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DEM-based analysis of the morphometry of lava domes; a case study from the
Taupo Volcanic Zone, New Zealand
Conference Paper · June 2015
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DEM-based analysis of the morphometry of lava domes; a case study
from the Taupo Volcanic Zone, New Zealand
Szabolcs Kósik¹*, Károly Németh¹, Jonathan Procter¹, Gábor Kereszturi¹, Shane J. Cronin¹ ²
*email: [email protected]
1. Ins tute of Agriculture and Environment, Massey University, Palmerston North, New Zealand, 2. School of Environment, University of Auckland
INTRODUCTION
Lava dome with volume
Lava dome with volume
Lava dome with volume
Lava dome with volume
The Taupo Volcanic Zone (TVZ) has about 300 silicic lava domes and coulees, emplaced over the last 500 000 years. In comparison with
scoria cones (F
., 2012), the syn-erup ve morphometry of lava domes is much more diverse due to the greater variability in
the physical and chemical proper es of the erup ng magmas. The shape of a growing lava dome is influenced mostly by the viscosity of
the erup ng melt, the inclina on of the pre-erup on surface and erosive processes, such as collapses, but other factors have an
influence, such as magma yield strength, cooling rates, degassing processes, effusion rates and the dura on of the erup on (H
., 2014; Y
, 2005). The TVZ provides an ideal loca on for the geomorphological characterisa on and classifica on of lava
domes. Domes related to the TVZ caldera system are generally aligned and clustered around the NE-trending fault system, and are
distributed across a number of volcanic centres of varying ages. The extractable morphometric parameters (slope angles, edifice
volume, elonga on of the volcanic edifice and its orienta on) together define the morphometry of the lava domes, which clearly
reflects both the syn-erup ve (e.g. the viscosity of the magma, explosive behaviour during of dome growth, dome collapsing) and the
post-erup ve processes such as faul ng, erosion, valley incision and degree of mantling.
Pohaturoa
Okataina
25 km
Oh.
Reporoa
Fig. 1a. Edifice elonga on
orienta on of the lava domes
of the TVZ.
170°
35°
TV
Whakamaru
40°
Age: 133-168 ky
A: 0.43+ km²
H: 262.1 m
V: 0.03+ km³
Age: 14 ky
A: 1.99+ km²
H: 165.3 m
V: 0.21+ km³
Age: 0.7 ky
A: 3.0 km²
H: 489.5 m
V: 0.86 km³
45°
Taupo
2 km
2 km
Te Horoa
Mokauteure
Age: 68-125 ky
A: 5.82+ km²
H: 302.5 m
V: 0.83+ km³
Age: 128-524 ky
A: 3.61+ km²
H: 383 m
V: 0.49+ km³
1 km
Age: 8 ky
A: 7.45+ km²
H: 188.3 m
V: 0.93+ km³
1 km
Tongariro
Ngauruhoe
1 km
5 km
Fig. 2. Examples for different lava dome morphologies and three morphometric parameter from the TVZ. (A = Area, H = Height, V = Volume) At coulees the arrows show the main
flow direc ons.
Fig. 1. Spa al distribu on and edifice volumes of the lava domes and coulees
within TVZ. The inset (b) shows the outlines of 324 domes (the dome
posi ons at the inset do not reflect their real loca ons).
Ruapehu
MATERIALS AND METHODS
We mapped the volcanic structures of the TVZ (Fig 1.) using DEM derivates (eg. slope, aspect) of a Digital Eleva on Model with 8 m
resolu on, 1:250K geological maps of New Zealand and the 1:50K geological map of Okatania Volcanic Centre. The 8 m DEM was
primarily derived from contour lines with 20 m intervals (LINZ Topo50). The spa al accuracy is within ±22 metres horizontally and
within ±10 metres ver cally. For GIS analyses we used ESRI ArcGIS 10 and Golden So ware Surfer 10 so wares. We precisely delimited
the lava domes based on the morphological parameters of the surface. As a result we could calculate the dome parameters, such as
area, height, average slope, volume, circularity and orienta on. In this study we used the averaged ages of the ages are given on the
1:250K geological maps (Fig. 7d). In the first stage, we have applied the Height/Diamater ra o to evaluate the lava domes within the
TVZ (B
, 1990) (Fig. 4). Finally, we inves gated the slope and eleva on distribu ons of the domes (Fig. 3), and we determined the
height posi on of the steepest slopes for individual lava dome edifices (Fig. 6).
750
dacite
rhyolite
es
om
s
nD
e
om
D
ava
L
w
-P
elé
ea
550
e=
p
Slo
- Lo
b
pe
=1
.06
Wahanga
5
0.5
Slo
400
Mokauteure
Name of Volcano
Loca on
Year of
emplacement
Rock
type
Nevados de Chillan
Chile
1981
andesite
Shiveluch
Russia
1980
andesite
Puluweh
Indonesia
1981
andesite
Novy (Bezymianny)
Russia
1956
andesite
Great Sitkin
USA
1974
andesite
Mt. St. Helens
USA
1984
dacite
Mt. Pelée
Mar nique
1903
andesite
Lamington
Papua New
Guinea
1955
andesite
San aguito
Guatemala
1922
dacite
Lassen Peak
USA
~1000 BC?
dacite
Rangitukua
350
Pohaturoa
200
TED
Te Horoa
150
100
c
Fig. 4b. Lava domes used for parametriza on
of Peléan Domes by Blake (1990).
50
0
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
3
80%
2
60%
1
40%
1
20%
2
0
10
20
30
40
50
60
0%
70
80
90
rela ve frequency of steepest
slopes (degree)
5
RANGITUKUA
80%
60%
2
40%
1
20%
2
0
0%
20
30
40
50
60
rela ve eleva on (degree)
70
80
90
10
0
60%
2
40%
1
1
20%
0%
20
30
40
50
60
70
80
90
rela ve eleva on (degree)
100%
3
80%
10
120%
4
10
3
0
140%
1
100%
10
0
cumula ve
frequency (%)
rela ve eleva on (degree)
120%
rela ve frequency of steepest
slopes (degree)
100%
WAHANGA
4
5
5
MOKAUTEURE
80%
60%
2
40%
4
1
0
10
1
20
2
30
40
20%
3
50
0%
60
rela ve eleva on (degree)
70
80
90
3
10
0
80%
2
60%
1
40%
1
1
20
20%
1
30
40
0%
50
60
70
80
90
rela ve eleva on (degree)
100%
3
120%
100%
10
120%
1
TARAWERA EASTERN DOME
0
140%
4
140%
4
10
0
cumula ve
frequency (%)
rela ve frequency (%)
120%
100%
1.5
80%
1
60%
40%
0.5
2
120%
100%
1.5
80%
1
60%
40%
0.5
20%
0
20%
0%
10
20
30
40
50
slope angle (degree)
0
10
60
20
30
40
50
60
70
80
90
0%
100
rela ve eleva on (%)
Two morphometric classifica ons exist for lava domes. The first one was carried
out by B
(1990) based on field observa ons and laboratory experiments, and has
been dis nguished four types of lava domes (Upheaved plugs, Peléan domes, Low lava
domes and Coulees) by the height versus diameter ra o of the edifice. We have reviewed
those results and we found three important circumstances about the inves gated Peléan
domes; the volcanoes produced lava domes are located in volcanic arcs, all the domes
were piled up above a central vent of a composite volcano; and there was no lava dome
with rhyoli c chemical composi on. The other classifica on was based on improved
laboratory experiments, field observa ons and photographic analyses (F
G
,
1998). The classifica on schemes grouping the lava domes into four types (spiny, lobate,
platy, and axisymmetric) that eventually relates to erup on condi ons, the morphology
and the surface texture of the dome, and the thickness of the forming carapace. Their
study did not provide any quan fiable data about morphometrical parameters of the
dis nc ve classes. GIS-based morphometric characteriza on of 29 worldwide lava domes
was carried out by K
., (2013) with the aim of rela ve da ng of lava domes
using slope angles. Since K
. (2013) did not classify the examined domes, thus
rela ve ages are tenta ve as long as it is presumable, that condi ons during dome growth
are reflected on the slope angles and posi on of the steepest slopes too. The lava domes
within the TVZ have o en complex morphology, therefore do not fit into Blake`s
classifica on (Fig. 4). Thus we tried to find a new method for classifica on, namely we
examined the loca ons of the steepest slopes as a func on of rela ve eleva on (Fig. 6).
We believe, steepest slopes posi on reflects the differences of viscosity and magma yield
strength during emplacement, however it can be modified by erosion.
140%
TE HOROA
120%
4
3
25
120
#
100%
80%
#
a: volume
100
b: circularity
20
60%
2
80
40%
15
1
1
0
10
20
30
40
20%
1
50
60
rela ve eleva on (degree)
60
0%
70
80
90
10
0
10
40
Fig. 6. The steepest slopes (highest 200 values and addi onal 2 degree of slope percent from slope raster) as a func on of its rela ve height for the example domes (Fig. 1, 2, 3,
4 and 5). These histograms show mul ple modes, here we interpreted these modes due to erup ve processes, such as number of extrusion phases (numbers in yellow). In
contrast, the coulees (Tarawera Eastern Dome and Te Horoa) are characterized by only one lava erup on should show a con nuous values with low rela ve frequency of the
steepest heights. each peak belongs to one erup on, Steep slopes are also generated by faults and river incision a er the dome emplacement, thus the effected areas with
external factors should be eliminated.
20
5
0
0.25
0.5
0.75
1.0
1.25
1.5
1.75
35
#
20°
c: average slope
30
d: age of the domes
3
18°
35
16°
74
54
12°
25
7
69
14°
58
R² = 0 .1275
3
8°
0
50
100
150
200
250
300
350
400
(ky)
450 age500
20
15
10
5
0
55
10
10
15
20
15
20
slope (degrees)
0
0.2
10°
We examined the morphology of lava domes in the Taupo Volcanic Zone using DEMs and DEM derivates. We obtained various
morphometric parameters such as edifice volume, edifice height, average and maximum slope (Fig. 7). In comparison with other
studies (K
, 2013), our slope data show significantly higher values for maximum slopes (average max slope for
323 TVZ edifice is 43.1 degree). The height and diameter ra os do not fit to the regression lines specified by B
(1990), which can
be par ally explained by the complex emplacement history and post-emplacement burial and erosion of domes in the TVZ. The exis ng
lava dome classifica ons can be taken into account with doubt or cannot be used for comparison with real data. TVZ’s dome
morphologies show complex, some mes polygene c evolu on, which could be demonstrated by the defini on of the height posi ons
of steepest slopes (Fig. 6). The height distribu on clearly shows the number of dis nct lava erup ons or the changes in magma yield
strength during the emplacement. We presume, that the lava domes can be characterized by higher viscosity and lower yield strength,
the steepest slopeswill be located at the upper third of rela ve height due to the debris flows of the talus apron do not allow steeper
slope than 30-40 degrees (F
M
, 1990). Contrary, steepest slopes at the lower third of the rela ve height of the dome
indicate lower magma viscosity, and probably the rela vely fast-cooling, bri le part (talus) will provide the steepest slopes with similar
values like apron at viscous domes. Based on morphology, we can dis nguish the two extremes: ver cally growing and laterally growing
domes (coulees).
2.0
volume (km³)
CONCLUSIONS
25
25
30
30
35
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Fig. 7. Histograms of three morphometrical parameters of
the domes of the TVZ.
Volumes: For precise calcula ons it is essen al to obtain the borders and the total height
of the edifices. Using our raw data we could only provide minimum volumes or surficial
volume in many cases. 40% of the edifice volumes are less than 0.1 km³.
Dome circularity and orienta on: There are two significant peaks of the circularity
distribu on. The lower peak at 0.55 which is the manifesta on of the tectonically
influenced fissure orienta ons. The orienta ons of the dome elonga on are parallel with
the extensional axis of the TVZ (Fig 1a).
Average slopes: At this stage of the research we could only provide average slopes for all
the edifices, but the results clearly show the effects of faults in the distribu on. At the
inves ga on of individual edifices we eliminate these effects and others like river incision.
Age of the domes: First approxima on of the average ages from geological maps, allows
us to make a rough es ma on on the temporal distribu on of the domes. We found
5 periods, when the majority of the domes were formed: 0-25ka, 55-80ka, 150-170ka,
195-230ka and 320-340ka. Compared the average ages with average slopes we found a
slightly decreasing trend of slope angles with me.
REFERENCES
B
F
F
F
H
K
Y
View publication stats
140%
10
0
5
rela ve frequency of steepest
slopes (degree)
120%
140%
cumula ve
frequency (%)
POHATUROA
4
5
rela ve frequency of steepest
slopes (degree)
140%
rela ve frequency of steepest
slopes (degree)
rela ve frequency of steepest
slopes (degree)
5
cumula ve
frequency (%)
cumula ve
frequency (%)
edifice radius (m)
Fig. 5. Panoramic photos of three example
lava domes. a: Pohaturoa, b: Rangitukua,
c: Wahanga
cumula ve
frequency (%)
300
250
ELEVATION
140%
2
cumula ve
frequency (%)
edifice height (m)
450
160%
MORPHOMETRIC CLASSIFICATION OF LAVA DOMES
TED = Tarawera Eastern Dome
500
2.5
Fig. 3. Slope (orange) and eleva on (green) histograms of Pohaturoa lava dome (Fig. 5) with cumula ve frequency
(black and red lines). Both histograms show that distribu ons have two peaks due to two an ini al, low profile dome
overlaid by a more viscous dome (Fig. 6).
650
600
160%
SLOPE
a
Fig. 4. Radius versus height of lava domes (with chemical composi on) of the TVZ. The Peléean Domes values are
lower than the world average previously given by Blake (1990). The domes encompassed by the pink dashed line
area are probably buried, therefore their total heights are underes mated.
andesite
2.5
cumula ve
frequency (%)
Rangitukua
b
2 km
rela ve frequency (%)
vent
700
175°
Z
Slope angle
3° >
3° - 7°
7° - 13°
13° - 18°
18° - 23°
23° - 28°
28° - 34°
34° - 40°
40° <
Rotorua
Topographical margins of silicic
calderas (Oh. = Ohakuri)
Tarawera Eastern Dome
Wahanga
< 0.1 km³
0.1 km³ - 1.0 km³
1.0 km³ - 2.0 km³
> 2.0 km³
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, R.W. 1998, Morphology, erup on rates, and rheology of lava domes: Insights from laboratory model. Journal of Geophysical Research, 103/B1,
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