RESEARCH PROJECT:
MODELING OF PYROCLASTIC FLOW
By: Jess Rositano
GPH 904: Research Analysis
Spring 2012
INTRODUCTION: VOLCANOES
• Lava: What most people think of
• Pyroclastic Flow: Even more
destructive than lava
INTRO: PYROCLASTIC FLOWS
• What are they?
• Formation:
• Column collapse
• Dome collapse
• Dilute clouds interact with
topography
• Velocity: up to 150mph
• Temperature: up to 800˚C (1472˚F)
Pyroclastic Flow Link
PYROCLASTIC FLOW:
SIGNIFICANCE OF RESEARCH
PYROCLASTIC FLOW RISK MODELING
•
No one best way to model
•
Small scale:
• Models concentrate on one or a few particular hazards
• Even this can become quite complex
• Benefits: allow for focus and more detailed understanding of
hazard(s)
• To take into account: Variations on how to calculate movement,
damage, composition, etc of the hazard
•
Large scale:
• Models take many variables into account
• Benefits: perhaps better for a large scale risk assessment
• To take into account: Variations on which hazards to include and
how each hazard may affect the assessment of “risk”
PILOT PROJECT
• Goal: Create a model based off of equations from the Toyos et al. (2007)
model using ArcGIS for a small volume pyroclastic flow from Mt. St. Helens.
• Equations to be Integrated:
• Run-out distance: ∆H/L = 2.03V-0.15
• L= run-out distance
• ∆H = change in elevation
• V = volume of pyroclastic flow
• Max potential vel: v = 0.38∆h0.68
• v = velocity
• ∆h = change in elevation
PILOT PROJECT
• Data required:
• Elevation data for the volcano and surrounding area (DEM, raster),
Pyroclastic flow volumes
• Method:
• Data collection: Web search
• 1st: Write script for equations w/in ArcGIS
• 2nd: Use already established ArcGIS tools
Figure: Mt. St. Helens
elevation raster
PILOT PROJECT
Figure. Focal flow output for Mount St. Helens.
Figure. Slope output for Mount St. Helens.
PILOT PROJECT:
UNDERSTANDING THE RUN-OUT DISTANCE
∆H
∆H/L = 2.03V-0.15
Distace (m)
Run-out Distance
10000.0
9000.0
8000.0
7000.0
6000.0
5000.0
4000.0
3000.0
2000.0
1000.0
0.0
Vol 1x10e5
Vol 1x10e6
Vol 1x10e7
0
500
1000
∆H (m)
1500
2000
volume
Run-out
Run-out
Run-out
(m3)
Vol 1x10e5
Volume (m3) Vol 1x10e6 volume (m3) Vol 1x10e7
50
100000
138.5
1000000
195.6 10000000
276.4
100
100000
277.0
1000000
391.3 10000000
552.7
120
100000
332.4
1000000
469.6 10000000
663.3
140
100000
387.8
1000000
547.8 10000000
773.8
160
100000
443.2
1000000
626.1 10000000
884.3
180
100000
498.6
1000000
704.3 10000000
994.9
200
100000
554.0
1000000
782.6 10000000
1105.4
220
100000
609.4
1000000
860.8 10000000
1216.0
240
100000
664.8
1000000
939.1 10000000
1326.5
260
100000
720.2
1000000
1017.4 10000000
1437.1
280
100000
775.6
1000000
1095.6 10000000
1547.6
300
100000
831.0
1000000
1173.9 10000000
1658.2
320
100000
886.4
1000000
1252.1 10000000
1768.7
340
100000
941.9
1000000
1330.4 10000000
1879.2
360
100000
997.3
1000000
1408.7 10000000
1989.8
380
100000
1052.7
1000000
1486.9 10000000
2100.3
400
100000
1108.1
1000000
1565.2 10000000
2210.9
420
100000
1163.5
1000000
1643.4 10000000
2321.4
440
100000
1218.9
1000000
1721.7 10000000
2432.0
460
100000
1274.3
1000000
1800.0 10000000
2542.5
480
100000
1329.7
1000000
1878.2 10000000
2653.0
500
100000
1385.1
1000000
1956.5 10000000
2763.6
520
100000
1440.5
1000000
2034.7 10000000
2874.1
540
100000
1495.9
1000000
2113.0 10000000
2984.7
560
100000
1551.3
1000000
2191.3 10000000
3095.2
580
100000
1606.7
1000000
2269.5 10000000
3205.8
600
100000
1662.1
1000000
2347.8 10000000
3316.3
620
100000
1717.5
1000000
2426.0 10000000
3426.9
PILOT PROJECT:
UNDERSTANDING MAXIMUM POTENTIAL VELOCITY
∆H
v = 0.38∆h0.68
Potential Velocity
70.00
Potential Velocity
60.00
50.00
40.00
30.00
Potential Vel.
20.00
10.00
0.00
0
500
1000
Elevation Change
1500
2000
Potential Vel.
50
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380
400
420
440
460
480
500
520
540
560
580
600
620
640
660
680
5.43
8.71
9.85
10.94
11.98
12.98
13.95
14.88
15.79
16.67
17.53
18.37
19.20
20.01
20.80
21.58
22.35
23.10
23.84
24.57
25.29
26.01
26.71
27.40
28.09
28.77
29.44
30.10
30.76
31.41
32.05
PILOT PROJECT
• Results/Conclusions:
• Creating own tools may be the best option
• Visual Basic
METHODOLOGY
•
Step 1: Data gathering
• Elevation data that can be used in ArcGIS
• Make sure you’re using an appropriate projection and coordinate system
• Pyroclastic flow volume
•
Step 2a: Learn to write code in Visual Basic
•
Step 2b: Write script in VB to accommodate the run-out distance and velocity equations
METHODOLOGY
•
Step 3: Template for
• ArcGIS
• QuantumGIS
• etc
•
Step 4: Interface allowing user specified values. Namely:
• Height of the source
• Pyroclastic flow volume
CONCLUDING THOUGHTS
•
What I used  very simple and incomplete.
•
Other variables to be taken into account when calculating areas to be impacted:
• pressure buildup
• initial velocity
•
If only looking at risk from a small volume pyroclastic flow: Toyos et al.’s model
•
If you want total risk to an area from a volcano, may want to consider a more complex
model
• Ex. Mount St. Helens
REFERENCES
•
Volcanic Phenomena at Pompeii. 1997.
http://www.arch.virginia.edu/struct/pompeii/volcanic.html -Pyroclastic animation, img
•
Toyos, G.P., P.D.Cole, A. Felpeto, and J. Marti. 2007. A GIS-based methodology for
hazard mapping of small volume pyroclastic density currents. Natural Hazards. 41:1. 99112
•
1980 eruption of Mount St. Helens. Wikipedia.com
~FIN~