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34-623: The Hauraki Rift is an active NeS-to NWeSE-striking rift valley system in the North Island of New Zealand that has produced the Firth of Thames and the Hauraki Plains . It is approximately 25 kilometres (16 mi) wide and 250 kilometres (160 mi) long. The rift valley in the north appears to be delimited in the west by the line of the Firth of Thames Fault and to the east by

68-419: A complex system of ancient lunar rift valleys, including Vallis Rheita and Vallis Alpes . The Uranus system also has prominent examples, with large 'chasma' believed to be giant rift valley systems, most notably the 1492 km long Messina Chasma on Titania, 622 km Kachina Chasmata on Ariel, Verona Rupes on Miranda, and Mommur Chasma on Oberon. Rio Grande rift The Rio Grande rift

102-429: A downward hinge on the other. Which side of the basin has the major fault or the hinge alternates along the rift. The alternation between these half-grabens occurs along transfer faults, which trend across the rift to connect the major basin-bounding faults and occur between basins or, in places, within basins. The Precambrian basement changes relief sharply in this area, from 8,700 metres (28,500 ft) below sea level at

136-503: A fault breaks into two strands, or two faults run close to each other, crustal extension may also occur between them, as a result of differences in their motions. Both types of fault-caused extension commonly occur on a small scale, producing such features as sag ponds or landslides . Many of the world's largest lakes are located in rift valleys. Lake Baikal in Siberia , a World Heritage Site , lies in an active rift valley. Baikal

170-452: A long time, because it provides a north–south route that follows a major river. The Rio Grande follows the course of the rift from southern Colorado to El Paso, where it turns southeast and flows toward the Gulf of Mexico . Important cities, including Albuquerque , Santa Fe , Taos , Española , Las Cruces , El Paso , and Ciudad Juárez , lie within the rift. The Rio Grande rift represents

204-670: A part of the western Eistla, and possibly also Alta and Bell Regio have been interpreted by some planetary geologists as rift valleys. Some natural satellites also have prominent rift valleys. The 2,000 km long Ithaca Chasma on Tethys in the Saturn system is a prominent example. Charon's Nostromo Chasma is the first confirmed in the Pluto system, however large chasms up to 950 km wide observed on Charon have also been tentatively interpreted by some as giant rifts, and similar formations have also been noted on Pluto. A recent study suggests

238-412: A pure-shear rifting mechanism, in which both sides of the rift pull apart evenly and slowly, with the lower crust and upper mantle (the lithosphere ) stretching like taffy . This extension is associated with very low seismic velocities in the upper mantle above approximately 400 kilometres (250 mi) depth associated with relatively hot mantle and low degrees of partial melting. This intrusion of

272-499: A rift valley called the Ottawa-Bonnechere Graben . Þingvallavatn , Iceland's largest natural lake, is also an example of a rift lake. Rift valleys are also known to occur on other terrestrial planets and natural satellites. The 4,000 km long Valles Marineris on Mars is believed by planetary geologists to be a large rift system. Some features of Venus, most notably, the 4,000 km Devana Chasma and

306-734: Is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in the north to the state of Chihuahua , Mexico , in the south. The rift zone consists of four basins that have an average width of 50 kilometres (31 mi). The rift can be observed on location at Rio Grande National Forest , White Sands National Park , Santa Fe National Forest , and Cibola National Forest , among other locations. The Rio Grande rift has been an important site for humans for

340-729: Is both the deepest lake in the world and, with 20% of all of the liquid freshwater on earth, has the greatest volume. Lake Tanganyika , second by both measures, is in the Albertine Rift , the westernmost arm of the active East African Rift . Lake Superior in North America , the largest freshwater lake by area, lies in the ancient and dormant Midcontinent Rift . The largest subglacial lake, Lake Vostok , may also lie in an ancient rift valley. Lake Nipissing and Lake Timiskaming in Ontario and Quebec , Canada lie inside

374-400: Is fairly complex. The fundamental change in the western margin of the North American plate from one of subduction to a transform boundary occurred during Cenozoic time. The Farallon plate continued to be subducted beneath western North America for at least 100 million years during Late Mesozoic and early Cenozoic time. Compressional and transpressional deformation incurred by

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408-538: Is in the south. The crustal thickness underneath the rift is on average 30–35 kilometres (19–22 mi), thinner by 10–15 kilometres (6.2–9.3 mi) than the Colorado Plateau on the west and the Great Plains to the east. Formation of the rift began with significant deformation and faulting with offsets of many kilometers starting about 35 Ma. The largest-scale manifestation of rifting involves

442-691: Is intersected in northern New Mexico by the NE-SW trending Jemez Lineament which extends well into Arizona . The lineament is defined by aligned volcanic fields and several calderas in the area, including the Valles Caldera National Preserve in the Jemez Mountains . The Jemez Lineament is thought to be a hydrous subduction zone scar, separating Precambrian basement rock of the Yavapai - Mazatzal transition zone from

476-522: Is now dominated by the much more recent Taupō Rift (2 million years old at most) associated with the Taupō Volcanic Zone (TVZ) to which it is off-set by 60 degrees. TVZ eruptive output of 240,000 years ago, being Mamaku ignimbrite from the Rotorua caldera has filled in the far southern extremes. Thermal springs along the rift edges and center are found throughout the region with a heat output of

510-506: Is responsible for anomalously high earthquake activity in the vicinity, including the largest rift-associated earthquakes in historic times (two events of approximately magnitude 5.8) in July and November 1906. Earth and space-based geodetic measurements indicate ongoing surface uplift above the Socorro magma body at approximately 2 mm/year. The Rio Grande rift's tectonic evolution

544-455: Is the oldest of the three major basins, and contains 7,350 metres (24,110 ft) of Paleogene clastic sediments deposited on Precambrian basement. The southernmost Albuquerque basin contains pre-rift volcanic deposits , while the central and northern portions contain volcanics erupted during rifting. In cross-section, the geometry of the basins within the rift are asymmetrical half-grabens , with major fault boundaries on one side and

578-732: The East African Rift , Rio Grande rift and the Baikal Rift Zone , which are currently active, as well as a fourth which may be, the West Antarctic Rift System . In these instances, not only the crust but entire tectonic plates are in the process of breaking apart forming new plates. If they continue, continental rifts will eventually become oceanic rifts. Other rift valleys are the result of bends or discontinuities in horizontally-moving (strike-slip) faults. When these bends or discontinuities are in

612-587: The Hauraki Fault . The mountains of the Coromandel (which include andesitic and basaltic back arc volcanoes) and Kaimai Range to the east and the Hunua Range to the west give it the appearance of a full graben although it has also been described as a simple structure of 2 to 3 half-grabens so the term Hauraki Graben for the low lying portions would be incorrect. However the apparent line in

646-628: The Laramide Orogeny lasted until about 40  Ma in New Mexico. This deformation may have been a result of the coupling between the subducting Farallon plate and the overlying North American Plate . Crustal thickening occurred due to Laramide compression. After the Laramide Orogeny and until 20 Ma, a major period of volcanic activity occurred throughout the southwestern United States. Injection of hot magmas weakened

680-673: The asthenosphere into the lithosphere and continental crust is thought to be responsible for nearly all of the volcanism associated with the Rio Grande rift. The sedimentary fill of the basins consists largely of alluvial fan and mafic volcanic flows. The most alkalic lavas erupted outside the rift. The sediments that were deposited during rifting are commonly known as the Santa Fe Group . This group contains sandstones , conglomerates , and volcanics. Aeolian deposits are also present in some basins. The Rio Grande rift

714-407: The lithosphere was hot, the brittle-ductile transition was relatively shallow. There is evidence that the second period of extension began earlier in the central and northern Rio Grande rift than in the south. A third period of extension may have begun in the early Pliocene . One theory is that the Colorado Plateau acts as a semi-independent microplate and one way of explaining the creation of

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748-664: The Mazaztl Province proper. Also on the Colorado Plateau but further north lies the San Juan volcanic field in the San Juan Mountains of Colorado. The youngest eruptions in the rift region are in the Valley of Fires , New Mexico, and are approximately 5,400 years old. The Socorro, New Mexico , region of the central rift hosts an inflating mid-crustal sill-like magma body at a depth of 19 km that

782-426: The Rio Grande rift is by the simple rotation of the Colorado Plateau 1-1.5° in a clockwise direction relative to the North American craton. Other explanations that have been offered are that the extension is driven by mantle forces, such as large-scale mantle upwelling or small-scale mantle convection at the edge of the stable craton; collapse of over-thickened continental crust; initiation of transform faulting along

816-672: The San Luis is roughly 120 by 80 kilometres (75 by 50 mi). These basins may contain smaller units within them, such as the Alamosa basin within the San Luis, which is bounded by the San Juan and Tusas mountains on the west and the Sangre de Cristo Mountains in the east. The Albuquerque basin is the largest of the three basins, spanning 160 kilometres (99 mi) north–south and 86 kilometres (53 mi) east–west at its widest points. It

850-500: The bottom of the Albuquerque basin to 3,300 metres (10,800 ft) above sea level in the nearby Sandia Mountains , which flanks the Albuquerque basin to the east. Flanking mountains are generally taller along the east side of the rift (although some of this relief may be Laramide in origin). The thickness of the crust increases to the north beneath the rift, where it may be as much as 5 kilometres (3.1 mi) thicker than it

884-532: The easternmost manifestation of widespread extension in the western U.S. during the past 35 million years. The rift consists of three major basins and many smaller basins, less than 100 square kilometres (39 sq mi). The three major basins (from northernmost to southernmost) are the San Luis , Española , and Albuquerque basins. The rift's northern extent is delineated by the upper Arkansas River basin between Leadville and Salida, Colorado . Further south,

918-439: The lithosphere and allowed for later extension of the region. Cenozoic extension started about 30 million years ago (Ma). There are two phases of extension observed: late Oligocene and middle Miocene . The first period of extension produced broad, shallow basins bounded by low-angle faults. The crust may have been extended as much as 50% during this episode. Widespread magmatism in mid- Cenozoic time suggests that

952-714: The northern boundary might come ashore in Northland, near Whangārei and that the southern boundary while modified by events after the formation of the Mangakino caldera complex continued to be active. Work using geolocation on the Hauraki Rift reveals a widening rate of 0.9 mm (0.035 in)/year although some of the raw data suggests that at the Te Poi end it might be up to 1.5 mm (0.059 in)/year which would be consistent with this. However, in this region it

986-622: The order of 6.5MW in total. At the far side of the Coromandel Peninsula there is a parallel structure of Late Miocene /Quaternary origin extending north, that has been called the East Coromandel Rift. To the south east is the Tauranga Volcanic Centre which is likely related to activity in the old Taupō Volcanic Zone and the postulated Omanawa Caldera would have been at the intersection of

1020-527: The rift is defined by a network of smaller, less topographically distinct alternating basins and ranges. The distinction between these smaller basins and those of the Basin and Range Province becomes blurred in northern Mexico . Basin size generally decreases to the north in the rift, though the Española covers approximately 120 kilometres (75 mi) north–south and 40 kilometres (25 mi) east–west, and

1054-460: The same direction as the relative motions along the fault, extension occurs. For example, for a right lateral-moving fault, a bend to the right will result in stretching and consequent subsidence in the area of the irregularity. In the view of many geologists today, the Dead Sea lies in a rift which results from a leftward discontinuity in the left lateral-moving Dead Sea Transform fault. Where

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1088-559: The south of the Firth of Thames Fault no longer follows the apparent horst structure to the west and some believe the line of the Waikato River after it leaves the old Taupō Rift gives a better guide to the western line of the rift as structures have been heavily modified in the last 26,000 years in the south, and the Waikato River historically used the graben in its route to the sea. The active intra-rift Kerepehi Fault in

1122-550: The southern portion of the Hauraki Rift is complex and has the potential for large earthquakes. Initially between 10 and 5 million years ago the rift developed in a back arc region to the now extinct Coromandel volcanoes. It has a basement of mesozoic greywacke and argillite and at least two andesitic volcanoes erupted within it. To the north the rift is filled with 2.5–3 kilometres (1.6–1.9 mi) thick Tertiary and Quaternary terrestrial sediments and beyond Waiheke Island it opens up into an oceanic basin. Early work suggested

1156-562: The two rifts about 2 million years ago. Rift valley The most extensive rift valley is located along the crest of the mid-ocean ridge system and is the result of sea floor spreading . Examples of this type of rift include the Mid-Atlantic Ridge and the East Pacific Rise . Many existing continental rift valleys are the result of a failed arm ( aulacogen ) of a triple junction , although there are three,

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