Jökull - 01.12.1982, Page 44

Fig. 3. Bathymetry of Jökulsárlón. Water depths are measured in metres below the mean water surface
for summer 1975 of 5.1 (± 0.1) m above sea level. The level of the water surface during this summer
fluctuated by ± 0.6 m about the mean. The lake lies entirely within the area from which the glacier has
retreated since the Little Ice Age glacial maximum.
Mynd 3. Dýptarmynd af Jökulsárlóni.
TABLE 2. Values of z : zm and Dl for some
North American lake basins produced by contin-
ental ice (after Hutchinson, 1957).
TAFLA 2. Gildi hlutfallsins z : zm °g DL viðýmis
v'ótn í Norður-Ameríku semjökulskjóldurinn gróf á síðasta
jökulskeiði.
Lake dl
Stöðuvatn z : zm
Superior 0.47 2.93
Huron 0.34 3.1
Michican 0.27 2.6
Great Bear — 3.3
Erie 0.33 2.1
Winnipeg 0.69 3.4
Ontario 0.40 2.8
Great Slave — 3.6
rock basin in view of the steep bounding slopes of
the central basin. The seismic survey shows this to
be incorrect, and that the basin was excavated en-
tirely from unlithified sediments with no apparent
bedrock control.
SEISMIC STRy\TIGRAPHY
OF JÖKULSÁRLÓN
In order to establish the nature of the materials in
which the lake basin is cut, and the character and
distribution of sediments within it, a series of con-
tinuous seismic reflection profiles were undertaken
in summer 1976. These employed a 100 element
multi-electrode sparker in conjunction with an
omnidirectional Hunting hydrophone, trailed from
a 6 m rubber boat. An eneigy level of 300 watt-
seconds was used throughout, with a firing interval
of 0.25 seconds. Recordings were made in the 400-
1000 Hz range, which gave records ofgood quality.
40 JÖKULL 32. ÁR