1. Hazard due to eruptions and floods from
Katla and Eyjafjallajökull, south Iceland
Magnús T. Guðmundsson1, Jónas Elíasson2, Guðrún Larsen1, Ágúst Gunnar Gylfason3, Páll
Einarsson1, Tómas Jóhannesson4, Kristín Martha Hákonardóttir4 and Helgi Torfason5
1: Institute of Earth Sciences University of Iceland 2: Institute of Engineering, University of Iceland
3: Civil Protection Department, National Commissioner of the Icelandic Police
4: Icelandic Meteorological Office 5: Institute of Natural History
This presentation is a summary of project funded by the Government of Iceland. The results are found in a
special publication available on the web-page of the Civil Protection Department of the National Commissioner
of the Icelandic Police – see end of presentation for details

2. Mýrdalsjökull
Eyjafjallajökull
Katla caldera
Eyjafjallajökull
Summit caldera
10 km
Kortagrunnur utan jökla: Landmælingar Íslands
Botn Mýrdalsjökuls: Helgi Björnsson o.fl. 12
Botn Eyjafjallajökuls: Sara M. Strachan 13

3. Eruptions and
associated floods
caused by ice
melting a major
hazard
- Unrest (seismicity, inflation, geothermal activity)
- Catastrophic floods to the east well known
- New: floods to west more frequent than previously thought
Tasks of hazard assessment for area to the west of the
volcanoes:
- Estimate eruption frequency for sectors of the volcanoes
- Estimate likely flood magnitude
- Estimate which areas would be affected by floods

4. Katla caldera – 400-700 m thick ice
About two eruptions / century
1918
eruption
site

5. Katla - Large phreatomagmatic eruptions
Katla eruption 1918

6. Katla eruptions cause catastrophic jökulhlaups
- the 1918 event the largest of its kind in the 20th
century
Peak discharge 100-300·103 m3s-1
• ~1 km3 of sediments transported
• 3 km long peninsula formed at coast
• Katla jökulhlaups one of the largest
volcanological hazards in Iceland
From Larsen (2000) Kjartan Guðmundsson 1918

7. Eyjafjallajökull - ice covered stratovolcano
Eruptions once every few hundred years
1821-1823
eruption

8. Evidence for hazardous floods towards west
ng á
Channels of
a
ri-R pre-historic jökulhlaups
E y st
Drumbabót:
Jökulhlaup sediments ~1200 BP
Þverá
Sediments indicate
repeated large
jökulhlaups ll
Aff a eruption
r
Á la
site
1822
ót
rflj
Eyjafjallajökull Katla
rka
Ma
Austur-Landeyjar:
sediments from a
large jökulhlaup
~1600 BP
Pathways of 1822 Minor flooding
jökulhlaups 1822
5 km

9. Types of eruptions: a gos undir þykkum jökli a thick ice
ís
a: Katla 1918, Gjálp 1996
b
sprungugos
b thin ice
í hlíð
- flank
ís
b: Grímsvötn 1998,
Eyjafjallajökull ~920
c
sprengigos með c pyroclastic
gjóskuflóði út á
jökul flow
ís
c: Redoubt 1990,
Eyjafjallajökull 1821-23?
d d dome
gúlagos í jökli
ís
eruption
d: Mount St. Helens 2004 -

10. Ice thickness in Eyjafjallajökull and Mýrdalsjökull
Radio-eccho soundings (Helgi Björnsson er al., 2000; Sara Strachan, 2001)
Water divides in glaciers
0 100 200 300 400 500 600 700 800
meters
Eyjafjallajökull Katla
5 km

11. Recurrence time of eruptions Ny
rð
ri E
< 100 years ms
tru
100-1.000 years á
1.000-10.000 years Syð
ri E
MNV Mýrdalsjökull - northwest part mst Sléttjökull
ru á
MV Mýrdalsjökull - west flank En
MSV Mýrdalsjökull - southwest flank t tu
jó jö
EN Eyjafjallajökull - north flank rfl k ul
ka l
ar
ES Eyjafjallajökull - south flank M
Ljósá
MNV
Þröngá
Markarfljót
Jökulsá Stei Krossá
Ak nh Krossárjökull
st olt Hv
að Langanes sá an
ná
aá
MV
Hrunar
EN Tungna-
kvíslajökull
ES MSV
Írá
á la á
il
sk
Fjallg
ð
l
Mi
ku l
á
sá
óg
il
lt
jö
sár g
Ho
Sk
ma
Sv
La ug
l
h ei
Jöku
að
bæ
fsá
Sól
ar á
kli
li sá
lda
Ka
5 km

12. Magnitude of jökulhlaups caused by eruptions Ny
rðr
maximum discharge: iE
ms
tru
1: < 3.000 m3 /s á
2: 3.000-10.000 m3 /s Sy ð
ri E
3 ms Sléttjökull
3: 10.000-30.000 m /s t ru á
3
4: 30.000-100.000 m /s En
t tu
jó j ök
3
5: > 100.000 m /s rfl u
ka ll
ar Ljósá
M
Þröngá
Markarfljót
S
Jökulsá tein Krossá
A ho
ks lts Hv Krossárjökull
ta Langanes á an
ða ná
á
Hrunar
Tungna-
kvíslajökull
Írá
á
ála
il
k
Fj allg
iðs
l
kul
á
M
óg
sá
il
lt
ajö
lsárg
Ho
Sk
m
Sv
L au g a
hei
Jöku
að
á
b
S ól
fs
æl
kli
rá
isá
lda
Ka
5 km

13. Catastrophic jökulhlaup (300,000 m3/s)
AQUARIVER flood simulation
Timing of flood wave from start of eruption

14. Floods due to eruptions
hazard areas - travel times of floods
No eruption-
generated
floods
Water divides
15-30 min from
start of eruption Hazard zone boundaries

15. Floods from Ljósá and Þröngá – path and travel times
reccurence time of eruptions 1,000-10,000 years
15-30 min
3 hours
Time from source
Water divides
Path of flood

16. Floods Eyjafjallajökull caldera – path and travel times
reccurence time of eruptions 100-1,000 years
1 - 1.5 hours
15-30 min
Time from source
Water divides
Path of flood

17. Results - Hazard assessment
• Recurrence time of eruptions varies between
areas - from 50 to 10,000 years
• Recurrence time of large floods to west 500-800
years
• Largest pre-historic floods from Katla caldera
~250,000 m3/s (2 x Amazon River)
• Magnitude of floods due to eruptions on flanks of
volcanoes mostly 3,000-10,000 m3/s
• GIS presentation important to convey
information to inhabitants and authorities

18. This presentation is a short summary of:
Magnús T. Guðmundsson, Jónas Elíasson, Guðrún Larsen, Ágúst Gunnar Gylfason,
Páll Einarsson, Tómas Jóhannesson, Kristín Martha Hákonardóttir og Helgi Torfason.
2005: Yfirlit um hættumat vegna eldgosa og hlaupa frá vesturhluta Mýrdalsjökuls
og Eyjafjallajökli. (in Icelandic), (Overview of hazard due to volcanic eruptions and
jökulhlaups from the western part of Mýrdalsjökull and Eyjafjallajökull) In: Magnús T.
Guðmundsson and Ágúst Gunnar Gylfason (editors): Hættumat vegna eldgosa og
hlaupa frá vestanverðum Mýrdalsjökli og Eyjafjallajökli, 11-44. Ríkislögreglustjórinn og
Háskólaútgáfan.
In addition to the above overview, the publication on hazard assessment has
11 specialized papers on varous aspects of hazard assessment for the area.
All the papers are available on the web-page of the Civil Protection
Department of the National Commissioner of the Icelandic police
(Ríkislögreglustjóri, Almannavarnadeild):
http://www.almannavarnir.is/
or
http://www.almannavarnir.is/displayer.asp?cat_id=183