The Tyrrell Sea , named for Canada Canadian geologist Joseph Tyrrell , is another name for prehistoric Hudson Bay , namely as it existed during the retreat of the Laurentide Ice Sheet . Roughly 8,000 years before present BP , the Laurentide Ice Sheet thinned and split into two lobes, one centered over Quebec Labrador , the other over Keewatin . This drained Glacial Lake Ojibway , a massive proglacial lake south of the ice sheet, leading to the formation of the early Tyrrell Sea. ref name Lajeuness cite journal url http pubs.nrc cnrc.gc.ca rp rppdf e02 085.pdf last Lajeuness first Patrick first2 Michael last2 Allard title The Nastapoka drift belt, eastern Hudson Bay implications of a stillstand of the Quebec Labrador ice margin in the Tyrrell Sea at 8 ka BP journal Canadian Journal of Earth Science volume 40 year 2003 pages 65 76. ref The weight of the ice had isostasy isostatically depressed the surface as much as 270 280 meters m below its current level, making the Tyrrell Sea much larger than modern Hudson Bay. ref name Lajeuness Indeed, in some places the shoreline was 100 to 250 km farther inland than at present. ref name amu http geoinfo.amu.edu.pl wpk geos GEO 6 GEO PLATE C 24.HTML Geomorphology From Space, Plate C 24 Hudson Bay Shorelines. Accessed 3 7 06 ref It was at its largest at roughly 7,000 years BP. ref name Pielou Isostatic uplift proceeded rapidly after the retreat of the ice, as much as .09 m per year, causing the margins of the sea to regress quickly towards its present margins. ref name Lajeuness The rate of uplift decreased with time however, and in any event was nearly matched by sea level rise from the melting ice sheets. ref name amu When the Tyrrell Sea became Hudson Bay is difficult to define, as Hudson Bay is still shrinking from isostatic rebound. ref name Pielou cite book last Pielou first E. C. title After the Ice Age location Chicago publisher University of Chicago Press year 1991 pages 222 224 isbn 0226668118 ref References Reflist Ca ... more details
Image NorthSaaremaaCoast.JPG thumb 300px right Beach ridges on the north coast of Saaremaa , Estonia. Image Lake Ontario Beach Ridge 1895.jpg thumb 300px right Beach ridge, Lake Ontario , New York , 1895. Image Miocene Beach San Diego County CA 1905.jpg thumb 300px right Miocene beach ridges, San Diego County , California , 1905. Image Ridge Rd Orleans County NY 1889.jpg thumb 300px right Road built on crest of Glacial Lake Iroquois beach ridge, Orleans County, New York Orleans County , New York , 1889. A beach ridge is a Ocean surface wave wave swept or wave deposited ridge running parallel geometry parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called littoral transport . Movement of material parallel to the shoreline is called Longshore drift longshore transport . Movement perpendicular to the shore is called on offshore transport . A beach ridge may be capped by, or associated with, dune sand dunes . The height of a beach ridge is affected by wave size and energy. A fall in water level or an uplift of land can isolate a beach ridge from the body of water that created it. Isolated beach ridges may be found along dry lakes in the western United States and inland of the Great Lakes of North America , where they formed at the end of the last ice age when lake levels were much higher due to glacier glacial melting and obstructed outflow caused by glacial ice. Some isolated beach ridges are found in parts of Scandinavia , where glacial melting relieved pressure on land masses and resulted in subsequent crustal lifting or post glacial rebound . A rise in water level can submerge beach ridges created at an earlier stage, causing them to erosion erode and become less distinct. Beach ridges may become routes for roads and trails. See also Beach Strand plain Isostasy Machair geography Machair Marine terrace Sources Water Resource Availability in the Maumee River ... more details
In geology , a forebulge is a flexural bulge in front of a load on the lithosphere . This load causes the lithosphere to flex by depressing the plate beneath it. Because of the flexural rigidity of the lithosphere, the area around the load is uplifted by a height that is 4 of that of the depression under the load. This load and resulting flexure place stress on the mantle geology mantle , causing it to flow into the area around the loaded area. The subsidence of the area under the load and the uplift of the forebulge continue until the load is in isostasy isostatic equilibrium, a process which takes on the order of 10 20 thousand years. Because of the coupling with the mantle, the rate of forebulge formation and collapse is controlled by mantle viscosity . Glacial One cause for forebulge formation is loading of the continental lithosphere by ice sheet s during continental glaciation s. Because of the removal of the ice sheets, these formerly glaciated areas are currently rising in a phenomenon known as post glacial rebound . Because of the coupling of the mantle with the plates, data from post glacial rebound are used as a direct probe of the viscosity of the upper mantle. As the ice melts and the land under it rises by isostatic recovery, the forebulge also subsides. Forebulge subsidence is the reason why the Netherlands and parts of southern England have been slowly sinking in the present day. ref p54 in Doggerland a Speculative Survey , by B.J.Coles, Proceedings of the Prehistoric Society , 64 1998 pp 45 81. ref One estimate ref Glacial deposits of Britain and Europe general overview , by D.Ehlers, P.Gibbard, & Tj.C.E van Weering, 1979 in Glacial Deposits in Britain and Ireland , edited by J.Ehlers, P.Gibbard, & J.Rose, pp 493 501, Rotterdam Balkema . ref is that the centre of the North Sea rose by about 170m 558 feet during the Ice Age because of forebulging. Clarify Is this from ice? It takes 1 km of glacier for 40 m of forebulge, so this is 4 km of glacie ... more details
be of the same order mm yr as sea level changes. Some land movements occur because of isostasy isostatic ... s surface Isostasy Thermal isostasy temperature density changes in earth s interior Local effect Glacio isostasy loading or unloading of ice Local effect 10 mm yr Hydro isostasy loading or unloading of water Local effect Volcano isostasy magmatic extrusions Local effect Sediment isostasy deposition ... geol445 hyperglac sealevel2 index.htm Properties of isostasy and eustasy http sealevel.jpl.nasa.gov ... more details
In geology , epeirogenic movement from Greek epeiros , land, and genesis , birth refers to upheavals or depressions of land exhibiting long wavelength s and little fold geology folding apart from broad undulations. ref name Duff cite book title Holmes principles of physical geology author Arthur Holmes, Doris L. Holmes url http books.google.com books?id E6vknq9SfIIC&pg PT109 page 92 isbn 0748743812 edition 4rth publisher Taylor & Francis year 2004 ref The broad central parts of continents are called cratons , and are subject to epeirogeny. ref name Huggett cite book title Fundamentals of geomorphology author Richard J. Huggett page 76 url http books.google.com books?id Y7j trP2goC&pg PA76 isbn 0415241464 year 2003 publisher Routledge ref The movement may be one of subsidence toward, or of uplift from, the centre of the Earth. The movement is caused by a set of forces acting along an Earth radius, such as those contributing to isostasy and Fault geology faulting in the lithosphere . Epeirogenic movement can be permanent or transient. Transient uplift can occur over a thermal anomaly due to convecting anomalously hot Mantle geology mantle , and disappears when convection wanes. Permanent uplift can occur when igneous material is injected into the crust geology crust , and circular or elliptical structural uplift that is, without folding over a large radius tens to thousands of km is one characteristic of a mantle plume . ref name Buchan cite book title Mantle plumes their identification through time url http books.google.com books?id X4W9aGXDa9cC&pg PA215 page 215 editor Richard E. Ernst, Kenneth L. Buchan author AMC eng r chapter Elevation as an indicator of mantle plume activity isbn 0813723523 year 2001 publisher Geological Society of America ref ref name Johnson cite book title The nature and origin of compression in passive margins author SP Holford et al. editor Howard Johnson et al. url http books.google.com books?id e7DORk8T6gcC&pg PA112 page 112 chapter Neog ... more details
Karl Ledersteger 11 November 1900, Vienna 24 September 1972 near Vienna was an important geodesy geodesist and geophysics geophysicist . After studies of astronomy , mathematics and geodesy he worked in Germany and later in the National Survey of Austria . Later he set up the scientific department of the Federal Office for Metrology and Survey BEV , Vienna. In the 1950s he was appointed as a professor of geodesy and astrometry at the Technical University of Vienna . He was head of many research projects, and author of about 200 scientific articles. Still a standard work of Astrogeodesy astronomical and physical geodesy is his textbook of Erdmessung Vol. V of the series Handbuch der Vermessungskunde , 871 p. published 1969. In 1958 59, Ledersteger was the first geodesist in Central Europe who published on the future fields of satellite geodesy . Other topics of his research were Theory of National survey Landesvermessung and practical computation of the ZEN Zentraleurop isches Netz, Berlin 1940 and of parts of the ED50 Theory of Hydrostatic equilibrium equilibrium figures of Earth and planet s Isostasy of the Earth s crust and its effect on geoid determination a main part was published posthumously by his successor Kurt Bretterbauer the system of vertical deflection s and the definition of reference ellipsoid s. Ledersteger was in intensive contact with the scientific community of whole Europe, USA and Russia e.g. Viktor Ambartsumian , B.Gutenberg, Friedrich Hopfner F.Hopfner , W.Heiskanen, Max Kneissl M.Kneissl , Sir Harold Jeffreys , Vening Meinesz, Helmut Moritz H.Moritz , A.Prey, H.H. Schmid , Ernst Wiechert E.Wiechert and S.Zhongolovitch , and he liked scientific discussions at symposia and in journals. For almost 20 years he was chair of KIE Austrian Commission for international Geodesy and a member of many international commissions and research groups, e.g. in IUGG , Deutsche Geod tische Kommission DGK and scientific academies of Austria, Germany and Hungary. ... more details
The term dynamic topography is used in geodynamics and oceanography to refer to elevation differences caused by the flow within the Earth s Mantle geology mantle and the ocean water , respectively. Geodynamics In geodynamics, dynamic topography refers to topography generated by the motion of zones of differing degrees of buoyancy convection in the Earth s mantle. ref name hager richards 1989 cite journal last1 Hager first1 B. H. last2 Richards first2 M. A. title Long Wavelength Variations in Earth s Geoid Physical Models and Dynamical Implications journal Philosophical Transactions of the Royal Society A Physical, Mathematical and Engineering Sciences volume 328 pages 309&ndash 327 year 1989 doi 10.1098 rsta.1989.0038 issue 1599 ref It is also seen as the residual topography obtained by removing the isostasy isostatic contribution from the observed topography i.e., the topography that cannot be explained by an isostatic equilibrium of the crust or the lithosphere resting on a fluid mantle and all observed topography due to post glacial rebound . Elevation differences due to dynamic topography are frequently on the order of a few hundred meters to a couple of kilometers. Large scale surface features due to dynamic topography are mid ocean ridge s and oceanic trench es. ref name hager richards 1989 Other prominent examples include areas overlying mantle plume s such as the African superswell . ref cite journal journal Nature journal Nature volume 395 pages 269&ndash 272 doi 10.1038 26212 title Dynamic topography, plate driving forces and the African superswell last1 Lithgow Bertelloni first1 Carolina last2 Silver first2 Paul G. url http www.nature.com nature journal v395 n6699 abs 395269a0.html year 1998 issue 6699 ref The mid ocean ridges are high due to dynamic topography because the upwelling hot material underneath them pushes them up above the surrounding seafloor. This provides an important driving force in plate tectonics called ridge push the increased gravita ... more details
of isostasy , ref name Allen cite book title Earth Surface Processes author PA Allen url http books.google.com books?id e5i8cRGRCuwC&pg PA36 page 36 ff chapter Isostasy in zones of convergence ... chapter 5.5 Isostasy page 170 url http books.google.com books?id K4IgLIDbZicC&pg PA170 author Gerard ... style vertical movements have been explained primarily by the process of isostasy ... more details
pp protected expiry 2012 06 26T11 01 51Z small yes More footnotes section date March 2009 File Earth internal structure.png thumb 350px Earth cutaway from Core geology core to Crust geology crust , the asthenosphere lying between the upper mantle and the lithospheric mantle detail not to scale The asthenosphere from Greek language Greek asthen s weak sphere is the highly viscous, mechanically weak and ductility ductilely deforming region of the upper Mantle geology mantle of the Earth . It lies below the lithosphere , at depths between 100 and 200 km 62 and 124 miles below the surface, but perhaps extending as deep as convert 700 km mi abbr on . Characteristics The asthenosphere is a portion of the upper layer just below the lithosphere that is involved in Plate tectonics plate tectonic movement and Isostasy isostatic adjustments. In spite of its high temperature, pressures keep it Plasticity physics plastic , and it has a relatively low density. Seismology Seismic waves pass relatively slowly through the asthenosphere compared to the overlying lithospheric mantle, thus it has been called the low velocity zone LVZ , although the two are not exactly the same. The lower boundary of the LVZ lies at a depth of 180&ndash 220 km, ref name Condie cite book last Condie first K.C. title Plate tectonics and crustal evolution publisher Butterworth Heinemann year 1997 page 282 isbn 978 0 7506 3386 4 url http books.google.co.uk books?id HZrA6OQzsvgC&pg PA123&dq mantle 22low velocity zone 22 anisotropy&cd 8 v onepage&q mantle 20 22low velocity 20zone 22 20 20anisotropy&f false accessdate 21 May 2010 ref whereas the base of the asthenosphere lies at a depth of about 700 km. ref name Kearey cite book last1 Kearey first1 P. last2 Vine first2 F.J. title Global Tectonics url http books.google.co.uk books?id usiqam9p7GAC&pg RA1 PA41&lpg RA1 PA41&dq asthenosphere lvz v onepage&q asthenosphere 20lvz&f false accessdate 21 May 2010 edition 2 year 1996 publisher Wiley Blackwe ... more details
for mass concentration in chemistry Concentration Mass versus volume Image MareSmithiiTG.jpg thumb 250px Topography top and corresponding gravity bottom signal of Moon lunar Mare Smythii containing a significant mascon. In astronomy or astrophysics mass concentration or mascon is a region of a planet or moon s crust that contains a large positive Gravity anomaly gravitational anomaly . In general, the word mascon can be used as a noun to describe an excess distribution of mass on or beneath the surface of a planet with respect to some suitable average , such as Hawaii . ref name Allen cite web url http seismo.berkeley.edu rallen eps122 lectures L17.pdf title Gravitational Constraints Lecture 17 page 9 author Richard Allen work Berkeley course Physics of the Earth and Planetary Interiors accessdate 2009 12 25 ref However, this term is most often used to describe a geologic structure that has a positive gravitational anomaly associated with a feature e.g. depressed basin that might otherwise have been expected to have a negative anomaly, such as the mascon basins on the Moon . Type examples of mascon basins on the Moon are the Mare Imbrium Imbrium , Mare Serenitatis Serenitatis , Mare Crisium Crisium and Mare Orientale Orientale impact basins, all of which possess prominent topographic lows and positive gravitational anomalies. Examples of mascon basins on Mars include the Argyre Planitia Argyre , Isidis Planitia Isidis , and Utopia Planitia Utopia basins. Theoretical considerations imply that a topographic low in Isostasy isostatic equilibrium would exhibit a slight negative gravitational anomaly. Thus, the positive gravitational anomalies associated with these impact basins indicate that some form of positive density anomaly must exist within the crust or upper mantle that is currently supported by the lithosphere . One possibility is that these anomalies are due to dense Lunar mare mare basaltic lavas , which might reach up to 6 kilometers in thickness for the Moon ... more details
Image Hudson Highlands.JPG thumb 425px Wind Gate, the northern entrance to the Hudson Highlands, as seen from Newburgh city , New York Newburgh . Breakneck Ridge is to the left, Storm King Mountain New York Storm King Mountain to the right with Bannerman s Island in the middle of the river and United States Military Academy West Point visible in the distance The Hudson Highlands are mountain s on both sides of the Hudson River in the U.S. state of New York , between Newburgh Bay and Haverstraw Bay , which form the northern region of the New York New Jersey Highlands . The Hudson River enters this region in the south at Dunderberg Mountain near Stony Point, New York Stony Point , and from the north in the vicinity of Storm King Mountain New York Storm King Mountain and Breakneck Ridge near Cornwall, New York . These highlands played a significant role in America s military, cultural and environmental history. History The bedrock of the Highlands is part of the Reading Prong and more than a billion years old, formed during the Grenville Orogeny . It represents the very core of the Applachian range, which has been formed by successive mountain building events orogenies . The present mountains have been exposed by the process of isostasy through the late Cenozoic Era . The hills were given their rounded form when glacier s cut through the Appalachian Mountains here, the Highlands are among the lowest summits in that range indeed, the Appalachian Trail reaches its lowest elevation in the Trailside Zoo between Bear Mountain State Park and Bear Mountain Bridge . Conversely, the river becomes narrower and deeper through the Highlands, reaching its deepest point of 216 feet 66 m , near Garrison, New York Garrison . Many stretches are challenging to seamanship navigate , earning nicknames like World s End. Henry Hudson and his crew on the Halve Maen Half Moon were the first European ethnic groups European s to see the Highlands when they explored the river in 1609. The mounta ... more details
Infobox scientist name William Bowie image William Bowie NOAA.jpg image size 200px caption William Bowie birth date May 6, 1872 birth place Grassland Annapolis Junction, Maryland Grassland , Annapolis Junction, Maryland death date August 28, 1940 death place Washington, DC residence citizenship nationality United States American ethnicity field Geodesy work institutions alma mater doctoral advisor doctoral students known for author abbrev bot author abbrev zoo influences influenced prizes religion footnotes signature William Bowie , B.S., C.E., M.A. May 6, 1872 August 28, 1940 was an United States American geodetic engineer. Background and education He was born at Grassland Annapolis Junction, Maryland Grassland , an historic estate near Annapolis Junction, Maryland Annapolis Junction , Anne Arundel County, Maryland , to Thomas John Bowie and Susanna Anderson. He was educated in public schools, at St. John s College United States St. John s College in Annapolis, Maryland , Trinity College Connecticut Trinity College in Hartford, Connecticut B.S. 1893 M.A. 1907 Sc.D. 1919 , and Lehigh University Lehigh C.E. 1895 Sc.D. 1922 . He received honorary degrees LL.D. 1936 from the University of Edinburgh , Scotland , at the meeting of the International Union of Geodesy and Geophysics of which he was President, and from George Washington University Sc.D. 1937 . ref name flem Citation last Fleming first J . A. title William Bowie, 1872 1940 A Biographical Memoir publisher National Academy of Sciences date 1951 location Washington D.C. pages 61 63 url http books.nap.edu html biomems wbowie.pdf isbn ref Career In 1895 he entered the U.S. National Geodetic Survey United States Coast and Geodetic Survey . During World War I he served in the United States Army Corps of Engineers Corps of Engineers in the army as a major. He represented the United States at various international geodetic conferences and congresses. His scientific researches had to do with the theory of isostasy and ... more details
for the librarian Thomas Hill Jamieson Infobox scientist name Thomas Francis Jamieson birth date 1829 death date 1913 death date and age 1948 02 25 1878 03 14 citizenship United Kingdom nationality Scotland Scottish field geologist , chemist work institution University of Aberdeen alma mater University of Aberdeen doctoral students prizes footnotes Thomas Francis Jamieson 1829 1913 was a Scotland Scottish scientist most associated with his studies of sea level and glacial isostasy during the Quaternary . ref Cite book last1 Hancock first1 Paul L. last2 Skinner first2 Brian J. last3 Dineley first3 David L. title The Oxford Companion to The Earth publisher Oxford University Press year 2000 isbn 0 19 854039 6 postscript None ref Born the son of a jewellry jeweller , Jamieson was raised in Aberdeen and educated at Aberdeen Grammar School and the University of Aberdeen , at which he was appointed Fordyce Lecturer in Agriculture in 1862, ref cite web url http www.scottish places.info people famousfirst2418.html title Thomas Francis Jamieson biography accessdate 2008 09 12 work publisher Gazetteer for Scotland date ref a post he held for 15 years. He was also elected a Fellow of the Chemical Society , Fellow of the Institute of Chemistry and member of the French National Society of Agricultural Chemistry. ref Aberdeen Weekly Journal , 5 April 1899, p7 ref The France French government awarded him the title of L gion d honneur Chevalier of the Legion of Honour for work done in agricultural research. Interested in geology from an early age, Jamieson corresponded widely with other scientists, including Charles Lyell and Charles Darwin . ref cite web url http www.darwinproject.ac.uk darwinletters namedefs namedef 2540.html title Thomas Francis Jamieson, 1829 1913 accessdate 2008 09 12 work publisher Correspondence of Charles Darwin Darwin Correspondence Project date ref After early research on petrology , Jamieson studied the glaciated rocks of Scotland , providing evidence for ... more details
Claude Hillaire Marcel Royal Society of Canada FRSC born April 1, 1944 in Salies de B arn , Pyr n es Atlantiques is a Canadian geoscientist working in Quaternary geology Quaternary research. He is known for his research on the Natural environment environment , climate change , and oceanography . He is a Fellow of the Royal Society of Canada and professor at Universit du Qu bec Montr al l Universit du Qu bec Montr al . Hillaire Marcel was born and educated in France . He received advanced degrees at the Coll ge de Sorbonne Sorbonne in 1968, and the University of Paris in 1979. He moved to Canada and became a professor at l Universit du Qu bec Montr al. From between 1970 and 2003, Claude Hillaire Marcel authored or co authored over 150 scientific papers. He supervised 20 doctoral dissertations and 37 M.Sc. and D.E.A. theses, and in addition he had 13 scientists working with him as postdoctoral fellows from Belgium , Canada, Denmark , France , Germany , Mexico , the United Kingdom UK and the United States U.S. . His early papers covered Pleistocene Marine ocean marine fauna and Isostasy isostatic rebound near Montreal . Later he broadened his geographic scope to include Ungava Bay and Hudson Bay . In 1976, he began writing about Isotopes of oxygen oxygen and Isotopes of carbon carbon isotopes . By 1980 he was involved in dating studies utilizing isotopes of Isotopes of uranium uranium and Isotopes of thorium thorium . Between 1985 and 1991, Hillaire Marcel participated in, or was chief scientist on various scientific marine expeditions, including six cruises on Canadian ships CSS Dawson & CSS Hudson and a cruise aboard the French research ship Marion Dufresne in Greenland waters in 1999. In 1994, a special issue of the Canadian Journal of Earth Sciences featured Labrador Sea studies. Nine of the 12 articles were co authored by Claude Hillaire Marcel. In 2001, he was lead author on a paper in Nature journal Nature entitled Absence of deep water formation in the ... more details
William Richard Peltier , Doctor of Philosophy Ph.D. , Doctor of Science D.Sc. honorary degree hc http newsrelease.uwaterloo.ca news.php?id 4861 born 1943 , is a university professor of physics at the University of Toronto . He is director of the Centre for Global Change Science http www.cgcs.utoronto.ca and principal investigator of the Polar Climate Stability Network http www.pcsn.ca . He is a fellow of the Royal Society of Canada and of the American Geophysical Union . His research interests include atmospheric and oceanic waves and turbulence, geophysical fluid dynamics, physics of the planetary interior, and planetary climate. He is notable for his involvement in global glacial reconstructions from the last glacial maximum to present. He has been a major or the primary contributor to the global reconstructions ICE 3G, ref cite journal doi 10.1029 90JB01583 title Ice 3G A New Global Model of Late Pleistocene Deglaciation Based Upon Geophysical Predictions of Post Glacial Relative Sea Level Change year 1991 last1 Tushingham first1 A. M. last2 Peltier first2 W. R. journal Journal of Geophysical Research volume 96 pages 4497 bibcode 1991JGR....96.4497T ref ICE 4G, ref cite journal doi 10.1126 science.265.5169.195 title Ice Age Paleotopography year 1994 last1 Peltier first1 W. R. journal Science volume 265 pages 195 201 pmid 17750657 issue 5169 bibcode 1994Sci...265..195P ref ICE 5G VM2 , ref cite journal doi 10.1146 annurev.earth.32.082503.144359 title Global glacial isostasy and the surface of the ice age Earth the ICE 5G VM2 Model and GRACE year 2004 last1 Peltier first1 W.R. journal Annual Review of Earth and Planetary Sciences volume 32 pages 111 bibcode 2004AREPS..32..111P ref and the upcoming ICE 6G VM5 in press . These models are important for the quantification of post glacial rebound and late Pleistocene to Holocene variations in sea level . Education 1967 B.Sc., University of British Columbia 1969 M.Sc. in Physics, University of Toronto 1971 Ph.D. in Phys ... more details
of isostasy . Early bent plate models predicting fractures and fault movements have evolved into today s kinematic and flexural models. ref name Watts cite book author AB Watts title Isostasy and flexure ... more details
About the process that forms volcanoes and other igneous formations the 18th century geological theory Plutonism File Plate tectonics map.gif thumb 400px right Plate tectonics map Volcanism is the phenomenon connected with volcano es and volcanic activity. It includes all phenomena resulting from and causing magma within the crust geology crust or Mantle geology mantle of a planet to rise through the crust and form volcanic rock s on the surface. Volcanic processes Magma from the planet s mantle rises through the planet s crust, if the magma from the mantle reaches the planet s surface it behaves differently depending on the viscosity of the molten constituent rock geology rock . Viscous thick magma produces volcanoes characterised by explosive eruption s, while non viscous runny magma produce volcanoes characterised by an effusive eruption s pouring large amounts of lava onto the surface. In some cases, rising magma can cool and solidify without reaching the surface of a planet. Instead, the cooled and solidified igneous mass freezes within the crust geology crust of a planet to form an igneous intrusion . Driving forces of volcanism Main Plate tectonics Image Tectonic plate boundaries.png thumb right 450px Three types of plate boundary. Movement of molten rock in the planet s mantle, caused by thermal convection currents, coupled with isostasy gravitational effects of changes on the earth s surface erosion , deposition sediment deposition , even asteroid impact and patterns of Post glacial rebound snow fall and melt drive plate tectonic motion and ultimately volcanism. Aspects of volcanism Volcanoes Main Volcano div class thumb tright div class thumbinner style width 300px File Volcano scheme.svg frameless class thumbcaption style background none colspan 2 Cross section through a stratovolcano vertical scale is exaggerated valign top 1. Large magma chamber br 2. Bedrock br 3. Conduit pipe br 4. Base br 5. Sill br 6. Dike br 7. Layers of ash emitted by the volcano ... more details
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