Jökull - 01.06.2000, Page 54

Aeromagnetic measurements over Mýrdalsjökull
-580000 -570000 -560000 -550000 -540000 -530000
330000
340000
350000
360000
370000
Figure 4. Shaded relief presentation of the contour map of Figure 3. Illumination is from the southeast. Dotted
line: topographic caldera cf. Figure 1. – Hliðarlýst lágmynd af sömu gögnum og á 3. mynd. Ímyndað sólskin er
úr suðaustri og dregur sérstaklega fram drætti sem stefna þvert á það. Punktalínan sýnir legu öskjurimans.
be 7 x 10 km in size, i.e. smaller than the topographic
caldera but concentric to it. The center is at 63  38’N,
19  09’W. Within this thermal caldera anomaly we
choose the upper surface of the magnetic columns at
some depth below the actual topography and calculate
the magnetic effect as before. In the calculated profi-
les, the regional field has been adjusted to agree with
the observed data far away from the caldera.
As seen in Figure 6 we cannot distinguish between
a shallow unmagnetized bowl in strongly magnetized
material or a deeper bowl in less magnetized matter.
The model, however, limits the width of the bowl,
with an uncertainty on the order of 1 km.
JÖKULL No. 49 53