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)