Rit (Vísindafélag Íslendinga) - 01.06.1936, Blaðsíða 34

34
600 m. in diameter. The walls of this crater which con-
sisted of pyroclastic substances, were in most places per-
pendicular and 30 m. high at their highest point. In addi-
tion to this main crater the expedition found two other
blast craters a great deal smaller. The craters were situ-
áted on a line which followed the direction of the south
ánd west walls of the fault-valley. The distance between
the craters was about 0,5 km. (cf. the map). There was
water in all the craters on which many icebergs were
flöating, and between them floated pumice and ash, which
together formed a thick coagulated mass. The walls of
the two smaller craters sloped at an angle of about 30°
down to the water. In May 1935 while the former expedi-
tion in this year was present at the scene of eruption the
largest crater still issued at intervals gas-exhalations and
smoke.
As a result of researches into Icelandic authorities
Sapper came to the conclusion that Grímsvötn lay about
(”etwa”) lat. 64° 12' N. and long. 17° 25' W. (29). Thor-
oddsen gives no more exact indication of the position of
Grímsvötn than that they are in Vatnajökull to the east
of Hágöngur (30). From the directions indicated by the
volcanic cloud as seen from many places in the country in
1934 Th. Thorkelsson calculated the position of the scene of
the eruption to be lat. 64° 26' N. and long. 17° 31' W. (27).
Our measurements show that the chief crater lies at lat.
64° 23'. 6 N. and long. 17° 21'. 3 W. (cf. the map). It is
therefore somewhat farther west than Wadell places
”Svíagígur” (4) but there is no doubt that this is the same
volcanie outlet.
If the connection of Grímsvötn with volcanic areas near
the edge of Vatnajökull is considered, it will be seen that
Grímsvötn lies on a line connecting Laki and Kverkfjöll.
The nunataks, Geirvörtur, Þórðarhyrna and also Háa-
bunga all lie on the same line and although as yet it is
not possible to give a complete account of the formation
óf these mountains, yet it is possible to assert that vol-
canic forces have taken part in it. On the part of Vatna-