Structural geology

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This low-angle thrust fault occurs in the Brúarjökull 1890 end moraine complex. Credit: Ólafur Ingólfsson.

"Structural Geology [as a science is] a unified and integrated approach to the description and interpretation of deformation in the earth's crust, ranging from the microscopic scale, through mesoscopic structures, and up to the largest scale plate tectonic and orogenic structures."[1]

Theoretical structural geology[edit]

Geological structure shows strata under lateral tension producing horst and graben. Credit: U.S. Geological Survey.

Lateral tension on rigid rock strata may produce a horst and graben structure.

Faults[edit]

The image shows a portion of the San Andreas Fault in California USA on Earth. Credit: Robert E. Wallace, USGS.
This is a normal fault, where the younger strata has slid downwards to sit beside the older strata. Credit: Ashley Dace.
The "faille des Causses" is a geological fault in the Grands Causses, as seen from Bédarieux (Hérault, France). Credit: Xhienne.

Def. a "fracture in a rock formation causing a discontinuity"[2] is called a fault.

"Possibly the most obvious fault line in Britain. The red rock with reduction horizons is Triassic Merica mudstone (MMS), to the left is Jurassic interbedded marls and muds (with evapourites like gypsum). You can tell this is a normal fault because the Jurassic strata is younger than the MMS. This means the Jurassic strata has slid downwards to sit beside the MMS. Also near the fault in the MMS the lighter reduction horizons are dipping downwards probably due to marginal drag. The line of the fault runs along the beach, shown by the rock/sand divide."[3]

Active faults[edit]

The Emerson fault is one of the segments that ruptured in the M7.2 1992 Landers, Calfornia earthquake. Credit: Kerry Sieh, Caltech.

Def. a "fault that is likely to have another earthquake sometime in the future"[4] is called an active fault.

"Faults are commonly considered to be active if they have moved one or more times in the last 10,000 years."[4]

Thrust faults[edit]

Jón Björn discovered a beautiful low-angle thrust fault in the 1890 end moraine. Credit: Ólafur Ingólfsson.
A large thrust fault resulted from glacial movement at Melabakkar, Iceland. Credit: Ólafur Ingólfsson.

"When Brúarjökull surged, large ice-marginal moraines which can be traced over many kilometers, were produced in front of the glacier. Todtmann (1952, 1955) identified two types of ice-marginal moraine; ‘stauchendmoräne’ and ‘blockendmoräne’ which are equivalent to push and probably dump moraines in modern terminology. Push moraines are the result of proglacial thrusting [as in the image at the top of the page] and folding of material, whereas, dump moraine might have resulted from material avalanching down a steep ice-front (Krüger et al., 2003a), although the specific processes at Brúarjökull are unknown."[5]

The second image on the right shows Late Weichselian proglacial deformation. A large thrust fault has resulted from glacial movement at Melabakkar, Iceland.

Blind thrust faults[edit]

Diagram is of a blind thrust fault. Credit: Stephen Nelson, Tulane University.

Def. a "thrust fault that does not rupture all the way up to the surface so there is no evidence of it on the ground"[6] is called a blind thrust fault.

"It is "buried" under the uppermost layers of rock in the crust."[6]

Locked faults[edit]

Locked faults may store strain for extended periods that is eventually released in an earthquake when frictional resistance is overcome. Credit: Geological Survey of Canada.

Def. "a fault that is not slipping because frictional resistance on the fault is greater than the shear stress across the fault"[7] is called a locked fault.

Transform faults[edit]

Shaded and colored image from the Shuttle Radar Topography Mission elevation model of New Zealand's Alpine Fault, Northwest is towards the top. Credit: NASA/JPL/NGA.
Transform faults often extend from oceanic ridges. Credit: USGS.

Def. "a special variety of strike-slip fault that accommodates relative horizontal slip between other tectonic elements, such as oceanic crustal plates"[8] is called a transform fault.

"The Alpine fault runs parallel to, and just inland of, much of the west coast of New Zealand's South Island. This view was created from the near-global digital elevation model produced by the Shuttle Radar Topography Mission (SRTM) and is almost 500 kilometers (just over 300 miles) wide. Northwest is toward the top. The fault is extremely distinct in the topographic pattern, nearly slicing this scene in half lengthwise."[9]

"In a regional context, the Alpine fault is part of a system of faults that connects a west dipping subduction zone to the northeast with an east dipping subduction zone to the southwest, both of which occur along the juncture of the Indo-Australian and Pacific tectonic plates. Thus, the fault itself constitutes the major surface manifestation of the plate boundary here. Offsets of streams and ridges evident in the field, and in this view of SRTM data, indicate right-lateral fault motion. But convergence also occurs across the fault, and this causes the continued uplift of the Southern Alps, New Zealand's largest mountain range, along the southeast side of the fault."[9]

"Two visualization methods were combined to produce this image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast (image top to bottom) direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations."[9]

"Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices."[9]

The Alpine fault is "495 kilometers (307 miles) by 162 kilometers (100 miles). Location: 43.2 degrees South latitude, 170.5 degrees East longitude. Orientation: Northwest toward the top".[9]

Strike-slip faults[edit]

The satellite image shows a part of the Piqiang Fault (China). Credit: NASA Earth Observatory images by Robert Simmon and Jesse Allen, using Landsat data from the USGS Earth Explorer.

Def. a "fault where two blocks move horizontally in opposite directions along the fault line"[10] is called a strike-slip fault.

The Piqiang Fault (China) is "a northwest trending strike-slip fault that runs roughly perpendicular to the thrust faults for more than 70 kilometers (40 miles). The colored sedimentary rock layers are offset by about 3 kilometers (2 miles) in this area."[11]

"The reddish, greenish and brownish bands are continental Devonian sandstones, Silurian deeper marine sediments and Cambro-Ordovician limestones, respectively. They form one of several parallel ridges (up to 1200 m high) which all are composed of the same stack of rocks and belong to the Keping Shan thrust belt immediately south of the Southern Tien Shan Mountains."[12]

Dextral faults[edit]

East-West dextral strike-slip fault cross-cut a quartz vein near the Picolo San Bernardo pass (Italian Alps). Credit: Jide~commonswiki.

Def. "a strike-slip fault that shows right lateral movement [movement of the right-hand block toward the observer standing across the fault plane]"[13] is called a dextral fault.

The strike-slip fault in the image on the right is a dextral fault.

Sinistral faults[edit]

There has been about 15 to 20 centimetres of movement along the fault with the left side moving toward the observer. Credit: Franck Bouttemy.

Def. "a strike-slip fault that shows left lateral movement [movement of the left-hand block toward the observer standing across the fault plane]"[14] is called a sinistral fault.

Alternating layers of mudstone and sandstone of the Sidi Bettache Basin of Carboniferous age, cut by a normal fault in Seppap Gorge near Sidi Bettache, Morocco, shown in the image on the right. The outcrop is about 5 metres high.

Surface faults[edit]

The Hector Mine surface rupture is after 1999 earthquake in southern California. Credit: Katherine Kendrick, U.S. Geological Survey.

On the right is an example of a surface fault. Here, the surface above the Hector Mine ruptured after 1999 earthquake in southern California.

Deformed strata[edit]

Glaciotectonically "rolled up" soils are from the Brúarjökull 1890 end moraine. Credit: I.Ö. Benediktsson.
These are heavily deformed marine sediments, Bogen, Kongsoya. Credit: Ó. Ingólfsson.
Glaciotectonic deformations are from the Brúarjökull 1890 end moraine. Credit: L.R. Bjarnadóttir.
Folded strata are from the Carboniferous and Permian in Ingeborgfjellet, Van Mienfjorden, Spitsbergen. Credit: Ó. Ingólfsson.

In the image on the right are glaciotectonically "rolled up" soils from the Brúarjökull 1890 end moraine.

The second image on the right shows additional glaciotectonic deformations from the Brúarjökull 1890 end moraine.

On the left are heavily deformed marine sediments from the Svalbard Kongsoya near Bogen.

The second image on the left shows folded strata dated to the Carboniferous and Permian in Ingeborgfjellet, Van Mienfjorden, Spitsbergen.

Volcanic arcs[edit]

A chain of volcanoes (volcanic arc) sometimes forms on the land when an oceanic plate collides with a continental plate and then slides down underneath it (subduction). Credit: Lynn Fichter, James Madison University.

Def. a "chain of volcanoes that sometimes forms on the land when an oceanic plate collides with a continental plate and then slides down underneath it (subduction)"[15] is called a volcanic arc.

Accretionary wedges[edit]

Sediments are a wedge that accumulates and deforms where oceanic and continental plates collide. Credit: USGS.

Def. sediments, "the top layer of material on a tectonic plate, that accumulate and deform where oceanic and continental plates collide"[16] are called an accretionary wedge.

"These sediments are scraped off the top of the downgoing oceanic crustal plate and are appended to the edge of the continental plate."[16]

Def. an "accumulation of surface sediment formed between a subducting oceanic crustal plate and a continental tectonic plate, as it is scraped from off the top of the oceanic crustal plate"[17] is called an accretionary wedge.

Folded strata[edit]

Glaciotectonically deformed sediments have small folds in the Kringilsa section. Credit: I.Ö. Benediktsson.

On the right are extensively folded strata from the Kringilsa section in the forefield of Brúarjökull. These folded strata were produced by a glacial surge.

Abrasion platforms[edit]

A wave-cut abrasion platform at Bracken Bay is only visible at low tide. Credit: Walter Baxter.

Def. a "sloping or nearly flat bedrock surface extending out from the foot of a marine cliff under shallow water of a breaker (wave) zone, that was created by marine abrasion"[18] is called an abrasion platform.

The rock surface in the image on the right at the foot of the Heads of Ayr cliffs is the result of wave abrasion on the headland.

Abyssoliths[edit]

Half Dome is a granite monolith in Yosemite National Park and part of the Sierra Nevada batholith. Credit: Jon Sullivan.

Def. a "mass of igneous rock deep in the crust with no known bottom; a large batholith"[19] is called an abyssolith.

"According to systematic deduction from a host of facts the feeders of volcanoes appear to be abyssoliths, molten masses injected upward into the Earth's crust from a vitreous, gas-charged substratum of basalt."[20]

The Sierra Nevada Batholith of which the image on the right is a part has no known bottom.

Allochthons[edit]

Def. a "geological formation not formed in the region where found and moved to its present location by tectonic forces"[21] is called an allochthon.

Anticlines[edit]

Anticline is in the Barstow Formation (Miocene) at Calico Ghost Town near Barstow, California. Credit: Wilson44691.

Def. a "fold with strata sloping downwards on each side"[22] is called an anticline.

Anticlinoriums[edit]

The rocks of the Maitai Seiies in the Dun Mountain Subdivision have been folded into an anticlinorium and into a synclinorium lying to the west of the anticlinorium. Credit: James Mackintosh Bell, Edward de Courcy Clarke, Patrick Marshall.

Def. a "series of parallel anticlinal folds on a regional-scale anticline"[23] is called an anticlinorium.

On the right is a map of an anticlinorium near Nelson, Australia. The observations made by the writers seem to show that the rocks of the Maitai Seiies in the Dun Mountain Subdivision have been folded into an anticlinorium, mainly occupied now by the intrusions of the Mineral Belt, and into a synclinorium lying to the west of the anticlinorium.

Aulacogens[edit]

Def. a "tectonic trough on a craton that is formed as the failed arm of a triple-rift junction"[24] is called an aulacogen.

Autochthons[edit]

Def. a rock formation native to the place where found is called an autochthon.

Autogeosynclines[edit]

Def. a "parageosyncline that subsides as an elliptical basin or trough nearly without associated highlands"[25] is called an autogeosyncline.

Backarcs[edit]

Def. the "landward region of a volcanic chain, opposite the subduction zone"[26] is called a backarc.

Batholiths[edit]

Def. a "large irregular mass of intrusive igneous rock that has melted or forced itself into surrounding strata"[27] is called a batholith.

Diapirs[edit]

Geological cross section is through the Northwestern Basin of Germany. Credit: Hannes Grobe.

Def. an "intrusion of a ductile rock into an overburden"[28] is called a diapir.

The geological cross section through the Northwestern Basin of Germany (Ostfriesland-Nordheide) above shows the record and deposits since the Permian (about 250 Ma). Salt domes of the Zechstein have penetrated the overburden layers and intruded close to the surface.

Dikes[edit]

Def. a "body of once molten igneous rock that was injected into older rocks in a manner that crosses bedding planes"[29] is called a dike.

Diatremes[edit]

Def. a "cone-shaped volcanic vent produced by the explosion of gas-filled magma"[30] is called a diatreme.

Eugeosynclines[edit]

Def. a "narrow rapidly subsiding geosyncline usually with volcanic materials mingled with clastic sediments"[31] is called a eugeosyncline.

Geanticlines[edit]

Def. a "large-scale anticline; a large upward lift in the earth's surface"[32] is called a geanticline.

Geologic joints[edit]

Def. a "fracture in rock in which (unlike a fault) the strata do not move relative to each other"[33] is called a geologic joint.

Geosynclines[edit]

Def. a "large, linear depression in the Earth's crust in which sediment accumulates"[34] is called a geosyncline.

Grabens[edit]

Def. an "elongated block of the Earth's crust that has dropped relative to the surrounding blocks"[35] is called a graben.

Horsts[edit]

Def. "an area of the earth's surface which is raised relative to surrounding land"[36] is called a horst.

Hydrolaccoliths[edit]

Def. a "frost mound that has a core of ice and resembles a laccolith in cross-section"[37] is called a hydrolaccolith.

Intrusions[edit]

Hand specimen of Alaskite (leucogranite) from the Mount Evans Batholith. Credit: James St. John.

Def. magma "forced into other rock formations; the rock formed when such magma solidifies"[38] is called an intrusion.

Def. "a large body of igneous rock within which distinct stratification continues over many miles"[39] is called a layered intrusion.

Def. the "metamorphism of plutonic rock into magma in the lower levels of the crust"[40] is called anatexis.

Def. an "intrusion of the continental crust subject to anatexis"[41] is called a leucogranite.

Isoclines[edit]

Def. a "tightly folded syncline or anticline in which the two sides are almost parallel"[42] is called an isocline.

Laccoliths[edit]

Def. "a mass of igneous or volcanic rock found within strata which forces the overlaying strata upwards and forms domes"[43] is called a laccolith.

Lava domes[edit]

Image of the rhyolitic lava dome of Chaitén Volcano during its 2008–2010 eruption. Credit: Sam Beebe.
One of the Mono Craters is an example of a rhyolite dome. Credit: Daniel Mayer.
Lava domes in the crater of Mount St. Helens. Credit: Willie Scott, USGS.
Photo showing the bulging cryptodome of Mt. St. Helens on April 27, 1980. Credit: Peter Lipman.
Chao dacite coulée flow-domes (left center), northern Chile, is viewed from Landsat 8. Credit: Robert Simmon, NASA Earth Observatory, USGS Earth Explorer.

Def. a roughly circular mound-shaped bulge that builds up from the slow eruption of viscous felsic lava from a volcano is called a lava dome.

Lava domes are rarely seen in shield volcanos, but are common in stratovolcanos because the latter have more silicic magmas.

"Mount St. Helens has been building a new lava dome since the May, 1980 eruption."[44]

"Streams of molten rock that ooze from gaps or vents in the Earth’s surface are called lava flows. Though generally slow-moving, these rivers of rock pose a hazard to everything in their paths. They can bury or burn homes and roads, ruin farmland for generations, and transform glaciers into muddy landslides (lahars)."[45]

"Lava flows can take many shapes and move at very different rates depending on the viscosity of the magma, the slope of the land, and the rate of an eruption. Some of the speediest flows travel 60 kilometers (40 miles) per hour; the slowest creep along at less than 1 kilometer (0.6 miles) per hour. They can sometimes even flow for more than a year after an eruption has ended."[45]

"Viscous (or sticky), non-explosive flows produce distinctive landforms known as lava domes. These circular mounds form as lava slowly oozes from a vent and piles up on itself over time. Lava domes tend to have steep, cliff-like fronts at their leading edge and wrinkle-like pressure ridges on their surfaces."[45]

"The Chao dacite is a type of lava dome known as a coulée. These elongated flow structures form when highly-viscous lavas flow onto steep surfaces. On May 14, 2013, the Operational Land Imager (OLI) on NASA’s Landsat 8 satellite acquired the image above, which highlights some of the distinctive features of a coulée."[45]

"The Chao dacite sits between two volcanoes in northern Chile: the older and partially-eroded Cerro del Leon and the younger Paniri. The dome itself is a giant tongue of rock that extends southwest from the vent. Curved pressure ridges known as ogives dominate the surface of the 14 kilometer (9 mile) dome."[45]

"Volcanologists think the Chao dacite dome formed over a period of about 100 to 150 years. A pyroclastic flow during the Chao I phase left light-brown deposits of tephra and pumice at the leading edge of the flow. Pyroclastic flows are avalanche-like events that bring mixtures of hot gas and semi-sold rocks surging down the flanks of volcanoes at speeds as fast as 100 kilometers (60 miles) per hour."[45]

"This period was followed by the Chao II phase, when 22.5 cubic kilometers (5.4 cubic miles) of lava erupted. This flow has 400-meter tall (1,312 feet) fronts that stand out with their dark shadows on the southwest end. The final, Chao III phase added another 3.5 cubic kilometers (0.8 cubic miles) of denser lava with a lower viscosity. This type of lava is less likely to form pressure ridges, so surfaces in this part of the flow are comparatively smooth."[45]

"It’s not clear why the Chao dacite erupted as a flow and formed a dome rather than erupting explosively. However, some researchers have noted that there are a number of other domes in the area (such as Chillahuita), suggesting that the domes may be the leading edge of a broader magmatic system that erupted along pre-existing faults. Though much larger, a series of lava domes along the eastern side of California’s Sierra Nevada range—the Mono-Inyo chain—offers a possible analog for what might be happening in this part of Chile."[45]

Lopoliths[edit]

Def. "a mass of volcanic or igneous rock found within strata which has spilled downward into underlaying strata and forms depressed regions"[46] is called a lopolith.

Miogeoclines[edit]

Def. an "area of sedimentation that occurs along the passive margin of a continent"[47] is called a miogeocline.

Orthogeosynclines[edit]

Def. a "linear geosynclinal belt lying between continental and oceanic cratons, and having internal volcanic belts (eugeosynclinal) and external nonvolcanic belts (miogeosynclinal)"[48] is called an orthogeosyncline.

Overfolds[edit]

Def. a "fold whereby the strata are forced through an angle of more than 90 degrees, so that younger strata lie below older ones"[49] is called an overfold.

Overshifts[edit]

Def. an "overhang caused by seismic shift"[50] is called an overshift.

Overthrusts[edit]

Def. a "form of thrust fault from beneath a hanging wall of rock"[51] is called an overthrust.

Palaeoshorelines[edit]

Def. the "shoreline as it was in the geologic past"[52] is called a palaeoshoreline.

Palaeosubductions[edit]

Def. a "subduction that occurred in the geologic past"[53] is called a palaeosubduction.

Parageosynclines[edit]

Def. a "geosyncline within or adjacent to a craton and usually less elongated, shallower, and less persistent than an orthogeosyncline"[54] is called a parageosyncline.

Rifts[edit]

A huge iceberg, a quarter the size of Wales, is poised to break off from the Larsen C ice shelf. Credit: Adrian Luckman.
A 60 km crack opened in Ethiopia in 2005 and has been expanding ever since. Credit: Tim Wright.
Rifts are converging on the Gulf of Aden. Credit: Cynthia Ebinger, Royal Holloway, University of London.
Ash and pumice is thrown out at a vent site at the northern tip of the 60 km-long Boina tectono-magmatic segment. Credit: Cynthia Ebinger, Royal Holloway, University of London.
Researchers have long recognised that the Afar region, an inhospitable depression in north-eastern Ethiopia, has been contorted by similar forces in recent geological time. Credit: BBC News.

"An iceberg [in the image on the right] expected to be one of the 10 largest ever recorded is ready to break away from Antarctica."[55]

"A long-running rift in the Larsen C ice shelf grew suddenly in December and now just 20 km of ice is keeping the 5,000 sq km piece from floating away."[56]

"Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it."[56]

"Researchers have been tracking the rift in Larsen C for many years, watching it with some trepidation after the collapse of Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002."[56]

In "December [2016] the speed of the rift went into overdrive, growing by a further 18 km in just a couple of weeks."[56]

"The rift is about 100 m wide but is estimated to be half a kilometre deep."[56]

This "is a geographical and not a climate event. The rift has been present for decades, but it has punched through at this particular time."[55]

"The collapse of the Larsen B ice shelf which occurred in 2002 followed on from a large rift calving event."[56]

"We would expect in the ensuing months to years further calving events [from Larsen C], and maybe an eventual collapse - but it's a very hard thing to predict, and our models say it will be less stable; not that it will immediately collapse or anything like that."[55]

"Even the sea level contribution of this area is not on anybody's radar; it's just a big geographical event that will change the landscape there."[55]

"Geologists working in the remote Afar region of Ethiopia say the ocean will eventually split the African continent in two, though it will take about 10 million years."[57]

"In 2005, a 60 km long stretch of the earth [in the image second down on the right] opened up to a width of eight metres over a period of just ten days."[57]

"Hot, molten rock from deep within the Earth is trickling to the surface and creating the split."[57]

"Underground eruptions are still continuing and, ultimately, the horn of Africa will fall away and a new ocean will form."[57]

Parts "of the [Afar] region are below sea level and the ocean is only cut off by about a 20-metre block of land in Eritrea."[58]

"Eventually this will drift apart. The sea will flood in and will start to create this new ocean. It will pull apart, sink down deeper and deeper and eventually... parts of southern Ethiopia, Somalia will drift off, create a new island, and we'll have a smaller Africa and a very big island that floats out into the Indian Ocean."[58]

"The 60 km-long rift was initially sparked by an earthquake in September."[59]

"It betrays events deep beneath the ground, where some of the tectonic plates that form Africa are gradually moving apart from the Arabian plate, causing the crust to stretch and thin."[59]

"As rifts appear [shown in the third image down on the right], molten rock bubbles up from beneath the surface, hardening to form a new strip of ocean floor."[59]

"We think if these processes continue, a new ocean will eventually form. It will connect to the Red Sea and the ocean will flow in."[60]

"We've been able to work up all the satellite data and get a very precise map. It's the biggest rifting episode at least since the 1970s and possibly in hundreds of years. It's the first time we've been able to use satellite images to investigate the fundamental processes behind rifting."[60]

"It's the first large event we have seen like this in a rift zone since the advent of some of the space-based techniques we're now using. These techniques give us a resolution and a detail to see what's really going on and how the Earth processes work."[61]

"2.5 cubic km (0.6 cubic mile) of magma has flowed up through the crack in the Earth's crust."[59]

An "8 m rift develop in the ground in just three weeks in the Afar desert region last September."[62]

"It began with a large earthquake on the 14th of the month and continued with a swarm of moderate tremors."[62]

"About a week into the sequence, there was a volcanic eruption. A lot of ash was thrown up in the air, and a lot of cracks appeared in the ground; some of which were more than a metre wide [shown in the fourth image down on the right]. Using satellite techniques we can see ground deformation, and about a month after the sequence, we could see a 60 km long section had opened up, and it opened up about 8 m in its central part. It appears that we've seen the birth of an ocean basin."[63]

A more regional map is shown in the fifth image down on the right which geographically locate the Afar desert.

Hypotheses[edit]

Main source: Hypotheses
  1. All or nearly all folded rocks are produced by glacial surges scraping sediment off bedrock while the sediment is still water soaked.

See also[edit]

References[edit]

  1. Robert J. Twiss (12 April 1992). Structural geology. Macmillan. pp. 532. ISBN 0716722526. http://books.google.com/books?hl=en&lr=lang_en&id=14fn03iJ2r8C&oi=fnd&pg=PR9&ots=Ji9tweQzRK&sig=vOzRLa0ZfHg71w92vWp5UGjkV5o. Retrieved 2014-11-25. 
  2. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  3. Ashley Dace (2011). "ST0343 : The Blue Anchor Fault". United Kingdom: Geograph.org. Retrieved 2014-11-29. 
  4. 4.0 4.1 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  5. Kurt Kjær and Ólafur Ingólfsson (2005). "The Brúarjökull Project: Sedimentary environments of a surging glacier". Iceland: Landsvirkjun. Retrieved 2014-11-25. 
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  20. Reginald A. Daly (August 1938). "The roots of volcanoes". Eos, Transactions American Geophysical Union 19 (1): 35-9. doi:10.1029/TR019i001p00035. http://onlinelibrary.wiley.com/doi/10.1029/TR019i001p00035/full. Retrieved 2016-03-08. 
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  24. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  25. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  26. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  27. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  28. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  29. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  30. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  31. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  32. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  33. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  34. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  35. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  36. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  37. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  38. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  39. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  40. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  41. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  42. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  43. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  44. Cite error: Invalid <ref> tag; no text was provided for refs named LavaDomeWikt
  45. 45.0 45.1 45.2 45.3 45.4 45.5 45.6 45.7 Erik Klemetti and Adam Voiland (21 November 2013). The Shapes that Lavas Take, Part 1. Washington, DC USA: NASA. http://earthobservatory.nasa.gov/IOTD/view.php?id=82424. Retrieved 2015-02-18. 
  46. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  47. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  48. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  49. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  50. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  51. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  52. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  53. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  54. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  55. 55.0 55.1 55.2 55.3 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  56. 56.0 56.1 56.2 56.3 56.4 56.5 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  57. 57.0 57.1 57.2 57.3 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  58. 58.0 58.1 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  59. 59.0 59.1 59.2 59.3 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  60. 60.0 60.1 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  61. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  62. 62.0 62.1 Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).
  63. Lua error in Module:Citation/CS1 at line 3505: bad argument #1 to 'pairs' (table expected, got nil).

Further reading[edit]

External links[edit]

{{Geology resources}}