Jökull - 01.12.1978, Page 56

Mynd. 1. Lega Esjufjalla og grjótjöklanna.
and fringed by a large snow bank. Ridge
backslopes are deflated leaving an oxidized
lag surface — grey fines revealed on the fron-
tal slopes result from debris moving downs-
lope and disturbance of the debris cover. The
surfaces of the second and third lobes are
much more highly disturbed and an arcuate
ridge form is only poorly exhibited (Fig. 4). If
disturbance of the debris cover indicates for-
ward creep of the ice-core rather than degra-
dation of the ice-core then the lobes are mov-
ing throughout their length. The rock glaciers
appear to have encroached onto a surround-
ing surface of scree debris (Fig. 2). Debris
moving down the frontal slope of the lobes is
responsible for the burial of the frontal fring-
ing snow bank. The ice-core of the rock glacier
was penetrated at a number of localities at
depths ranging from 30 cm to 60 cm, is inter-
stitial and suggests refreezing of percolating
meltwater as a superimposed ice layer. The
nature of the ice-core below this surface layer,
i. e. whether it is glacier ice or snow bank ice, is
not known but is thought to be snow bank ice
(see below).
To the north of the rock glacier lobes is a
glacierette, lacking any supraglacial debris,
lying against a steep rockwall. The glacierette
extends approximately 150 m from the back-
wall and has a low-angled uncrevassed sur-
face, composed of superimposed ice, that ter-
Fig. 2. Rock glacier
lobes 1, 2 and 3. In the
background a glacierette
(4) and a frontal ice-cored
moraine ridge (5). Note
the bouldery degraded
protalus — rampart (6).
54 JÖKULL 28. ÁR