Reconstructing the maximum extent of Lake Balaton (Transdanubia, Hungary) with respect to vertical crustal movements

Abstract

The quality and resolution of digital elevations models (DEMs) are rapidly improving and the analyses they provide are
sutiable tools for reconstructions. This study considers a reconstruction of the former inundation levels which characterize the
maximum extent of lakes using DEMs and it focuses on Lake Balaton. However, the static filling algorithms which model the
inundation in a DEM by a pre-set level often do not produce reliable results. To achieve more reliable models it is suggested
that it is necessary to take into account the results of repeated and precise levellings as well. According to these results, the
northern shore and foreland of Lake Balaton is being uplifted, in contrast to the southern one. The rate of this relative
movement is a few tenths of a millimetre per year. Assuming the rate of uplift has been constant over the past few millennia, in
the Early and Middle Holocene the level of the northern embayments (especially the one far to the north at Tapolca) were lower
by 2-3 metres compared to the southern ones (especially the one far to the south at Nagyberek). Using this method (DEMs with
repeated levellings) more reliable results can be obtained; this approach results in an outline of the lake which fits well to the
lacustrine sediments mapped by LÓCZY. Furthermore, there is still no overflow on the southern edge of the watershed. The
small differences between this outline and the extent of mapped lacustrine sediments, however, may reflect the small temporal
variations of the vertical movements over the recent millennia.