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62-620: Noctis Labyrinthus is located in the heart of Tharsis at the western end of the Valles Marineris , manifesting as a network of graben that extends in a spider-like network before coalescing into a coherent, relatively shallow graben swarm that curves in a semicircular fashion towards the south into the Claritas Rise. The graben are known as the Claritas Fossae beyond this point. The Noctis Labyrinthus fracture zone

124-469: A karstic nature, in which constituent carbonate rock is dissolved by meteoric water that has been acidified by acids originating in volcanic gases. This hypothesis has been challenged because carbonate spectral signatures have not been detected in the Noctis Labyrinthus network. The walls of the valleys of Noctis Labyrinthus have been widened significantly by slumps that have canvassed

186-653: A 1.5-bar CO 2 atmosphere and a global layer of water 120 m thick. Martian magmas also likely contain significant amounts of sulfur and chlorine . These elements combine with water to produce acids that can break down primary rocks and minerals. Exhalations from Tharsis and other volcanic centers on the planet are likely responsible for an early period of Martian time (the Theiikian ) when sulfuric acid weathering produced abundant hydrated sulfate minerals such as kieserite and gypsum . Two European Space Agency probes have discovered water frost on Tharsis. Previously, it

248-446: A perpendicular direction in the vicinity of Noctis Labyrinthus. Some authors have also proposed that Noctis Labyrinthus' chasmata may have formed due to extensional faulting in weakened rocks composed of interlayered tuff and lava flows, known to produce pit crater chains parallel to graben. Other authors have suggested that phreatomagmatic processes were associated with the formation of the Noctis Labyrinthus chasmata. This hypothesis

310-473: A sandcastle will only stand up when it is made with damp sand. The water offers cohesion to the sand which binds the sand particles together. However, pouring water over the sandcastle destroys it. This is because the presence of too much water fills the pores between the grains with water creating a slip plane between the particles and offering no cohesion causing them to slip and slide away. This holds for hillsides and creeps as well. The presence of water may help

372-406: A system of immense northwest-oriented valleys up to 200 kilometres (120 mi) wide. These northwestern slope valleys (NSVs) - which debouch into Amazonis Planitia - are separated by a parallel set of gigantic "keel-shaped" promontories. The NSVs may be relics from catastrophic floods of water, similar to the huge outflow channels that empty into Chryse Planitia, east of Tharsis. Central Tharsis

434-536: A volcano grows in size and weight, the stress field underneath the volcano changes from compressional to extensional. A subterranean rift may develop at the base of the volcano where the crust is wrenched apart. This volcanic spreading may initiate further structural deformation in the form of thrust faults along the volcano's distal flanks, pervasive grabens and normal faults across the edifice, and catastrophic flank failure (sector collapse). Mathematical analysis shows that volcanic spreading operates on volcanoes at

496-453: A wide range of pH and water availability conditions . The pit is the only one of its kind in Noctis Labyrinthus and has a greater variability than almost any other location yet observed on the planet. Using CRISM spectral data on HiRISE visual images for context, the researchers proposed that the variability of this pit is a result of hydrothermal alteration, with the dissolution of extant calcium-rich minerals (e.g. plagioclase ) diminishing

558-487: A wide range of scales and is theoretically similar to the larger-scale rifting that occurs at mid-ocean ridges ( divergent plate boundaries ). Thus, in this view, the distinction between tectonic plate , spreading volcano, and rift is nebulous, all being part of the same geodynamic system. According to Borgia and Murray, Mount Etna in Sicily is a good terrestrial analogue for the much larger Tharsis bulge, which to them

620-401: Is a type of creep characterized by the slow, downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress. Creep may appear to an observer to be continuous, but it really is the sum of numerous minute, discrete movements of slope material caused by the force of gravity . Friction, being

682-520: Is approximately 3,500 kilometres (2,200 mi) long and includes most of the region covered by the Tharsis quadrangle and the northwestern portion of the adjoining Phoenicis Lacus quadrangle to the south. Olympus Mons and its associated lava flows and aureole deposits form another distinct subprovince of the Tharsis region. This subregion is about 1,600 kilometres (990 mi) across. It lies off

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744-496: Is bounded to the west by a highly elevated zone of fractures ( Claritas Fossae ) and mountains (the Thaumasia Highlands ) that curves south then east to northeast in a wide arc that has been compared to the shape of a scorpion’s tail. The plateau province is bounded to the north by Noctis Labyrinthus and the western three-quarters of Valles Marineris . It is bounded to the east by a north-south oriented ridge called

806-483: Is centered at the heart of the Tharsis Rise, dividing a plateau of Hesperian-Noachian age that is understood to be of a basaltic composition. The valleys of Noctis Labyrinthus fractured into three distinct trends (NNE/SSW, ENE/WSW, WNW/ESE) in an interlinked pattern that has been compared to the terrestrial fault systems that have formed over terrestrial domes . The formation of the fracture zone have been dated to

868-439: Is commonly used in a broad sense to represent a continent -sized region of anomalously elevated terrain centered just south of the equator around longitude 265°E. Called the Tharsis bulge or Tharsis rise, this broad, elevated region dominates the western hemisphere of Mars and is the largest topographic feature on the planet, after the global dichotomy . Tharsis has no formally defined boundaries, so precise dimensions for

930-420: Is defined by the three massive Tharsis Montes volcanoes ( Arsia Mons , Pavonis Mons , and Ascraeus Mons ), a number of smaller volcanic edifices, and adjacent plains consisting of young (mid to late Amazonian) lava flows. The lava plains slope gently to the east where they overlap and embay the older (Hesperian-aged) terrain of Echus Chasma and western Tempe Terra . To the west, the lava plains slope toward

992-473: Is divided into two broad rises: a northern and a larger southern rise. The northern rise partially overlies sparsely cratered, lowland plains north of the dichotomy boundary. This region is dominated by Alba Mons and its extensive volcanic flows. Alba Mons is a vast, low-lying volcanic construct that is unique to Mars. Alba Mons is so large and topographically distinct that it can almost be treated as an entire volcanic province unto itself. The oldest part of

1054-507: Is not widely favored because chaos terrain morphology, proposed to form from this mechanism, is not found in the Noctis Labyrinthus fracture network. Chasmata and pit crater chains like those of Noctis Labyrinthus are likewise also not observed near areas where phreatomagmatic activity is strongly believed to have occurred, such as the Sisyphi Montes . Others have proposed that the chasmata of Noctis Labyrinthus are collapse features of

1116-507: Is observed in this region. An unnamed depression near the southernmost extent of the Noctis Labyrinthus system, near the divide of Syria Planum and Sinai Planum and at the western end of the Valles Marineris , was found to be one of the most mineralogically diverse sites yet observed on the planet. These deposits, dated to the late Hesperian, post-date most Martian deposits of hydrated minerals. Based on CRISM spectral imagery, authors studying this depression have interpretatively identified

1178-399: Is one immense volcano they call Tharsis Rise. Mount Etna is a complex spreading volcano that is characterized by three main structural features: a volcanic rift system that crosses the summit in a north-northeast direction; a peripheral compression belt (thrust front) surrounding the base of the volcano; and an east-northeast trending system of transtensional (oblique normal) faults that connect

1240-414: Is slope. For steep slopes, diffusional sediment flux is more appropriately modeled as a non-linear function of slope q s = k d S 1 − ( S / S c ) 2 {\displaystyle q_{s}={\frac {k_{d}S}{1-(S/S_{c})^{2}}}\,\!} where S c {\displaystyle S_{c}\,\!}

1302-648: The HiRISE camera, and the Mars Orbital Laser Altimeter that this heat source was a volcano near the northeast end of the labyrinthus that they dubbed Noctis Mons , which would be the seventh-highest mountain on Mars at 9,028 m (29,619 ft), and that the eastern part of its base was home to multiple glaciers with potential for hosting life, which could make it a highly valuable candidate target for astrobiology missions. Calcium-rich pyroxenes have been spectrally observed elsewhere in

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1364-532: The Smithsonian Institution ), Erwan Garel ( University of Maine in France), Yves Lagabrielle ( University of Western Brittany ), and Marie-Hélène Cormier ( Columbia University ) proposed a model for rifting on Mars initiated by the deflation of magma chambers, forming pit crater chains tracking directionally with simple graben. The researchers offered the first theoretical explanation as to how

1426-527: The Tharsis Montes . The tallest volcano on the planet, Olympus Mons , is often associated with the Tharsis region but is actually located off the western edge of the plateau. The name Tharsis is the Greco-Latin transliteration of the biblical Tarshish , the land at the western extremity of the known world. Tharsis can have many meanings depending on historical and scientific context. The name

1488-559: The Coprates rise. These boundaries enclose a broad high plateau and shallow interior basin that include Syria , Sinai, and Solis Plana (see list of plains on Mars ). The highest plateau elevations on the Tharsis bulge occur in northern Syria Planum , western Noctis Labyrinthus , and the plains east of Arsia Mons . Between the northern and southern portions of the Tharsis bulge lies a relatively narrow, northeast-trending region that may be considered Tharsis proper or central Tharsis. It

1550-483: The Late Hesperian based on crater counting age dates, concurrent with the formation of the lava plains of the adjacent Syria Planum province. Some researchers have modeled the formation of such chasmata on Mars on the propagation of simple graben underlain with dikes . As the underlying magma body drains, the chamber's pressure decreases and it begins to deflate. A chain of crater-like depressions forms, where

1612-411: The Tharsis region may be a single giant volcano. This is the thesis of geologists Andrea Borgia and John Murray in a Geological Society of America special paper published in 2010. The key to understanding how a vast igneous province like Tharsis can itself be a volcano is to re-think the notion of volcano from one of simple conical edifice to that of an environment or " holistic " system. According to

1674-571: The acidity and thus kinds of minerals observed. The variability was explained without evoking a global warm and wet Martian climatic condition for the period. Tharsis Tharsis ( / ˈ θ ɑːr s ɪ s / ) is a vast volcanic plateau centered near the equator in the western hemisphere of Mars . The region is home to the largest volcanoes in the Solar System , including the three enormous shield volcanoes Arsia Mons , Pavonis Mons , and Ascraeus Mons , which are collectively known as

1736-430: The bottom Noachian -age layer. Some researchers have counterproposed that rather than a sequentially reversed depositional event, this basin formed in a single, highly heterogeneous event. This is not necessarily indicative of a global alterational phenomenon, but is most likely tied to a localized heat source such as a volcano or an impact crater. In 2024, scientists Pascal Lee and Sourabh Shubham found evidence from CRISM,

1798-504: The center of the Tharsis Rise. Other authors have proposed an alternate origin for Noctis Labyrinthus, linking its formation to the Valles Marineris and likening its initial formation to the expansion and collapse of a dense lava tube network. Supporters of the lava tube hypothesis note that no evidence of lateral lava flows from the chasmata have been observed, suggesting against the notion that dikes must be required to underlie

1860-483: The center of the bulge that stretches halfway across the planet. Geologic evidence, such as the flow direction of ancient valley networks around Tharsis, indicates that the bulge was largely in place by the end of the Noachian Period, some 3.7 billion years ago. Although the bulge itself is ancient, volcanic eruptions in the region continued throughout Martian history and probably played a significant role in

1922-519: The chasmata of Noctis Labyrinthus formed. In 2012, a collaboration of French researchers Patrick Thollot, Nicolas Mangold, Véronique Ansan, and Stéphan Le Mouélic ( University of Nantes ), along with a cadre of American researchers including John F. Mustard ( Brown University ), Ralph E. Milliken ( University of Notre Dame ), and Scott Murchie ( Applied Physics Laboratory ) reported on an unnamed basin in southeastern Noctis Labyrinthus showing an extremely wide assemblage of minerals known to form across

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1984-501: The contraction results in consolidation at the new offset. Objects resting on top of the soil are carried by it as it descends the slope. This can be seen in churchyards, where older headstones are often situated at an angle and several meters away from where they were originally erected. Vegetation plays a role in slope stability and creep. When a hillside contains much flora their roots create an interlocking network that can strengthen unconsolidated material. They also aid in absorbing

2046-509: The conventional view in geology, volcanoes passively build up from lava and ash erupted above fissures or rifts in the crust. The rifts are produced through regional tectonic forces operating in the crust and underlying mantle. Traditionally, the volcano and its magmatic plumbing have been studied by volcanologists and igneous petrologists , while the tectonic features are the subject for structural geologists and geophysicists . However, recent work on large terrestrial volcanoes indicates that

2108-479: The course of many years. Furthermore, opaline silica deposits observed within this depression display spectra that may occasionally suggest interpersal with the iron sulfate mineral jarosite and the phyllosilicate mineral montmorillonite. The latter material is interpreted as such from an unusual doublet shape resolved on its spectra. The minerals in this basin were most likely formed as a result of an initially acidic hydrothermal alteration of basaltic terrain, with

2170-419: The crust horizontally as large tabular bodies, such as sills and laccoliths , that can cause a general doming and fracturing of the overlying crust. Thus, the bulk of Tharsis is probably made of these intrusive complexes in addition to lava flows at the surface. One key question about the nature of Tharsis has been whether the bulge is mainly the product of active crustal uplifting from buoyancy provided by

2232-416: The dissolution of plagioclase and calcium-rich pyroxenes increasing the pH steadily and causing the other minerals to precipitate. In this basin in particular, the mafic smectite layer overlays sulfates, aluminum phyllosilicate clays, and opaline silica deposits. The order of this layering is unique to the unnamed depression and is typically reversed in most Martian contexts, with the mafic smectites forming

2294-465: The distinction between volcanic and tectonic processes is quite blurry, with significant interplay between the two. Many volcanoes produce deformational structures as they grow. The flanks of volcanoes commonly exhibit shallow gravity slumps, faults and associated folds . Large volcanoes grow not only by adding erupted material to their flanks, but also by spreading laterally at their bases, particularly if they rest on weak or ductile materials. As

2356-510: The equator between 4.2 and 3.9 billion years ago. Such shifts, known as true polar wander , would have caused dramatic climate changes over vast areas of the planet. A more recent study reported in Nature agreed with the polar wander, but the authors thought the eruptions at Tharsis happened at a slightly different time. Spacecraft exploration over the last two decades has shown that volcanoes on other planets can take many unexpected forms. Over

2418-466: The excess water in the soil to help keep the slope stable. However, they do add to the weight of the slope giving gravity that much more of a driving force to act on in pushing the slope downward. In general, though, slopes without vegetation have a greater chance of movement. Design engineers sometimes need to guard against downhill creep during their planning to prevent building foundations from being undermined. Pilings are planted sufficiently deep into

2480-405: The extent of the collapse dictated by how deeply the magma body is located. Noctis Labyrinthus is estimated to have experienced collapses from the drainage of magma chambers up to 5 km below the chasmata floors. In Noctis Labyrinthus in particular, some researchers have speculated that the fracture zone's corridors may connect deeper intrusive structures, forming a plumbing network more akin to

2542-448: The hillside stay put and give it cohesion, but in a very wet environment or during or after a large amount of precipitation the pores between the grains can become saturated with water and cause the ground to slide along the slip plane it creates. Creep can also be caused by the expansion of materials such as clay when they are exposed to water. Clay expands when wet, then contracts after drying. The expansion portion pushes downhill, then

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2604-403: The magma produced in a large igneous province erupts at the surface as lava. Much of it stalls in the crust where it slowly cools and solidifies to produce large intrusive complexes ( plutons ). If the magma migrates through vertical fractures it produces swarms of dikes that may be expressed at the surface as long, linear cracks ( fossae ) and crater chains (catenae). Magma may also intrude

2666-413: The main topographic bulge, but is related to the volcanic processes that formed Tharsis. Olympus Mons is the youngest of the large Tharsis volcanoes. Tharsis is commonly called a volcano-tectonic province, meaning that it is the product of volcanism and associated tectonic processes that have caused extensive crustal deformation. According to the standard view, Tharsis overlies a hot spot , similar to

2728-547: The northern reaches of the Noctis Labyrinthus fracture zone. In 1980, Philippe Masson of the University of Paris-Sud offered an integrated interpretation of the structural geochronology of Valles Marineris , Noctis Labyrinthus, and Claritas Fossae in light of imagery from Mariner 9 and the Viking Orbiter . In 2003, Daniel Mège ( Pierre and Marie Curie University ), Anthony C. Cook ( University of Nottingham and

2790-630: The northern rise consists of a broad topographic ridge that corresponds to the highly fractured terrain of Ceraunius Fossae . The ridge is oriented north-south and forms part of the Noachian-aged basement on which Alba Mons sits. Also located in the northern rise are lava flows of the Ceraunius Fossae Formation, which are somewhat older than the Amazonian-aged flows that make up much of the central Tharsis region to

2852-518: The one thought to underlie the island of Hawaii . The hot spot is caused by one or more massive columns of hot, low-density material (a superplume ) rising through the mantle. The hot spot produces voluminous quantities of magma in the lower crust that is released to the surface as highly fluid, basaltic lava . Because Mars lacks plate tectonics , the lava is able to build up in one region for billions of years to produce enormous volcanic constructs. On Earth (and presumably Mars as well), not all of

2914-407: The presence of: Of the hydrated iron sulfate minerals observed in the basin, some of them - such as ferricopiapite - are not stable in modern Martian conditions. However, researchers have suggested that they appear to coexist because the different deposits may have been exposed to the open atmosphere at different times, and some of these minerals do only fully dehydrate under Martian conditions over

2976-474: The primary force to resist gravity, is produced when one body of material slides past another offering a mechanical resistance between the two which acts to hold objects (or slopes) in place. As slope on a hill increases, the gravitational force that is perpendicular to the slope decreases and results in less friction between the material that could cause the slope to slide. Water is a very important factor when discussing soil deformation and movement. For instance,

3038-483: The production of the planet's atmosphere and the weathering of rocks on the planet's surface. By one estimate, the Tharsis bulge contains around 300 million km of igneous material. Assuming the magma that formed Tharsis contained carbon dioxide (CO 2 ) and water vapor in percentages comparable to that observed in Hawaiian basaltic lava, then the total amount of gases released from Tharsis magmas could have produced

3100-442: The region are difficult to give. In general, the bulge is about 5,000 kilometres (3,100 mi) across and up to 7 kilometres (4.3 mi) high (excluding the volcanoes, which have much higher elevations). It roughly extends from Amazonis Planitia (215°E) in the west to Chryse Planitia (300°E) in the east. The bulge is slightly elongated in the north-south direction, running from the northern flanks of Alba Mons (about 55°N) to

3162-464: The same time period, geologists were discovering that volcanoes on Earth are more structurally complex and dynamic than previously thought. Recent work has attempted to refine the definition of a volcano to incorporate geologic features of widely different shapes, sizes, and compositions throughout the Solar System. One surprising and controversial conclusion from this synthesis of ideas is that

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3224-569: The south. The larger southern portion of Tharsis (pictured right) lies on old cratered highland terrain. Its western boundary is roughly defined by the high lava plains of Daedalia Planum , which slope gently to the southwest into the Memnonia and Terra Sirenum regions. To the east, the southern Tharsis bulge consists of the Thaumasia Plateau , an extensive stretch of volcanic plains about 3,000 km wide. The Thaumasia Plateau

3286-556: The southern base of the Thaumasia highlands (about 43°S). Depending on how the region is defined, Tharsis covers 10–30 million square kilometres (4–10 million square miles), or up to 25% of Mars’ surface area. The greater Tharsis region consists of several geologically distinct subprovinces with different ages and volcano-tectonic histories. The subdivisions given here are informal and may rise all or parts of other formally named physiographic features and regions. Tharsis

3348-421: The spreading has produced a rift through the summit of the rise and a system of radial tear faults that connect the rift to a basal compression belt. The tear-fault system on Tharsis is represented by the radial fossae , of which Valles Marineris is the largest example. The thrust front is visible as the Thaumasia Highlands. Unlike on Earth, where the rifting of plates produces a corresponding subduction zone ,

3410-436: The summit rift to the peripheral thrust front. The volcano's peak contains an array of steep summit cones, which are frequently active. The entire edifice is also peppered with a large number of small parasitic cones. The structural similarities of Mount Etna to Tharsis Rise are striking, even though the latter is some 200 times larger. In Borgia and Murray's view, Tharsis resembles a very large spreading volcano. As with Etna,

3472-447: The surface material to guard against this action taking place. For shallow to moderate slopes, diffusional sediment flux is modeled linearly as (Culling, 1960; McKean et al., 1993) q s = k d S {\displaystyle q_{s}=k_{d}S\,\!} where k d {\displaystyle k_{d}\,\!} is the diffusion constant, and S {\displaystyle S\,\!}

3534-409: The surface of the modern-day collapse features as there is no evidence that such a near-surface intrusion has breached the surface in the Noctis Labyrinthus region. Critics of a purely tectonic hypothesis have also noted that although pit crater chains (central to the diking hypothesis) are generally aligned and coincident with graben, they are occasionally found to bifurcate and to cross coeval graben in

3596-505: The terrestrial Thulean mantle plume , which was responsible for the formation of the North Atlantic Igneous Province . In the chasmata of Noctis Labyrinthus, these pit crater chain collapse zones propagate directionally with a V-shaped tip, and can be used as an indicator of the direction into which magma withdraws from its underlying chamber. These V-tipped morphologies are generally found to propagate away from

3658-503: The thick lithosphere of Mars is unable to descend into the mantle. Instead, the compressed zone is scrunched up and sheared laterally into mountain ranges, in a process called obduction . To complete the analogy, the huge Olympus Mons and the Tharsis Montes are merely summit cones or parasitic cones on a much larger volcanic edifice. Downhill creep Downhill creep , also known as soil creep or commonly just creep ,

3720-434: The underlying mantle plume or whether it is merely a large, static mass of igneous material supported by the underlying lithosphere . Theoretical analysis of gravity data and the pattern of faults surrounding Tharsis suggest the latter is more likely. The enormous sagging weight of Tharsis has generated tremendous stresses in the crust, producing a broad trough around the region and an array of radial fractures emanating from

3782-498: The valley floors with debris taking the form of mudflows and boulders. Some authors have attributed the steady collapse of the valley walls to creep tied to thermal cycling , which could cause the repeated freezing and thawing of ground ice. Because of its location at the center of the Tharsis uplift, the melting associated with this creep could have been facilitated by increased heat flow to this area during periods of increased magmatic activity. No evidence of fluvial or aeolian erosion

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3844-473: Was thought that water frost on Mars was impossible. The total mass of the Tharsis bulge is approximately 10 kg, about the same as the dwarf planet Ceres . Tharsis is so large and massive that it has likely affected the planet's moment of inertia , possibly causing a change in the orientation of the planet's crust with respect to its rotational axis over time. According to one recent study, Tharsis originally formed at about 50°N latitude and migrated toward

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