Jökull - 01.06.2000, Page 11

Guðrún Larsen
H 1597
6400±80 BP
0
1
2
3
m
K 1918
K 1755
K 1660
K 1625
K 1612
K≈1500
K 1416
K 1262
V 1477
H 1389
H 1206
Eldgjá
Fires
≈934 (938)
V≈871
(877)
SILK-YN
1676±12 BP
SILK-UN
2660±50 BP
SILK-MN
2975±12
SILK-LN
3139±40
H-S 3515±55 BP
SILK-N4
A4
SILK-N3
A2
A3
A5
SILK-A7A6
SILK-A8
SILK-A9
Hólmsá
Fires
≈6800 BPH-4 3826±12 BP
SILK-N2 A11
A12
A13 7505±42
SILK-A1
SILK-N1
Figure 5. Composite soil section from areas east of
Mýrdalsjökull ice cap, showing the regional tephra
stratigraphy and where the products of the Eldgjá
fires and Hólmsá fires fit in (from Larsen et al., in
press). Historical dates are A.D. while for prehis-
toric dates B.P. is preferred over B.C. (from Thorar-
insson, 1975; Larsen, 1979, 1984; Hammer et al.,
1980; Dugmore, 1989; Dugmore et al., 1995; Grön-
vold et al., 1995; Zielinski et al., 1995, 1998; Ols-
son, Larsen and Vilmundardóttir, unpubl. data). Dark
layers (blackish, brownish) are shown as grey bands,
the majority being basaltic Katla layers. The silicic
Katla layers (greenish) are shown as black bands.
Light- or two-coloured marker tephras from other vol-
canic systems are ruled. The Eldgjá tephra layer, the
lava flows and several jökulhlaup-deposits fit into the
regional tephra stratigraphy of S-Iceland at a spe-
cific stratigraphical level, here indicated by the tephra
alone. K: Katla, H: Hekla, V: Veiðivötn systems.
SILK: silicic Katla layers. The letters N and A re-
fer to localities in the field. – Samsett jarðvegssnið
með gjóskulögum, sem sýnir gjóskulagaskipan aust-
an Mýrdalsjökuls (samkvæmt Guðrúnu Larsen o.fl., í
prentun). Aldur gjóskulaga á forsögulegum tíma er
gefinn í geislakolsárum, í samræmi við töflu 3. Dökk
gjóskulög (svört eða brúnleit í jarðvegi) eru höfð grá
á teikningunni, flest þeirra eru basísk Kötlulög. Súru
Kötlulögin (grænleit í jarðvegi) eru höfð svört. Ljósleit
eða tvílit leiðarlög frá öðrum eldstöðvakerfum eru
strikuð. Sýnt er hvar gosefni frá Eldgjárgosi (táknað
með gjóskulaginu) og Hólmsáreldum (strik vísar á legu)
eru í jarðvegsstaflanum. K: Kötlu-, H: Heklu-, V: Veiði-
vatnakerfi. Bókstafirnir N og A ásamt tölustaf vísa til
sýnatökustaða.
The volume of airborne silicic tephra varies be-
tween eruptions but does not exceed 0.5 km

in any
layer mapped so far. The largest and most widespread
is the tephra layer UN (Figure 7). The area within
the 0.2 cm isopach on land is about 15.000 km  , and
compacted volume is 0.16 km

, corresponding to 0.27
km

of uncompacted tephra. The second largest is
layer LN with an uncompacted tephra volume of 0.2
km

. The remaining layers are smaller still and the
smallest ones are estimated to be less than 0.01 km

in volume. Maximum thickness values are not known
for any of the layers as the proximal part of the tephras
was deposited on ice. Maximum observed thickness
amounts to 12 cm at a distance of 30 km from the cen-
tre of the caldera.
10 JÖKULL No. 49