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Topic: Rift (geology)


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In the News (Thu 27 Jun 19)

  
  Rift (geology) - Wikinfo
In geology, a rift is a place where the Earth's lithosphere is expanding.
the rift in the middle of the Gulf of Corinth in Greece
The Reelfoot Rift, an ancient buried failed rift underlying the New Madrid Seismic Zone in the Mississippi embayment.
www.wikinfo.org /wiki.php?title=Rift   (712 words)

  
 Rift valley Summary
Rifts commence as intracratonic, down-thrown blocks dominated by normal or oblique-extensional (transtensional) faults (e.g., the Rhine Graben in Germany and the East African Rift).
In early simple-shear rift models, a through-going shear zone was proposed to extend from the upper crust to the upper mantle.
Rift valleys typically appear as a downdropped graben between a pair of faults, or vertical Earth movements.
www.bookrags.com /Rift_valley   (920 words)

  
 Geology and Geological History - Albuquerque's Environmental Story
This physiographic demarcation is formed by the Rio Grande Rift, a great fracture in the earth's surface which extends more than 450 miles from Leadville, Colo., to Las Cruces, N.M. The Rift was formed by down-dropping of a large block of the earth's crust, yielding an elongated trough bounded on either side by mountains.
The rise of this immense fragment of the earth's crust is somewhat analogous to opening a trap door; the open door is marked by the gently sloping eastern side of the Sandias, whereas the hinge is found in the intensely crumpled rocks of the Cedar Crest area.
The Rift has fractured the earth's crust and caused the mountainous margins to rise thousands or tens of thousands of feet relative to the subsiding inner valley.
www.cabq.gov /aes/s1geol.html   (974 words)

  
 Rift Sequences of the Southern Margin of the Gulf of Corinth (Greece) as Exploration / Production Analogues, by Richard ...
The onshore area of the rift is up to approximately 40 km in width and 120 km long and includes both seismically inactive and active fault systems, and associated syn-rift sediment fill.
Thus the rift consists of one broad alluvial half-graben at this time, >16km wide, bounded by the Kalavrita Fault in the south and with a hangingwall extending to the north of the Mamousia-Pirghaki Fault (Figures 2 and 3).
The majority of the exposed rift sediments in the Kalavrita half-graben are interpreted as part of the progradational syn-rift package, with older syn-rift sediments exposed along the footwall onlap surfaces, west of Kalavrita.
www.searchanddiscovery.com /documents/2004/collier/index.htm   (2829 words)

  
 Geology of Thingvellir
The rift valley narrows from about 20-25 km in the NE to about 10 km in the SW.
Rifting within the graben is episodical, with the last major earthquake activity occurring in 1789.
The ├×ingvellir graben is surrounded by volcanoes, that illustrate the connection between rifting and volcanism.
www.hi.is /~oi/geology_of_thingvellir.htm   (1051 words)

  
 THE MIDCONTINENT RIFT
This tear or rift, known as the Midcontinent Rift System, extended for 950 miles from what is now Lake Superior to Oklahoma, and was on its way to becoming a full-fledged ocean when the process halted.
As the rift grew and the valley floor sank, still more volcanic rocks were deposited, ultimately reaching tens of thousands of feet in thickness.
The rift system covers 42,000 square miles of Iowa's geologic "basement" and is dominated by the central horst (see map above), bounded by fault zones (heavy lines), and by a series of flanking basins.
www.igsb.uiowa.edu /browse/rift97/rift97.htm   (619 words)

  
 MIDCONTINENT RIFT SYSTEM IN IOWA
The Midcontinent Rift System (MRS) is a billion year old rip in the continental crust that represents an episode of crustal stress that nearly ended in the complete severing of the southeastern part of North America and the formation of a new ocean.
In Iowa, the MRS are dominated by a huge, uplifted block (called a horst) of basalt that follows the axis of the rift across Iowa from south-central Minnesota to southeastern Nebraska near Lincoln.
The rock units, or stratigraphy, of the MRS in Iowa is very similar to the rocks of the MRS exposed in the Lake Superior area and seen from subsurface samples from Minnesota.
www.igsb.uiowa.edu /browse/rift/mrs.htm   (685 words)

  
 references
Geology Of The Musandam Peninsula (Sultanate Of Oman) And Its Surroundings.
The Geology Of The Iran-Gulf Of Oman Region: A Synthesis.
Redetermined Magnitudes Of Earthquakes In The Afro-Eurasian Junction.
atlas.geo.cornell.edu /ctbt/references.html   (14779 words)

  
 Geology   (Site not responding. Last check: 2007-11-06)
This movement has been accompanied by extensive faulting, shattering, uplifting and sinking of the rocks of the earth’s crust along its boundary, and this led to the formation of the rift valley.
The rift is still considered to be active, and the movement to date is about 107 km.
The Wadi Arabah Earthquake Project, directed by Dr Tina Niemi of the University of Missouri-Kansas City, is attempting to document the earthquake history of the Wadi Arabah using archaeological excavation, geophysical surveys, and geologic subsurface probes.
www.wadiarabahproject.man.ac.uk /opening/menu/Geology/geologytext.htm   (679 words)

  
 Kenya Geology Photographs
Rifts form where the forces of plate tectonic cause large blocks of the upper mantle and earth crust to move apart, allowing magma to rise from the upper mantle.
Lake Bogoria is one of a chain of lakes situated in the East African Rift.
Ground waters are heated by rising magmas and hot rocks, and the lighter hot water and steam rises to the surface by the force gravity.
web.umr.edu /~rhagni/Kenya.html   (476 words)

  
 John Hawks Anthropology Weblog
The Great Rift is an ocean being born, as parts of East Africa pull away from the rest of the continent, leaving a sinking basin in their wake.
This geology is not limited to Africa, but stretches into West Asia, causing the Dead Sea to occupy the lowest continental basin on Earth, and continuing to generate earthquake activity as far north as Anatolia.
Recently, discoveries to the west of the rift, including those at Bahr el Ghazal and Toros-Menalla in Chad, have pointed to the possibility that hominids existed in Central and West Africa as well.
johnhawks.net /weblog/topics/geology/rift   (673 words)

  
 The Chronicle OnLine: Okanogan County Geology   (Site not responding. Last check: 2007-11-06)
Some 17 million or so years ago there is evidence that the earth was struck by an asteroid, not the first time, and as on the other occasions, it was as if the earth, given such a blow and wound, bled as a result.
Today, as a result of continued study, matching of fossils from both sides of the Atlantic, checking of the magnetism of the rocks on both sides of the mid-ocean rifts and much other detective study, the plate techtonics theory is pretty well accepted.
This extruded rock slowly moves from the rift valley toward the continents on both sides and proceeds like a conveyor belt toward the those continents.
www.omakchronicle.com /geology/geodex.shtml   (2210 words)

  
 InsaneScouter - Helping todays youth one click at a time   (Site not responding. Last check: 2007-11-06)
Geology in the interior of the plates is relatively inactive.
Geology along transform zones is usually restricted to earthquake activity.
The geology along an ocean-continental collision is similar to an ocean-ocean collision to some degree.
www.insanescouter.com /t276/files/geology/Tectonics.html   (1917 words)

  
 t61c in fm00
While continental rifting and steady state seafloor spreading have been extensively studied, the interaction between lithospheric extension, mantle flow and melting during the transient period when continental rifting progresses into seafloor spreading is still not well understood.
The most plausible explanation is that rifting occurred along a lithosphere-cutting master fault with a steep scarp forming on the footwall block and numerous smaller faults developing in the subsiding hanging wall block, prior to establishment of the new spreading axis within the intervening trough.
Active rifting is localized in a narrow region along an east-west trending basin, where a shallow-dipping normal fault west of the spreading tip delineates the boundary between the downflexed Woodlark Rise to the north and the block-faulted Pocklington Rise to the south.
www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm00&database=/data/epubs/wais/indexes/fm00/fm00&maxhits=200&="T61C"   (7193 words)

  
 DuluthStreams - regional geology
Continental rifting is a common and recurring process in the history of the earth that leads to break-up of continents and the formation of ocean basins.
The Midcontinent Rift began to form 1109 million years ago along a 2000-km-long arcuate break that extended in two arms from the Lake Superior region - one to the SW to Kansas; the other to the SE to Lower Michigan.
The sandstone that buried the igneous rocks of the rift are exposed near Fond du Lac in the stream bed of Mission Creek.
www.duluthstreams.org /understanding/geology.html   (721 words)

  
 rift | English | Dictionary & Translation by Babylon
In geology, a rift is a place where the Earth's crust and lithosphere are being pulled apart.
Rifts are distinct from Mid-ocean ridges, where new oceanic crust and lithosphere is created by seafloor spreading.
Typically the transition from rifting to spreading develops as three converging rifts over a hotspot.
www.babylon.com /definition/rift   (259 words)

  
 Craters of the Moon NM & Preserve: Geologic History
A volcanic rift zone is a concentration of volcanic landforms and structures along a linear zone of cracks in the earth's crust.
The Great Rift volcanic rift zone is a zone of cracks running approximately northwest to southeast across almost the entire eastern part of the Snake River Plain.
On the basis of recent eruptive history, the Craters rift set is due for another eruption within the next thousand years, perhaps as soon as within 200 years.
www.nps.gov /crmo/geologyb.htm   (867 words)

  
 A Pictorial History of Albuquerque Area Geology - Albuquerque's Environmental Story
The geological history that led to the city's familiar mountain/valley/mesa trough shape is long and complex, extending hundreds of millions of years.
Continued erosion of the Sandia mountains carries sand and mud westerly down steep arroyos to the rift and down more gentle arroyos and streams to basins on the eastern side of the mountains.
The Rio Grande follows the rift zone depositing on its flood plain materials which add to the fertility of the alluvial materials eroded from the mountains.
www.cabq.gov /aes/s1picgeo.html   (633 words)

  
 3D-GEO Extension; Rift Basin Geology Structural Seismic Restoration Geology Solutions; Case with Studies from Papua New ...
Pressure compartmentalisation is common in rift basins, from semi-regional transfer faults to cryptic (hidden) cross-cutting faults on a reservoir scale, leading to migration shadows, unexpected production barriers or offset fluid contacts.
Rift and Strike Slip Fault Basin Case Studies in Extensional Geology Terrains such as the North West Shelf Australia
He received a BS in Geology from the University of Illinois followed by an MS from Utah State University studying the structural styles of deformation and thrust interactions in the Idaho-Wyoming-Utah Thrust Belt.
www.3d-geo.com /extension/extensional_structural.asp   (3364 words)

  
 Lake Baikal - A Touchstone for Global Change and Rift Studies - USGS Fact Sheet
Understanding the origin of the Lake Baikal rift contributes to understanding one of the fundamental phenomena by which the history of the Earth is reconstructed.
Continental rifts, like the Lake Baikal rift, and their end products, such as passive continental margins like the east coast of the United States, are ubiquitous in the Earth's geologic record.
USGS and Russian cooperative studies have begun to resolve the three-dimensional geometry of the Lake Baikal rift.
pubs.usgs.gov /fs/baikal/index.html   (1059 words)

  
 Rift Basin Architecture & Evolution
The reasons for this interest include: (1) Rift basins are found on all passive (Atlantic-type) continental margins and provide a record of the early stages of (super)continental breakup.
The three sides of the triangle are the border fault, the rift-onset unconformity between prerift and synrift rocks, and the postrift unconformity between synrift and postrift rocks (or, for modern rifts, the present-day depositional surface).
Thus, the end of rifting, the initation of inversion, and probably the initiation of seafloor spreading are diachronous along the central Atlantic margin (i.e., during earliest Jurassic time in the southeastern United States and Early to Middle Jurassic time in the northeastern United States and Maritime Canada) (Withjack et al., 1998).
www.ldeo.columbia.edu /~polsen/nbcp/breakupintro.html   (3417 words)

  
 Potential for New Nickel-Copper Sulfide Deposits in the Lake Superior Region
The continental rifting and associated voluminous igneous activity in all three regions formed in response to the rise of a hot plume of mantle material from deep in the Earth, fracturing the overlying continental crust (fig.
Although the Midcontinent rift appears to be a likely setting for Ni-Cu sulfide mineralization to form, the next question is where the mineralized areas may be located within the rift.
In the Midcontinent rift, compression late in its history resulted in uplift and tilting of the crust, exposing several intrusions along the margins of the rift.
pubs.usgs.gov /info/mwni_cu   (2381 words)

  
 RegionalGeo.html   (Site not responding. Last check: 2007-11-06)
The Midcontinent Rift System (MRS) in northern Minnesota consists of volcanic flows and intrusive rocks that were emplaced during a relatively short interval (approximately 23 Ma) during the Middle Proterozoic (1109-1086 Ma).
Early studies (e.g., Grout, 1918) suggested that the layered igneous rocks of the rift were part of a single lopolithic intrusion.
Briefly, the evolution of the rift can be divided into early, main, and late stages.
www.macalester.edu /geology/sonju/RegionalGeol.html   (363 words)

  
 UMD Geology: John Green
Green's interests are in mineralogy and petrology, volcanology (especially plateau lavas), geology of the Lake Superior region and the Midcontinent Rift System, and environmental geology.
Geology on Display: Geology and Scenery of Minnesota's North Shore State Parks, St. Paul, Minnesota Dept. of Natural Resources, 70 p (1996).
Geology of Keweenawan extrusive rocks, in Geology and Tectonics of the Lake Superior Basin - A Review, R.J. Wold and W. Hinze, eds., Geol.
www.d.umn.edu /geology/people/fsbios/green.html   (479 words)

  
 John Hawks Anthropology Weblog
The Great Rift is an ocean being born, as parts of East Africa pull away from the rest of the continent, leaving a sinking basin in their wake.
This geology is not limited to Africa, but stretches into West Asia, causing the Dead Sea to occupy the lowest continental basin on Earth, and continuing to generate earthquake activity as far north as Anatolia.
Recently, discoveries to the west of the rift, including those at Bahr el Ghazal and Toros-Menalla in Chad, have pointed to the possibility that hominids existed in Central and West Africa as well.
www.johnhawks.net /weblog/topics/geology/rift   (691 words)

  
 Continental Rifting.
The basic idea is that rifting tends to occur along old orogenic axis, so that these become the edges of the rifted continental fragments, which eventually collide to form mountain belts, setting up the axis for the next rifting episode.
Continental rifts are locations of continental crustal extension/divergence, crustal thinning, sedimentary basin formation, and often thermal and igneous activity.
Describes a variant on the Wernicke model and applies it to continental margins, discussing the effect of the inherent asymmetry of Wernicke's and their model on margin development.
maps.unomaha.edu /Maher/plate/week3/contrift.html   (802 words)

  
 GEOLOGY
The East African Rift System, which is part of a 5,000-km/3,100 mi fracture zone extending from the Limpopo valley in the south to the Jordan valley in the north, came into existence in its southern part in the late Mesozoic, and was associated with voluminous igneous activity.
Further extensive igneous activity is seen in the Tertiary to recent volcanics of the northern part of the rift, which originated in mid-Tertiary times.
Fault movement forming the rift valley took place mainly in Miocene and Pleistocene times, and the area is still marked by seismic activity, volcanism, and high heat flow through the crust.
www.fortunecity.com /oasis/skegness/394/geology.htm   (1416 words)

  
 ScienceDaily: Geological Demolition Derby: New View On Tibetan Plateau's Rift Valleys
The rift valleys actually curve away -- some to the east, some to the west -- from the point where India is punching into the gut of Tibet.
The article, "India Punch Rifts Tibet," by Kapp and Jerome H. Guynn, a doctoral candidate in UA's department of geosciences, is in the November issue of the journal Geology.
In fall of 2003, he was teaching structural geology, and as he worked on the lecture about stress in the crust from continents colliding, he realized that collisional stress caused the pattern of Tibet's rift valleys.
www.sciencedaily.com /releases/2004/11/041116234241.htm   (1058 words)

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