Jökull - 01.12.1977, Page 10

At961- - A1961
G1934- —G1934
G1922- Á1919 r —G1922 - K1918
K 1918
- V1910 -þ 1903 — V 1897 *
G1892— -V 1892 *
V1887“ —V1887
G1883 — — Gl883
Al875 — —G'873
-G,V 1867 - Tr 1862—64
G 1861
G1854- •• 1851*
- H 1845
G1838 — - G'838
Vl823 — - V 1823
.. 1816*
1796 * “ V1794
G1784 - - G1784
L 1783
G1774 ~ 21769 _ — G 1774
2 1768 * V1766 - V1766
K1755 - _ K 1755
V1753 - - V 1753
? 1739- _ Kv 1729
21720- - Ö 1727 V 1726
Kyi7i7 =a - G 1716
P1716- Kv17H - V 1711-12
2 1707 =a _ G 1706
V1706 - V 1702
2 1697— - G,Kv 1684-5 ~ V 1681
K1661 K 1660-61
G1659 m * G 1659
suggested by Thorarinsson (1950) on the basis
of floods in Jökulsá in the 17th and 18th cen-
turies, i.e. in the years 1655, 1684, 1711—12,
1716, 1717, 1729. At least four of these floods
(1684, 1716, 1717, 1729) were considered volcano-
genic by Thorarinsson (op. cit.) in that they
coincided witli recorded eruptions in Vatna-
jökull. Furthermore, the floods of 1711 and 1729
occurred in the summer or autumn, excluding
the possibility of theirs being caused by ice
barricades in the river itself. Thorarinsson
therefore considered them of volcanic origin as
well.
However, he points out that eruptions in
Kverkfjöll themselves, or in the immediate
vicinity, would not be likely to cause large
jökulhlaups, and suggested, therefore, that the
source of the hlaups, and the centre of the
volcanic activity in the period 1655 to 1729 was
SW of Kverkfjöll, on a line defined by Þórdar-
liyrna, Háabunga, Grímsvötn. Thorarinsson
(1950) concludes his article by pointing out the
coincidence in time between the Jökulsá floods
and the Mývatn Fires in the early 18th century,
suggesting a connection between the two vol-
canic districts.
In 1973 Williams ir Thorarinsson published
in Jökull an ERTS-1 image of Vatnajökull (re-
produced here as Fig. 1), showing a set of
cakleras in and immediately south of Kverkfjöll,
that together are comparable in area to Gríms-
vötn and Askja. It seems reasonable, therefore,
to assign the hlaups in question to the Kverk-
fjöll system.
Finally, therc is sorne eviclence of recent vol-
canic activity in Ivverkfjöll: Jónsson (1945, II,
Fig. 4. Correspondence between likely or pos-
sible tephras to be found in the Bárdarbunga
ice core (right liand column), ancl the tephras
actually found there according to tlie present
interpretation (left side). Asterisk: Only a jökul-
hlaup reported.
Mynd 4. Samrami gjóskulaga sem hefðu getað
fundist i Bárðarbungukjarnanum skv. eldgosa-
sögu svœðisins (hœgri hlið), og þeirra laga sem
fundust i kjarnanum. Stjarna (*) eftir ártali
merkir, að heimildir geti aðeins um hlaup, en
ekki gos.
8 JÖKULL 27. ÁR