Isostasy Greek wikt sos equal , wikt st sis standstill is a term used in geology to refer to the state of gravity gravitational equilibrium between the earth s lithosphere and asthenosphere such that the tectonic plate s float at an elevation which depends on their thickness and density. This concept is invoked to explain how different topographic heights can exist at the Earth s surface. When a certain area of lithosphere reaches the state of isostasy, it is said to be in isostatic equilibrium . Isostasy is not a process that upsets equilibrium, but rather one which restores it a negative feedback . It is generally accepted that the earth is a dynamic system that responds to loads in many different ways. However, isostasy provides an important view of the processes that are happening in areas that are experiencing vertical movement. Certain areas such as the Himalayas are not in isostatic equilibrium, which has forced researchers to identify other reasons to explain their topographic heights in the case of the Himalayas, which are still rising , by proposing that their elevation is being propped up by the force of the impacting India Indian plate . In the simplest example, isostasy is the principle of buoyancy where an object immersed in a liquid is buoyed with a force equal to the weight of the displaced liquid. On a geological scale, isostasy can be observed where ... adjustments. Isostatic models File Airy Isostasy.jpg thumb right Simplified diagram of Airy Isostasy Three principal models of isostasy are used The George Airy Airy Veikko Aleksanteri Heiskanen Heiskanen ... b sub 1 sub 5 h sub 1 sub big File airy.jpg thumb left Simplified diagram of Airy s Isostasy In the case ... in context with sea level change , the implication is that both eustasy and isostasy are at work ... changes . Elsevier Oceanography Series, 8 cite book author AB Watts year 2001 title Isostasy and Flexure ... of the historical development. See also Clarence Dutton , who coined the term isostasy in 1889 John ... more details
Epirogenetic or epeirogenetic movements are simultaneous rising and falling movements of continents, which maintain isostasy . Uncategorized date February 2011 geology stub ... more details
Orphan date November 2010 Jamieson Ridge coor dm 80 27 S 25 53 W is a narrow ridge 1 nautical mile 1.9 km long, rising to about 1,200 m at the southwest end of the Herbert Mountains , Shackleton Range . Photographed from the air by the U.S. Navy , 1967, and surveyed by British Antarctic Survey BAS , 1968 71. In association with the names of glacial geologists grouped in this area, named by the United Kingdom Antarctic Place Names Committee UK APC in 1971 after Thomas F. Jamieson 1829 1913 , Scottish geologist whose work on the ice worn rocks of Scotland developed the true origin of glacial striae in 1862 originator of the theory of isostasy in 1865. usgs gazetteer Category Geography of Antarctica EAntarctica geo stub ... more details
Unreferenced auto yes date December 2009 Veikko Aleksanteri Heiskanen 23 July 1895, Kangaslampi &ndash 23 October 1971, Helsinki was a famous Finland Finnish geodesist . He is mostly known for his refinement of the theory of isostasy by George Airy and for his studies of the global geoid . 1931 1949 Professor of Geodesy, Helsinki University of Technology 1933 1936 Member of Finnish Parliament 1949 1961 Director, Finnish Geodetic Institute 1951 1961 Research professor, Ohio State University Links http www2.hu berlin.de leibniz sozietaet archiv 20sb 104 07 kakkuri.pdf Veikko Heiskanen and Helmut Moritz presentation Persondata Metadata see Wikipedia Persondata . NAME Heiskanen, Veikko Aleksanteri ALTERNATIVE NAMES SHORT DESCRIPTION DATE OF BIRTH 1894 PLACE OF BIRTH DATE OF DEATH 23 October 1971 PLACE OF DEATH DEFAULTSORT Heiskanen, Veikko Aleksanteri Category 1894 births Category 1971 deaths Category Finnish scientists Category Ohio State University faculty Category Recipients of the Order of the White Star, 2nd Class Finland scientist stub Geoscience bio stub de Veikko Heiskanen pt Veikko Aleksanteri Heiskanen fi Veikko Heiskanen ... more details
Infobox Scientist name John Fillmore Hayford box width image John Fillmore Hayford.JPG image width caption John Fillmore Hayford birth date May 19, 1868 birth place Rouses Point, New York death date March 10, 1925 death place Evanston, Illinois residence citizenship nationality United States ethnicity field geodesy work institutions alma mater doctoral advisor doctoral students known for isostasy author abbrev bot author abbrev zoo influences influenced prizes religion footnotes signature John Fillmore Hayford May 19, 1868 March 10, 1925 was an eminent United States geodesist . His work involved the study of isostasy and the construction of a reference ellipsoid for approximating the figure of the Earth . The crater Hayford crater Hayford on the far side of the Moon is named after him. ref http planetarynames.wr.usgs.gov jsp FeatureTypesData2.jsp?systemID 3&bodyID 11&typeID 9&system Earth&body Moon&type Crater, 20craters&sort AName&show Fname&show Lat&show Long&show Diam&show Stat&show Orig USGS Gazetteer of Planetary Nomenclature ref Bibliography Citation pmid 17795741 last Hayford first publication date 1917 Apr 13 year 1917 title GRAVITY AND ISOSTASY. volume 45 issue 1163 periodical pages 350 354 doi 10.1126 science.45.1163.350 journal Science first1 JF Citation pmid 17815861 last Hayford first publication date 1911 Feb 10 year 1911 title THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE THE RELATIONS OF ISOSTASY TO GEODESY, GEOPHYSICS AND GEOLOGY. volume 33 issue 841 periodical pages 199 208 doi 10.1126 science.33.841.199 journal Science first1 JF Citation pmid 17817509 last Hayford first publication date 1909 Jun 4 year 1909 title THE NEW COLLEGE OF ENGINEERING, AN OPPORTUNITY. volume 29 issue 753 periodical pages 887 891 doi 10.1126 science.29.753.887 journal Science first1 JF Citation pmid 17771974 last Hayford first publication date 1907 Jan 11 year 1907 title REPORT OF THE GENERAL SECRETARY. volume 25 issue 628 periodical Science journal Science pages ... more details
An epeiric sea also known as an epicontinental sea is a shallow sea that extends over part of a continent . Epeiric seas are usually associated with the Marine ocean marine Transgression geology transgressions of the Geology geologic past, which have variously been due to either global Eustasy eustatic sea level changes, local Plate tectonics tectonic deformation, or both, and are occasionally semi cyclic. They can be warm or cold several were present at the end of the last Ice Age , when sea level rose more rapidly than some areas could Isostasy isostatically adjust. Modern examples are the Java Sea in Indonesia, Persian Gulf, ref cite book last McCabe first Peter J. editor Judith Totman Parrish title Controls on the Distribution and Quality of Cretaceous Coals publisher Geological Society of America date 1992 isbn 0813722675 ref the North Sea , and Hudson Bay . Examples Champlain Sea Sundance Sea Turgai Sea Tyrrell Sea Western Interior Seaway Zechstein Zechstein Sea See also Inland sea geology Sequence stratigraphy References reflist Category Historical geology Category Bodies of water palaeogeography stub ca Mar epicontinental et elfimeri es Mar epicontinental fr Mer picontinentale it Mare epicontinentale nn Grunnhav pl Morze epikontynentalne uk ... more details
Orphan date February 2009 The Hawaiian Trough , also known as the Hawaiian Deep , is a depression geology depression of the sea floor surrounding the Hawaiian Islands , where the massive weight of the island chain downwarps the oceanic lithosphere surrounding the islands like a moat , it is roughly 5500 meters deep. http www.mbari.org volcanism Hawaii HR FlexArch.htm However, in accordance with the principle of isostasy , the sinking of the lithosphere is balanced by a corresponding rise beyond it, known as the Hawaiian Arch . http www.mbari.org volcanism Hawaii HR FlexArch.htm The Big Island itself is still subsiding, at a rate of about 2.5 millimeters per year. http volcano.und.edu vwdocs hawaii review intro intro.html Sources http www.mbari.org volcanism Hawaii HR FlexArch.htm Hawaiian Submarine Volcanism http volcano.und.edu vwdocs hawaii review intro intro.html Volcano World Introduction to Hawaiian Volcanoes External links http pubs.usgs.gov sim 2004 2824 SIM 2824 pamphlet.pdf Overview of Hawaiian Arch geology PDF http www.usssp iodp.org PDFs Greatest Hits Rhythms Garcia.pdf New Evidence for Massive Landslides from the Hawaiian Islands PDF See also Hawaiian Arch Submarine landslide Category Geology of Hawaii Category Oceanography Category Marine geology geology stub ... more details
A raised shoreline is an ancient shoreline exposed above current water level. ref http www.encyclopedia.com doc 1O112 raisedshorelines.html ref These landforms are formed by a relative change in sea level due to global sea level rise, isostatic rebound , and or tectonic uplift . These surfaces are usually exposed above modern sea level when a heavily glaciated area experiences a glacial retreat , causing water levels to rise. This area will then experience post glacial rebound , effectively raising the shoreline surface. br Examples of raised shorelines can be found along the coasts of formerly glaciated areas in Ireland ref www.askaboutireland.ie ... changing sea levels ref and Scotland, as well as in North America. Raised shorelines are exposed at various locations around the Puget Sound of Washington State. ref http www3.interscience.wiley.com journal 118781323 abstract ref Related links Isostasy Landform Machair Marine terrace Glen Roy Parallel Roads of Glen Roy Raised beaches Terrace geology Terrace geology wave cut platform References reflist coastal geography DEFAULTSORT Raised Shorelines Category Coastal geography Category Coastal and oceanic landforms ... more details
Franz Kossmat 22 August 1871 in Vienna &ndash 1 December 1938 in Leipzig was an Austria n Germany German geologist , for twenty years the director of the Geological Survey of Saxony under both the Kingdom of Saxony kingdom and the subsequent Weimar Republic German Republic . Kossmat was professor of Mineralogy and Geology at the Graz University of Technology . From 1913 to 1934 Kossmat was the director of the Geological Survey of Saxony and director of the Geological Paleontological Institute of the University of Leipzig . In 1920 he presented the first gravity measures for middle Europe. It was published in 1921. In his life he published over twenty books himself, and collaborated on numerous others. He is most known for his work on isostasy and his opposition to Alfred Wegener Wegener s theories of continental drift . Selected works 1906 Pal ogeographie Geologische Geschichte der Meere und Festl nder The Geological History of the Oceans and Continents G.J. G schen, http worldcat.org oclc 11245502 OCLC 11245502 , a second edition was published in 1916. 1921 Die mediterranen Kettengebirge in ihrer Beziehung zum Gleichgewichtszustande der Erdrinde The Mediterranean Mountain Chain in its relationship with the Isostasy of the Earth s Crust Abh. d. Math. Phys. Klasse der S chs. Akad. d. Wiss. Proceedings of Math and Physics Classes of the Saxony Academy of Science , vol. 38, no. 2, Teubner, Leipzig 1936 Pal ogeographie und Tektonik Paleogeography and Tectonics Gebr der Borntraeger, Berlin, http worldcat.org oclc 8420779 OCLC 8420779 References Drost, Kerstin 2004 Franz Kossmat 1871 1938 Dresden Museum f r Mineralogie und Geologie, Dresden, http worldcat.org oclc 163338505 OCLC 163338505 , in German External links http www.forsten.sachsen.de umwelt download geologie Kossmat g.JPG Photograph of Franz Kossmat Geological Survey and Archive of Saxony http www.biologie.uni rostock.de wranik socotra pictures 7.8.JPG Photograph of Franz Kossmat University of Rostock Persondata ... more details
File SubZone.jpg thumb right 350px The outer trench swell , outer trench high , or outer rise is a subtle ridge on the seafloor near an oceanic trench , where a descending plate begins to flex and fault in preparation for its descent into the Earth s mantle mantle at a subduction zone . The lithosphere is bent upwards by plate stresses, and is not in isostasy isostatic equilibrium distinguish from the outer ridge of a forearc . Typically, the gravity field over the outer swell is about 50 Gal unit mGal 0.5 metre per second squared mm s higher than expected from isostasy, while gravity over the oceanic trench trench is about 200 mGal 2 mm s less than that expected from isostatic considerations. The bending of the plate is associated with tension in the upper 20 km, and shallow earthquake s, caused by tensional failure induced by the downward bending of the oceanic plate are common about 20 extensional outer rise earthquakes with magnitude 5 or greater occur annually. Most tension axes are perpendicular to the trench, independent of the direction of relative motion between the two plates, indicating that failure is controlled by bending stresses in the plate. Plate bending also causes deeper down to 50 km earthquakes due to compression. The wavelength and amplitude of this flexure can be used to constrain the state of stress mechanics stress across the plate boundary. The width of the outer rise is directly related to the flexural rigidity of the lithosphere. The thickness of the elastic lithosphere varies between 20 and 30 km for most trench profiles. Faulting related to plate bending and stair stepping of the descending slab into the trench may allow seawater to infiltrate deep into the crust and perhaps upper mantle. This may lead to large scale formation of serpentinite in the upper Mantle geology mantle of the downgoing plate Ranero et al., 2003 . Geologic fault Faulting of the downgoing plate results in a Horst geology horst and graben structure that allows sedi ... more details
This is a list of articles related to plate tectonics and tectonic plate s. Articles for individual plates List of tectonic plates African Plate Anatolian Plate Antarctic Plate Arabian Plate Cocos Plate Eurasian Plate Explorer Plate Farallon Plate Gorda Plate Juan de Fuca Plate Halmahera Plate Indo Australian Plate Pacific Plate Molucca Sea Plate Nazca Plate North American Plate Philippine Sea Plate South American Plate Sunda Plate Paleaocontinents Gondwana Laurasia Pangaea Panthalassa Rodinia Terrane Other articles relating to specific locations Benham Plateau Emperor Seamounts Geology of the Alps Great Rift Valley Indian subcontinent Mariana Trench Mid Atlantic Ridge Mohorovi i discontinuity Molucca Sea Collision Zone Pacific Antarctic Ridge Philippine Mobile Belt San Andreas Fault Tethys Ocean Tethys Sea Earthquakes Blind thrust earthquake Earthquake Intraplate earthquake s Interplate earthquake s Megathrust earthquake s Other plate tectonics articles Alpine Fault Asthenosphere Back arc basin Continent Continental drift Convergent boundary Crust geology Crust Divergent boundary Fault geology Island arc Isostasy List of tectonic plate interactions Mantle geology Mantle Mountain Obduction Oceanic ridge Oceanic trench Orogeny Paleoclimatology Paleomap Passive margin Ridge push Rift geology Seafloor spreading Seamount Strain Subduction Supercontinent Transform boundary Transform fault Volcano Category Geology lists Plate tectonics Category Plate tectonics Category Indexes of articles Plate tectonics topics ... more details
Unreferenced date February 2009 Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics . Because mid ocean ridges lie at a higher elevation than the rest of the ocean floor, gravity causes the ridge to push on the lithosphere that lies farther from the ridge. As molten magma rises at a mid ocean ridge it heats the rocks around it. The heat expelled by the magma expands the lithosphere and asthenosphere at the ridge, pushing them above the surrounding ocean floor . As time passes, the heated rocks cool and their density increases. When this happens gravity pulls the weighty lithosphere away from the mid ocean ridge, down the sloping asthenosphere, which, in turn, allows new molten magma to well up. This fresh magma will eventually become new lithosphere. The cooling rock exerts a force on spreading lithospheric plates, helping to drive their movements. The force is called ridge push. It can be calculated by the principle of isostasy , making a balance between the mid ocean ridge and the old ocean floor. Notably, in such a calculation, the force depends only on the temperature of the asthenosphere at the ridge the same in all normal ridges, though higher at Hotspot geology hotspots , and not on the spreading rate of the ridge. Another force, that for some plates exceeds ridge push, is slab pull , where the weight of a Subduction subducting slab pulls the plate at the surface along. References Cite web url http powerpoints.geology guy.com pipkin pipkin chapter3.pdf title Plate tectonics, based on Geology and the Environment , 5 ed Earth , 9 ed Cite journal author White, R. and McKenzie, D. year 1989 title Magmatism at rift zones The generation of volcanic continental margins and flood basalts journal J. Geophys. Res. volume 94 pages 7685 7729 tectonics stub physical oceanography expanded other Category Geodynamics Category Tectonics ... more details
Unreferenced date July 2009 Image Unintentional Humor, Way In, No Entry.jpg 250px right thumb Topological tube map of the London Underground In cartography and geology , a topological map refers to a map that has been topology simplified so that only vital information remains and unnecessary detail has been removed. These maps lack scale, and distance and direction are subject to change and variation, but the relationship between points is maintained. A good example of a topological map is the tube map of the London Underground . The name topological map is derived from topology , the branch of mathematics that studies the properties of objects that do not change as the object is deformed, much as the tube map retains useful information despite bearing little resemblance to the actual layout of the underground system. Not to be confused with a topographic map . See also Portal Atlas Main Outline of cartography Multicol 800 Aerial photography Animated mapping British Cartographic Society Cartogram Cartographic relief depiction Cartographic generalization Contour line Critical cartography Digital Cadastral DataBase Fantasy map Figure ground in map design Multicol break Four color theorem Gazetteer Geocode Geographic information system Geographic Information System GIS Geovisualization Here be dragons Isostasy Japanese map symbols List of cartographers Multicol break Locator map Map projection National Geospatial Intelligence Agency OpenStreetMap , a free project mapping the world s roads using Global Positioning System GPS Orthophoto Pictorial maps Planetary cartography Point of Beginning Sea level Terra incognita The article titled great circle distance explains how to find that quantity if one knows the two latitudes and longitudes. Multicol end Category Map types Cartography stub el ... more details
other Weight distribution Mass distribution is a term used in physics and mechanics and describes the spatial distribution of mass within a solid body. In principle, it is relevant also for gas es or liquid s, but on earth their mass distribution is almost homogeneous. Astronomy In astronomy mass distribution has decisive influence on the development e.g. of nebula e, star s and planet s. The mass distribution of a solid defines its center of gravity and influences its dynamical behaviour e.g. the oscillation s and eventual rotation . Mathematical modelling A mass distribution can be modeled as a Measure mathematics measure . This allows point masses, line masses, surface masses, as well as masses given by a volume density function. Alternatively the latter can be generalized to a distribution mathematics distribution . For example, a point mass is represented by a Dirac delta Generalizations delta function defined in 3 dimensional space . A surface mass on a surface given by the equation f x,y,z 0 may be represented by a density distribution g x,y,z f x,y,z , where math g mid nabla f mid math is the mass per unit area. The mathematical model ling can be done by potential theory , by numerical methods e.g. a great number of point mass mass point s , or by theoretical mechanical equilibrium equilibrium figures. Geology In geology the aspects of rock density are involved. Rotating solids Rotation Rotating solids are affected considerably by the mass distribution, either if they are homogeneous or inhomogeneous see Torque , moment of inertia , wobble , imbalance and stability . Related topics gravity , mass function , Bouguer plate , critical mass angular momentum , asymmetry , geoid , isostasy , polar motion mass spectrum , molar mass distribution , atmosphere External links http www.geod.uni bonn.de apmg projekte dfg schwerpunkt texte mass transport proposal spp.pdf Mass distribution of the Earth Category Mechanics Category Celestial mechanics Category Geophysics C ... more details
Image MoonTopoLOLA.png thumb right 345px alt Topography of the Moon measured from the Lunar Orbiter Laser Altimeter on the mission Lunar Reconnaissance Orbiter , referenced to a sphere of radius 1737.4 km Topography of the Moon. The topography of the Moon has been measured by the methods of laser altimetry and stereo image analysis, most recently from data obtained during the Clementine mission . The most visible topographic feature is the giant far side South Pole Aitken basin , which possesses the lowest elevation s of the Moon. The highest elevations are found just to the north east of this basin, and it has been suggested that this area might represent thick ejecta deposits that were emplaced during an oblique South Pole Aitken basin impact event. Other large impact basins, such as the Lunar mare maria Mare Imbrium Imbrium , Mare Serenitatis Serenitatis , Mare Crisium Crisium , Mare Smythii Smythii , and Mare Orientale Orientale , also possess regionally low elevations and elevated Rim craters rim s. Another distinguishing feature of the Moon s shape is that the elevations are on average about 1.9 Kilometre km higher on the far side than the near side. If it is assumed that the Crust geology crust is in Isostasy isostatic equilibrium , and that the density of the crust is everywhere the same, then the higher elevations would be associated with a thicker crust. Using gravity, topography and Seismology seismic data, the crust is thought to be on average about nowrap 50 15 km thick, with the far side crust being on average thicker than the near side by about 15 km. ref name W06 cite journal last Mark Wieczorek and 15 coauthors title The constitution and structure of the lunar interior journal Reviews in Mineralogy and Geochemistry volume 60 pages 221 364 date 2006 doi 10.2138 rmg.2006.60.3 first1 M. A. ref References reflist The Moon Category Lunar science Category Topography Category Geodesy ... more details
the basin to subside further because of isostasy . A basin can continue having sediment deposited into it, and continue ... also Isostasy Plate tectonics Structural basin Drainage basin Endorheic basin Sink geography Category ... more details
This article is about a geographic landform. For the TV series, see Machair TV series Image Berneray Machair hazelisles .jpg thumb The machair on Berneray, North Uist Berneray , Outer Hebrides The Gaelic language Gaelic word machair or machar refers to a fertile low lying grassy plain found on some of the north west coastline s of Ireland and Scotland , in particular the Outer Hebrides . Two distinct types exist A type of Dune sand dune pasture , subject to agricultural cultivation, which prevails in wet and windy conditions The land between a beach and the area where sand encroaches on Bog peat bog s further inland. Image Berneray Machair.jpg thumb The machair on Berneray Geology In both cases, a machair is a former beach , left higher in elevation than the current adjacent beach following a drop in sea level or isostasy . Machairs largely owe their fertility to the fact their sand has a high animal shell seashell content sometimes as high as 90 . This sand is blown inland, acts to neutralize the acidity of the peatbogs and results in the fertility of the grassland. Ecology Machairs have received considerable ecological and conservation biology conservational attention, chiefly because of their unique ecosystem s. They can house rare species rare carpet flower s, such as Spiranthes Irish Lady s Tresses , Orchidaceae orchids and Yellow Rattle , ref http www.wildlifehebrides.com environment machair Machair Profile ref along with a diverse array of bird species including the corn crake , twite , dunlin , redshank and ringed plover , as well as rare insects such as the northern colletes bee. Some machairs are threatened by erosion caused by rising sea levels as well as by recreational use of vicinity beaches. References Angus, S. 1997 . The Outer Hebrides the Shaping of the Islands . The White Horse Press. ISBN 1 874267 33 2 cite Endnotes reflist External links http www.wildlifehebrides.com environment machair Wildlife Hebrides wildlife in the Outer Hebrides of Scotlan ... more details
otherpersons John Pratt John Henry Pratt 4 June 1809 28 December 1871 was a British clergyman and mathematician who devised a theory of crustal balance which would become the basis for the isostasy principle. Life He was the second son, born in London , of Josiah Pratt . He graduated B.A. from Caius College, Cambridge , as third wrangler in 1833, was elected to a fellowship there, and proceeded M.A. in 1836. He was appointed a chaplain of the East India Company , through the influence of Bishop Daniel Wilson , in 1838. He became Wilson s domestic chaplain, and was in 1850 appointed archdeacon of Calcutta . He died at He died in Ghazipur , India, on 28 December 1871. At the instance of Bishop Milman, a memorial to Pratt was erected in Calcutta Cathedral . Works Pratt was the author of Mathematical Principles of Mechanical Philosophy 1836 , subsequently expanded and renamed On Attractions, Laplace s Functions and the Figure of the Earth 1860, 1861, and 1865 . This work, known as Pratt s Mechanical Philosophy , had full title The Mathematical Principles of Mechanical Philosophy and their application to Elementary Mechanics and Architecture, but chiefly to The Theory of Universal Gravitation , a textbook of some 600 pages. While serving as archdeacon, Pratt arrived at his theory of crustal balance, based on a survey of India. He also published a small work entitled Scripture and Science not at Variance 1856 , which went through numerous editions and, in 1865, edited from his father s manuscript Eclectic Notes, or Notes of Discussion on Religious Topics at the Meetings of the Eclectic Society, London, during the years 1798 1814 see Eclectic Society Christian . References Dictionary of National Biography , Pratt, Josiah 1768 1844 , evangelical divine, by J. H. Overton. Published 1896. External links MacTutor Biography id Pratt http tigger.uic.edu rdemar geol107 pratt.htm Extracts from the Royal Society of London http www.google.co.uk books?vid OCLC08190296&id 87HzYZNMbuIC ... more details
The Eemian sea was a body of water located approximately where the Baltic sea is now during the last or Eemian Stage , Marine isotopic stage MIS 5e , roughly 130,000 to 115,000 Before present BP . Sea level was 5 to 7 meters higher globally than it is today, due to the prior release of glacial water. Although Eemian rightly applies only to the north European glacial system, some scientists use the term in a wider sense to mean any high level body of water in the last interglacial . File Sea level temp 140ky.gif 300px thumb Sea level was 5 to 7 meters higher during MIS 5e, resulting in submersion of much of the Baltic region. The early Eemian sea connected with the White sea along the line of the White Sea Baltic Canal . Karelia was inundated and Lakes Lake Ladoga Ladoga and Lake Onega Onega were mere depressions in the shallow end of the Eemian sea. At the other end the sea connected more broadly to the North Sea . Much of north Europe was under shallow water. Scandinavia was an island. The salinity of the Eemian sea was comparable to that of the Atlantic . Scientists reach these conclusions from a study of types of microorganisms fossilized in the clay sediments laid down in the Eemian sea, and from the included pollen of Corylus , Carpinus and Betula . During MIS 5e, the mean annual temperature was 3 C higher than today. At its end, during the cooler prelude of 5d, c, b and a, the region continued to rise isostasy isostatically . Some water was recaptured in ice. Levels in the Eemian sea dropped and the opening to the White Sea was blocked. The post Eemian brackish lake did not last long geologically speaking, but was covered totally with ice. The Weichselian glaciation starting fully in MIS 4, with an interstadial in 3 and a greatest extent in 2, was, at its maximum in 20,000 18,000 BP, more than km to mi 3 high. As the lake bed was only a few hundred meters deep, no lake could have existed. The ice extended southward into north Europe as far as France and eastwa ... more details
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 http pubs.nrc cnrc.gc.ca rp rppdf e02 085.pdf Lajeuness, Patrick, and Michael Allard. 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. Canadian Journal of Earth Science, Vol. 40, 2003, pp. 65 76. Accessed 3 7 06 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 Pielou, E.C. After the Ice Age . Chicago University of Chicago Press, 1991. pp 222 224 ref References Reflist Category Historical geology Category Geology of Canada Category Holocene palaeo geo stub Pleistocene Lake ... 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 Sources Water Resource Availability in the Maumee River Basin, Indiana ... more details
ref In 1889, Dutton proposed the term isostasy for the concept of a general balance within the Earth ... Problems of Physical Geology. Bull. Phil. Soc. Wash., 11 51 64. Proposed the new term isostasy ... more details
Only core subjects that are of interest to all geologists should be listed here. Consider the subjects that are covered in secondary school or undergraduate Introduction to geology courses before geology majors start to specialize. See the Talk Page. Please develop a list of subtopics here before moving articles from the main list into them, so that we know what categories we have to choose from. This is a list of all articles related to geology that cannot be readily placed on the following subtopic pages col begin col 3 Geologic time scale List of compounds List of earthquakes List of elements by name Geology of the English counties col 3 List of geologists List of fluvial topics List of landform s List of minerals List of oil fields col 3 List of plate tectonics topics List of rock types List of tectonic plates List of volcanoes col end compactTOC2 A Asthenosphere Astrogeology Aulacogen B Batholith Beach Bolide C Calcium Canyon Cave Cement Cementation Cenozoic Coast Concretion Conglomerate geology Conglomerate Continent Convergent boundary Crag and tail Crust geology Crust D Datum geodesy Deposition sediment Deposition Dike geology Dike Divergent boundary Drumlin E Earth science Eustasy Environmental engineering Environmental geography Eon geology Eon Epigenesis Epoch geology Epoch Era geology Era F Falls line Felsic G Geologic age Fault geology Geologic fault Geologic modeling Geologic period Geologic time scale Geological phenomenon Geologist Geology of the Alps Geomorphology Geostatistics Geyser Glaciation Graben H Horst geology Hotspot geology Igneous rock I Isostasy J Karst L Laccolith List of geologists List of tectonic plates List of rock types Lithosphere M Mafic Mantle geology Mass wasting Matrix geology Metamorphic rock Meteorite Mineral Mining engineering Mud pot Mud volcano N Empty section date July 2010 O Orogeny P Paleontology Pedology soil study Permeability fluid Petroleum engineering Phosphate Piercement structure Plate tectonics Proterozoic Porp ... more details
about the use of the term in geography and physical geology File North Ridge of Mount Rohr.jpg thumb A hiker standing on a mountain ridge File Tsubakurodake from Otenshodake 2002 8 22.jpg thumb A mountain ridge in Japan A ridge is a geological feature that features a chain of mountains or hills that are of a continuous elevated crest for some distance. Ridges are usually termed hill s or mountain s as well, depending on size. There are several main types of ridges Dendritic drainage Dendritic ridge In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges. These are by far the most common ridges. These ridges usually represent slightly more erosion resistant rock, but not always they often remain because there were more Joint geology joint s where the valleys formed, or other chance occurrences. This type of ridge is generally somewhat random in orientation, often changing direction frequently, often with knobs at intervals on the ridge top. Stratigraphic ridge In places such as the Ridge and valley Appalachians , long, even, straight ridges are formed because they are the uneroded remaining edges of the more resistant stratum strata that were Fold geology folded laterally. Similar ridges have formed in places such as the Black Hills , where the ridges form concentric circles around the igneous core. Sometimes these ridges are called Hogback geology hogback ridges . Mid ocean ridge Oceanic spreading ridge In tectonic spreading zones around the world, such as at the Mid Atlantic Ridge , the volcanic activity forming new plate boundary forms volcanic ridges at the spreading zone. Isostasy Isostatic settling and erosion gradually reduce the elevations moving away from the zone. Crater ridges Large meteorite strikes typically form large impact crater s bordered by circular ridges. Volcanic caldera ridges Large volcano es often leave collapsed central caldera s that are bordered by circular ridges. Fault ridges Fault geology Faults o ... more details
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