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Explosion deep seismic sounding data sections of high quality had been obtained with RV Meteor in the Reykjanes Iceland Seismic Project (RRISP77 [Angenheister, G., Gebrande, H., Miller, H., Goldflam, P., Weigel, W., Jacoby, W.R., Palmason, G., Bjornsson, S., Einarsson, P., Pavlenkova, N.I., Zverev, S., Litvinenko, I.V., Loncarecic, B., Solomon, S., 1980. Reykjanes Ridge Iceland Seismic Experiment (RRISP 77). J. Geophys. 47, 228–238]) which close an information gap near 62°N. Preliminary results were presented by Weigel [Weigel, W., 1980. Aufbau des Reykjanes Ruckens nach refraktionsseismischen Messungen. In: Weigel, W. (Ed.), Reykjanes Rucken, Island, Norwegischer Kontinentalrand. Abschlusskolloquium, Hamburg zur Meteor-Expedition, vol. 45. DFG, Bonn, pp. 53–61], and here we report on the data and results of interpretation. Clear refracted phases to 90 km distance permit crustal and uppermost mantle structure to be modelled by ray tracing. The apparent P-wave velocities are around 4.5, 6–6.5, 7–7.6 and 8.2–8.7 km/s, but no wide-angle reflections have been clearly seen. Accompanying sparker reflection data reveal thin sediment ponds in the axial zone and up to 400 m thick sediments at 10 Ma crustal age. Ray tracing reveals the following model below the sediments: (1) a distinct, 1–2 km thick upper crust (layer 2A) with Vp increasing with age (to 10 Ma) from

An increasing data set exists on the nature and thickness of the Iceland crust. This paper relates topography, i.e., elevation and bathymetry (TOP), Bouguer gravity anomalies (BA) and Moho depths to each other to assess the consequences of the “thick crust model” for Iceland in the context of the North Atlantic. Results of regression of TOP and BA vs. Moho depth are converted into “Airy densities” Δρ* (mantle crust density contrasts in the case of ideal Airy isostasy). For Iceland, Δρ* is very low (105±10 kg/m3); for the adjacent continental margins and relicts, it is high and intermediate for the Jan Mayen Ridge. The values are affected by lithosphere cooling and systematic variations of internal crustal structure, and reductions for these effects are applied. For Iceland, the thermal reduction leads to slightly enhanced value of Δρ* (112±8 kg/m3), thus part of the observed topography is due to the cooling effect, while the upper crust reduction reduces the value, implying that part of topography is compensated by internal crustal structure. With both reductions combined, Δρ* is 103±10 kg/m3. The differences between gravity- and topography-derived values are compatible with undulation widths similar to Moho depths (half-wavelengths of order 30 km). Regional variations of Δρ* values in Iceland suggest differences in crustal generation and evolution. “Modern” Iceland (MI; surface lava ages ≤3.1 Ma) produced from the currently active and recent axes is remarkably homogeneous while the extinct Skagi–Snaefellsnes zone has extremely low values and the older Westfjords and East Iceland regions have slightly enhanced values. The Iceland–Faeroe Ridge (IFR) resembles Iceland (after thermal reduction) while the Greenland–Iceland Ridge has extremely high values. The Iceland “Moho” and the Iceland “lower crust” are special features of ridge–plume interaction and differ from continental Moho and lower crust. Lower crust, only 100 kg/m3 less dense than uppermost mantle, is assumed to be a plume-generated transitional layer which, directly above the plume centre, belongs rheologically to the asthenosphere. The regionalized regression results are used to construct a new Moho depth map from the gridded topography file. It compares reasonably to other recent maps. A notable feature is a band of crustal thickening along the SE Iceland shelf edge continuing northward across eastern Iceland to the Jan Mayen Ridge. This and other features suggest an evolution of the North Atlantic where a continental edge splinter carried into eastern and perhaps northern parts of Iceland, beside the Jan Mayen Ridge.

Objectives To determine whether high-dose fish oil is superior to low-dose supplementation for symptomatic and structural outcomes in knee osteoarthritis (OA). Methods A randomised, double-blind, multicentre trial enrolled 202 patients with knee OA and regular knee pain. They were randomised 1:1 to high-dose fish oil (4.5 g omega-3 fatty acids) 15 mL/day or (2) low-dose fish oil (blend of fish oil and sunola oil; ratio of 1:9, 0.45 g omega-3 fatty acids) 15 mL/day. The primary endpoints were Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain score at 3, 6, 12 and 24 months, and change in cartilage volume at 24 months. Secondary outcomes included WOMAC function, quality of life, analgesic and non-steroidal anti-inflammatory drug use and bone marrow lesion score. Results Although there was improvement in both groups, the low-dose fish oil group had greater improvement in WOMAC pain and function scores at 2 years compared with the high-dose group, whereas between-group differences at 1 year did not reach statistical significance. There was no difference between the two groups in cartilage volume loss at 2 years. For other secondary endpoints, there was no difference between the two groups at 2 years. Conclusions In people with symptomatic knee OA, there was no additional benefit of a high-dose fish oil compared with low-dose fish oil. The combination comparator oil appeared to have better efficacy in reducing pain at 2 years, suggesting that this requires further investigation. Trial registration number Australian New Zealand Clinical Trials Registry (ACTRN 12607000415404).