Aureole deposits of the Martian volcano Olympus Mons

Morris, E. C.

doi:10.1029/jb087ib02p01164

Cited by 124 publications

(69 citation statements)

References 34 publications

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“…While we agree with Morris [ 1982] on some of his observations and interpretations of the Olympus Mons aureole deposits, we note that he has rather seriously distorted our hypothesis of a subglacial origin for the volcano's basal pedestal and surrounding scarp [Hodges and Moore, 1979]. Morris dismisses our postulate by stating that it requires an ice sheet more than 10 km thick--which, indeed, it does not.…”

mentioning

confidence: 43%

Comment on ‘Aureole deposits of the Martian volcano Olympus Mons’ by Elliot C. Morris

Hodges¹,

Moore²

1982

J. Geophys. Res.

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While we agree with Morris [ 1982] on some of his observations and interpretations of the Olympus Mons aureole deposits, we note that he has rather seriously distorted our hypothesis of a subglacial origin for the volcano's basal pedestal and surrounding scarp [Hodges and Moore, 1979]. Morris dismisses our postulate by stating that it requires an ice sheet more than 10 km thick--which, indeed, it does not.It is true that according to our analogy with table mountains in Iceland, the initial height of the Olympus Mons scarp up to the base of the subaerial lava flows would indicate the maximum thickness of ice under which eruptions occurred. However, because of the scarp's susceptibility to failure by mass movement, as we explicitly acknowledged, the height of the scarp would increase with time as erosion progressed upslope on the flanks of the shield. Therefore, the thickness of our postulated ice cap is most nearly approximated by the minimum height of the present scarp (about 3 km on the south flank), not its maximum, as implied by Morris. Indeed, the highest sections of the scarp [U.S. Geological Survey, 1981] are on the northwest (9 to 11 km), where debris deposited by processes of mass movement is most apparent. Moreover, extensive deformation apparently occurred on the northwest flank, where the slope of the shield decreases from >3.5 ø in its uppermost two thirds to about 1.5 ø, forming a broad bench bounded by two radial faults adjacent to this highest section of the basal scarp; along narrow ridges at the top edge of the northwest scarp, slopes are reversed inward toward the volcano's center. The entire perimeter escarpment has been modified substantially, both by mass wasting and by lava cascades from the shield, so that its initial height is problematical. However, it is the present minimum height that constrains the maximum thickness of ice required by our hypothesis.We agree with Morris' interpretation that the textural patterns of the aureoles suggest eruptions from several distinct centers within the lobes rather than derivation by landsliding from the scarp. We also agree that the large positive gravity anomaly coincident with the aureole deposits further supports that interpretation and thus is compatible with both our hypothesis and that of Morris. We are skeptical, however, that 'very fluid ash flows' would develop, by either primary or secondary processes, the distinctive textures exhibited by the aureoles. Lack of any adequate terrestrial counterpart makes interpretation speculative at best, but we believe that the erosional patterns developed on the primary textures of moberg deposits in Iceland more closely approximate the rugged textures of the aureoles than do any thus far observed on terrestrial ignimbrites. Scott and Tanaka [1982, p. 1184, Figure 4] pointed out that pressure ridges (as described by Morris on the aureoles) are 'common on lava flows but absent on ash flows. ' We wish to emphasize that regardless of other deficiencies in our subglacial-eruption hypothesis for the origin...

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confidence: 43%

Comment on ‘Aureole deposits of the Martian volcano Olympus Mons’ by Elliot C. Morris

Hodges¹,

Moore²

1982

J. Geophys. Res.

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“…Aunque parte de la aureola está formada por un terreno rugoso parecido al de la aureola de Arsia, no aparece en ella terreno estriado. Asimismo, el análi-sis de las imágenes de esta aureola no ha mostrado hasla el momento ningún signo de estratificación (Morris, 1982). Aunque en la vertiente NO del escarpe que rodea al volcán aparece un terreno muy similar al lobulado de Arsia.…”

Section: Discussionunclassified

“…La aureola de Olympus Mons es la más grande -700 km en dirección NO-y compleja de todas al estar formada por varios lóbulos superpuestos (Morris, 1982). De las aureolas de los tres volcanes de Tharsis la de Arsia Mons es la mayor y mejor estudiada.…”

Section: Introductionunclassified

Untitled

González¹,

Virella²

1994

Estud. geol.

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Al pie de los grandes volcanes marcianos del domo de Tharsis aparecen unas formas lobuladas que han recibido el nombre de aureolas. El origen de estas estructuras ha sido objeto de un largo debate entre dos hipótesis principales que las interpretan como deslizamientos de ladera o como glaciares de montaña. En este trabajo se estudia la mejor desarrollada de estas aureolas, la de Arsia Mons, llegándose a la conclusión de que la hipótesis glaciar explica mejor las características del depósito, y en concreto la existencia de estratificación, las crestas (que se interpretan como glaciotectónicas) y los terrenos lobulados. Por último se discute la conexión de estos depósitos con los modelos paleoclimáticos actuales sobre Marte, lo que lleva a la conclusión de que las aureolas deben ser depósitos glaciares recientes relacionados con repetidos episodios de clima cálido (ciclos de Baker), provocados por la acción de los canales de desbordamiento. Palabras clave: Marte, Arsia Mons, aureolas, glaciares, océanos. ABSTRACTHuge lobate deposits called aureoles are covering the base of the giant Martian volcanic constructs of Tharsis dome. The origin of these structures has been a matter of debate between two competing hypotheses: volcanic landslides or mountain glaciers. Here we consider the most important of the aureoles, near Arsia Mons, concluding that the glacier model explains best the deposit features, such as the layering, the ridges (interpreted as glaciotectonic ones), and the lobated terrain. We then discuss the fit of these proposed glacier deposits in the present paleoclimatic Martian models. The aureoles could be key elements in the confirmation of the «Baker cycle» model of repeated episodes of temperate, humid, sea-dominated climates coincident in time with the outflow channels activity.

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“…All the images show the distinct presence of slope streaks at various locations, confirming one of the most widespread features occurring on Mars 11 . Streaks on steep Martian slopes are modern enigmatic features first observed in Viking Orbiter images [11][12][13][14][15][16] , but no plausible explanations on their origin as well as morphology could be given due to the resolution limitations of earlier data. They exhibit a fan-shaped pattern, are thought to originate from a point source and are strongly believed to be erosional features.…”

Section: Slope Streaks Their Occurrence and Morphologymentioning

confidence: 99%

“…These are discussed below. In the first model, according to Morris 15 , when the erosion-driven disaggregated, dark debris outcrops get mixed with the residual debris, a sharp contrast in streaks is observed. Another model suggests that the streak contrast results from staining and darkening of slope materials by aqueous discharge 29 .…”

Section: Morphological Evidences Favouring the Dust Avalanche Originmentioning

confidence: 99%

Morphology of Slope Streaks within Nicholson Crater, Mars:Records of Recent Wind Activity

Desai

Murty

2018

Current Science

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Wind is currently the dominant active geological agent bringing about constant changes over the Martian surface. One of the most conspicuous resultant morphology derived is the formation of slope streaks, highly transient features that tend to develop and may completely disappear within a few ten of years. In this article a detailed analysis on the pattern, morphology and appearance of slope streaks within the central mound of the Nicholson crater on Mars, has been made and plausible reasons for their formation as well as darkening and fading mechanisms are discussed. We focus on some observations which indicate the role of wind in carving specific streak patterns. The morphological observations discussed, strongly support active aeolian processes and provide evidences in favour of the dust avalanche theory for the formation and current morphology of slope streaks in the Nicholson crater.

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Aureole deposits of the Martian volcano Olympus Mons

Cited by 124 publications

References 34 publications

Comment on ‘Aureole deposits of the Martian volcano Olympus Mons’ by Elliot C. Morris

Comment on ‘Aureole deposits of the Martian volcano Olympus Mons’ by Elliot C. Morris

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Morphology of Slope Streaks within Nicholson Crater, Mars:Records of Recent Wind Activity

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