Jökull - 01.12.1985, Page 57

TABLE 2: Chemical composition (in mg/1) of major
elements in thermal water from four hot springs of the
Vellir thermal field.
TAFLA 2: Efnagreiningar (í mgll) á vatni úr fjórum
hverum á Vellishverasvœðinu.
Sturlu- Reykir Badlauga- hver Vellir Snaeldubeins- stadahver
°c 96.5 86 100 100
pH/°C 9.42/19 9.34/19 9.48/17 9.36/18
sío2 165.0 160.0 166.5 167.0
Na 80.2 79.7 81.0 78.7
K 2.8 2.6 2.8 2.8
Ca 2.6 2.4 2.9 2.6
Mg 0.00 0.00 0.09 0.01
co2 24.0 35.1 29.9 33.1
so4 58.7 58.0 57.2 56.8
h2s 1.87 1.73 1.84 2.13
CI 34.3 32.4 33.4 33.0
F 3.03 3.24 3.22 3.24
Diss. solids 377.0 386.0 388.0 367.0
£>d(%o)-1) -74.2 -72.8
Tchd(°C) 126 126 130 133
1) Árnason (1976).
heating of the Sturlu-Reykir farm. At present the hot
spring displays activity with a period of of one minute.
Half a minute of vigorous boiling and discharge is
followed by a half minute lapse. There is no record of
geyser action in the lower hot spring Lúsahver.
The Hagahús Line
It comprises a group of insignificant warm springs (no.
13) in a bog southeast of the Vellir geyser. The line is
about 300 m long and has a trend close to N30—35°W.
The measured temperature ranges from 12 to 53°C but
the discharge is negligible.
THE GEOLOGY OF THE OUTER
REYKHOLTSDALUR VALLEY
The geology of the areas adjacent to the Vellir ther-
mal field has been studied in detail by Gudbergsson et
al. (1971) and Pálsson etal. (1971). The geological map
has recently been revised and extended.
The lava flows in the Vellir area have a strike close to
N45°E and dip 8°SE. The lava pile consists of basaltic
lavas intercalated by thin red beds, believed to be
palaeosoil. The base of the valley is covered by a few
tens of metres of unconsolidated Finiglacial marine
sediments, which prevent observation of the relation-
ship between hot springs and basements features, like
faults and dykes.
The main tectonic features of the Vellir thermal field
and the adjacent areas are shown in Fig. 4. The area is
characterized by two types of faults and joints. Firstly,
NW-SE to N-S trending faults and fractures which
Fig. 3. An eruption of the Vellir
geyser, view towards west. Photo by
L.S.G. 1980.
3. mynd. Gos í Velli eftir að sápa hafði
verið sett í hann, horft til vesturs.
JÖKULL 35. ÁR 55