Complex pockmarks with carbonate-ridges off mid-Norway: Products of sediment degassing

Hovland, Martin; Svensen, Henrik; Forsberg, Carl Fredrik; Johansen, H.; Fichler, Christine; Fosså, Jan Helge; Jonsson, René; Rueslåtten, Håkon

doi:10.1016/j.margeo.2005.04.005

Cited by 189 publications

(161 citation statements)

References 30 publications

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“…Pockmarks off Norway are accompanied by authigenic carbonate deposits associated with anerobic oxidation of methane (Hovland et al, 2005). Pockmarks range in size from meters to kilometers (Hovland et al, 2005), with one 700 km 2 example on the Blake Ridge (Kvenvolden, 1999).…”

Section: Pockmarksmentioning

confidence: 99%

“…It generated a tsunami in what is now the United Kingdom (Smith et al, 2004). The Storegga slide area contains methane hydrate deposits as indicated by a seismic BSR (Bunz and Mienert, 2004;Mienert et al, 2005;Zillmer et al, 2005a, b) corresponding to the base of the hydrate stability zone at 200-300 m, and pockmarks (Hovland et al, 2005) indicating gas expulsion from the sediment.…”

Section: Observationsmentioning

confidence: 99%

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Methane hydrate stability and anthropogenic climate change

2007

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Abstract. Methane frozen into hydrate makes up a large reservoir of potentially volatile carbon below the sea floor and associated with permafrost soils. This reservoir intuitively seems precarious, because hydrate ice floats in water, and melts at Earth surface conditions. The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth's radiation budget equivalent to a factor of 10 increase in atmospheric CO 2 .Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.The potential climate impact in the coming century from hydrate methane release is speculative but could be comparable to climate feedbacks from the terrestrial biosphere and from peat, significant but not catastrophic. On geologic timescales, it is conceivable that hydrates could release as much carbon to the atmosphere/ocean system as we do by fossil fuel combustion.

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Section: Pockmarksmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

Methane hydrate stability and anthropogenic climate change

2007

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“…Gas hydrates have originally been inferred from the Nyegga area on the basis of bottom-simulating reflections (BSRs) [47][48][49] as well as seabed topography and biology [50,51]. Physical sampling of shallow gas hydrates was first reported in 2006 [52], though the Nyegga gas hydrates have long been studied "geophysically" [53][54][55].…”

Section: Figmentioning

confidence: 99%

First-Order Estimation of In-Place Gas Resources at the Nyegga Gas Hydrate Prospect, Norwegian Sea

2010

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Gas hydrates have lately received increased attention as a potential future energy source, which is not surprising given their global and widespread occurrence. This article presents an integrated study of the Nyegga site offshore mid-Norway, where a gas hydrate prospect is defined on the basis of a multitude of geophysical models and one shallow geotechnical borehole. This prospect appears to hold around 625 GSm 3 (GSm 3 = 10 9 standard cubic metres) of gas. The uncertainty related to the input parameters is dealt with through a stochastic calculation, giving a spread of in-place volumes of 183 GSm 3 (P90) to 1431 GSm 3 (P10). The resource density for Nyegga is found to be comparable to published resource assessments of other global hydrate provinces.

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“…Further evidence of degassing processes in the Nyegga complex pockmark (G11) comes in the form of authigenic carbonate crusts (Hovland et al 2005;Mazzini et al 2006). Geochemical and petrological investigations of crust samples indicate precipitation of methane-derived aragonite.…”

Section: Introductionmentioning

confidence: 99%

Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

Mienert

Vanneste

Haflidason

et al. 2010

Int J Earth Sci (Geol Rundsch)

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A series of en echelon cracks run nearly parallel to the outer shelf edge of the mid-Norwegian margin. The features can be followed in a *60-km-long and *5-km-wide zone in which up to 10-m-deep cracks developed in the seabed at 400-550 m water depth. The time of the seabed cracking has been dated to 7350 14 C years BP (8180 cal years BP), which corresponds with the main Storegga Slide event (8100 ± 250 cal. years BP). Reflection seismic data suggest that the cracks do not appear to result from deep-seated faults, but it cannot be ruled out completely that tension crevices were created in relation to past movements on the headwall of the Storegga slide. The cracking zone corresponds well to the zone where the base of the hydrate stability zone (BHSZ) outcrops. Evidence of fluid release in the BHSZ outcrop zone comes from an extensive pockmark field. We suggest that post-glacial ocean warming triggered the dissociation of gas hydrates while the interplay between dissociation, overpressure, and sediment fracturing on the outer shelf remains to be understood.

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Complex pockmarks with carbonate-ridges off mid-Norway: Products of sediment degassing

Cited by 189 publications

References 30 publications

Methane hydrate stability and anthropogenic climate change

Methane hydrate stability and anthropogenic climate change

First-Order Estimation of In-Place Gas Resources at the Nyegga Gas Hydrate Prospect, Norwegian Sea

Norwegian margin outer shelf cracking: a consequence of climate-induced gas hydrate dissociation?

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