The Botany of Iceland - 01.12.1930, Page 21

STUDIES ON THE VEGETATION OF ICELAND
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the difference between the coldest and the warmest montlis is thus
great, 17.2° C. The precipitation is sliglit and storms are frequent.
To this must further be added a probably very thick and at any
rate constant covering of snow in winter.
Of interest in connection with plant geography is further the
situation of the jökulls and the snow-line. We have previously seen
that most of the jökulls gather along a line connecting the two places
where the waters of the Gulf Stream and the polar waler meet,
respectively to the south-east and the north-west of Iceland. The
line begins with tlie large Vatnajökull on the south-east and extends
north-westwards over Tungnafellsjökull, Hofsjökull, Langjökull, and
Eiríksjökull until it terniinates in Gláma and Drangajökull in Vest-
lirðir. To the north of the range of jökulls there are only a few
small jökulls on the peninsula hetween tlie Eyja- and Skagafjörður
while to the south we have the large Mvrdalsjökull and some smaller
ones, more especially Snæfellsjökull.
The area of the jökulls is largest towards the cold, humid, and
foggy eastern regions and decreases strongly towards the north-west.
The area of Vatnajökull is about 8000 km2; of Hofsjökull about
1350 km2, of Langjökull 1300 km2, of Gláma about 60 km2, and
of Drangajökull 350 km2. Vatnajökull’s greatest altitude above sea
level is 2119 m., that of Hofsjökull 1700 m., of Langjökull 1400 m.,
of Gláma and Drangajökull about 900 ni.
The snow-line lies at very different altitudes, coming down lowest
on the south side, while on the north side it lies somewhat higlier,
the east and west sides occupying an intermediate position. On
Vatnajökull the snow-line on the north side lies at a lieight of
1300 m., on the north side of Hofsjökull at 1200 m., and on the
norlh side of Langjökull at a height of 1100 m. On the soutli side
the snow-line lies at a level of 900 m. In Vestfirðir tlie height of
the snow-line above the sea is 400—650 m. On Mvrdalsjökull the
snow-line lies at a heiglit of 1100 m. on the north side, and 800—
900 m. on the south side.
Below the snow-line proper comes a zone with snow-drifts
which either never melt, the permanent snow-drifts, or only
melt in very hot summers, the variable snow-drifts. It is
difíicult to set any lower limit to these two zones. On Arnarvatns-
heiði north-east of Langjökull, wliere the snow-line lies at a height