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September 2010 1Master of Science in Geological & Mining & Sciences
Michigan Technological University – College of Engineering
Historic Activity Records of Galeras Volcano, Nariño, Colombia
A time series analysis example
Federica Lanza
September 2010 Master of Science in Geological & Mining & Sciences 2
Volcano Galeras, southwestern Colombia
Most active volcano in Colombia, near the city of Pasto
Stratovolcano (complex volcano)
Andesitic in composition
Long-term extensive hydrothermal alteration
Two major sector collapses (late Pleistocene)
Strike-slip context (Romeral-Buesaco fault system)
What kind of Volcano?
September 2010 Master of Science in Geological & Mining & Sciences 3
Main features of eruptions
Main central crater and smaller craters (i.e El Pinta Vent, El Viejo, Baston etc.)
Eruptions (mostly vulcanian type) consist of:
- central vent eruptions- explosive eruptions (VEI 2 – 3)- phreatic explosions- lava dome extrusions- radial fissure eruption (1993)
Pyroclastic flowsWidespread tephra depositsLava flows (rare)Lahars
From Smithsonian – GVN web source
From Google Images
September 2010 Master of Science in Geological & Mining & Sciences 4
Eruptive History
Spreadsheet: database
Data sources: Smithsonian Institution - GVN
34 data points (eruptive events)
Long span of time investigated: from 7050 BC till now (2010)
High dispersion around the mean value
Great uncertainty
Start End VEIDuration -
daysDuration -
yearsrepose before -
daysrepose after -
days
10/21/2008 09/14/2010 3 693.00 1.90 278.0010/04/2007 01/17/2008 3 105.00 0.29 449.00 278.0011/24/2005 07/12/2006 2 230.00 0.63 290.00 449.0007/16/2004 02/07/2005 3 206.00 0.56 770.00 290.0006/07/2002 06/07/2002 1 0.00 0.00 750.00 770.0003/21/2000 05/18/2000 1 58.00 0.16 2479.00 750.0001/14/1993 06/07/1993 2 144.00 0.39 182.00 2479.0001/07/1990 07/16/1992 2 921.00 2.52 243.00 182.0002/19/1989 05/09/1989 2 79.00 0.22 1877.00 243.0006/01/1974 12/31/1983 1 3500.00 9.59 8670.00 1877.0001/12/1950 09/05/1950 2 236.00 0.65 4886.00 8670.0002/09/1936 08/27/1936 2 200.00 0.55 1077.00 4886.0010/10/1932 02/27/1933 2 140.00 0.38 1783.00 1077.0010/01/1924 11/23/1927 3 1148.00 3.15 174.00 1783.0012/08/1923 04/10/1924 2 124.00 0.34 11769.00 174.006/15/1891 9/17/1891 2 94.00 0.26 550.00 11769.007/3/1889 12/12/1889 2 162.00 0.44 6939.00 550.00
10/2/1865 7/4/1870 3 1736.00 4.76 11278.00 6939.007/19/1834 11/16/1834 2 120.00 0.33 140.00 11278.0010/24/1828 3/1/1834 3 1954.00 5.35 1949.00 140.006/17/1823 6/24/1823 2 7.00 0.02 7913.00 1949.0011/1/1796 10/17/1801 2 1810.00 4.96 14694.00 7913.006/6/1754 8/9/1756 2 795.00 2.18 6687.00 14694.00
6/20/1670 2/14/1736 3 23979.00 65.70 9671.00 6687.006/2/1641 12/28/1643 3 939.00 2.57 9099.00 9671.007/4/1616 7/4/1616 3 0.00 0.00 12993.00 9099.00
12/7/1580 12/7/1580 3 0.00 0.00 16527.00 12993.007/3/1535 9/8/1535 3 67.00 0.18 235037.00 16527.00
6/15/0890 12/28/0891 2 561.00 1.54 503007.00 235037.0007/19/-490 4/30/-488 2 651 1.78 244474.50 503007.00
08/26/-1160 10/03/-1160 2 37 0.10 518036.50 244474.5010/13/-2580 05/16/-2579 2 218 0.60 205699.50 518036.5003/05/-3150 03/22/-3143 3 2572 7.05 1423174.00 205699.5002/28/-7050 01/27/-7049 1 334 0.92 1423174.00
Mean 1288.82 3.53 98895.32Sd 4093.12 11.21 272875.28
Galeras Eruptions, GVN website source
September 2010 Master of Science in Geological & Mining & Sciences 5
Assumptions
start date when neither the day nor the month is reported: 15th June or approximately in the middle of the year
stop date when it is unknown: year, month and day have been inferred from dataset
start date and/or stop date when no day (or month) is reported: 1st of the month in which the eruption has occurred or according to data trend
Dataset criteria
September 2010 Master of Science in Geological & Mining & Sciences 6
Time series analysis (I) - Size
Frequency of size or “magnitude” of each eruption
Volcanic Explosivity Index (VEI)
Moderate to moderate-large eruptions
02468
101214161820
0 1 2 3 4 5 6 7 8
Fre
qu
en
cy
VEI
Explositivy
0
1
2
3
4
2008
2007
2005
2004
2002
2000
1993
1990
1989
1974
1950
1936
1932
1924
1923
1891
1889
1865
1834
1828
1823
1796
1754
1670
1641
1616
1580
153589
0-4
90-1
160
-258
0-3
150
-705
0
VEI
years
VEI
BC AC
Ordered dates
0
1
2
3
4
200019001800170016001500
VEI
-Ave
rage
Decade
Size (average)
September 2010 Master of Science in Geological & Mining & Sciences 7
Time series analysis (II) – Duration of eruptions
Short duration eruptions
Consistency of data except for one event (1670 peak)
0
10
20
30
40
50
60
70
2008
2007
2005
2004
2002
2000
1993
1990
1989
1974
1950
1936
1932
1924
1923
1891
1889
1865
1834
1828
1823
1796
1754
1670
1641
1616
1580
153589
0-4
90-1
160
-258
0-3
150
-705
0
Dur
ation
(yea
rs)
date
Duration of eruptions
0
2
4
6
8
10
12
14
16
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Num
ber o
f Ev
ents
Duration - years
Frequency of duration of eruptions
0
5
10
15
20
25
200019001800170016001500
Ave
rage
of d
urati
on o
f eru
ption
s (ye
ars)
Decade
Duration of eruptions (average)
September 2010 Master of Science in Geological & Mining & Sciences 8
Time series analysis (III) – Repose time
BC events included/not included
Decreasing pattern of repose time with time, why? Sampling resolution?
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
2008200419931974193218911834179616411535
repo
se ti
me
befo
re (d
ays)
years
Repose time
1
10
100
1000
10000
100000
1000000
10000000
2008200419931974193218911834179616411535-1160
repo
se ti
me
befo
re (d
ays)
years
Repose time (moving average)
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
2008200419931974193218911834179616411535-1160
repo
se ti
me
befo
re (d
ays)
years
Repose time (moving average)
September 2010 Master of Science in Geological & Mining & Sciences 9
y = -29.114x + 59771R² = 0.5329
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
1400 1500 1600 1700 1800 1900 2000 2100
repo
se ti
me
(day
s)
years
Repose time (linear regression)
Linear relationship between years and interval time between periods of eruption (BC data are not considered)
Changes in the volcano behavior?
Wide range of values
Reliability?
Time series analysis (IV) – Repose time
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35 40 45
Fre
qu
ency
Repose time (years)
Periods of inactivity Frequency
Cumulative %
September 2010 Master of Science in Geological & Mining & Sciences 10
Time series analysis (V) – Volume of material emitted
Linear relationship between the volume of material and the duration of activity
- short and weak eruptions
- short but strong eruptions
- very long and vigorous eruptions
Start End VEIDuration -
daysDuration -
yearsrepose before -
daysrepose after -
daysVolume - m^3
01/14/1993 06/07/1993 2 144.00 0.39 182.00 2479.00 2500000.0001/07/1990 07/16/1992 2 921.00 2.52 243.00 182.00 280000.0002/19/1989 05/09/1989 2 79.00 0.22 1877.00 243.00 400000.0010/2/1865 7/4/1870 3 1736.00 4.76 11278.00 6939.00 2900000.006/15/0890 12/28/0891 2 561.00 1.54 503007.00 235037.00 1200000.0007/19/-490 4/30/-488 2 651 1.78 244474.50 503007.00 2100000.00
08/26/-1160 10/03/-1160 2 37 0.10 518036.50 244474.50 1300000.0010/13/-2580 05/16/-2579 2 218 0.60 205699.50 518036.50 1200000.0003/05/-3150 03/22/-3143 3 2572 7.05 1423174.00 205699.50 8700000.00
Galeras Eruptions, GVN website source
0
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
9000000
10000000
0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00
Volu
meo
f mag
ma
emitt
ed
Duration - days
Volume of material emitted
September 2010 Master of Science in Geological & Mining & Sciences 11
Problems regarding the data criteria of eruptions
What do we mean by “eruption”
Dating methods
Stochastic process (randomness)
Assumptions
Uncertainty: caution and evaluation of representativeness
Photo courtesy of Marta Calvache, August 27,1936 (INGEOMINAS-Observatorio Vulcanológico del Sur).
September 2010 Master of Science in Geological & Mining & Sciences 12
Forecasting based on historical and prehistoric activity
Caveats for long-term hazards assessment
Obliteration by subsequent events of older records
Unreliable average repose interval due to the wide range of time intervals between eruptions
Changes in eruption habits
Unprecedented events
Change of hazardous area locations due to changes in the size and shape of volcanoes with time
Conclusions
September 2010 Master of Science in Geological & Mining & Sciences 13
Can the Galeras dataset be used for forecasting purposes?
Random pattern in the timing of historical eruptions
No evidence of cyclical behavior
Wide variation in the repose times between eruptions
Combine different tools to reduce uncertainty:
Monitoring approach & Basic Research
Thermal radiation SeismicityElectromagnetic, magnetic data
From Seidl (2003)
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