Jökull - 01.12.1999, Page 65

Figure 4. An enlarged section of the geomorpholog-
ical map showing the central part of forefield. —
Stœkkuð mynd afhluta sandsins við Höfðabrekkujökul
(sjá landmótunarkort). Jökulgarðar frá síðustu 50
árum eru best varðveittir á þessu svæði.
range of slightly older end moraines, so-called “ green
moraines” (Figures 5 and 6). According to Kruger
(1985) Höfðabrekkujökull has been advancing in this
region up to 10 m per year in 1979-1982 and about 32
m per year during 1982-1984.
Ground moraines
Patches of ground moraine are present in the south-
ern and central part of the Höfðabrekkujökull fore-
field, between the 1890-1900 's end moraine range
Figure 5. View of the central part of the Höfðabrekku-
jökull forefield, as seen from the glacier, a) present
day ice-moraine ridge, b) end moraines from sev-
eral years ago, c) end moraines from 1945, d) end
moraines from the 1890"s. — Horft af Höfðabrekku-
jökli yfirfjórar kynslóðir jökulgarða við miðbik hans
(sbr. 4. mynd); a) Yngstu garðarnir; b) jökulgarð-
ar myndaðir fyrir nokkrum árum; c) jökulgarðar frá
1945; d) jökulgarðar frá lokum síðustu aldar.
and the glacier snout. In the northern part of this
area ground moraine covers 800 to 1500 m wide ex-
panses, but is heavily intersected by numerous, nar-
row proglacial channels. Individual fragments of the
preserved ground moraine have flat, undulated, hum-
mocky, or fluted surfaces and traces of drumliniza-
tion. The ground moraine is largely made up of
till and many erratic boulders. The till has a thick-
ness commonly up to 0.7 m. The level of the flat
ground moraine does not fluctuate beyond one metre
whereas the level of the undulated moraine can vary
1-3 m and the hummocky moraine significantly more.
Fluted ground moraine is characterized by low, paral-
lel ridges, perpendicular to the glacier snout. These
forms, have a height of up to 30 cm and a width of
about 1 m are made up of sediments from the basal
movement and reflect the local glacier movements as
they are not subordinated to the relief of their imme-
diate bed.
JÖKULL, No. 47 63