Structure of the Earth from Glacio-Isostatic Rebound

Walcott, R. I.

doi:10.1146/annurev.ea.01.050173.000311

Cited by 119 publications

(73 citation statements)

References 38 publications

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“…We chose as 6,000 years B.P., because eustatic sea level has been stable since 6,000 years B.P. according to WALCOTT (1972bWALCOTT ( , 1973WALCOTT ( , 1980 and PATERSON (1972).…”

Section: Resultsmentioning

confidence: 99%

“…Although CATHLES (1975) regarded this similarity as being accidental, it would be more natural to understand that these free-air gravity anomalies mainly correspond to the present remaining uplift that has not yet relaxed. As was indicated by WALCOTT (1972bWALCOTT ( , 1973, it is not certain that the observed negative free-air gravity anomalies in the glaciated area correspond perfectly to the remaining uplift. However, considering the good correlation between the shape of the glaciated area and the zone of the observed negative free-air gravity, and Kaula's indication that negative free-air anomalies do appear to be commonly associated with areas of rebound (KAULA, 1972), WALCOTT (1972bWALCOTT ( , 1973 suggested that most of the observed negative free-air gravity anomalies in Laurentide correspond to the pres- Figure 4 and Fig.…”

Section: Free-air Gravity Anomaliesmentioning

confidence: 91%

“…The data have been analyzed under the assumptions of Newtonian rheology and laterally homogeneous structure. Based on his analysis, WALCOTT (1972aWALCOTT ( , 1973WALCOTT ( , 1980 suggested that most deformation associated with the postglacial relaxation occurs in the upper mantle. This idea is mathematically represented by a model with channel low viscosity layer.…”

Section: Introductionmentioning

confidence: 99%

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Rheological structure of the earth's mantle derived from glacial rebound in Laurentide.

Nakada

1983

J,Phys,Earth

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The theological structure of the earth's mantle was determined based on data from the postglacial isostatic adjustment in Laurentide. According to a linear analysis with a Newtonian rheology, the apparent viscosity derived from the observed relative sea level data is about ten times larger in the central part of the glaciated region than that in the surrounding region. Namely, the and estimated remaining uplift, does not reflect the non-linearity of the means that the lower mantle viscosity is greater than 1024 poise, regardless of Newtonian or non-Newtonian rheology. According to the analysis for a thin channel viscosity model with a powerdeviatoric stress, the observed relative sea level variations and free-air gravity anomalies in the glaciated region in Laurentide can be explained almost satisOur calculation therefore indicates that the viscosity of the lower mantle is so high that a thin channel viscosity model is a good approximation of the mantle flow, and that the upper mantle rheology is governed by the power-law creep and apparent viscosity estimated in the present work are 1,500K to 1,700K, 2.8/HH2sec-1, 0.22H bar, and 0.04H3 poise, respectively, where H represents the thickness of the low viscosity channel in cm. The relationship between strain rate and deviatoric stress is consistent with an extrapolation of high strain rate laboratory data.

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“…We chose as 6,000 years B.P., because eustatic sea level has been stable since 6,000 years B.P. according to WALCOTT (1972bWALCOTT ( , 1973WALCOTT ( , 1980 and PATERSON (1972).…”

Section: Resultsmentioning

confidence: 99%

Section: Free-air Gravity Anomaliesmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Rheological structure of the earth's mantle derived from glacial rebound in Laurentide.

Nakada

1983

J,Phys,Earth

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“…In addition to the climatic time variables of air temperature, accumulation, melt, equilibrium line elevation, and sea level, there are geological variables. For example, the mantle takes about 10,000 years to adjust to a given loading (WALCOTT, 1973). Thus, the bed elevations are time variables out of phase with the ice thickness (e.g.…”

Section: Other Work and Future Workmentioning

confidence: 99%

Objective Reconstructions of the Late Wisconsinan Laurentide Ice Sheet and the Significance of Deformable Beds

Fisher¹,

Reeh²,

Langley³

2007

gpq

156

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A three dimensional steady state plastic ice model; the present surface topography (on a 50 km grid); a recent concensus of the Late Wisconsinan maximum margin (PREST, 1984); and a simple map of ice yield stress are used to model the Laurentide Ice Sheet. A multi-domed, asymmetric reconstruction is computed without prior assumptions about flow lines. The effects of possible deforming beds are modelled by using the very low yield stress values suggested by MATHEWS (1974). Because of low yield stress (deforming beds) the model generates thin ice on the Prairies, Great Lakes area and, in one case, over Hudson Bay. Introduction of low yield stress (deformabie) regions also produces low surface slopes and abrupt ice flow direction changes. In certain circumstances large ice streams are generated along the boundaries between normal yield stress (non-deformable beds) and low yield stress ice (deformabie beds). Computer models are discussed in reference to the geologically-based reconstructions of SHILTS (1980) and DYKE ef al. (1982).À partir d'un modèle théorique tridimensionnel de plasticité de la glace, de la topographie actuelle (sur un canevas de 50 km2), du nouveau consensus quant à la limite maximale de la marge glaciaire (PREST, 1984) et d'une carte des seuils de plasticité de la glace, les auteurs ont élaboré des modèles de la calotte glaciaire laurentidienne. On a donc reconstitué par ordinateur une calotte asymétrique à dômes multiples, sans idée préconçue quant aux directions de l'écoulement des glaces. On a évalué les conséquences de la présence éventuelle de lits non résistants en se fondant sur les très bas seuils de plasticité de la glace proposés par MATHEWS (1974). En raison des bas seuils de plasticité (lits non résistants), les modèles démontrent qu'une glace peu épaisse couvrait les Prairies et la région des Grands Lacs, ainsi que la baie d'Hudson, dans un des deux cas. La prise en considération de régions à bas seuils de plasticité (lits non résistants) montre également la présence de pentes faibles et des changements brusques de direction de l'écoulement glaciaire. Dans certains cas, de grands courants glaciaires se manifestent le long des limites entre les endroits où les seuils de plasticité sont normaux (lits rigides) et les endroits où les seuils de plasticité sont bas (lits non résistants). Les modèles obtenus par ordinateur sont ensuite comparés aux reconstitutions de SHILTS (1980) et de DYKE et al. (1982), élaborées à partir des données géologiques.Ein dreidimensionales konstantes Modell der Eis-Plastizitat, die gegenwàrtige Oberflâchentopographie (auf einem Gitternetz von 50 km), ein neuer Konsensus ùber den maximalen glazialen Rand des spâten Wisconsin (PREST, 1984) und eine einfache Karte der Eis-Plastizitàts-Schwelle werden benutzt, um ein Modell der Laurentischen Eisdecke herzustellen. Eine vielfach gewôlbte, asymmetrische Rekonstruktion ist hergestellt worden, ohne vorgefapte Meinung ùber die Richtung des FlieBens. Die Wirkungen von môglicherweise vorhandenen nachgiebigen Betten werden...

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“…The principal uplift of North America (the Laurentide uplift) and the Fennoscandian uplift have many points of similarity : in both regions the shield merges in one direction with a continental platform and in the other with heavily glacierized mountains; both have a broadly elliptical shape with an ellipticity of about 0.8 (Walcott, 1973). But as described earlier, the difference of North American and Fennoscandian uplift areas is in horizontal velocity -in North America there is no radial pattern visible in uplift area as it is in Fennoscandia.…”

Section: Case Studymentioning

confidence: 99%

Lithospheric thickness recovery from horizontal and vertical land uplift rates

Kollo

Vermeer²

2010

Journal of Geodynamics

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As a result of the BIFROST studies of the Fennoscandian postglacial rebound, it is known that in addition to uplift, there also exists a horizontal movement of the Earth's surface, so that points on it move away from the uplift centre at a rate of about 10% of that of the uplift.We aim to study the vertical and horizontal postglacial motion in order to determine the lithospheric thickness from observed rates.We conjecture that the cause of the radial movement is that, while a thin lithosphere will move up radially from the Earth's centre, in the case of a thick lithosphere, the mantle blocks may slightly rotate due to the land uplift gradient. This phenomenon is investigated and modelled for further analysis.In the computations, the BIFROST dataset for Fennoscandia is used to test our hypothesis. Unfortunately for the North-American land uplift area our method did not produce reasonable results; we suspect one reason is the fragmented nature of the lithosphere in this area.

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Structure of the Earth from Glacio-Isostatic Rebound

Cited by 119 publications

References 38 publications

Rheological structure of the earth's mantle derived from glacial rebound in Laurentide.

Rheological structure of the earth's mantle derived from glacial rebound in Laurentide.

Objective Reconstructions of the Late Wisconsinan Laurentide Ice Sheet and the Significance of Deformable Beds

Lithospheric thickness recovery from horizontal and vertical land uplift rates

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