Rit (Vísindafélag Íslendinga) - 01.06.1976, Blaðsíða 174

inner and higher parts of the country to the lowland and that the
flow was mainly directed by hydrostatic pressure in the ground.
According to Einarsson, therefore, the flow direction is essentially
independent of the tectonics and the deep groundwater can flow
transverse to the tectonic lines as well as along them.
As discussed previously, the ðD-value of the thermal water to-
gether with the deuterium map can be used to trace the approxi-
mate recharge area of the corresponding groundwater system and
its general flow pattern underground. The present work, therefore,
offers an excellent opportunity of studying the general flow pat-
tern of thermal groundwater systems and thus the importance of
the tectonics and the hydrostatic pressure in affecting the direction
of the groundwater flow.
In some cases, the main flow direction of the deep thermal water
is found to follow the main tectonic lines. This is for example the
case for the following thermal areas: a) in the areas Laugames,
Seltjarnarnes and Hengill in Southwest Iceland, where the thermal
water flows mainly towards the south-west, parallel to the main
tectonic lines in this part of the country; b) the thermal water in
Eyjafjörður and S-Þingeyjarsýsla which seems to flow towards the
north and thus follow the main tectonic lines in North Iceland.
In many cases, however, the main flow direction of the deep
thermal water seems to be transverse to the main tectonic lines.
This is for instance the case for the following thermal areas: a) at
Hveravellir, where the flow direction of the water is from either
the east or the south-west; b) the thermal water in Reykholtsdalur
in the Borgarfjörður area which obviously flows towards the west;
c) the water in the hot spring Sælingsdalur in West Iceland which
seems to originate in the nearest mountainous area and thus flows
towards the east.
The above examples show that although in some cases the main
flow direction of the thermal water is obviously the same as the
direction of the main tectonic lines, there are also several cases
where the thermal water flows across them. In all cases, however,
the flow direction is the same as would be expected if the water
flow were only directed by the hydrostatic pressure.
Consequently, it is reasonable to believe that, as the thermal
water flows at a great depth, its flow pattern is mainly directed
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