Module 5 - Lecture 5 (Mature Oceans)

mantle plumes

decompression melting as pressure comes off - plumes of mineralize water (this is where extremophiles live) - very important for creation of rich plumes of water and rich metal deposits - hot water scavenges and precipitates them

ridge jump

due to plate moving both absolute movement and relative movement (iceland spreading but moving westward, plume stays immoble)

conglomerate

rock made up of fragments of older material where fragments are rounded - pieces are rounded (roll along bottom of river)

Explain the Wilson Cycle

The Wilson cycle is a model where a continental rift breaks up a continent leading to the formation of an ocean basin between two lithospheric plates. The separation of the two plates is then followed by convergence that leads to the closure of the ocean basin, and eventually to the collision of the two continental blocks. The model is named after its originator John Tuzo Wilson[1]. The term "Wilson cycle" was introduced in 1974 by Kevin C. A. Burke, who was a colleague and friend of John Tuzo Wilson[2]. It has been suggested that Wilson cycles on Earth started about 3 Ga (3 billion years) ago in the Proterozoic Eon of Earth's history.[3] A Wilson cycle is not the same as a supercontinent cycle, which is the break-up of one supercontinent and the development of another and takes place on a global scale. The Wilson cycle rarely synchronizes with the timing of a supercontinent cycle.[4] However, supercontinent cycles and Wilson cycles were both involved in the creation of Pangaea and Rodinia.[5]

moberg mountains - what are they?

The origin of the term comes from Tuya Butte, one of many tuyas in the area of the Tuya River and Tuya Range in far northern British Columbia, Canada. While still in graduate school in 1947, Canadian geologist Bill Mathews published a paper titled, "Tuyas, Flat-Topped Volcanoes in Northern British Columbia", in which he coined the term "tuya" to refer to these distinctive volcanic formations. Tuya Butte is a near-ideal specimen of the type, the first such landform analyzed in the geological literature, and this name has since become standard worldwide among volcanologists in referring to and writing about these formations. Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near the boundary with Yukon. Around the same time that Mathews published his paper, the Icelandic geologist Guðmundur Kjartansson had distinguished between "móberg" ridges and tuyas in Iceland and proposed the hypothesis that they were formed during subglacial and intraglacial eruptions. The term tuya may be derived from a Tahltan word.[3] A volcanic mesa near Santa Fe, New Mexico, known in English as Black Mesa and resembling a tuya, is known in Tewa as Tu-yo[1].

Define tephra; what does it look like?

When a volcano erupts it will sometimes eject material such as rock fragments into the atmosphere. This material is known as tephra. The largest pieces of tephra (greater than 64 mm) are called blocks and bombs. Blocks and bombs are normally shot ballistically from the volcano (refer to the gas thrust zone described in the direct blast section). Because these fragments are so large they fall out near their source. Blocks and bombs as large as 8-30 tons have fallen as far away as 1 km from their source (Bryant, 1991). Small blocks and bombs have been known to travel as far away as 20-80 km (Scott, 1989)! Some of these blocks and bombs can have velocities of 75-200 m/s (Bryant, 1991). Smaller ejecta such as lapilli (2-64 mm) and ash (<2 mm) which are convected upward by the heat of the eruption will fall out farther from the volcano. Most particles greater than a millimeter in size will fall out within 30 minutes of the time they are erupted (W.I. Rose personal communication). The smallest particles which are less then .01 mm can stay in the atmosphere for two or three years after a volcanic eruption. Sometimes these particles produce fantastic sunsets such as was seen after the eruptions of Krakatau in 1883 and Pinatubo in 1991. Some scientists believe that these particles may contribute to global warming. The size of particles that fall out is largest near the volcano and gets progressively smaller further from the volcano. The thickness of material usually decreases the further away from the volcano. Occasionally, as occurred in Ritzville, Washington when Mount St. Helens erupted in 1980, secondary thickening will occur. Secondary thickening means that ash deposits are thicker in a particular area than in surrounding areas. This results when ash particles and water form clumps which produce larger particles that have higher terminal velocities and so fall out of the ash cloud. When these particles hit the ground they break apart and produce a thicker deposit of ash than in surrounding areas.

smokers

active hydrothermal vents - bacterial colonies and animals without eyes, only heat sensors. origin of geobiology. people believe a snapshot of earlier life on earth. chemotrophic organisms

jokhulaups (and one above)

floods coming from mountains (volcano under ice) - flash flood

french revolution

gas vlouds subsided over europe, ash in atmosphere precluded light and caused crops to fail

hydrothermal water Iceland

high temp hot spring used to heat cold groundwater which is piped to the down - moving towards generating electricity with geothermal steam (infinite resource courtesy of plate tectonics). heat exchanger - because hydrothermal water itself has too many minerals that will clog pipes- existing large pipes to ciruclate must be large and bent and permit flexibility since iceland is spreading at rate of 9mm/year due to being on top of a mid ocean ridge

hot spots and what they prove

hot spot tracks are where immobile magma flumes intrude the above mobile plate, a volcano moves way from its source and becomes dormant, but another volcano springs up in the trajectory of the plume as the plate moves over it. evidence that plates move.

hyaloclastite

igneous rocks broken by contrast with water (like squash soup blender stfx)

dike formation is smoking gun of plate tectonics

intrusion of magma into many sheets catalyzes movement

What fuels plate tectonics?

magma

*midterm - pillow basalts and sheeted dikes* describe the onion model

magma chamber forcing up magma with cooling at margins, and the cooled rock pushed to either side due to hot magma - pushed up to form sheets of thousands of dykes. if you drill to ocean floor find huge amounts of pillow basalt and underneath are the sheeted dikes - forms pillowed basalt

who is responsible for identifying magnetic sedimentation in iceland, and why does it happen on a physical level, and what causes it? what is it proof of?

magnetic sedimentation due to reversal in polar fields in iceland - graduate student who solved problem was *fred vine* (vineyard = stripes) resulting from seafloor spreading. (youngest to oldest) - mobilism, not permanentism - plate tectonics.

ophiolites

refers to green skin of a snake - rocks become green throug metamorphosis once exposed to hot water - mantle derived rock - exposure to basalt. (salted by hydrothermal process/serpentization)

hyaloclastite breccia

rock made up of many pieces of prexiting rock broken up into many shards (breccia) - we can inform ourselves about parent rock and circumsatnces in which it arose. Hyaloclastite is a volcanoclastic accumulation or breccia consisting of glass (from the Greek hyalus) fragments (clasts) formed by quench fragmentation of lava flow surfaces during submarine or subglacial extrusion. It occurs as thin margins on the lava flow surfaces and between pillow lavas as well as in thicker deposits, more commonly associated with explosive, volatile-rich eruptions as well as steeper topography. Hyaloclastites form during volcanic eruptions under water, under ice or where subaerial flows reach the sea or other bodies of water. It commonly has the appearance of angular flat fragments sized between a millimeter to few centimeters. The fragmentation occurs by the force of the volcanic explosion, or by thermal shock and spallation during rapid cooling. Several minerals are found in hyaloclastite masses. Sideromelane is a basalt glass rapidly quenched in water. It is transparent and pure, lacking the iron oxide crystals dispersed in the more commonly occurring tachylite. Fragments of these glasses are usually surrounded by a yellow waxy layer of palagonite, formed by reaction of sideromelane with water. Hyaloclastite ridges, formed by subglacial eruptions during the last glacial period, are a prominent landscape feature of Iceland and the Canadian province of British Columbia. Hyaloclastite is usually found at subglacial volcanoes, such as tuyas, which is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. In lava deltas, hyaloclastites form the main constituent of foresets formed ahead of the expanding delta. The foresets fill in the seabed topography, eventually building up to sea level, allowing the subaerial flow to move forwards until it reaches the sea again.[1]

What produces columnar basalt?

slow cooling of lava flow

tuyas relevance; what causes them?

the height of them os nevr higher than ice and allows us to map the height of ice, cold climate etc

tephra

volcanic ash (rocks puvlerized into ash) - nothing is burning, this is what causes the eruption

jökulhlaup

A jökulhlaup (Icelandic pronunciation: ​[ˈjœːkʏlˌl̥œip]) (literally "glacial run") is a type of glacial outburst flood.[1] It is an Icelandic term that has been adopted in glaciological terminology in many languages. It originally referred to the well-known subglacial outburst floods from Vatnajökull, Iceland, which are triggered by geothermal heating and occasionally by a volcanic subglacial eruption, but it is now used to describe any large and abrupt release of water from a subglacial or proglacial lake/reservoir. Since jökulhlaups emerge from hydrostatically-sealed lakes with floating levels far above the threshold, their peak discharge can be much larger than that of a marginal or extra-marginal lake burst. The hydrograph of a jökulhlaup from Vatnajökull typically either climbs over a period of weeks with the largest flow near the end, or it climbs much faster during the course of some hours. These patterns are suggested to reflect channel melting, and sheet flow under the front, respectively.[2] Similar processes on a very large scale occurred during the deglaciation of North America and Europe after the last ice age (e.g., Lake Agassiz and the English Channel), and presumably at earlier times, although the geological record is not well preserved. Piotrowski has developed a detailed analytic model of the process, which predicts a cycle as follows:[5] Meltwater is produced as a result of geothermal heating from below. Surface ablation water is not considered as it would be minimal at the glacial maximum and evidence indicates that surface water does not penetrate more than 100 meters into a glacier. Meltwater initially drains through subglacial aquifers. When the hydraulic transmissivity of the substratum is exceeded, subglacial meltwater accumulates in basins. Water accumulates sufficiently to open the ice blockage in the tunnel valley which accumulated after the last discharge. The tunnel valley discharges the meltwater excess—turbulent flow melts out or erodes the excess ice as well as eroding the valley floor. As the water level drops, the pressure decreases until the tunnel valleys again close with ice and water flow ceases. The Eyjafjallajökull volcano can cause jökulhlaups. The 2010 eruption caused a jökulhlaup with a peak flow of about 2,000 to 3,000 m3/s.[14][15] North America[edit] In July 1994, an ice-dammed surface lake drained via a subglacial tunnel through Goddard Glacier [sv], in the British Columbian Coast Mountains, resulting in a jökulhlaup. The flood surge of from 100 to 300 m3/second flowed 11 km through Farrow Creek to terminate in Chilko Lake, causing significant erosion. The ice dam has not reformed. Similar British Columbian jökulhlaups are summarized in the table below.[16]

shield volcanoes

A shield volcano is a wide volcano with shallowly-sloping sides. Shield volcanoes are formed by lava flows of low viscosity - lava that flows easily. Consequently, a volcanic mountain having a broad profile is built up over time by flow after flow of relatively fluid basaltic lava issuing from vents or fissures on the surface of the volcano. Many of the largest volcanoes on Earth are shield volcanoes. The largest is Mauna Loa on the Big Island of Hawaii; all the volcanoes in the Hawaiian Islands are shield volcanoes. There are also shield volcanoes, for example, in Washington, Oregon, and the Galapagos Islands. The Piton de la Fournaise, on Reunion Island, is one of the more active shield volcanoes on earth, with one eruption per year on average.

dyke and fissure eruptions

DIKE: A dyke (or dike) in geology is a type of later vertical rock between older layers of rock. Technically, it is any geologic body which cuts across: flat wall rock structures, such as bedding. massive rock formations, usually igneous in origin. Dikes can therefore be either pushed in between (intrusive) or laid down (sedimentary) in origin. The most usual thing that happens is that later volcanic activity pushes lava through strata which were laid down earlier in a sedimentary fashion, or through earlier igneous rocks. On the Isle of Arran, for example, there are hundreds of igneous dykes giving rise to the term dyke swarm. Alternatively, sedimentary rocks can be laid down in vertical gaps between strata. Or, after underwater earthquakes, gaps caused by the earthquake can be filled in with breccia, that is, broken rocks. Dykes are a common, almost universal, feature of the older Palaeozoic rocks. Another type of intrusion is the sill, where later rock is formed between older layers, not through them. FISSURE: magma creates a fissure and pushes up through it via a plume - Fissure eruptions should not be considered in isolation, because they are also intimately related to Hawaiian eruptions. However, the unique character of fissure eruptions warrants a separate description here. In contrast to the point-source, centralized eruptions that typify most volcanoes, fissure eruptions are generated at several contemporaneous sites along a linear fracture, or along an en echelon (parallel, but offset) fracture system, such as that shown in the image here. Regional fracture systems can appear where the Earth's crust is broken and pulled apart by tensional forces. If these regions are underlain by reservoirs of basaltic magma, this low-viscosity melt will utilize the fractures and ascend through the crust to generate a fissure eruption. For example, Mid-oceanic ridges (divergent plate margins) typically extrude basaltic magma from fissure eruptions because these are areas where global-scale extension is coincident with the rise of partially molten asthenosphere. Because Iceland is the subaerial extension of the Mid-Atlantic Ridge, it is one of the world's most active sites for basaltic fissure eruptions. For this reason, fissure eruptions are also known as Icelandic eruptions. The largest lava flow in recorded history was generated by a fissure eruption in south central Iceland in 1783. Known as the Laki flow, it erupted from a 25-kilometer-long fissure to produce 12 cubic kilometers of lava, filling two deep river valleys and covering an area greater than 500 square kilometers. Fissure eruptions are also common on the flanks of many large volcanoes and, therefore, they are not restricted to areas undergoing regional extension. Magma-filled fissures radiating from the summit regions of active volcanoes like Mt. Etna, Mauna Loa, and Kilauea propagate outward from the central vent system. Extrusion from these propagating fissures can produce elongate volcano morphologies, such as those that are typical of many Hawaiian shield volcanoes. Note, for example, the axial elongation of the Mauna Loa shield volcano shown in the image to the left. Mauna Loa fissure eruptions are generated along two axial rift zones connected at the Mokuaweoweo summit crater. Each rift zone is underlain by magma-filled fissures. The image here displays several lava flows radiating downslope from these axial rift zones. Most of these erupted in historic times. ERUPTION STYLE: the "Curtain of Fire" As fluid, gas-poor basaltic magma rises up through a fissure, it is extruded at the surface as a wall of incandescent, liquid-to-plastic fragments known as a curtain of fire. Two such eruptions are shown below from extrusive events on the Kilauea volcano, Hawaii. Fissure eruptions are quiescent, and the height of the airborne eruptive material is small, often only a few tens of meters. The basaltic fragments in the curtain of fire thus remain largely liquid when they hit the ground. These coherent lumps of hot, fluid lava are called spatter. When they land, they can be hot and fluid enough to fuse together to form an aggregate called agglutinate, or agglutinated spatter. Spatter commonly builds up as banks along the fissure sides to produce spatter ramparts. Curtain of Fire Curtain of Fire Spatter Ramparts Linear vents with aligned spatter cones and spatter ramparts -- Fissure eruptions will generate a linear system of spatter cones and ramparts. If the eruption becomes concentrated on a single vent, then scoria cones may develop from more explosive Strombolian activity. All of these features are exhibited here from a Neolithic eruption in western Saudi Arabia. When fissures cease to erupt, the remaining magma residing in the fissure will cool and crystallize into an igneous rock intrusion. The resulting rock structure is called a dike. Dikes are tabular in shape, and they cut discordantly across adjacent rock layers. In areas of ancient volcanism, dikes are often delineated as resistant walls standing above more easily eroded rock types. Columbia RiverBasalt Dike Dike from Shiprock,New Mexico Dikes are often recognized by glassy selvages that develop along their margins where they cool rapidly against the rocks that they intrude, and by contractural cooling joints that generate columnar jointing parallel to their cooling surface, as demonstrated by the two dikes shown here from the Deccan flood basalt province. A 25-km-long dike located northwest of the town of Dhule, India. The dike is one of a swarm of E-W to ENE-WSW dikes in the central Deccan flood basalt province. Photo curtesy of Hetu Sheth. A 20-km-long dike in the western coastal region of the Deccan flood basalt province, where most dike swarms have N-S to NNW-SSE trends. The dike forms a dam across the Surya River near the coastal town of Dahanu. Photo curtesy of Hetu Sheth. FISSURE-FED FLOOD BASALT PROVINCES Massive fissure eruptions in the geological past have generated extraordinarily voluminous lava flows that form large continental flood basalt provinces. Individual provinces can cover hundreds of square kilometers, with average thicknesses of one kilometer. These flood-basalt eruptions are rare in the geologic record. They generate huge volumes of basalt over a very short time intervals, typically in only 1-2 million years. Well-known examples include (1) the Columbia River flood basalts, the bulk of which erupted from 17-14 million years ago in the northwestern United States, (2) the Deccan flood basalts, which erupted about 65 million years ago in western India, and (3) the Siberian flood basalts, which erupted about 245 million years ago in northern Siberia. Columbia River Flood Basalts Deccan Flood Basalts(Courtesy of Hetu Sheth) Flood-basalt eruptions are often intimately related to rifting or to stretching of the earth's crust above a region of hot mantle. This process can generate huge volumes of magma that rises through fractures to produce massive fissure eruptions on the surface. Basalt filled fissures on the Columbia Plateau, are currently exposed as dikes. About 14 million years ago, 700 cubic kilometers of basalt erupted from a single such fissure on the Columbia Plateau to form the Roza flow. The Roza flow is typical in volume to many of the larger flows in the Columbia River Basalt Province. These flow volumes dwarf the 12 cubic kilometers of the largest historic basaltic flow (the 1783 Laki flow), by more than an order of magnitude. Whereas the Laki flow advance ~40 kilometers from its source fissure, the largest of the Columbia River Basalt flows travelled up to 500 kilometers west of their source fissures.

Reykjanes Ridge

Reykjanes Ridge Expedtion R/V Knorr June 15- July 15, 2007 Home |Scientist & Crew |Science Overview|R/V KNORR| Daily Log | Photos | Links | Resources Science Overview Introduction Many areas along the Mid-Atlantic Ridge (MAR) have been surveyed in considerable detail. Surprisingly, the part of the Reykjanes Ridge connecting to Iceland is not one of these areas, although this is arguably the most important part of the ridge system to survey to understand plume-ridge interactions. The position of Iceland over the Mid Atlantic Ridge (MAR) provides an ideal setting in which to investigate mid-ocean ridge processes and the effects of hotspots on these processes (e.g. RIDGE 2000 Integrated Study Site Proposal for Hotspot-Influenced Oceanic Spreading Centers: Iceland and the Reykjanes and Kolbeinsey Ridges). Iceland is one of only two places on Earth where an oceanic spreading center rises above sea level, which allows nearby work on the submarine ridges to be placed in the extensive geological and geophysical context established for subaerial Iceland. These studies have established the basic pattern of present-day kinematics, geochronology of plate boundary shifts, and geochemical characteristics of the plume, and demonstrate strong plume interaction with the MAR at the Reykjanes Ridge. The Reykjanes Ridge (RR) separates the North American and Eurasian plates in the north Atlantic south of Iceland (Fig. 1). It is the longest oblique spreading ridge in the world, extending about 900 km from Iceland to the Bight transform fault near 56.5°N. The Bight transform is a 15 km left-stepping displacement of the ridge axis along 092º, with an associated fracture zone extending into at least 36 Ma crust (Müller and Roest, 1992), that marks a change in ridge orientation from near orthogonal to the south to highly oblique in the north. On average, the RR trends ~036° with a spreading direction of ~099°, representing an average spreading obliquity of 27° (Vogt et al., 1971; Fleischer, 1974; Keeton et al., 1997). However, there is an increase in obliquity towards Iceland, reaching a maximum on the Reykjanes Peninsula, where it is ~065° (Johnson and Jakobsson, 1985). The average spreading rate along this slow spreading ridge is about 20 mm/yr (Talwani et al., 1971, DeMets et al., 1994). The RR is unusual in that it lacks any transform faults, and also in terms of its general physiology. South of ~59°N the RR axis forms a prominent axial valley ~40 km wide and ~1 km deep, typical for slow spreading ridges not influenced by hotspots. Closer to Iceland the ridge axis shallows and the axial valley is replaced by a robust axial high more characteristic of a fast-spreading ridge (Laughton et al., 1979; Murton and Parson, 1993; Parson et al., 1993; Searle et al., 1998; Fig. 2). In general this is attributed to effects of a mantle plume currently situated under Iceland (e.g. Morgan, 1971; Vogt, 1971, 1974; Schilling, 1973, 1986; White et al. 1995; White, 1997; Wolfe et al., 1997; Allen et al., 1999; Allen, 2001). Distinctive diachronous V-shaped ridges are observed in the gravity (Fig. 1) and bathymetry (Fig. 2) data, progressively terminating transform faults in what had been a more typical orthogonal ridge/transform system (Talwani et al., 1971; Vogt, 1971). These V-ridges have thicker crust than normal (White et al., 1995; Weir et al., 2001; Smallwood and White, 2002), consistent with formation at higher mantle temperatures, and there is a strong plume geochemical signature along much of the RR (e.g. Schilling, 1973, 1975; White et al., 1976; Schilling et al., 1982). That these V-ridges are associated with the Iceland hotspot and possible plume seems inescapable, although exactly what the relationship is remains a subject of debate. They have usually been interpreted to result from "pulses" of the plume and subsequent subaxial flow of magma (e.g., Vogt, 1971; Vogt and Johnson, 1975; White et al., 1995; Ito, 2001), although there is an alternative hypothesis involving ridge jumps (Hardarson et al., 1997) that we propose to test. Iceland Tectonics The RR rises above sea level at the southwestern tip of Iceland at the Reykjanes Peninsula (63.8°N). The island of Iceland straddles the MAR and is the largest area of sub-aerially exposed mid-ocean ridge on Earth. Over Iceland the MAR is spreading at ~19 km/m.y. along an average direction of ~110°. The unusually high rate of volcanism that generates the Iceland bathymetric high can be related to the combined contributions from the Iceland hotspot and the mid-ocean ridge (Morgan, 1971; Schilling, 1973). The geometry of the present day MAR plate boundary through Iceland is complicated (Fig. 3), with spreading occurring on 3 principal rift zones, the Western (Reykjanes-Langjökull) Volcanic Zone (WVZ), the Eastern Volcanic Zone (EVZ), and the Northern Volcanic Zone (NVZ), with two principal transform zones, the South Iceland Seismic Zone (SISZ) and the Tjörnes Fracture Zone (TFZ) (Ward, 1971; Saemundsson, 1974, 1979; Jacobsen, 1979; Björnsson et al., 1979; Jóhannesson, 1980; Gudmundsson, 1995; 2000; Hardarson et al., 1997; Thordarson and Hoskuldsson, 2002). It has been established that the position of the plate boundary has shifted repeatedly to the east during the 16 Ma history of present day Iceland (e.g. Ward, 1971; Burke et al., 1973; Saemundsson, 1979; Johannesson, 1980; Aronson and Saemundsson, 1975; Helgason, 1984; Vink, 1984; Thordarson and Hoskuldsson, 2002). The rift zones evidently adjust to the westward movement of the MAR away from the center of the Iceland plume, now thought to lie below the northern part of the Vatnajökull glacier (Johannesson, 1980; Ryan, 1990; Gudmundsson, 1995; Wolfe et al., 1997; Shen et al., 1998; Allen, 2001), by episodically jumping east to stay near the hotspot. This explains the offset of the EVZ/NVZ from the RR/Kolbeinsey ridge system, and the growth of the SISZ and TFZ (Ward, 1971; Fig. 3). In northern Iceland, there was a major eastward ridge jump at ~15-16 Ma from Vestfirdir, in the extreme NW of Iceland, to the Skagi Peninsula, and another beginning ~7 Ma from Skagi to the NVZ (Saemundsson, 1974, 1979; Helgason, 1985; Hardarson et al., 1997). In southern Iceland there was a rift relocation from the Snaefellsnes Peninsula (Fig. 3) to the Reykjanes Peninsula ~6-9 Ma (Hardarson et al., 1997; Kristjansson and Jonsson, 1998). The most recent plate boundary shift, the ridge jump thought to be in progress from the WVZ to the EVZ beginning some 2-4 Ma ago (Johannesson, 1980; Gudmundsson, 1995), formed the southern EVZ that extends from the Vatnajökull glacier in the north to Surtsey and the Vestmann Islands off the south coast of Iceland, the latter possibly at the tip of a southward propagating rift (Meyer et al., 1985; Saemundsson, 1986; Mattson and Hoskuldsson, 2003). Instead of occurring instantaneously, these shifts occurred gradually over a period of a few m.y. while spreading was distributed over both the old and new rift zones. Proposed Research The hypotheses we propose to test are that there were rift relocations (ridge jumps) along the RR that were associated with the known rift relocations on Iceland, and that these jumps are associated with the V-shaped ridges extending south from Iceland. The data necessary to test these hypotheses are magnetic anomalies, gravity, and multibeam bathymetry across the part of the RR closest to Iceland (N of 62°N), collected along the flowline of relative plate motion to minimize complexities that ridge jumps produce, and maximize the signal/noise ratio of these jumps to facilitate our modelling effort. The test is straightforward. We will model each magnetic profile using our Magbath program (Fig. 10) as well as modelling the contoured magnetics using our PRMap program (e.g. Fig. 8) to determine whether the observed asymmetry in the V-shaped ridges results from small ridge jumps or from asymmetric spreading with no resolvable jumps. If the V-shaped ridges are associated with ridge jumps, and if these jumps occur in patterns characteristic of propagating rifts (Fig. 11), they will lie along pseudofaults or failed rift sequences forming part of propagating rift wakes that will be revealed by our data and modelling. If the asymmetry does not result from jumps, there will be no failed rifts or pseudofaults. If there were jumps, we will determine how the pattern relates to the known pattern on land, to produce a seamless history of the North America-Eurasia plate boundary geometry on and near Iceland during the past 18-20 Ma. Our results would almost certainly add to the understanding of the rift relocations on Iceland, where the detailed ridge jump history is buried by lavas from the eventually successful plate boundary. If there were no jumps along the RR, we will determine what it means for the regional tectonic evolution to have had ridge jumps on Iceland but not the RR, and how this has influenced the evolution of Iceland, e.g. the predictable growth and increasing obliquity of the Reykjanes Peninsula and South Iceland Seismic Zone. This would constrain geodynamic models of processes such as sublithospheric magma flow. A comparison between the "flow down a pipe" plume pulse model (e.g. Vogt, 1971), and the propagating rift model (Fig. 9), shows one essential difference that will allow us to test between these hypotheses. If the seafloor spreading process itself is symmetric, as commonly assumed because of the extreme dependence of lithospheric strength on temperature (Morgan, 1968), the simple pipe flow model (Fig. 9A) predicts symmetric accretion of lithosphere to the 2 plates. In contrast, the propagating rift model (Fig. 9B) requires the transfer of lithosphere between plates, and thus predicts systematic asymmetric accretion, such as that seen in the Talwani et al. (1971) profiles (Fig. 5). We propose a marine geophysical survey to determine the 0-20 Ma seafloor spreading history of the part of the RR nearest Iceland. The critical areas of seafloor flanking the RR have not been previously surveyed systematically by ship, making it currently impossible to determine if there is a pattern of oceanic ridge jumps that should relate to those observed on Iceland. It is important to do this to test between competing hypotheses for the major V-shaped patterns of bathymetry and gravity, and to extend the documented effects of plume-ridge interaction to more peripheral locations relative to the plume center. Although various "pulsing plume" hypotheses to explain this pattern have long been favored, recently an alternative "rift relocation" hypothesis has been proposed. The Hardarson et al. (1997) hypothesis argues that the RR is normally very elevated, with the V-shaped ridges actually being defined by the valleys between them which result from magmatic deficiency during times that ridge jumps prevent some of the plume magma from reaching the RR. It thus predicts some sort of strong correlation between the ridge jump pattern and the V-ridge pattern, although exactly what the correlation should be in detail is uncertain. What is certain is that if there is a pattern of offshore jumps that correlates with the onshore pattern, it will be possible to use the seafloor data to understand the detailed evolution of Iceland much better, because ridge jumps on Iceland are associated with voluminous volcanism that overwrites and deeply buries the preexisting crust, whereas the seafloor record of jumps is written and preserved on a much finer scale. If correlations are not found between the seafloor and Icelandic patterns of jumps or between the jumps and the V-shaped ridges, this would argue that some sort of plume pulse mechanism is responsible for the V-ridges rather than the Hardarsson et al. hypothesis. Of course hybrid hypotheses involving plume pulses causing ridge jumps are also possible and will be constrained by our data. Our goal is a seamless history of the plate boundary geometry both at sea and on land. We regard this as an essential step toward the full understanding of Iceland and the geodynamic influence of the hotspot or mantle plume on the mid-ocean ridge system.

Eyjafjallajokull Volcano

You know the one! The towering glacier-capped strato volcano Eyjafjallajokull is probably the most famous volcano in the world today. Eyjafjallajökull the volcano with the name that no one outside Iceland seem to be able to pronounce. Have you tried it? Can you say Eyjafjallajokull three times really fast? There aren't many non-Icelanders that can, but all the more respect to those who can, right? 484 €Per person South Iceland Express Road Trip 5 days / 4 nightsView tour Eyjafjallajokull is one of the smaller ice caps of Iceland. The volcano has erupted relatively frequently since the last glacial period, most recently in 2010. Eyjafjallajokull consists of a volcano which is completely covered by an ice cap. The ice cap covers an area of about 100 square kilometres (39 sq mi) and it has many outlet glaciers. The main outlet glaciers are to the north: Gigjokull that flows into Lonid, and Steinholtsjokull which flows into Steinholtslon. The mountain itself stands 1,651 metres (5,417 ft) at its highest point. It has a crater 3-4 kilometres (1.9-2.5 mi) in diameter that opens to the north. Eyjafjallajokull eurption - the eruption that stopped the world On March 20, 2010 Eyjafjallajokull began spewing molten lava in an uninhabited area in south Iceland, after being dormant for 180 years. On April 14th, 2010, after a brief intermission, the volcano resumed erupting from the top crater in the center of the glacier. The renewed eruption caused massive flooding, which required an evacuation of 800 people. This second eruption threw volcanic ash several kilometers up in the atmosphere. The ash plume could be seen from miles away. That led to air traffic disruption in North-West Europe. The disruption lasted for six days, from April 15th to April 21st, that stranded thousands of travelers. It happened again in May, which resulted in the closure of airspace over many parts of Europe. The eruption also created electrical storms. On May 23rd, the London Volcanic Ash Advisory Commission declared the eruption to have stopped. The volcano continued to have several earthquakes daily, with volcanologists watching the mountain closely. As of August 2010, Eyjafjallajökull was dormant. Today the aftermath of the volcanic eruption can be seen in Thorsmork Glacier Valley, the natural oasis that lies just behind the volcano. You can also see a part of the ice cap is still covered in ash, though that is slowly disappearing under layers of snow. Perhaps you would like to go on a snowmobile tour on the ice cap and see the crater, which also offers you a great view of southern part of Iceland. We fully recommend it, and don't worry, it's completely safe. What type of volcano is Eyjafjallajokull? Eyjafjallajokull is a strato volcano. It is a conical volcano built by many layers of hardened lava, tephra, pumice and volcanic ash. Strata volcanoes are among the most common volcanoes. Due to the glacier on top of Eyjafjallajokull eruptions are explosive and contain much ash. A large magma chamber under the mountain feeds Eyjafjallajokull. The chamber derives magma from the tectonic divergence of the Mid-Atlantic ridge. The volcano is a part of the chain of volcanoes that stretch across Iceland, including volcanoes like Hekla, Katla and Grimsvotn. Eyjafjallajokull and Katla, neighbouring volcanoes, are believed to be related. Eruptions of Eyjafjallajokull have usually been followed by eruptions of the volcanoe Katla, which is a far larger and more powerful volcano than Eyjafjallajokull. As former president, Olafur Ragnar Grimsson, said referring to Katla: "You ain't seen nothing yet!" Are there more volcanoes in Iceland? Yes, there are over 130 active volcanoes in Iceland, and you can see them and the effect they've had on the land almost everywhere. Not far from Eyjafjallajokull volcano is a very nice museum dedicated to the volcanoes in Iceland, called Lava center. You can find it in Hvolsvollur village. Eyjafjallajokull and the South Shore of Iceland Eyjafjallajokull and neighbouring Myrdalsjokull dominate the landscape in South-Iceland and can be seen miles away. We recommend that you make a stop at viewpoints and admire the volcanoes from afar. There are a few along the road. Making a stop at Seljalandsfoss waterfall is almost mandatory and walk behind the waterfall. In the summer the waterfall can be a bit crowded, just as Skogarfoss waterfall, since both are popular tourist attractions. If you're driving 4×4 vehicle we recommend making a stop in Thorsmork Nature Reserve. It is more than worth it, since the small valley is beautiful, serene and peaceful. If you do stop there, make the hike to the top of Valahnukur, which is about 1.5 miles long. The hike offers a superb and panoramic view of the surrounding mountains and Thorsmork Valley. How to pronounce Eyjafjallajökull? What's Eyjafjallajokull's meaning? There are many words in Icelandic that sound strange and alien to native English speakers. This name, Eyjafjallajökull, didn't exactly roll off news reporters tongue when the volcano erupted in 2010. The word is a compound of three different words. First, Eyja which means islands, but that refers to the Vestmannaeyjar Islands just off Iceland's coast. Then, fjalla which means mountains, and last jökull, which means glacier. So the compound itself means the Glacier on Island Mountains, which is rather transparent, don't you think? You can try it for yourself, it isn't so hard to pronounce if you just follow this simple guide. Just a quick tip, perhaps you should try this first alone, for even seasoned news reporters seemed to struggle with it. How to get to Eyjafjallajokull? Driving along the South Shore brings you close to the volcano. The Mountain Range is visible as soon as you drive east following road 1 from Reykjavik and you pass Hellisheidi heath. There you can find Hellisheidi Geothermal Plant, which is visible from the road. You will see many volcanoes tower over the southern part of Iceland, among them mt. Hekla and mt. Katla, which are both active and powerful volcanoes. Eyjafjallajokull is between the two, standing high not far from the village Hvolsvollur, where you can visit the beautiful Saga center. If you follow Road 1 eastwards along the South Shore you will eventually pass a great exhibition, where you can learn a great deal about the 2010 eruption. The Exhibition is at Þorvaldseyri visitor center, which is a family run exhibition about this massive and intersting volcano. Make sure you don't miss it. Explore Eyjafjallajokull Here are a few great tours we recommend where you can explore Eyjafjallajokull to the fullest: South Coast and Eyjafjallajokull Explore the South Shore in a Super-jeep and get closer to the area of the magnificent 2010 Eyjafjallajokull eruption. Your driver-guide will take you across fertile farmlands, where Njall's Saga, one of the greatest Icelandic medieval stories, took place. Continue towards the glaciers Eyjafjallajokull admiring the surrounding panorama. Thorsmork Valley and Eyjafjallajokull Volcano Sight A day to discover the beautiful Thorsmork Natural Reserve on board of a Super Jeep and crossing some rugged terrains in South Iceland. On this classic Iceland day tour for nature's lovers, you will board a Super Jeep and head to Thorsmork Natural Reserve driving across the Icelandic south shore. Check out our complete guide to the South Coast.