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Topic: Reelfoot Rift


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In the News (Wed 11 Nov 09)

  
  The Review - Adventures on Earth
Rift valleys began to form - certain signs that tectonic plates are beginning to sever the ties.
The Reelfoot Rift, and New Madrid fault, run roughly under the present day course of the Mississippi river, which flows along this zone of fractured and weakened rock.
So the power that could be unleashed if the Reelfoot Rift erupts as strongly as it did in 1811-12 could easily equal or exceed the most powerful quakes on record, with catastrophic damage in the immediate area and significant damage well beyond -all the way to the East Coast.
www.zwire.com /site/news.cfm?newsid=17032644&BRD=1680&PAG=461&dept_id=40301&rfi=6   (664 words)

  
 New Madrid Seismic Zone - Wikipedia
The New Madrid Seismic Zone, also known as the Reelfoot Rift or the New Madrid Fault Line, is a major seismic zone located in the mideastern United States.
The New Madrid Seismic Zone is made up of reactivated faults that formed when North America began to split or rift apart during the breakup of the supercontinent Rodinia in the Neoproterozoic Era (about 750 million years ago).
This rift is known as the Reelfoot Rift and coincides with the northernmost portion of the Mississippi embayment.
en.wikipedia.org /wiki/New_Madrid_Fault_Zone   (852 words)

  
 2000 Field Trip, Lafayette Geological Society - A professional organization for earth scientists
A sketch of the batholith outcrop and the embedded xenolith is reproduced from Howard's brochure.
During the reactivation of the Reelfoot Rift in the Late Cretaceous, magma moved upward.
Reelfoot Rift becomes failed arm of tripartite aulacogen, subsides, and fills with sediments from depositional environments ranging from deep ocean trench to deep-water deltas.
www.lgsweb.org /field00a.html   (961 words)

  
 Rift (geology) - Wikipedia, the free encyclopedia
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.wikipedia.org /wiki/Rift   (249 words)

  
 Rift (geology) - Open Encyclopedia   (Site not responding. Last check: 2007-10-19)
Rifts are located at divergent boundaries between two tectonic plates.
Between oceanic plates the rifts occur as oceanic ridges and where these oceanic ridges intersect continental crust rift valleys result as the continent begins to split.
The Reelfoot Rift, an ancient buried failed rift underlying the New Madrid Seismic Zone in the Mississippi embayment.
www.open-encyclopedia.com /Rift_%28geology%29   (160 words)

  
 New Madrid Seismic Zone - Open Encyclopedia   (Site not responding. Last check: 2007-10-19)
Situated 25 miles below the surface, it could be considered a "failed rift", because it does not split the North American plate.
The New Madrid Seismic Zone is made up of reactivated faults that formed when North America temporarily rifted apart.
This second trend coincides with an intrusive igneous body which lies deeply buried beneath the sediments of the rift zone.
www.open-encyclopedia.com /New_Madrid_Fault_Zone   (888 words)

  
 Rift (geology) - Wikinfo
Rifts are located at divergent boundaries between two tectonic plates.
Between oceanic plates the rifts occur as oceanic ridges and where these oceanic ridges intersect continental crust rift valleys result as the continent begins to split.
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 Summary
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.
Lake Baikal, the bottom of the lake is the deepest continental rift on the earth.
www.bookrags.com /Rift   (2002 words)

  
 GSA - Earthquake Hazards
Although the rift, called the Reelfoot Rift, failed each time before it completely ruptured the crust, the pulling apart of the rocks caused the formation of many faults.
Development of the Reelfoot Rift began nearly 600 million years ago (A) as the forces that drive the motion of the earth's plates began to tear the continent apart.
Later, the rifting stopped (B) and the area sank and was buried deeply by sediments that accumulated in a shallow inland sea that covered the area.
www.gsa.state.al.us /gsa/geologichazards/earthquakes/madrid.html   (635 words)

  
 [No title]   (Site not responding. Last check: 2007-10-19)
A new contour map of the basement of the Reelfoot rift constructed from drill hole and seismic reflection data shows the general surface configuration as well as several major and minor structural features.
The basins are oriented normal to the northeast trend of the rift.
The rift basins are interpreted as having formed as opposing half graben, and the structural highs are interpreted as having formed as as sociated accommodation zones.
www.agu.org /pubs/abs/tc/97TC03551/tmp.html   (254 words)

  
 Commerce Geophysical Lineament CGL New Madrid Central US
It is parallel to the trend of the Reelfoot graben, but offset ~40 km to the northwest of the western margin of the rift floor.
The Reelfoot Rift is considered to be the one of the main sources of the seismic activity that defines the New Madrid Seismic Zone (NMSZ) (Hildenbrand, et al., 1996).
The bounding and axial faults of the rift appear to be major contributors to the seismic activity in the NMSZ (Hildenbrand, et al., 1996).
www.showme.net /~fkeller/quake/commerce2.htm   (2393 words)

  
 Mississippi Embayment
The old rift zone was a natural downwarped basin and allowed a natural course for sea level to enter the continental interior as well as exit.
This is the remnant zone of the Reelfoot Rift during the break up of supercontinent Rodinia.
The Reelfoot Rift is named after Reelfoot Lake, which was created by the 1811-1812 earthquakes.
www.emporia.edu /earthsci/student/salley3/index.htm   (1187 words)

  
 SEMP: Evidence-based disaster management: preparedness, response, recovery, and mitigation.
A rift is a split in the crust.
The history of the Reelfoot Rift began during the late Precambrian period, 750 million years ago, when powerful geologic forces from deep within the upper mantle shot upward, penetrating the lower crust and then the upper crust of a supercontinent called Rodinia.
In the New Madrid Rift Complex area, the Mesozoic Era stresses caused the area to uplift, caused old areas of weakness to fracture again (faulting), and allowed molten igneous rock (magma) to force its way into some of the faults near the margins of the rift zone.
www.semp.us /publications/biot_reader.php?BiotID=328   (2203 words)

  
 MGSC: The Illinois Basin
The basin began as a failed rift or aulacogen (Reelfoot rift and Rough Creek graben) concurrent with the breakup of a supercontinent during Early and Middle Cambrian time.
After the rifting episode, the basin began to form, initially by thermal subsidence (Late Cambrian through Middle Ordovician), as a thick succession of sandstone and carbonate rocks deposited in a depocenter situated over the rift complex.
For the remainder of the Paleozoic Era, tectonic subsidence apparently was driven primarily by an isostatically uncompensated mass in the lower crust beneath the Reelfoot rift.
sequestration.org /basin.htm   (572 words)

  
 Faults Structures Near New Madrid
The New Madrid Fault system is a collection of reactivated faults that formed long ago when North America began rifting apart.
The rifting halted before the continent broke apart, but the structures that formed then are still part of the crust and they have been rejuvenated by the present-day stresses transmitted through the North American Plate.
Little evidence of the existence of these faults is visible at Earth's surface but the main structures are outlined by earthquake activity such as that indicated by circles on the map to the right.
www.eas.slu.edu /Earthquake_Center/EQInfo/Flyers/CUS/NMstructure.html   (161 words)

  
 Neo/Sci Catalog
Lying in wait beneath the cities of the American midlands is the Reelfoot Rift, a potential epicenter of seismic activity.
Follow the rift from its formation millions of years ago, to the havoc it reeked in 1811 and, finally, to the threat it poses today.
Through actual footage of the area, interviews with scientists and animated clips, your students will explore the "hidden fury" of the rift as well as the potential damage it may cause when its fury is released.
www.neosci.com /catalog.asp?sid=119355022&showID=536&content=cn_showitem   (100 words)

  
 MGSC: The Illinois Basin
The basin began as a failed rift or aulacogen (Reelfoot rift and Rough Creek graben) concurrent with the breakup of a supercontinent during Early and Middle Cambrian time.
After the rifting episode, the basin began to form, initially by thermal subsidence (Late Cambrian through Middle Ordovician), as a thick succession of sandstone and carbonate rocks deposited in a depocenter situated over the rift complex.
For the remainder of the Paleozoic Era, tectonic subsidence apparently was driven primarily by an isostatically uncompensated mass in the lower crust beneath the Reelfoot rift.
www.isgs.uiuc.edu /mgsc/basin.htm   (572 words)

  
 EOM Archives
The base of the Illinois basin is filled with rift sediments that infilled the Reelfoot Rift Complex, a late Proterozoic/early Cambrian continental rift valley system.
One arm of the Reelfoot Rift Complex, essentially a series of valleys not unlike the East African Rift Complex, extended off the main north-south valley into present-day west Kentucky.
Continental-scale faults, some due to reactivated rift faults, and others apparently resulting from even larger crustal scale weaknesses, also resulted in deformation of the overlying basin sediments.
www.eomonline.com /Common/Archives/Oct95/fairs.htm   (2051 words)

  
 memphisaqu.html
As upwelling ceased, the rift subsided (due to the heaviness of the rock).
Plutons were formed along the flanks and axis of the rift.
Rifting then ceased and as before, the ocean advanced over the area.
www.msstate.edu /dept/GeoSciences/CT/TIG/WEBSITES/LOCAL/Summer2003/Thomas_Donna/memphisaqu.html   (486 words)

  
 Origin of New Madrid Fault earthquake Activity
Once again the rifting ceased and again, the ocean advanced over the area and receded; this time the sands, clays and gravels it deposited were not buried deeply enough, or long enough to become rock.
This rift is known as the Reelfoot Rift and coincides with the northernmost portion of the Mississippi embayment.
the granite-rhyolite terranes were laid down as a consequence of the impact associated with lunar genesis; widespread rifting of the NA plate occurred as a consequence of the Yellowstone impact circa 1.2 bya, but this was before the NA plate existed as such, still forming a portion of Pangaea at that time.
www.showme.net /~fkeller/quake/origins.htm   (1710 words)

  
 UALR Arkansas Earthquake Center - The Reelfoot Rift - Rodinia, Laurentia, Rifts, Mississippi Embayment, New Madrid ...   (Site not responding. Last check: 2007-10-19)
This rift was detected using geophysical instruments and was named the "Reelfoot Rift." The Reelfoot Rift extends from Illinois soutwest toward the Gulf of Mexico.
Even though the Reelfoot Rift is called "inactive", the Reelfoot Rift continues to infuence the central United States region.
The Mississippi Embayment Synclinorium is another interesting Arkansas geologic feature that is believed to have developed when ocean sediments accumulated in the Reelfoot Rift.
quake.ualr.edu /public/reelfoot.htm   (185 words)

  
 Energy and Geoscience Institute Instructional Services Catalog   (Site not responding. Last check: 2007-10-19)
The Reelfoot Rift is an only recently discovered system as it is covered by Cretaceous and younger sediments of the Mississippi Embayment.
Much of its history must therefore be inferred from knowledge of regional tectonic events and correlation of sedimentary sections from boreholes to exposed stratigraphy.
Reelfoot rift survey: Map data held by ESRI252 3.
associates.egi.utah.edu /Database/ReportReview.cfm?Record=128   (179 words)

  
 Is the Midwest Overdue for a New Madrid Fault Megaquake? - Associated Content
The New Madrid Reelfoot Rift fault zone is well-known for severe megaquakes, with four astounding quakes with a magnitude of at least 7.0 on the Richter scale between late 1811 and early 1812.
Since earthquake magnitude is somewhat determined by size of the fault line, the 150 mile long stretch of the Reelfoot Rift is a serious threat.
They were formed when the earth was relatively new, a split in the plates made weaker by later flooding in the area and sedimentary deposit, which made the Reelfoot Rift scar worse.
www.associatedcontent.com /article/56393/is_the_midwest_overdue_for_a_new_madrid.html   (641 words)

  
 Uncovering Hidden Hazards in the Mississippi Valley
The Reelfoot Rift is called a failed rift because the Earth's crust did not separate enough to create a new ocean basin.
However, the crust was disturbed enough to form major faults that mark the axis and margins of the rift and now contribute to the occurrence of earthquakes in the NMSZ.
The locations of earthquakes within the NMSZ also appear to be strongly influenced by the presence of large bodies of igneous rock, which were formed by the cooling and solidification of molten rock beneath the Earth's surface.
quake.usgs.gov /prepare/factsheets/HiddenHazs   (1369 words)

  
 [No title]
The original Reelfoot slip triggered further slippage and up-thrusting along all nearby faults, each fault contributing in its turn to the intensity of the destruction-over 150 miles of built-up tectonic energy cutting loose at nearly the same instant.
But the Reelfoot rift and other mid-American fault structures are not situated on a plate boundary, like the San Andreas fault.
The rift never formed, but the geological action left behind weaknesses in the earth's crust, including the tangle of faults around New Madrid.
www.survivalprimer.com /Books/289-295_Geology_MidWest_Quake.htm   (2224 words)

  
 New Madrid Seismic Zone | Tectonic Setting
The main fault of the shear zone is the Reelfoot Rift, which is a failed allocogen (continental rift zone) that formed during the breakup of Rodinia around 750 million years ago.
The structurally controlled rivers, Paleozoic rocks in cratonic sedimentary basins, and the Mississippi Embayment, all associated with the buried rift complex, are also shown.
An uplifted and possibly anomalously dense lower crust is suggested as the cause of the linear positive gravity anomaly associated with the upper Mississippi Embayment.
www.geo.arizona.edu /geo5xx/geos577/projects/muhlenkamp/tectonics.htm   (265 words)

  
 May media highlights: GEOLOGY and GSA TODAY
Neotectonics of the southeastern Reelfoot rift zone margin, central United States, and implications for regional strain accommodation.
However, we present evidence that the southeastern Reelfoot rift margin may be the fault currently accommodating much of the northeastward movement of the western crust (rather than the central rift fault).
A sharp break in topography follows the southeastern rift margin for >150 km, and we have documented surface faulting of geologically young sediments along this topographic break.
www.eurekalert.org /pub_releases/2001-04/GSoA-MmhG-2204101.php   (1322 words)

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