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Program

Sammendrag

Jordens undergang – et filosofisk perspektiv
v. Claus Strue Frederiksen (PhD, Philosophy Unit, Department of Media Cognition and Communication)

Ifølge en række rapporter – eksempelvis fra FN, Verdensnaturfonden og World Economic Forum – vil vi inden for overskuelig fremtid opleve en alvorlig klima- og ressourcekrise, hvis vi ikke ændrer vores nuværende levevis radikalt. Spørgsmålet er, hvordan vi bør forholde os til det. Har vi et ansvar for at søge at imødekomme fremtidige katastrofer og gøre verden til et bedre sted? Claus Strue Frederiksen præsenterer i sit oplæg forskellige filosofiske tilgange til, hvordan vi bør forholde os til dystre prognoser om jordens snarlige undergang.

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Meteoritfaldet i Ejby – og historien om hvordan Solsystemet blev til
v. Henning Haack (Lektor, Statens Naturhistoriske Museum)

Lørdag d. 6. februar 2016 kl. 22:07 blev den mørke nattehimmel over det østlige Danmark pludselig oplyst af en meget voldsom ildkugle. Et par minutter senere hørtes voldsomme overlydsbrag over Københavnsområdet og få minutter senere begyndte der er falde meteoritter over Københavns Vestegn. Det nye meteoritfald er Danmarkshistoriens 5. observerede fald og er samtidigt det suverænt største bevarede fald.

Det nye meteoritfald er ligesom Aarhus meteoritten fra 1951 og Mern meteoritten fra 1878 en almindelig kondrit. Som navnet antyder, er der tale om den mest almindelige type meteorit. Over 80% af de meteoritter, der falder er almindelige kondritter. Ligesom andre kondrit-typer består almindelige kondritter af støv og partikler, der dannedes i frit kredsløb omkring den Solen, lige efter den var tændt – men inden den var færdigdannet. Omkring den unge sol var der en roterende skive fuld af gas, støv og partikler. Det er materialet fra denne skive, der senere samlede sig sammen til de planeter vi kender i dag. Kondritterne består af dette byggemateriale. De har været en del af små asteroider, der kun har haft en begrænset geologisk aktivitet. Kondritterne har aldrig været opsmeltede og det originale materiale er derfor bevaret.

Kondritter, ligesom det nye danske fald, giver os derfor mulighed for at rekonstruere det tidlige Solsystems udvikling. Vi kan datere de enkelte komponenter i kondritterne og da vi samtidigt kan sige noget om de betingelser, de blev dannet under, kan kondritterne bruges til at rekonstruere de første få millioner år af Solsystemets udvikling fra det blev dannet og frem til det tidspunkt, hvor planeterne blev dannet. Spor efter kortlivede radioaktive isotoper i materialet kan samtidigt sige noget om hvilke typer stjerner, der leverede materiale til den sky, hvorfra vores Solsystem blev til.

Caution, glacier terminus ahead: jökulhlaups, surges and large calving events
v. Michele Citterio (seniorgeolog, GEUS)

This presentation will look into the impact that glacier processes can have downstream, with special focus on catastrophic events that endanger life and property and leave significant evidences in the landscape. Several examples from the last few centuries will be illustrated.

Climate-driven glacier terminus fluctuations take place over timeframes of decades and longer. If the amount and seasonality of glacier meltwater runoff available for farming and other activities change significantly, human activities and subsistence can be affected even beyond the mountain range. However, these fluctuations do not pose sudden threat to human life and property. Findings like the Ötzi mummy (ca. 5300 BP) in the Alps, artefacts from prehistoric reindeer hunting melting out from ice patches in Norway, as well as Norse and Eskimo west Greenland sites are witness of the long and close coexistence of man and glaciers . Documents exist of damage to local communities in historical times. During the Little Ice Age in the Alps, the loss of high altitude summer pasture land prompted letters and popular petitions to kings and bishops to summon the help of their authority and discipline an unruly local glacier – or at least gain some tax relief…

While most glaciers in the world do not directly endanger the communities living downstream, sudden and catastrophic glacial processes are a recurrent feature of some glaciers. Jökulhlaups in Iceland lead to infrastructure damage when large volumes of meltwater linked to subglacial geothermal activity are suddenly released, in a classic example of glacier outburst flood. Large volumes of water can also be stored in ice-contact lakes at the side or at the front of glaciers, and create destructive floods when suddenly released. The existence and stability of these lakes is controlled by the geometry and dynamics of the glacier, bedrock and moraines damming it. Several glacial lake outburst floods large and small are known in Greenland, the Himalayas and South American glaciers, and are well documented through historical sources and contemporary remote sensing methods. The physical processes triggering most of the outbursts are mostly understood, and in some cases even mitigating actions can be undertaken. There is however a class of wintertime glacial lake outburst floods observed at some glaciers in Greenland for which no clear trigger has been identified yet.

Another catastrophic process occurring where glacier margins and water bodies interact is calving, the release of glacier ice blocks in the form of icebergs that can then travel long distances under the influence of ocean currents and wind. Large calving events like the ones from some tidewater outlet glaciers from the Greenland ice sheet can release enough seismic energy to be detected at great distance. While icebergs are an obvious and well known danger to navigation, much smaller events from freshwater calving into ice-contact lakes can also be dangerous. Improvident bystanders have been swept away by waves caused by calving, and proglacial moraines damming the lake may be destabilized and trigger a glacier flood.

Glacier surges are another spectacular phenomenon very well represented in both East and West Greenland. Once called ‘galloping glaciers’, surge-type glaciers most often cluster in well-defined regions, like the Disko-Nuussuaq surge cluster and the Stauning Alps. During a surge, ice velocity increases by one or two orders of magnitude and the glacier terminus advance up to several kilometres. The surge is followed by a quiescent phase that can last up to decades or centuries for the larger glaciers. These extreme fluctuations are not directly driven by climate, and several processes have been described as possible triggers for the initiation of a surge, but predicting these events is still not possible. At least one case is known of a small human-induced glacier surge, as it recently took place at the Kumtor gold mine in Kyrgyzstan where it progressed to damage some of the mine’s own infrastructure.

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Extreme sea-level events in the Danish Wadden Sea: Sedimentological and morphological impacts caused by the Storegga tsunami and the 1634 AD storm.
v. Mikkel Fruergaard (postdoc, University of Caen Lower Normandy)

Extreme events in coastal environments are often triggered by major storms and tsunamis. The impacts of extreme events and associated coastal recovery often result in rapid erosion and sediment accumulation and cause widespread and large-scale redistribution of sediments in the coastal zone. Furthermore, impacts of extreme events in coastal areas potentially cause substantial economic damage and are often a great threat to life along the world’s coasts. Storms and tsunami can exert a very strong control on coastal geomorphology and on short-term evolution of the coastal environment. Immediate impact of extreme events in coastal environments often results in rapid and widespread coastal response. However, the importance of these high-energy events in long-term coastal evolution and how they affect the stability and resilience of coastal environments is not well-understood.

This presentation investigates the impact of the Storegga tsunami and the 1634 AD storm in the Danish Wadden Sea. The Storegga tsunami was triggered by an enormous submarine landslide at the Norwegian shelf about 8150 years ago. The slide initiated series of long-crested waves impacting coasts along the margins of the Norwegian Sea and the North Sea. The 1634 AD storm resulted from a deep low-pressure system passing the Wadden Sea during the night of the 11 and 12 October. The storm and storm surge are also known as the second Grote Mandrenke because of the many people that drowned during the storm.

Both events caused significantly elevated water levels along the affected coast and resulted in distinct sedimentological and morphological imprints preserved in the coastal sedimentary successions. In the presentation I show how the Wadden Sea coastline rapidly responded and recovered from the impacts of two events and how in particular major storms can substantially affect shoreline dynamics and long-term coastal evolution.

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Katastrofisme, asteroider, vulkanisme, massedød
v. Finn Surlyk (Professor emeritus, IGN)

Katastrofisme er en doktrin, der siger, at væsentlige ændringer i jordens historie var forårsaget af katastrofer snarere end gradvise evolutionære processer. Neo-katastrofisme er en moderne doktrin, der siger, at de gradvise evolutionære processer, der former jorden, var suppleret i jordens historie af virkningerne af enorme naturkatastrofer.

Cuvier (1769-1832) var i det tidlige 1800-tal en fremtrædende fortaler for katastrofisme – men dog ikke I bibelsk forstand. Han fastslog uddøen som et faktum.
Lyell (1797-1875) var sin tids fremmeste geolog. Han populariserede Hutton’s ideer om uniformitarianisme – den teori der siger, at jorden formedes af de samme processer og med samme hastigheder, som kendes i dag – ’the present is the key to the past’.

I halvandet århundrede er den geologiske verden blevet domineret, man kan nærmest sige hjernevasket af Lyells gradualistiske uniformitarianisme. Men: Den geologiske historie er som soldatens liv: ’long periods of boredom and short periods of terror’ (Ager, 1973).

I 1979 ved et symposium om Kridt-Tertiær (KT) grænsen ved Københavns Universitet præsenterede Walter Alvarez for første gang hypotesen om et ekstraterrestrisk nedslag som årsag til masseuddøen ved grænsen.

I 1980 blev hypotesen publiceret i Science i lidt ændret form af L. Alvarez, W. Alvarez, F. Asaro og H. Michel: Iridiumanomali, asteroidenedslag, megatsunamier, gigantiske submarine skred, støv, mørke, ingen fotosyntese, uddøen.

Luis Alvarez var nobelpristager i fysik og var direkte involveret i udviklingen af atombomben under 2. verdenskrig. Han var med på et ledsagefly B-29 (’The Great Artiste’) til ’Enola Gay’, der kastede ’Little Boy’ over Hiroshima. Han var en mand med sans for katastrofer!

Hypotesen blev anset som yderst kontroversiel og diskuteres stadig. Den er nok det fremmeste eksempel på katastrofisme i geologien. Asteroidekrateret, Chicxulub, ligger ved Yucatan Halvøen og er c. 180 km i diameter, svarende til asteroidens diameter på mindst 10 km. Energien ved nedslaget var en milliard gange Hiroshima-Nagasaki bomberne og 5 millioner gange større end brintbomben Tsar Bomba, den største menneskeskabte eksplosion.

De fleste masseuddøener er samtidige med enorme vulkanprovinser. Deccan vulkanprovinsen i Indien begyndte ca ¼ mill. år før KT grænsen og spænder aldersmæssigt hen over grænsen. Den er blevet anset som det vigtigste alternativ til asteroide-nedslagshypotesen til at forklare KT massedøden. Rent virkningsmæssigt er der ikke den store forskel på de to hypoteser – med undtagelse af asteroidehypotesens pludselighed.

For nyligt er det påvist, at én af lavaenhederne, Wai Supergruppen, har et enormt volumen og blev dannet på geologisk meget kort tid. Den dannedes umiddelbart efter Chicxulub nedslaget og udgør 70% af Deccan lavaerne. Wai lavaerne var genereret af en puls af ’mantle plume-head-derived’ magma, der havde meget ringe kontakt med den overliggende skorpe.

Det er muligt og endog sandsynligt, at nedslaget var den direkte årsag til Wai udbruddene (Richards, Alvarez et al., GSA Bull. April 2015)!!
Deccan vulkanismen påvirkede klimaet og svækkede de globale økosystemer i slutningen af Kridt-tiden og forårsagede faser af uddøen i mange organismegrupper. Chicxulub-asteroidens nedslag var det endelige ’coup-de-grace’, der resulterede i massedødens abrupthed. Derved adskiller KT-døden sig markant fra de øvrige ’big five’ masseuddøener.

Stevns Klint blev i juni 2014 optaget på UNESCOs verdensarvsliste som et af de mest illustrative eksempler på masseuddøen i jordens historie, hvor op mod halvdelen af alle arter uddøde. Klintens lagserie er således et eksempel på omfattende ændringer forårsaget af et asteroide nedslag som indtil 2014 ikke fandtes i Verdensarvslisten. Valget var baseret på en kombination af blotningens kvalitet, fossil diversitet, og videnskabelig betydning (’impact’) som det fremgår af et sammenlignende studie af 500 KT lokaliteter verden over.

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Når naturkatastrofer møder sårbare samfund
v. Sara Edith Hoffritz (geolog, DGE)

Vulkaner påvirker udviklingslande i langt højere grad end industrilande af diverse omstændigheder, der både berører de geografiske forhold og formidlingsmulighederne i lokal samfund. Vulkaner tilfører frugtbar jord, som er yderst fordelagtig at beplante afgrøder i og drive kvæg på, og dette resulterer ofte i mange beboelser tæt omkring vulkaner. Det kan være svært at forstå, at en vulkan der ikke har rumlet i flere menneskealdre pludselig skulle udgøre en fare for ens hjem, kvæg, afgrøder og liv.

Risikovurderinger, nøje observation med vulkanens aktivitet og formidling af farer til lokal befolkning er nogen af de midler, der tages i brug for at forhindre store naturkatastrofers indflydelse på menneskeliv. Vulkaners opførsel er dog yderst variabel og fastlagte risikozoner er derfor ikke holdbare. Hvor langt bør man evakuere mennesker og hvordan evakuerer man større befolkningsmængder med kort varsel?

Går vi tilbage i historien er der mange betydningsfulde vulkanudbrud, som vi kan lære meget af og i dag sætter aktive vulkaner stadig deres præg på både lokal, regional og somme tider verdens skala. Feltarbejde verden rundt på vulkaner vil give et indblik i de historiske katastrofer og hvad vi gør i dag for at forhindre lignende katastrofer.

I 1783 blev vulkansk aktivitet og klima for første gang rigtigt koblet sammen, da den islandske Laki vulkan udsendte store mængder gasser ud, som resulterede i at 75 % af Islands afgrøder og kvæg døde bort og med fatal konsekvens for 25 % af den islandske befolkning. Udbruddet satte dog også sit mærke verden over med den koldeste sommer i 400 år. Ambrym vulkanen med sine to lavasøer i Vanuatu øriget er en af nutidens vulkaner, der emitterer flest gasser på verdensplan. Gasserne (CO2, SO2 og HF) danner syreregn, som ødelægger afgrøder, dominerer drikkevandet på øen og indbyggernes helbred i al almindelighed.

Gasserne er dog ikke det eneste vulkanske produkt, der skaber problemer. Volcán de Colima i Mexico har hyppigt pyroklastiske strømme drønende ned af vulkanens flanker, og intet mindre end 300.000 mennesker er bosiddende indenfor 40 km’s radius til vulkanen. De her pyroklastiske strømme kan nå temperaturer helt op til 1000 grader og hastigheder op til 700 km/t.
Andre konsekvenser af vulkanske udbrud, som også har taget mange liv er tsunamier, som eksempelvis Krakatoa udbruddet resulterede i i 1883, eller mudderstrømme (lahars) som blev dannet ved Nevado del Ruiz udbruddet små 100 år senere.
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Subsurface sediment remobilisation: fast and large-scale reorganising geology
v. Katrine Juul Andresen,  Department of Geoscience, Aarhus University

Subsurface sediment remobilisation is a relatively fast geological process capable of generating both small-scale structures known from cores and outcrops and large‐scale structures such as sand injectites and mud volcanoes visible in seismic data. The process involves mobilisation, transport and re‐settling of sometimes very large sediment volumes and can directly influence human life if the remobilised sediment reaches the land surface.

The critical factor for subsurface remobilisation is build‐up of excess fluid pressure and fluidization of a sealed source sediment. Fluidization and excess pore fluid pressure may arise from several processes including deposition‐related processes such as differential loading and disequilibrium compaction, migration of oil and gas, seismicity‐induced liquefaction, and tectonic stress. Following seal failure, the source sediment will be remobilised in order to obtain a new equilibrium state.

This remobilisation results in the formation of the very fascinating geological structures related to large‐scale sand injectites and mud volcanoes. The two types of structures have shown to be of critical importance for oil and gas exploration and for addressing the essential question related to how much natural leakage of hydrocarbons contribute to global warming. The talk will show several examples of sand injectites and mud volcanoes from around the world including the Danish North Sea.

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Hydraulic fracturing – Unlocking Danish North Sea chalks
v. Mike Mulrooney (Stimulation Team Leader, Maersk Oil & Gas Denmark)

In all but one Danish North Sea field operated by Maersk Oil, carbonate reservoirs consisting of chalks and limestones have been successfully produced since the early 1970’s and drove the global evolution of horizontal wells and well stimulation techniques in the 1980’s, 90’s and into the 2000’s.

This evolution has seen a variety of well architecture and stimulation techniques deployed on various fields, resulting in the economic production of Danish North Sea Chalks that were previously thought to be too challenging and marginal to sustain meaningful oil and gas production.

Some of the first economic production from Danish chalk reservoirs came from drilling long horizontal wells through the producing intervals.  Long wells have not proven to be enough however, and this has posed a challenge to engineers and geologists to understand the producing reservoirs, and how these reservoirs’ production can be stimulated to economic levels.

This talk will give a brief understanding of the reservoir types and inherent production challenges, as well as an overview of the stimulation techniques employed.  Focusing mainly on Hydraulic Fracturing stimulation techniques including Acid Fracturing and Proppant fracturing, we will discuss what fracturing is, where and why it is deployed, and more importantly, what it is not.

Though technically complicated as an entire process, incorporating geology, geomechanics, reservoir engineering, chemistry, hydraulics, surface equipment operations, the general principles can be explained quite easily.  This talk will attempt to come to a balance between technical and general.

As the Danish oil fields age, and new target reservoirs become more and more marginal, new, faster and more economical fracturing methods are needed.  An overview of where we started and where we are moving with respect to technology and methods will be discussed.

Hydraulic fracturing or “Fracking” has had a global history of over 100 years, and was introduced in Denmark both onshore and offshore as early as the 1960’s, but began to become commonplace offshore in the 1990’s.  Recent increases in onshore shale-gas fracturing activity in the USA and in Continental Europe have increased visibility of the environmental impact of not only fracturing, but oil and gas drilling in general.

This talk will touch on the cooperation that operators such as Maersk Oil have had and continue to have with the Danish Energy Agency (DEA) ant the Danish Environmental Protection Agency (DEPA) to regulate the drilling and completion process, chemical usage, and discharge of produced fluids.  A brief introduction to the chemicals used, and the regulatory processes in place will be given.

Time permitting; there will be an opportunity for questions and answers.

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Posterabstracts

Der var ingen posterer til årsmødet 2016