Pages in category "Fracture zones"
The following 19 pages are in this category, out of 19 total, this list may not reflect recent changes (learn more).
The following 19 pages are in this category, out of 19 total, this list may not reflect recent changes (learn more).
1. Fracture zone – A fracture zone is a linear oceanic feature—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics, lithospheric plates on either side of an active transform fault move in opposite directions, here, strike-slip activity occurs. In actual usage, many transform faults aligned with fracture zones are often referred to as fracture zones although technically. Mid-ocean ridges are divergent boundaries that push apart two plates, as the plates on either side of a mid-ocean ridge move, transform faults are created due to variances in plate motion. As the plates continue to move over time, these faults offset the mid-ocean ridge and these offsets cause fractures in the ocean floor that can extend for hundreds of kilometers out from a mid-ocean ridge. Fracture zones and the faults that form them are separate features. Transform faults are plate boundaries, meaning that on side of the fault is a different plate. In contrast, on side of a fracture zone, the crust belongs to the same plate. As many areas of the floor, particularly the Atlantic Ocean, are currently inactive. However, by observing the fracture zones, one can determine both the direction and rate of past plate motion and this is found by observing the patterns of magnetic striping on the ocean floor. By measuring the offset in the striping, one can then determine the rate of past plate motions. In a similar method, one can use the relative ages of the seafloor on either side of a zone to determine the rate of past plate motions. By comparing how offset similarly aged seafloor is, one can determine how quickly the plate has moved, the Blanco Fracture Zone is a fracture zone running between the Juan de Fuca Ridge and the Gorda Ridge. The dominating feature of the zone is the 150 km long Blanco Ridge. The Charlie-Gibbs Fracture Zone consists of two zones in the North Atlantic that extend for over 2000 km. These fracture zones displace the Mid-Atlantic Ridge a total of 350 km to the west, the section of the Mid-Atlantic Ridge between the two fracture zones is seismically active. The Mendocino Fracture Zone extends for over 4,000 km off the coast of California and separates the Pacific Plate and Gorda Plate. The bathymetric depths on the side of the fracture zone are 800 to 1,200 m shallower than to the south
2. Blanco Fracture Zone – The principal feature of the Blanco zone is the Blanco Ridge, a right lateral-moving fault which also incorporates some compression, thus accounting for the uplift expressed in the ridge. The ridge is not an oceanic spreading center, despite its name, whereas the Juan de Fuca, similarly confusing, the portion of the Blanco Fracture Zone which lies east of the rift zone spreading center is not technically a true fracture zone, but a transform fault zone. In March and April 2008, a series or swarm of earthquakes occurred both near and within the Blanco zone. The swarm began on March 30 when over 600 measurable tremors began occurring north of the zone within the Juan de Fuca Plate, on April 23, activity moved to the Blanco fault zone itself, near its junction with the Gorda Ridge. Geology of the Pacific Northwest Mendocino Fracture Zone Oregon State University – Earthquake Swarm Cascadia tectonic history
3. Charlie-Gibbs Fracture Zone – Charlie-Gibbs Fracture Zone is a system of two parallel fracture zones. It is the most prominent interruption of the Mid-Atlantic Ridge between the Azores and Iceland and it can be traced over more than 2000 kilometers, all the way from north-east of Newfoundland to south-west of Ireland. It took 90 million years for the fault to grow to this length, the transform fault of the southern fracture zone displaces the Mid-Atlantic Ridge, coming from the Azores Triple Junction, to the west over a distance of 120 km. At longitude 31. 75W a south to north seismically active rift valley with a length of 40 km connects the end of the southern transform to the eastern end of the northern transform. The northern transform fault displaces the spreading ridge over another 230 km to the west before it connects to the part of the Mid-Atlantic Ridge going to Iceland. Thus the total offset of the system is 350 kilometers, both transform faults continue eastward and westward as inactive fracture zones. In 1963 the existence of a fault near latitude 53N was first postulated on the basis of earthquake epicenter data by Bruce Heezen. Also the study of ocean currents indicated that there should be a passage through the Mid-Atlantic Ridge. In 1966 the area was investigated by USCGC Spar on its return from an Arctic survey, the fault was named Charlie Fracture Zone after the USCG Ocean Weather Station Charlie at 52°45′N 35°30′W, athwart the fault. In July 1968 USNS Josiah Willard Gibbs conducted a more extended survey and it was proposed that the fracture zone be renamed Gibbs Fracture Zone, as fracture zones are generally named for research vessels. The proposal was accepted only in part, and currently the name is Charlie-Gibbs Fracture Zone. Note that the name refers to the two parallel fracture zones together. The individual fracture zones have to be referred to as Charlie-Gibbs North and South, the transform area contains two named seamounts, Minia Seamount at 53°01′N 34°58′W. It is located inside the corner of the branch of the Mid-Atlantic Ridge. This seamount is named after the ship Minia of the Anglo-American Telegraph Company, the Minia is known for recovering bodies and artifacts from the Titanic. Hecate Seamount at 52°17′N 31°00′W, named after HMS Hecate and it is located on the northern wall of the southern transform fault east of the short spreading ridge. The Charlie-Gibbs Marine Protected Area is an area in the Charlie-Gibbs fracture zone in North Atlantic international waters. U. S. Coast Guard Cutter Spar WLB -403 out of Bristol RI,1966
4. Diamantina Fracture Zone – The Diamantina Fracture Zone is an area of the south-eastern Indian Ocean seafloor. It has a range of ridges and trenches and it lies to the south of the mideastern Indian Ocean features of the Wharton Basin and Perth Basin, and to the south west of the Naturaliste Plateau. Being parallel to the Southeast Indian Ridge, Diamantina Fracture Zone is not a fracture zone in the sense of plate tectonics. In fact its extension to the west is called Diamantina Escarpment and this is the southern border of the Broken Ridge Plateau. All these features are mirrored by corresponding topography on the side of the Southeast Indian Ridge. Broken Ridge Plateau was formed at the ridge together with the Kerguelen Plateau, Diamantina Fracture Zone was first detected by RV Vema and RV Argo in 1960. It is named after HMAS Diamantina, which did further exploration in 1961, the Diamantina Deep is the zones deepest location, located about 1125 km West-South-West of Perth, Western Australia, at 35°S 104°E. This is not the deepest point in the Indian Ocean, the CIAs Physical Map of the World lists the Java Trench as such. On the western side of the Diamantina Fracture Zone at 33°30′S 101°20′E is another, larger pit, named Dordrecht Hole and its maximum depth is 7079 m at 33. 42°S101. 48°E / -33.42,101.48. Dordrecht was the name of a vessel of the Dutch East India Company, the shallowest point in the area is the 1125-metre point in the Broken Ridge close to Ninety East Ridge. Oceanic trench Sunda Arc Location on Google map
5. Easter Fracture Zone – The Easter Fracture Zone is an oceanic fracture zone associated with the transform fault extending from the Tuamotu archipelago in the west to the Peru–Chile Trench to the east. The Easter Fracture Zone extends roughly 5900 kilometers from 20°S, 131°W to 26°S, the landscape consists of several ridges and isolated volcanos with maximal peak elevation above the seafloor of 3000m. Because the local seafloor has depths around 4000m to the north of the zone and 3400m to the south of the fracture zone. They do rise above sea level at the Pitcairn Islands and Easter Island, Easter Hotspot Easter Fracture Zone – Encyclopædia Britannica Online Map pointer to Easter fracture zone. Zoom out to see full extent
6. Great Lakes tectonic zone – Into the Lake Huron region near Sudbury, Ontario, Canada. This crustal boundary is the Great Lakes tectonic zone and it is 1,400 km long, and separates the older Archean gneissic terrane to the south from younger Late Archean greenstone-granite terrane to the north. Collision began along the Great Lakes tectonic zone with the Algoman mountain-building event, during the formation of the GLTZ, the gneissic Minnesota River Valley subprovince was thrust up onto the Superior provinces edge as it consumed the Superior provinces oceanic crust. Fragmentation of the Kenorland supercontinent began 2,450 million years ago and was completed by 2,100 million years ago, sedimentation from the GLTZ-rifting environment continued into the Penokean orogeny, which is the next major tectonic event in the Great Lakes region. Several earthquakes have been documented in Minnesota, Michigans Upper Peninsula, into the Sudbury, Ontario, Canada, region. The farthest west into South Dakota is 99°W, which is about 55 km from the Minnesota – South Dakota border and this crustal boundary is the Great Lakes tectonic zone. This gneissic terrane originally extended several hundred kilometers east to west, the boundary that separates the two colliding bodies is the Great Lakes tectonic zone, it is a fault zone of highly deformed rocks. Collision began along the GLTZ around 2,700 million years ago, the collision is interpreted to have happened obliquely at an angle, beginning in the west. The MRV subprovince experienced two distinct high-grade metamorphic events, one 3,050 million years ago and the other 2,600 million years ago, the first was probably during formation of the terrane, the second was during suturing. The growth of the Superior province greenstone-granitic terranes ended with the suturing of the Minnesota River Valley gneiss terrane to the basaltic Wawa subprovince, suturing, the last stage of closure, started in South Dakota and continued eastward. During the formation of the GLTZ, the MRV protocontinent consumed the Superior provinces oceanic crust as the subprovince came in from the south, suturing of one continental block onto another usually occurs because a subduction zone exists beneath one of the blocks. The subduction zone consumes the oceanic crust connected to the other block, after the oceanic crust is consumed, the two blocks meet and the subducting oceanic crust pulls the attached continental block under the other. After suturing, the region was quiet for a few hundred million years. The Algoman Mountains had been built and then eroded into sediments that covered the area, fragmentation of this Archean supercontinent began around 2,450 million years ago under a hotspot near Sudbury and was completed by around 2,100 million years ago. This is when the Wyoming province is hypothesized to have drifted away from the Superior province, the pattern of sedimentation from this rifting environment continued into the Penokean orogeny, which is the next major tectonic event in the Great Lakes region. During the Penokean orogeny, compression deformed the sequences in the Lake Superior region, recent geologic mapping in the Marquette, Michigan, U. S. area provides information of the structure for the zone along a 10 km strike. The GLTZ was an active dextral strike-slip zone south of Marquette, day suggest that the kinematics determined in the exposed GLTZ – which are consistent – are applicable to its entire length. In the Marquette area, the GLTZ is a zone of metamorphic rock about 2 km wide that was crushed by the dynamics of tectonic movements
7. Mendocino Fracture Zone – The Mendocino Fracture Zone is a fracture zone and transform boundary off the coast of Cape Mendocino in far northern California. It runs westward from a junction with the San Andreas Fault. It continues on west of its junction with the Gorda Ridge, many seismologists refer to the active segment as the Mendocino Fault or Mendocino fault zone. The fault section demarcates the boundary between the northwestward-moving Pacific Plate and the eastward-moving Gorda Plate, the Gorda Plate is subducting beneath the North American Plate just offshore of Cape Mendocino. Where the Mendocino Fault intersects the trench of the subduction zone. This seismically active intersection is called a junction, and specifically the Mendocino Triple Junction. In Tsunami studies, energy focusing around the zone has been noted, leading to increased wave heights in the area around Crescent City. The fracture zone is referred to as the Mendocino Escarpment in these studies and it forms the boundary of the Modoc Plateau and Columbia Plateau provinces with the Great Basin. Where it meets Honey Lake Fault, it bends to trend northeast across the northwest corner of Nevada, where it accompanies the geological trough that forms Black Rock Desert
8. Romanche Trench – The Romanche Trench, also called the Romanche Furrow or Romanche Gap, is the third deepest of the major trenches of the Atlantic Ocean, after the Puerto Rico Trench and the South Sandwich Trench. It bisects the Mid-Atlantic Ridge just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2°N to 2°S and from 16°W to 20°W. The trench has been formed by the actions of the Romanche Fracture Zone, a portion of which is an active transform boundary offsetting sections of the Mid-Atlantic Ridge. The trench has a depth of 7,761 m, is 300 km long and has a width of 19 km. Deep water flow through the trench is from west to east with a rate of 3.6 Sverdrups of 1.57 °C water, antarctic Bottom Water flows below the LNADW and reaches down to the seafloor. Formed around Antarctica, the AABW is cold, has low salinity, as it flows north, it is constrained by numerous obstacles on the seafloor. In the basin on the side of the MAR the Walvis Ridge blocks the northward passage. For LNADW and AABW, the Romanche and Chain Fracture Zones are the only deep passages in the MAR where interbasin exchange is possible, as AABW flows through the Romanche Fracture Zone, salinity and temperature increase significantly. The Romanche Fracture Zone offsets the Mid-Atlantic ridge by 900 km, according to the normal scenario for the opening of the South Atlantic, it is spreading at a rate of 1.75 cm/year and began forming about 50 Ma. North of and parallel to the zone is a transverse ridge which is particularly prominent over hundreds of kilometres east and west of the MAB of the South Atlantic. The western part of the ridge consists of fragments of uplifted oceanic crust. The summit of the ridge is capped by Miocene shallow water limestones that reached above sea level 20 Ma before subsiding abnormally fast. The eastern part of the ridge, however, consists of a thick sequence of stratified material called the Romanche Sedimentary Sequence. The transverse ridge separates the present trench from an 800 km -long aseismic valley where the Romanche transform was located until about 10–8 Ma, the hydrothermal vents of the MAR support many life forms. The Romanche and Chain Fracture Zones creates a gap in the MAR. Swarms of hydrothermal shrimps reminiscent of those found from northern MAR vent-sites have been found on the part of the southern MAR. Bivalve communities have been reported around vents further south and these species await a formal description and it is not known whether or not they represent communities distinct from those on the northern MAR. The flow of NADW through the Romanche and Chain Fracture Zones may serve as a conduit for larval transport from the western North Atlantic to the eastern South Atlantic
9. Vema Fracture Zone – The Vema Fracture Zone is a fracture zone in the equatorial Atlantic Ocean. It offsets the Mid-Atlantic Ridge by 320 km to the left and its transform valley has a depth of 5000m. The fracture zone can be traced for over 2500 km east to west, from temperature data gathered from the deep ocean on the German Meteor expedition Georg Wüst already suspected that there should be a passage through the Mid-Atlantic Ridge around latitude 9 North. The Vema Fracture Zone was then discovered in 1956 by G. R, hamilton on board RV Vema, with additional surveying taking place in the years 1959-1960. In the 1960s research was done by USNS Thomas Washington, RV Atlantis II, RV Chain, RV Argo, the southern wall of the transform valley is crowned by one of the longest and highest transverse ridges of the entire mid-ocean ridge system. This narrow ridge must have risen as a vertical slab 6.6 million years ago. Up to three years ago the ridge was at or even above sealevel. Later it subsided to its present depth of 450 meters, while the transform valley of the Vema Fracture Zone has a V-shaped profile, the next fracture zone to the south has a steep vertical wall on its southern side rising from a horizontal valley bottom. As an L would fit in here, this fracture zone is nicknamed Lema Fracture Zone. The north-south distance between the Vema and Lema fracture zones is 70 km, up to 2.2 million years ago the Vema transform fault was 40 km shorter than today, and the Lema fracture zone had a leftward offset of 40 km. Then the old spreading valley between Lema and Vema died, and spreading started from an axis 40 km to the east, the Vema transform was thus extended by 40 km, while the Lema fracture zone was reduced to zero offset. Spreading from the new axis has meanwhile increased the distance between the old and the new axis to 80 km