Surface deformation and crustal structure in the Myrdalsjökull area of south Iceland

Ground tilt measurements made once each year near the Myrdalsjokull ice field show an annual variation of tilt of 1.4–4.5 μrad. The direction of observed tilt is either toward or away from the central part of the ice field. The observed tilt correlates closely with the amount of snow on the ice field and is interpreted as the response of variable load on an elastic plate floating on liquid substratum. The thickness of this elastic crustal plate is found to be 6.5–8.5 km, and the relaxation time for the underlying liquid appears to be less than 2 weeks, and thus its viscosity is required to be less than 1013 poises, or less than that found for the earth's mantle from uplift of recently glaciated areas by about 8 orders of magnitude.