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- Sohn, Robert A., et al.
(författare)
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Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean
- 2008
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 453:7199, s. 1236-1238
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Tidskriftsartikel (refereegranskat)abstract
- Roughly 60% of the Earth's outer surface is composed of oceanic crust formed by volcanic processes at mid-ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid-ocean ridges, particularly at depths below the critical point for seawater (3,000 m)1. A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid-ocean-ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 85° E, to acquire photographic and video images of 'zero-age' volcanic terrain on this remote, ice-covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele)2, covering a large (>10 km2) area. At least 13.5 wt% CO2 is necessary to fragment magma at these depths3, which is about tenfold the highest values previously measured in a mid-ocean-ridge basalt4. These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge5 and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global mid-ocean ridge volcanic system.
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3. |
- Sircova, Anna, et al.
(författare)
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A global look at time : a 24-country study of the equivalence of the Zimbardo Time Perspective Inventory
- 2014
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Ingår i: SAGE Open. - : SAGE Publications. - 2158-2440. ; :4, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we assess the structural equivalence of the Zimbardo Time Perspective Inventory (ZTPI) across 26 samples from 24 countries (N = 12,200). The ZTPI is proven to be a valid and reliable index of individual differences in time perspective across five temporal categories: Past Negative, Past Positive, Present Fatalistic, Present Hedonistic, and Future. We obtained evidence for invariance of 36 items (out of 56) and also the five-factor structure of ZTPI across 23 countries. The short ZTPI scales are reliable for country-level analysis, whereas we recommend the use of the full scales for individual-level analysis. The short version of ZTPI will further promote integration of research in the time perspective domain in relation to many different psycho-social processes.
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