Jökull - 01.12.1984, Blaðsíða 64

Fig. 7. Acid fallout from the Hekla I eruption
1104 A. D. as seen in the Créte and Dye 3 ice
cores. Note the „noisy“ character of the Dye 3
acidity profile.
Mynd 7. Súr úrkoma frá Heklugosinu 1104 í ís-
kjörnum frá Créte og Dye 3.
The Hekla III eruption
This Hekla eruption took place some 3000
years ago and produced the biggest of Hekla’s
tephra layers, (Larsen and Thorarinsson 1977). It
produced 6 times more tephra than the 1104
eruption of Hekla, which suggests a relatively
high deposition of acids on the Greenland Ice
Sheet.
In the Camp Century record there is a high
acid deposition around 1120 ± 50 B.C., Fig. 8.
The high and sharply rising acidity in Fig. 8 are in
accordance with an Icelandic eruption, but there
are snakes in the Paradise, because no similar
high signal exists in the Dye 3 record. Even
though the Dye 3 core has not yet been precisely
dated back to 1100 B.C., the preliminary dating
is good enough to support the above statement.
Could it be, that it is not HIII traces we see in the
Camp Century core? Of course it could be so,
especially when the only verification is a high
acidity around 1100 B.C. in only one out of the
two existing ice cores, in which such Icelandic
events can be traced and dated.
Ice core data on volcanic eruptions like H III
are for the moment so scarce, that it is not
possible to avoid a fairly large amount of subjecti-
vity in their interpretation. Also the dating and
descriptions of volcanic eruptions, which took
place thousands of years ago, are in general not
very precise and exhaustive. Yet, it is worth
trying to identify the high acidity signals in the
Greenland ice cores as a first step toward a more
jJEQUÍV. H+/Kg.
breaks
Hekla 3
CAMP CENTURY
? i í i U
1120Í50 B.C.
1130
Fig. 8. High acid fallout in the Camp Century
core; approx. 1100 B.C. Probably caused by the
Hekla III eruption, but the absence of a corres-
ponding high acid signal in the Dye 3 core re-
mains to be explained. (Dye 3 data have not been
shown, as the dating is not completed).
Mynd 8. Súr úrkoma í ískjarna frá Camp Century
frá um 1100 f.Kr., sem etv. er frá svonefndu
Heklu III gosi.
62 JÖKULL 34. ÁR