ijsland excursie ppt

IJsland

Minniborg

Zwavel-fumarolen

Reykjanes HörgslandCottages

Reykjavik

BlueLagoon

Lunch, lezing Geologie

MidAtlantischeRug

KeridKerid

Thingvellir

Geysir GulfossSkjaldbreidur

Skogafoss

Eyjafjallajokull

Basaltkust & Myrdaljokull

Vik

Skaftafell

Jokulsarlon

Dag 6 vertrek

Dag 1

Dag 2

Dag 3

Dag 4

Dag 5

GEOLOGIE ALGEMEEN

Fig. 0.3. “Iceland is an elevated plateau in the middle of the North Atlantic, situated at the junction between theReykjanes and Kolbeinsey Ridge segments. Also shown: the axis of the Mid-Atlantic Ridge (heavy solid line), theNorth Atlantic basalt plateau (black) and their submarine equivalents (dark grey). The line with the dots shows theposition of the Iceland mantle plume from 65 million years to the present day.” (Thordarson and Larsen, 2007)

Figure 2.SeismicimageoftheuppermantlebeneaththeIcelandhotspot(Wolfeetal,1997).

Fig. 0.4. Topography of seafloor surrounding Iceland, clearly showing Iceland hotspot swell, Mid-Atlantic Ridge,Greenland-Scotland Ridge, and “V-shaped ridges at the MAR south of Iceland”. (Sigmundsson, 2006)

Fig. 0.5. Iceland and the Mid-Atlantic Ridge. Icelandic rift in dark gray, and extension of hot spot at 400 km depthshown as a black triangle. SiSZ = South Iceland Seismic Zone, TFZ = Tjörnes Fracture Zone, and V = Vatnajökullice cap. (Bergerat and Angelier, 2008)

RIFT JUMP

M.O.R.: Spreidingszone en transforme breuken.

spreidingszonebewegingsrichting van de platen.transforme breuk

Delen van een midoceanische rug divergeren minder snel dan andere delen. Terwijl we dus in het algemeen spreken van een divergente breuk/beweging, bewegen de delen met verschillende snelheden ten opzichte van elkaar dus ook transversaal. (zie bij A en B in de tekening)

Fig. 0.6. GPS velocities 1999-2004. White arrows from REVEL plate model. (Sigmundsson and Saemundsson,2008)

Fig. 0.7. “The principal elements of the geology in Iceland, outlining the distribution of the major geological subdivisions,including the main fault structures and volcanic zones and belts. RR, Reykjanes Ridge; RVB, ReykjanesVolcanic Belt; WVZ, West Volcanic Zone; MIB, Mid-Iceland Belt; SISZ, South Iceland Seismic Zone; EVZ, EastVolcanic Zone; NVZ, North Volcanic Zone; TFZ, Tjörnes Fracture Zone; KR, Kolbeinsey Ridge; VB, ÖræfiVolcanic Belt; and SVB, Snæfellsnes Volcanic Belt.” (Hoskuldsson et al., 2008)

Fig. 0.8. “(a) A stylised cross section showing the general structure of the Icelandic crust from the Snæfellsnespeninsula across the West Volcanic Zone. Loading by volcanism tilts the strata towards the volcanic zones forming ashallow syncline centred on the spreading axes and a shallow anticline in the region between the volcanic zones. (b)The spreading paths for crustal elements (black squares) formed within different parts of an actively spreadingvolcanic zone. Rocks formed near the edge of the zone follow a shallow spreading path, whereas those formed closeto the spreading axis follow a much steeper path.” (Hoskuldsson et al., 2008)

VERSCHILLENDE INZICHTENMagmatische differentiatie vs micro continent fractie theorie

Korstdikte

Fig. 0.12. Crustal thickness in the greater Iceland region. (Tronnes, 2009)

divergente zoneFig. 0.14. Icelandic rift zone dynamics. Black: mass trajectories. Blue: Age contours (Ma). Red: temperaturecontours (°C). “Partial melting of hydrated mafic lithologies will start at about 5 km depth under the central part ofthe rift zone.” (Tronnes, 2009)

Fig. 0.15. Cross section to 200 km of the region around Iceland, in east-west direction at 65N latitude. Uncertainty inlithospheric thickness shown. LAB: lithosphere-asthenosphere boundary. STZ: Sorgenfrei-Tornquist Zone.(Artemieva and Thybo, 2008)

Mantelpluim

Verzonken microcontinent

VULKANISME

Eruptietypes

effusief explosief gemengd

Types vulkanen IJsland

Fig. 0.20. Map of Iceland showing the location of central volcanoes known to have produced silicic rocks during theBrunhes magnetic epoch (<0.8 Ma). Shaded areas indicate Brunhes-age rocks. Dashed lines indicate the crest of thewestern and eastern rift-zones (WRZ and ERZ). The western, southern and eastern flank zones are delineated (WFZ,SFZ and EFZ) and the main transform zones are indicated (South Iceland Seismic Zone and Tjörnes Fracture Zone).Plate motion is shown by arrows. The central volcanoes in the rift zones are: Hengill (Hen), Geysir (Ge),Prestahnúkur (Pr), Þjófadalir (Þj), Kerlingarfjöll (Ke), Hofsjökull (Ho), Þórðrarhyrna (o), Hágöng (Ha), Vonarskarð(Vo), Askja (As), Fremri Námur (Fr), Krafla (Kr) and Þeistareykir (e). The central volcanoes in the western flankzone are: Snæfellsjökull (Sn), Lýsuskarð (Ly) and Ljósufjöll (Lj). In the southern flank zone the central volcanoesare: Hekla (Hek), Torfajökull (To), Tindfjallajökull (Ti), Eyjafjallajökull (Ey) and Katla (Ka). The central volcanoesin the eastern flank zone are: Öræfajokull (Ör), Esjufjöll (Es) and Snæfell (Sf). (Jonasson, 2007)

Fig. 0.21. “(a) The main structural elements of a volcanic system. Abbreviations: c, crustal magma chamber; ds,dyke swarm; cv, central volcano; fs, fissure swarm; fe, fissure eruption. (b) Injection and growth of a dyke feeding aneruption during a rifting episode. The numbers indicate the growth sequence of the dyke rising through the crust in amajor eruption episode.” (Hoskuldsson et al., 2008)

Fig. 0.22. Schematic cross section beneath volcanoes of southern Iceland. (Tewksbury, 2001)

SUBGLACIALE ERUPTIES

Subglaciale eruptie onder de landijskap tijdens het Weiselien

Fig. 0.30. Quaternary ice sheet in Iceland over last 5 Ma and evolution of rift system. (Hoskuldsson, 2008)

Tafelvulkanen

Fig. 2.6. Left: Stages in development of subglacial eruptions. Stage 1. Early eruptions – pillow lavas and hyaloclastite. Stage 2b. Formation of a subglacial mound. Stage 3b. Formation of a tuya (Geological Survey of Canada, 2009). Right: Pillow basalts on the south Pacific seafloor. (OAR/National Undersea Research Program, 2009)

hoogteprofiel mobergplateaus en tafelbergvulkanen

Aan de hand van het hoogteprofiel van deze vulkanen kon de dikte van de ijskap tijdens de laatste (Weichselien) glaciaal worden gereconstrueerd.

Subglaciale eruptie nu:The Bárdarbunga caldera and the lateral magma flow path to the Holuhraun eruption site.

Magnús T. Gudmundsson et al. Science 2016;353:aaf8988

Published by AAAS

Eyjafjallajokull 2010

REYKJANES

THINGVELLIR

Horsten en slenkenBij transversale breukzones kan naast horizontale verschuiving, door rek- en duwkrachten, ook verticale verschuiving optreden. Langs ontstane breuken vindt dan afschuiving of opschuiving plaats. De lage delen zijn slenken, hoge delen heten horsten Er ontstaat een breukgebergte.

Afschuiving vindt plaats door rek van de aardkorst.

Opschuiving door duwkrachten

Type A is typisch voor Reykjanes. Type B zien we bij Thingvellir.

touwlava

The shield volcano Skjaldbreiður

GEYSIR

Torfason (2009) describes different types of hot springs present at Geysir. These include:− Geysers such as Strokkur and Geysir, which spout hot water through narrow channels fromreservoirs deep in the crust.− Fumaroles, which emit only steam and gases at the surface. In Haukadalur, these are sometimesencrusted with yellow deposits of hydrogen sulfide (H2S), which precipitates from the steam andcarries with it a distinctive smell of rotten eggs.− Mudpots, bubbling springs of hot mud, found predominantly in the Þykkuhverir (“viscous hotsprings”) area, are actually hydrated fumaroles. They derive their water from either groundwateror surface water, and behave like fumaroles during dry spells. Exercise caution around mudpots:they tend to hollow out the subsurface around them, and are a scalding 70-80°C.

Fig. 2.11. A map of the hot springs near Geysir in Haukadalur. (Tewksbury, 2001, after Hróarsson and Jónsson,1992)

A concise description of the eruptive process comes from Tewksbury (2001):Robert Bunsen first described the mechanics of geyser eruption in the mid-nineteenthcentury after a visit to Iceland. • Water in the geyser shaft is heated nearly to the boiling point. • Boiling temperature, however, increases with increasing depth as the pressure of the

overlying water column increases. I• f the pressure in the column decreases suddenly (say, for example, when a small amount of

boiling at the surface ejects some of the water and decreases the pressure below), the deep water will be superheated in terms of the boiling point at the new pressure.

• The water flashes to steam, and the geyser erupts. • Deep rumbling sounds sometimes precede the eruption of a geyser, as large steam bubbles

collapse in the water column. • After the eruption, the geyser shaft is empty or partly empty. The shaft may refill quickly or

slowly, depending upon subsurface flow rates.• Refill is rapid for Strokkur, taking only a few minutes, and very slow for Geysir, taking as much

as 12.13 hours when Geysir can be induced to erupt (Hróarsson and Jónsson, 1992).

GULFOSS

Fig. 2.12. Cross section of Gullfoss. 1=grey basalt; 2=fine-grained sandstone; 3=sandstone;4=conglomerate; 5=tillite. (Tewksbury, 2001, after Einarsson, 1994)

KERID

VATNAJOKULL

Fig. 6.2. Geologic map of Öræfasveit showing geographic relation of Skeiðarársandur to surrounding glaciers and basalts of different ages. Latitude/longitude lines and approximate Route 1 highway trace added for references.(Short et al., 1985)

Fig. 6.3. Grænalón and surroundings. Blue lines indicate surface flows; dashed red lines estimate subglacial channellocations. (Scharrer et al., 2007)

Fig. 6.11. Local topographic relief at Skaftafell has been amplified since 5 Ma as subglacially erupted ridges and deepening valleys developed under thickening ice. (Helgason and Duncan, 2001)

Alterative hike towards Skaftafellsjökull glacier along Little Ice Age TimelineThis walk to/from the glacier front includes interpretive signs showing former glacial extent and subsequent retreat. The trail departs on the east side of the visitor center. Englacial debris bands, as described by Roberts et al. (2002) (Fig. 6.14), may be visible on the glacier. The hike remains on the flatvalley floor and so is a possibility for anyone

Fig. 6.15. Skaftafell area map (photo from Skaftafell Visitor Center).

Glaciale landschapsvormen

Ablatiekegels

Gletsjermeer Jokulsarlon