Gravity Profiles across Ice-Cored Topography

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Rampton, V. N., Walcott, R. I.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1974
• Subjects: General Earth and Planetary Sciences; Thermokarst
• Online Access: http://dx.doi.org/10.1139/e74-010; http://www.nrcresearchpress.com/doi/pdf/10.1139/e74-010

Gravity profiling at five different sites in an area of ice-cored topography indicates the usefulness of the technique as a method for the detection of ground ice and for estimating the thickness of the excess ice. Bouguer anomaly profiles using a density of 2.0 Mgm −3 provide a quick method of assessing the relative amount of ice along a profile, the thickness of ice and the elevation being inversely proportional to the Bouguer anomaly value along each profile. The average amount of excess ice in the topography along the profiles is obtained by removing linear trends, obtaining the Bouguer density of the topography, and calculating the proportion of frozen saturated sediment and ice required to produce this density. Variations in the thickness of the body are obtained from significant gravity residuals. Finally, models are given to show the distribution of the excess ice with the aid of supplementary information. The above technique is unable to detect changes in the amount of excess ice that have a linear trend over the complete profile or a uniform slab of ice underlying the complete profile. A model for a pingo is constructed using stacked concentric cylinders. Geologic data from the region indicate that all models give reliable estimates of the amount of excess ice and probable thermokarst subsidence if the area were thawed.