Eastern Iceland Research Articles

Harsh climate selects for small body size among Iceland's Arctic foxes

We studied the eff ect of the two environmental indices, the sub-polar gyre (SPG), and winter and summer North Atlantic Oscillation (NAO), together with mean annual winter and summer temperatures and geographic location on mandible size and body mass of Arctic foxes in Iceland (6345 and 2732 specimens, respectively) during the year of their death. We predicted that when favorable conditions prevailed, large specimens would be selected for, and vice versa. Body size and body mass were signifi cantly aff ected by the environmental parameters (i.e. SPG, NAO, ambient temperature and cloud cover) prevailing during the year of death. Th e eff ect of environmental conditions on body size was much stronger in the less productive region of eastern Iceland, apparently because in areas where food availability is meager, even a small diff erence in climate may tilt the balance from food suffi ciency to food shortage. Western Iceland comprises only a quarter of the total surface area of the country, but its productive seashores are twice as long as those of all the rest of the country combined. It is interesting to note that the eff ect of the SPG, a marine phenomenon in the oceans surrounding Iceland, is refl ected in the condition of the foxes more than the other climatic variables we used in this study, which are largely land-related. Because Arctic foxes in Iceland feed largely on marine birds and invertebrates, the SPG seems to encompass more accurate information regarding the direct ocean forces that aff ect food availability to the foxes.

Lost Paths. Climate Changes and the Forgotten Route to Skriðuklaustur Monastery, Eastern Iceland

Lost Paths. Climate Changes and the Forgotten Route to Skriðuklaustur Monastery, Eastern Iceland

Anatomy of an extinct magmatic system along a divergent plate boundary: Alftafjordur, Iceland

AbstractRecent rifting episodes highlight the role of magmatic systems with propagating dikes on crustal spreading. However, our knowledge of magmatic systems is usually limited to surface observations and geophysical data. Eastern Iceland allows direct access to extinct and eroded deeper magmatic systems. Here we collected field structural and AMS (anisotropy of magnetic susceptibility) data on 187 and 19 dikes, respectively, in the 10–12 Ma old Alftafjordur magmatic system. At a paleodepth of ~1.5 km, the extension due to diking is at least 1–2 orders of magnitude larger than that induced by regional tectonics, confirming magmatism as the key mechanism for crustal spreading. This magma‐induced extension, inferred from the aspect ratio of the magmatic system, was of ~8 mm/yr, lower than the present one. AMS data suggest that most of dikes have geometrically normal fabric, at least at the margins, consistent with prevalent subvertical magma flow and propagation.

Direct evidence of the feedback between climate and nutrient, major, and trace element transport to the oceans

Climate changes affect weathering, denudation and riverine runoff, and therefore elemental fluxes to the ocean. This study presents the climate effect on annual fluxes of 28 dissolved elements, and organic and inorganic particulate fluxes, determined over 26–42year period in three glacial and three non-glacial river catchments located in Eastern Iceland. Annual riverine fluxes were determined by generating robust correlations between dissolved element concentrations measured from 1998 to 2003 and suspended inorganic matter concentrations measured from 1962 to 2002 with instantaneous discharge measured at the time of sampling in each of these rivers. These correlations were used together with measured average daily discharge to compute daily elemental fluxes. Integration of these daily fluxes yielded the corresponding annual fluxes.As the topography and lithology of the studied glacial and non-glacial river catchments are similar, we used the records of average annual temperature and annual runoff to examine how these parameters and glacier melting influenced individual element fluxes to the oceans. Significant variations were found between the individual elements. The dissolved fluxes of the more soluble elements, such as Mo, Sr, and Na are less affected by increasing temperature and runoff than the insoluble nutrients and trace elements including Fe, P, and Al. This variation between the elements tends to be more pronounced for the glacial compared to the non-glacial rivers. These observations are interpreted to stem from the stronger solubility control on the concentrations of the insoluble elements such that they are less affected by dilution. The dilution of the soluble elements by increasing discharge in the glacial rivers is enhanced by a relatively low amount of water–rock interaction; increased runoff due to glacial melting tend to be collected rapidly into river channels limiting water–rock interaction. It was found that the climate effect on particle transport from the glacial rivers is far higher than all other measured fluxes. This observation, together with the finding that the flux to the oceans of biolimiting elements such as P and Fe is dominated by particulates, suggests that particulate transport by melting glaciers have a relatively strong effect on the feedback between continental weathering, atmospheric chemistry, and climate regulation over geologic time.

‘Do Not Let Anyone See This Ugly Scrawling’: Literacy Practices and the Women's Household at Hallfreðarstaðir 1817–1829

In 1817 an 11-year-old boy, Páll Pálsson (1806–1877), left his childhood home in eastern Iceland, to be fostered and educated by a friend of the family in another part of the country. Immediately a correspondence started between him and his family. Most of these letters have been preserved and give invaluable insight into the literacy practices of Páll Pálsson's family and friends over 60 years. Pálsson's grandmother, mother, and two younger sisters played a central role in this correspondence during the time that they were all alive. This article focuses on the 104 preserved letters written by these four women in the period of 1817 to 1829. Grounding its argument in theories on correspondence and literacy practices this article addresses the complicated nature of letter writing, such as the indistinct lines between individual and collective letter writing. The article shows how the skill of writing was disseminated within the family and how it was utilised, not only to keep in touch but also to strengthen networks and power relations. Furthermore, special attention is paid to gendered aspects of learning to write, and of the writing of letters, in the 1820s.

The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups

Simple flows (tabular) in the Neogene flood basalt sections of Iceland are described and their mode of emplacement assessed. The flows belong to three aphyric basalt groups: the Kumlafell group, the Hólmatindur group and the Hjálmadalur group. The groups can be traced over 50km and originate in the Breiðdalur–Thingmuli volcanic zone. The groups have flow fields that display mixed volcanic facies architecture and can be classified after dominating type morphology. The Kumlafell and the Hólmatindur groups have predominantly simple flows of pāhoehoe and rubbly pāhoehoe morphologies with minor compound or lobate pāhoehoe flows. The Hjálmadalur group has simple flows of rubbly pāhoehoe, but also includes minor compound or lobate flows of rubble and 'a'ā. Simple flows are most common in the distal and medial areas from the vents, while more lobate flows in proximal areas. The simple flows are formed by extensive sheet lobes that are several kilometers long with plane-parallel contacts, some reaching thicknesses of ~40m (aspect ratios <0.01). They have overlapping contacts and are free of tubes and inflation structures. Their internal structure consists generally of a simple upper vesicular crust, a dense core and a thin basal vesicular zone. The brecciated flow-top is formed by clinker and crustal rubble, the clinker often welded or agglutinated. The simple flows erupted from seemingly short-lived fissures and have the characteristics of cooling-limited flows. We estimate the effusion rates to be ~105m3/s for the simple flows of the Kumlafell and Hólmatindur groups and ~104m3/s for the Hjálmadalur group. The longest flows advanced 15–20km from the fissures, with lava streams of fast propagating flows inducing tearing and brecciation of the chilled crust. Compound or lobate areas appear to reflect areas of low effusion rates or the interaction of the lava with topographic barriers or wetlands, resulting in chaotic flowage. Slowing lobes with brecciated flow-tops developed into 'a'ā flows. The groups interdigitated with lava groups from the Reyðarfjörður volcanic zone to the east, and the exhumed Breiðdalur–Thingmuli volcanic zone which appear to have formed as a flank lineament parallel the main rift zone. Flood basalt volcanism in flank areas may support a mantle anomaly more pronounced and/or perhaps more widespread in the Neogene of Iceland than today. Eruptions of simple flows have not been observed in modern times and are significant for models of crustal accretion in Iceland and other Large Igneous Provinces.

Physicochemical and toxicological profiling of ash from the 2010 and 2011 eruptions of Eyjafjallajökull and Grímsvötn volcanoes, Iceland using a rapid respiratory hazard assessment protocol

The six week eruption of Eyjafjallajökull volcano in 2010 produced heavy ash fall in a sparsely populated area of southern and south eastern Iceland and disrupted European commercial flights for at least 6 days. We adopted a protocol for the rapid analysis of volcanic ash particles, for the purpose of informing respiratory health risk assessments. Ash collected from deposits underwent a multi-laboratory physicochemical and toxicological investigation of their mineralogical parameters associated with bio-reactivity, and selected in vitro toxicology assays related to pulmonary inflammatory responses. Ash from the eruption of Grímsvötn, Iceland, in 2011 was also studied. The results were benchmarked against ash from Soufrière Hills volcano, Montserrat, which has been extensively studied since the onset of eruptive activity in 1995.For Eyjafjallajökull, the grain size distributions were variable: 2–13vol% of the bulk samples were <4µm, with the most explosive phases of the eruption generating abundant respirable particulate matter. In contrast, the Grímsvötn ash was almost uniformly coarse (<3.5vol%<4µm material). Surface area ranged from 0.3 to 7.7m2g−1 for Eyjafjallajökull but was very low for Grímsvötn (<0.6m2g−1). There were few fibre-like particles (which were unrelated to asbestos) and the crystalline silica content was negligible in both eruptions, whereas Soufrière Hills ash was cristobalite-rich with a known potential to cause silicosis. All samples displayed a low ability to deplete lung antioxidant defences, showed little haemolysis and low acute cytotoxicity in human alveolar type-1 like epithelial cells (TT1). However, cell-free tests showed substantial hydroxyl radical generation in the presence of hydrogen peroxide for Grímsvötn samples, as expected for basaltic, Fe-rich ash. Cellular mediators MCP-1, IL-6, and IL-8 showed chronic pro-inflammatory responses in Eyjafjallajökull, Grímsvötn and Soufrière Hills samples, despite substantial differences in the sample mineralogy and eruptive styles.The value of the pro-inflammatory profiles in differentiating the potential respiratory health hazard of volcanic ashes remains uncertain in a protocol designed to inform public health risk assessment, and further research on their role in volcanic crises is warranted.

The mode of emplacement of Neogene flood basalts in Eastern Iceland: Facies architecture and structure of the Hólmar and Grjótá olivine basalt groups

Hólmar and Grjótá are two stratigraphically distinct transitional alkaline olivine basalt lava groups within the westward-dipping Neogene flood basalts of eastern Iceland. The Hólmar olivine basalt group, separated from the overlying Grjótá olivine basalt group by only a few tholeiite flows, can be traced over 80km north–south, with thicknesses varying from ~250m where thickest to ~30m where thinnest. The Grjótá group can be traced over 50km also north–south, reaching thicknesses of ~250m and thinning down-dip to ~10m. In contrast to other groups in eastern Iceland that thicken down-dip, the studied olivine basalt groups thicken up-dip. The groups filled topographic confinements and formed aprons around central volcanoes. We have estimated the minimum volumes to be ~119km3 for Hólmar and ~86km3 for Grjótá. Scoria cones are found in the Hólmar group, and two thick olivine dolerite sills cross-cut the Hólmar group and probably belong to the plumbing system that fed the Grjótá group. The architecture of the lava groups are near identical. The architecture is compound, with lobes stacked horizontally and vertically, varying from 1–15m thick and 2–200m long, but do also encompass a number of thicker (15–20m) and more extensive (>1km long) lava lobe in the stacks. Filled lava tubes are commonly observed within the lava flows. The constituent lobes of the flows are often directly emplaced or welded together, suggesting rapid buildup, but are also found interbedded with redbeds and thicker tuff deposits, and occasionally preserve tree molds. The internal structure follows the characteristics for lava lobe morphology in general, with an upper vesicular crust forming half to one third of the total thickness, a massive core with abundant vesicle cylinders, and a thin basal vesicular crust. Flow tops are of the pahoehoe type, seldom found with scoria or clinker. Inflation structures such as tumuli and inflation clefts were identified in the flows. The eruptions were dominantly fissure-fed, with a few vents evolving to short-lived point source volcanism. The pre-existing topography exerted control on the advancement of the flows and influenced the final architecture of the groups at each location. It is evident that the large and dense spatial distribution of these groups, including numerous thick lava units, suggests large volcanic episodes. Together, the groups imply a period with higher production of olivine basalts in Iceland and form well-defined stratigraphic markers. The transitional alkaline olivine basalt groups are interpreted to delineate a fossil southward propagating rift flank volcanic zone located east of a now extinct and buried mature rift zone.

Útgjöld ríkisins í Norðausturkjördæmi og tekjur ímyndaðs "Norðausturríkis"

Hlutdeild einstakra landshluta í tekjuöflun þjóðarinnar og skipting ríkisútgjalda milli höfuðborgar og landsbyggða eru meðal umdeildustu mála í íslenskri byggðaumræðu. Slík umræða endurspeglar ólík viðhorf til félagslegs réttlætis og ólíka hagsmuni íbúa mismunandi landssvæða. Þrátt fyrir harðvítugar deilur um mikla hagsmuni eru rannsóknir á dreifingu ríkisútgjalda eftir landsvæðum af skornum skammti. Í þessari rannsókn er sjónum beint að útgjöldum ríkisins í Norðausturkjördæmi á grundvelli fjárlaga ársins 2011 og viðbótarupplýsinga sem safnað var hjá einstökum stofnunum og ráðuneytum. Niðurstöður sýna að starfsemi ríkisins á Norðurlandi eystra er um 11% minni en mannfjöldi segir til um eða sem nemur rúmlega 74 þúsund krónum á hvern íbúa á ári. Starfsemi ríkisins á Austurlandi er um 23% minni en mannfjöldi segir til um eða sem nemur rúmlega 159 þúsund krónum á hvern íbúa á ári. Á hinn bóginn leggur ríkið til svipaða upphæð til að stuðla að því að þjónusta sveitarfélaga sé sambærileg því sem gerist annars staðar og til að styðja við landbúnað á þessum svæðum. Ef áætlaðar tekjur ríkisins eru bornar saman við útgjöld ríkisins í kjördæminu kemur í ljós að útgjöldin eru hærri sem nemur 625 Mkr eða 1,2% af skatttekjum miðað við fjárlög ársins 2011. Til samanburðar var halli af rekstri íslenska ríkisins skv. fjárlögum 2011 um 7,9% eftir vaxtagreiðslur. Þetta er vísbending um að ímyndað, sjálfstætt "Norðausturríki" gæti staðið á eigin fótum en til að svara því þyrfti þó mun viðameiri rannsóknir.

Magmatic emulsion texture formed by mixing during extrusion, Rauðafell composite complex, Breiðdalur volcano, eastern Iceland

The Rauðafell composite complex is part of the Neogene Breiðdalur volcano, eastern Iceland and is composed of a composite feeder dyke, a vent structure and a composite flow. The two end-members of the composite complex are rhyolite and basalt, and both are rich in plagioclase macrocrysts: bytownite in basalt and oligoclase in rhyolite. The rhyolite also includes ferroaugite macrocrysts. The mixed rocks are separated in three textural groups related to mixing proportions. When the basaltic end-member is dominant, a hybrid texture with a homogeneous matrix is observed and the only evidence of mixing is the presence of antecrysts of both end-members. When the basaltic end-member represents c. 65 to 30 % of the mixture, we observe emulsion textures composed of finely co-mingled basalt and rhyolite. The difference between these two textural expressions of mixing is due to effects of diffusion. The third texture shows mafic enclaves suspended in a rhyolitic matrix. In these rocks, the proportion of the basaltic end-member is inferior to 30 %, implying that the basalt froze solid in contact with the rhyolite. Zoning of plagioclase shows that the mixing processes are driven initially by highly efficient micro-mingling; the emulsification is possibly a result of compositional gradient stresses (Korteweg stress) between miscible basalt and rhyolite. This is followed by chemical diffusion (hybridisation) and tend to protect antecrysts from reaction with the primitive magmas. When antecrysts originated in the evolved magma, they undergo dissolution due to thermal disequilibrium during mingling and chemical disequilibrium during hybridisation. We argue that such mixing processes are important in producing intermediate rocks in Iceland and elsewhere that shows only the chemical attributes of an origin by mixing. The preservation of emulsion textures is rare and highly dependent on cooling history.

Waveform modeling of shear wave splitting from anisotropic models in Iceland

No quantitative model of seismic anisotropy beneath Iceland has yet explained the observed shear wave splitting results in Iceland. In this study we explore the structure of mantle seismic anisotropy associated with plume ridge interaction beneath Iceland by modeling synthetic waveforms using a pseudo‐spectral method. First, predicted SKS waveforms are shown to produce shear wave splitting results for two anisotropic layers that are in generally agreement with analytic solutions. Next, simple models in which anisotropy are imposed at different depths and geographic regions around Iceland are used to examine different hypothesized effects of plume‐ridge interaction. The model that is designed to represent crystallographic fabric due to mantle deformation associated with lithosphere spreading in western Iceland and along‐axis, channeled asthenospheric flow in eastern Iceland can predict the distinct shear wave splitting observations on the east and west sides of the island. Last, we analyze geodynamic models that simulate 3‐D mantle flow and evolution of mineral fabric. The predicted fast directions of shear wave splitting from the models with realistic spreading rate (10 km/Myr) and broad range of plume viscosities are consistent with the observations in central and eastern Iceland. However, because these models are symmetric about the ridge, none of them can predict the observed shear wave splitting results in western Iceland.

Iceland spar and its legacy in science

Abstract. In the late 17th century, Rasmus Bartholin and Christiaan Huygens investigated a curious optical property of crystals found at Helgustaðir in Eastern Iceland. This property which has been called double refraction, revealed in the 19th century a new aspect of light which turned out to be very useful as a probe of the internal structure of matter. Clear specimens of these crystals, an unusually pure variety of calcite, have since around 1780 been known as ''Iceland spar''. Few if any other localities yielding calcite crystals of comparable size and quality were discovered before 1900, and no alternatives for use in precision optical instrumentation were developed until the 1930s. Hundreds of tons of calcite were exported from Helgustaðir, mostly between 1850 and 1925. However, little information has been found on trading routes for the material of optical quality, so that some enigmas remain regarding its supply-demand situation. A study of the scientific literature in the period up to 1930 has revealed that results obtained with the aid of Iceland spar accelerated progress within the earth sciences (in mineralogy and petrology), physics, chemistry, and biology, even by decades. This has also influenced the development of technology and of medicine in various direct and indirect ways.

The sediments of Lake Lögurinn – A unique proxy record of Holocene glacial meltwater variability in eastern Iceland

The full Holocene development of the large (8100 km2) Vatnajökull ice cap in Iceland with its many outlet glaciers is poorly known. The idea of an early deglaciation, leading to a glacier-free period in mid-Holocene, followed by the Neoglaciation is still the main concept for the glacial history in the North Atlantic region, including Iceland. We have examined a continuous sediment record from the glacier-fed Lake Lögurinn in eastern Iceland to infer Holocene meltwater variability of Eyjabakkajökull, which is a surge-type outlet glacier of the Vatnajökull ice cap. We focus on the early and mid-Holocene, and our data show that Eyjabakkajökull receded rapidly during the final phase of the last deglaciation, and did not deliver glacial meltwater to Lake Lögurinn by 9000 years BP, suggesting that Eyjabakkajökull was significantly smaller than today at that time. The return of glacial meltwater transport to Lake Lögurinn, and thus a return of Eyjabakkajökull is dated to ca 4400 years BP, suggesting an almost 5000 years long glacier-free period during early and mid-Holocene. During this time period, we infer that the 8.2 ka cold event did not cause a significant expansion of Eyjabakkajökull, however, we note a marked decrease in the aquatic productivity in Lake Lögurinn, which is suggested to be the result of shorter ice-free seasons of Lake Lögurinn. The Holocene Thermal Maximum is inferred by a period of maximum Holocene aquatic productivity, and dated to ca 7900–7000 years BP. Following the re-formation of Eyjabakkajökull ca 4400 years BP, we suggest that the glacier reached stable conditions ca 1700 years BP, and remained fairly stable until the later part of the Little Ice Age, when Eyjabakkajökull reached its maximum Holocene extent.

Ian S. E. Carmichael (1930–2011)

Ian S. E. Carmichael, who had a highly imaginative research career and was legendary for his successful mentoring of graduate students, died in Berkeley, Calif., on 26 August 2011. Ian applied thermodynamic theory, experiment, and the ground truth of fieldwork to the study of magmatic rocks. Throughout the arc of his career, he played a critical role in transforming igneous petrology from a discipline that was largely descriptive to one that is rigorously quantitative. Ian was born in London on 29 March 1930 and was educated at Westminster School. He spent 2 years in the British Army (as a parachutist and a second lieutenant in the Corps of Royal Engineers), where he saw service in Egypt, Palestine, and Sudan. He obtained his B.A. and M.A. in geology at Cambridge University in 1954 and then traveled to Canada, where he prospected for copper and wintered in the Arctic. Ian returned to England and obtained his Ph.D. in 1958 at Imperial College London. His thesis, on Thingmuli volcano in eastern Iceland, addressed one of the most contentious issues in Earth science at the time (before the days of isotope geochemistry and plate tectonics), namely, the origin of silicic magma from basalt in the absence of preexisting continental crust. The problem went to the heart of crustal evolution.

Climatic control of the surge periodicity of an Icelandic outlet glacier

AbstractSurging outlet glaciers are important in draining large ice caps, but the mechanisms controlling surge periodicities are poorly known. We investigated a sediment sequence from the glacier‐fed Lake Lögurinn in eastern Iceland, and our unique annually resolved data, based on sedimentary varves, imply that Eyjabakkajökull, an outlet glacier of Vatnajökull, began surging about 2200 cal a BP (before 1950 AD). Approximately 1700 cal a BP, the glacier started to surge at a uniform 34‐ to 38‐year periodicity that prevailed until the coldest part of the Little Ice Age when the periodicity almost halved to 21–23 years. Since the late 1800 s the surge periodicity of Eyjabakkajökull has returned to a longer period of 35–40 years. We suggest that surge periodicities of Eyjabakkajökull are forced by climatically driven mass balance changes, which may be a common forcing factor for similar surge‐type outlet glaciers. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Three-dimensional geometry of concentric intrusive sheet swarms in the Geitafell and the Dyrfjöll volcanoes, eastern Iceland

Sheet intrusions (inclined sheets and dykes) in the deeply eroded volcanoes of Geitafell and Dyrfjoll, eastern Iceland, were studied at the surface to identify the location, depth, and size of their magmatic source(s). For this purpose, the measured orientations of inclined sheets were projected in three dimensions to produce models of sheet swarm geometries. For the Geitafell Volcano, the majority of sheets converge toward a common focal area with a diameter of at least 4 to 7 km, the location of which coincides with several gabbro bodies exposed at the surface. Assuming that these gabbros represent part of the magma chamber feeding the inclined sheets, a source depth of 2 to 4 km below the paleoland surface is derived. A second, younger swarm of steeply dipping sheets crosscuts this gabbro and members of the first swarm. The source of this second swarm is estimated to be located to the SE of the source of Swarm 1, below the present-day level of exposure and deeper than the source of the first swarm. For the Dyrfjoll Volcano, we show that the sheets can be divided into seven different subsets, three of which can be interpreted as swarms. The most prominent swarm, the Njardvik Sheet Swarm, converges toward a several kilometers wide area in the Njardvik Valley at a depth of 1.5 to 4 km below the paleoland surface. Two additional magmatic sources are postulated to be located to the northeast and southwest of the main source. Crosscutting relationships indicate contemporaneous, as well as successive activity of different magma chambers, but without a resolvable spatial trend. The Dyrfjoll Volcano is thus part of a complex volcanic cluster that extends far beyond the study area and can serve as fossil analog for nested volcanoes such as Askja, whereas in Geitafell, the sheet swarms seem to have originated from a single focus at one time, thus defining a single central volcanic complex, such as Krafla Volcano.

Cases of hydatid disease in medieval Iceland

AbstractEight individuals with calcified cysts preserved in the thorax and abdomen, one of which had a maximum diameter of 17–20 cm, were recovered during recent excavations at Skriðuklaustur, a medieval monastic site which also functioned as a hospital during its operation from AD 1493–1554 in Eastern Iceland. Hydatid cysts are the result of parasitic infection by Echinococci commonly in the liver and lungs of the accidental human host. Echinococcus granulosus was likely introduced to Iceland soon after the settlement period (9th century AD) and became endemic around AD1200 when dogs were introduced from Germany. It has since been eradicated in Iceland due to an extensive educational literature programme and government controls implemented since the mid‐1800s. Reviews of the palaeopathological literature mentioning calcified shell fragments indicated hydatism to be the most logical aetiology. The eight individuals in question were buried in close proximity to one another. This may indicate that this particular ailment (sullaveiki) had its own classification during the medieval period in Iceland and perhaps even a distinct treatment if not in life, at least in death. Copyright © 2010 John Wiley &amp; Sons, Ltd.

The Tip of the Iceberg: The Material of Skriðuklaustur Monastery and Hospital

Material objects from distant societies and cultures have long been an axis for archaeological research. In recent research, however, growing attention has been drawn to exploring simultaneously the conceptual meaning of material substances as the products of humans. The visual appearance of material is in this respect no more than the tip of an iceberg, where only a small part of something largely hidden is evident. In this article, Skriðuklaustur, an Augustinian monastery which operated in Eastern Iceland from ad 1493 to 1554 will thus be approached as embracing the remains of an internationally based society that flourished on the outskirts of the medieval monastic world. An excavation of its ruins has revealed residues of a society whose material is both domestic and international but still reflects the universally based meaning of monasticism. The Catholic Church is in this manner regarded as having fabricated phenomena through its pervasive institutions, upholding a distinct monastic identity. This view does not though involve a general denial of cultural or social changes as it rather underlines the hybrid character of everything that is and, at the same time, the significance of examining the materiality of past cultures as the creation of humans in their relational context.

Climate variability and glacial processes in eastern Iceland during the past 700 years based on varved lake sediments

Properties of varved sediments from Lake Logurinn in eastern Iceland and their link to climate and glacial processes of Eyjabakkajokull, an outlet glacier of the Vatnajokull icecap, were examined. A varve chronology, which covers the period AD 1262-2005, was constructed from visual observations, high-resolution images, X-ray density and geochemical properties determined from X-radiography and X-ray fluorescence scanning. Independent dating provided by 137Cs analysis and eight historical tephras verify the varve chronology. The thickness of dark-coloured seasonal laminae, formed mainly of coarser suspended matter from the non-glacial river Grimsa, is positively correlated (r=0.70) with winter precipitation, and our 743-year-long varve series indicates that precipitation was higher and more varied during the later part of the Little Ice Age. Light-coloured laminae thickness, controlled mainly by the amount of finer suspended matter from the glacial river Jokulsa i Fljotsdal, increased significantly during the AD 1972 surge of Eyjabakkajokull. As a consequence of the surge, the ice-dammed Lake Haoldulon formed and recurrently drained and delivered significant amounts of rock flour to Lake Logurinn. Based on these observations, and the recurring cyclic pattern of periods of thicker light-coloured laminae in the sediment record, we suggest that Eyjabakkajokull has surged repeatedly during the past 743 years, but with an increased frequency during the later part of the Little Ice Age.

Emplacement of magma in Eastern Iceland dikes: Insights from magnetic fabric and rock magnetic analyses

The anisotropy of magnetic susceptibility (AMS), coupled with mineral magnetic identification, has been investigated in about 640 samples from 27 basaltic dikes of Tertiary age in Eastern Iceland. The dikes are a few meters thick and they have been sampled all across. Three types of magnetic fabrics with well-defined mean principal axes of anisotropy are recognized. In the first one the maximum axis is vertical and the minimum axis coincides with the pole of the dike plan (“geometrically normal” fabric). The second fabric shows opposite orientation (“geometrically inverse” fabric). The third type is when these two fabrics coexist with the “normal” one at the margins and the “inverse” one in the center of the dike (“mixed” fabric). No relationship is observed between the type of fabric and the width of the dikes. Each fabric is carried by clear magnetic assemblages made of low ( x ∼ 0.15) Ti-content fine-grained magnetites for the “normal” one and high Ti-content (around TM60) coarse magnetite grains for the “inverse” fabric. Upon heating, the magnetic properties and the orientation of the anisotropy ellipsoid characterizing the “inverse” fabric in the mixed dikes change and evolve toward the “normal” type. These two geometrically “normal” and “inverse” fabrics are interpreted as primary ones, representing different physico-chemical conditions during the emplacement of the magma. The AMS results indicate that, during the volcanic events occurring about 10 Myr ago, the extrusion of the magma was vertical at the depth of the studied sites in eastern Iceland.