid prey selectivity. If escalation occurred within the system, less selectivity of prey may be apparent in the Paleogene compared to younger assemblages. We test this hypothesis for four Eocene Coastal Plain assemblages. Contrary to predictions, intraspecific prey size selectivity was well developed for nine of eleven bivalve prey species. Drillhole size (indicating predator size) correlated significantly with prey size, especially for successful drillholes. Few incomplete or nonfunctional drillholes occurred, except within corbulid species. Interspecific prey selectivity was less developed than for Neogene or Recent assemblages. Naticid prey preferences predicted by cost-benefit analysis were consistent with actual drilling frequencies only for the Bashi Marl Member of the Hatchetigbee Formation (Alabama). In the Piney Point Formation of Virginia, all prey items were drilled at equivalent frequencies, despite their different cost-benefit rankings. Upper Lisbon (Alabama) and Moodys Branch (Mississippi and Louisiana) assemblages showed limited agreement with preferences predicted by cost-benefit analysis. Prey selectivity thus appears less developed in the Paleogene compared to the Neogene and Recent, in accordance with the hypothesis of escalation

Evolution of the Naticid Gastropod Predator-Prey System: An Evaluation of the Hypothesis of Escalation

Previous work has suggested that escalation may have characterized the history of the naticid gastropod predator-prey system, based on apparent increases in drilling frequencies and the occurrence of antipredatory aptations among prey. We evaluate this hypothesis based on a comprehensive survey (over 40,000 specimens) of predation on molluscs from the Upper Cretaceous through lower Oligocene formations within the U.S. Gulf and Atlantic Coastal Plain. Patterns in drilling of both bivalve and gastropod prey are complex. Drilling frequencies were relatively low in the Cretaceous but increased sharply above the Cretaceous-Tertiary boundary, remaining high until the late Eocene. Following a significant decline near the Eocene-Oligocene boundary, drilling frequencies increased to a moderate level in the Oligocene. Contrary to our prediction based on the hypothesis of escalation, no temporal trend of increasing stereotypy of drillhole site occurred. However, significant increases in prey effectiveness (indicated by the incidence of incomplete drillholes and multiply bored shells) occurred between the Cretaceous and Oligocene. This pattern characterizes entire faunas as well as individual prey taxa that were consistently heavily drilled (turritellid gastropods and corbulid bivalves)

Spatial Variation of Naticid Gastropod Predation in the Eocene of North-America

Although, the fossil record of naticid gastropod drilling has played an important role in the controversy over predator-prey evolution, little is known about variation of drilling frequencies within single horizons or how predation patterns are influenced by environmental variables. Without an understanding of spatial variation in drilling, temporal patterns in drilling are difficult to interpret. We surveyed 27,554 specimens of molluscs from the Cook Mountain interval (upper middle Eocene) and Jackson Group (late Eocene) of the U.S. Gulf and Atlantic Coastal Plain to document spatial variation in naticid drilling frequencies. The Jackson Group assemblages from the Moodys Branch and Yazoo formations were sampled along a depth gradient in order to compare drilling frequencies to environmental variables within a single climatic zone. There was a statistically significant difference between drilling frequency of the inner to middle shelf Moodys Branch Formation (mean = 8.3%) and the outer shelf Yazoo Formation (mean = 21.2%; chi square = 49.58, P ≪ 0.001), but there was no significant bathymetric trend in drilling frequencies among the five assemblages of the Moodys Branch. Drilling frequency was not related to substrate type within the Moodys Branch. Drilling, however, was correlated with species diversity of Moodys Branch assemblages (r = 0.50, P \u3c 0.01). Drilling frequency was significantly correlated with the percentage of naticids in each assemblage (r = 0.77, P \u3c 0.001) and the percentage of certain prey species of the bivalve families Lucinidae and Corbulidae, and the gastropod families Turritellidae and Hipponicidae (r = 0.80, P \u3c 0.001). These preferred species represented 40% of the naticid victims, but only 16% of the assemblages. Cook Mountain assemblages represented marine inner to middle shelf environments from Virginia, Alabama, Louisiana, and Texas. Naticid drilling frequencies of the entire molluscan fauna ranged from 6.8-38.7% with a mean of 22%. In the Cook Mountain, three preferred species (of the families Turritellidae, Lucinidae, and Noetiidae), representing 24% of the total individuals, accounted for 44% of the drilled individuals. As in the Moodys Branch Formation, Cook Mountain assemblages showed a significant correlation between relative abundance of preferred species and drilling frequency of samples (r = 0.585, P \u3c 0.05). The dependence of naticid drilling on the availability of preferred prey species indicates a possible behavioral inflexibility in naticid predation patterns. The Virginia Cook Mountain fauna exhibited significantly greater drilling frequencies (mean = 30.3%, n = 4 samples) than did the Gulf Coast assemblages (mean = 18.0%, n = 11 samples; Mann-Whitney U-test, P \u3c 0.01). This result is consistent with a trend found by some previous workers of an equatorward decrease in naticid drilling