Rit (Vísindafélag Íslendinga) - 01.07.1962, Side 9

9
stages in the present area. Yet, especially in one area, east
of HöfSaströnd on the east side of Skagafjörður, large smooth
parts are left on the mountains between the deep valleys,
clearly remnants of a morphologic stage antedating the val-
ley erosion of the Younger 300 m stage. A great number of
smaller smooth patches capping other high mountains are
then recognized as corresponding also to such a stage, the
Older 300 m stage.
On the topographic map of the area (1:100.000) we can
without any undue guesswork connect the (say 100 m) con-
tour lines from one large smooth surface across a deep valley
to the other large patch and get a good impression of the
general character of the old land surface (cf. Fig. 2). The
most typical feature is the smoothness of the forms.
These forms can be traced from the highest summits at
about 1200 m down to elevations of 300—400 m. These old
smooth mountain sides were grooved by the shallow fore-
runners of the later deep valleys. Instead of the present 500
—700 m deep and steepsided valleys, Fig. 1, the old ones were
only 100—200 m deep while of a similar width as the pre-
sent ones. Also characteristic is the apparent lack of near-
horizontal floors far into the valleys which is common in the
valleys of the later stages. Instead, the floors seem to have
risen rather evenly along the whole valleys. The base-level
to which this smooth topography was graded seems to have
been close to that of the Younger 300 m base level and, for
lack of more precise figures, 300 m is used for hoth stages as
a fairly accurate simple figure. The great differene in the
forms is therefore probably due to climatic differences, pos-
sibly a greatly increased precipitation at the heginning of the
Younger 300 m stage, possibly also lowering of temperature,
leading to greater accumulation of snow, released as floods
of meltwater in spring.
It should be stated that in the Höfðaströnd area the hasalts
dip westwards not much differently from the general dip of
the erosion surface, but the two are not identical, the surface