Rit (Vísindafélag Íslendinga) - 01.06.1975, Síða 24

are seldom well developed in flói areas in the lowland. They are,
however, quite conspicuous in many parts of Melrakkaslétta, where
these ridges lie intermittently spaced straight across the flói areas.
They can he up to one metre in height and several metres wide.
Usually they are so disrupted that water does not collect to any >
measurahle extent above them. They are mostly covered with shruh
growth and moss is abundant, unlike the vegetation in the flói
itself. On the moors such ridges are more common, since slopes
are more freQuent there. This applies e.g. to various locations on
Fljótsheiði. But sometimes they are more dense and water then
often collects above them, especially in springtime and during
winter thaws. Nowhere have I witnessed as clear an example of
such formation as at Fagridalur in Brúaröræfi. The ridges are at
right angles to the direction of the slope and ahove most of them
small ponds develop, so that at a distance the scene is reminiscent
of a sloping irrigation project. Where the ponds dry up so early
in summer that their sites are fully covered with vegetation,
Eriophorum flói vegetation does not occ.ur but rather Carex nigra
and Calamagrostis. The origins of the mound ridges are probably
similar to those of the mounds in general, although more factors
must be taken into account. In Scandinavia, Auer has explored this
subject more fully than anyone else. In connection with these ridges
in Icelandic flói areas the following should be noted. They never
form unless the land has some gradient. They hardly ever develop
in lowland in the warmer parts of the country, but they are fairly
common in coastal districts with low summer temperatures and in
lower parts of the highland. At higher altitudes the ridge formation
proper disappears and hence they are hardly distinguishable from
tundra moor formations. I have studied three types of mound
ridges. 1) In a shghtly sloping flói at Kýlingar there were elon-
gated mounds, forming low ridges with pools in hetween. No traces
of solifluction are detectable, but rather a wave formation in the
primary stage has developed because of increased moisture content
in ihe soil. (Confer Auer, pp 55-63). 2) In shghtly sloping flói
areas with thick soil the ridges accumulate intermittently hut with- '
out any measurable water collecting above them. Plain type. 3)
Where the flói slope is more pronounced its surface becomes
terrace-formed with the ridges fronting the terraces, with ponds
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