Technical Note
Landslides (2013) 10:665–672
DOI 10.1007/s10346-013-0414-4
Received: 18 February 2013
Accepted: 16 May 2013
Published online: 30 May 2013
© Springer-Verlag Berlin Heidelberg 2013
Hidetsugu Yoshida
Decrease of size of hummocks with downstream
distance in the rockslide-debris avalanche deposit
at Iriga volcano, Philippines: similarities with Japanese
avalanches
Abstract A morphometric investigation of the longitudinal distribution of hummocks at the southeastern foot of Iriga volcano in the
Philippines showed that hummock size decreases away from the
volcano. Aerial photographs and GIS analysis revealed that the size–
distance relationship can be expressed as the exponential function A
=α exp (−β D), where A is the area of a hummock and D is its distance
from the source. This relationship is the same as that observed
previously for freely spreading debris avalanches in Japan, including
two avalanches at Bandai volcano. This size–distance relationship
provides information about the physical characteristics of the event:
the α value shows a strong correlation with the volume of the collapsed mass of the volcanic edifice, and the β value shows a strong
correlation with the coefficient of friction of the debris avalanche.
Thus, morphometric analysis of hummocks created by a volcanic
avalanche illuminates both the physical properties of the volcanic
body and the mobility of the avalanche. For the Iriga debris avalanche,
the observed longitudinal hummock distribution is clearly a function
of the volume of the collapsed mass and the coefficient of friction of
the avalanche. The relationships so defined appear to be a geometric
effect related to the areal extent of freely spreading hummocky avalanche deposits, especially their longitudinal dimensions.
Keywords Hummocks . Sector collapse . Morphometry .
Size–distance relationship . Bandai volcano . Iriga volcano .
Philippines
Introduction
Huge collapses of volcanic bodies have produced rockslide-debris
avalanches (e.g., Siebert 1984; Ui et al. 2000) and caused serious
damage at the foot of volcanoes and on adjacent lowlands.
Tsunamis and long runout lahars can be caused by such volcanic
debris avalanches (Kienle et al. 1987; Lipman et al. 1988; Siebert 1992;
Vallance et al. 1995; Vallance and Scott 1997; Begét 2000; Capra and
Macias 2002; Ward 2002; Thouret 2005; Carrasco-Núñez et al. 2006;
ten Brink et al. 2006, 2009; Silver et al. 2009). Moreover, catastrophic
sector collapses are sometimes followed by magmatic eruptions
(Lipman and Mullineaux 1981). Over the last 400 years, four or five
catastrophic collapses per century have been recorded (Siebert 1992).
Volcanic sector collapses form conspicuous landforms, such as Ushaped amphitheaters in volcanic edifices with hummocky terrain
farther downstream (Crandell et al. 1984; Siebert 1984; Ui and Glicken
1986; Crandell 1989; Alloway et al. 2005; Paguican et al. 2012a, b).
Hummocks vary widely in composition and structure, and can
include coherent or fractured bedrock segments and finer materials
of varying sizes. They are transported and distributed along the
course of an avalanche (Ui 1983; Siebert 1984; Glicken 1996;
Paguican et al. 2012a). Debris avalanche deposits are typically identified by the presence of hummocky landforms formed by blocks of a
few meters to hundreds of meters in diameter (Geronimo-Catane
1994; Ui et al. 2000). As observed at Mt. St. Helens in 1980, some
hummocks can be composed of both debris avalanche blocks which
are unconsolidated or poorly consolidated pieces of the old mountain transported relatively intact and finer materials that form the
matrix (Glicken 1996). Shea and van Wyk de Vries (2008, 2010)
reported that failures of volcanic masses consisting of alternating
lava and tephra deposits produce such hummocks when brittle
domains separate from each other during collapse.
An aim of this study was to build on the work of Yoshida et al.
(2010, 2012) on the relationship between the topographic characteristics of hummocks and the physical characteristics of the debris avalanche that formed them, investigating new geomorphological insights
of debris avalanche hummocks based on geometric approaches.
Previous investigations of hummock morphology
Recently, hummock morphology is receiving more scientific attention
because of its utility as a kinematic indicator reflecting landslide evolution and its emplacement mechanism (Shea and van Wyk de Vries 2008;
Paguican et al. 2012b). Distribution and shape of hummocks are attributed to the basal shear of the landslide mass, together with the extension
regime during avalanche movement (Dufresne and Davies 2009), and
faulting generating by the mass spreading (Lagmay et al. 2000; Shea and
van Wyk de Vries 2008; Paguican et al. 2012b). In addition to results
based on the numerical modeling of debris avalanche propagation
(Sosio et al. 2012), analogue modeling clarifies the kinematics of
rockslides showing the depositional structures and surface morphology
of hummocky landform evolution (Shea and van Wyk de Vries 2008;
Andrade and van Wyk de Vries 2010; Paguican et al. 2012b).
This paper further investigates new geomorphological aspects of
hummocks, in which hummock distribution and morphology correlates with failure volume, providing a useful tool in the assessment of
older avalanches where the source area is no longer visible (Yoshida
et al. 2010, 2012). In Yoshida et al. (2010, 2012), investigations of the
size–distance relationships of hummocks formed by freely spreading
debris avalanches in Japan have shown that hummocks generally
decrease in size downstream, as has been described elsewhere in the
world (Crandell et al. 1984; Siebert 1984; Glicken 1996; Ui et al. 2000).
Furthermore, quantitative analyses by Yoshida et al. (2010, 2012) of
hummocks in rockslide-debris avalanches at seven volcanoes in
Japan revealed the following relationships.
The size–distance relation can be expressed by the exponential
function:
A ¼ αexpð−βDÞ;
ð1Þ
where A is the plan area of a hummock, D is its distance from the
source, and α and β are the intercept and slope coefficient,
Landslides 10 & (2013)
665
Technical Note
respectively, of the exponential function. The average size of collapsed masses initially created at the source area, given by the
value of intercept α, is strongly correlated with the total volume of
collapsed volcanic material.
The rate of decrease of hummock size with distance from the
source (slope coefficient β), shows a strong negative correlation
with the “mobility” (reciprocal of the equivalent coefficient of
friction) of the rockslide-debris avalanche. Thus, the rate of decrease in the size of hummocks decreases with increasing mobility,
such that for short avalanches, hummock size decreases rapidly,
whereas for long avalanches hummock size decreases slowly.
On the basis of these findings, Yoshida (2012) reconsidered the
volume of the 1888 sector collapse of Bandai volcano, northeast
Japan (Fig. 1), which was the defining event for what are now
known as Bandai-type eruptions (Moriya 1980, 1988; Siebert et al.
1987). There are conflicting views among researchers about the
volume of the 1888 collapse, which occurred on the northern flank
of the volcano (Fig. 2). Although the 1888 collapse volume of ca. 1.2
km3 (Sekiya and Kikuchi 1889) has been accepted by many researchers (e.g., 1–1.5 km3 by Nakamura and Glicken (1997)), the
value of the intercept coefficient of the size–distance function of
Yoshida et al. (2012) implied a collapse volume of only ca. 0.6 km3.
Yonechi et al. (1989) and Yonechi (2006) proposed a collapse
volume of ca. 0.49 km3 by reconstructing the former volcanic
edifice from the detailed topographic analysis by Yonechi (1988),
where some dissected valleys have been assumed on the edifice.
Yoshida (2012), therefore, concluded that this estimate (0.49 km3)
is the most reliable of previous estimates, although another topographic reconstruction and volume estimation by Mizukoshi et al.
(1994) and Mizukoshi and Murakami (1997) proposed a significantly smaller value as 0.14±0.11 km3.
Fig. 1 Locations of Iriga volcano (Philippines) and Bandai volcano (Japan). The
underlying image is based on digital elevation models from the GTOPO30 data
666
Landslides 10 & (2013)
Fig. 2 Two large collapse scars on Bandai volcano. Dashed lines indicate the
rims of horseshoe calderas. Black arrows indicate the direction of rockslide-debris
avalanches that resulted from two sector collapses. The map image is based on
Digital Map 25,000 and 10-m mesh digital elevation data, both from the
Geographical Survey Institute of Japan
Yoshida (2013) also examined the collapse volume during a Late
Pleistocene event at Bandai volcano (Fig. 2), called the Okinajima
collapse, which was larger than the 1888 event. The collapse volume is not likely to exceed ca. 3.2 km3 and maybe ca. 2.5 km3,
based on a simple calculation of scar geometry. That is, scar size is
approximately five times larger than that of the 1888 collapse,
which suggests a collapse volume of the Okinajima event of ca.
2.5 km3, in comparison to ca. 0.5 km3 of the 1888 event. In addition
to this rough estimation, Yoshida (2013) used the size–distance
distribution of debris avalanche hummocks by Yoshida et al.
(2012) to calculate an expected collapse volume of ca. 2.0 km3
(1.96 km3), concluding that the volume is significantly smaller
than previous estimates of 4 km 3 or more (Inokuchi 1988;
Yamamoto and Suto 1996), and almost as large as that of Mount
St. Helens in 1980 (Voight et al. 1983; Glicken 1996).
Aim of this study
The primary aim of this study was to determine whether the
abovementioned size–distance relationships of hummocks in freely spreading debris avalanches in Japan are applicable to many
other volcanoes. To answer this question, a massive debris avalanche was examined that occurred at the Iriga volcano in the
Philippines in the historical age (Aguila et al. 1986; Belousova et al.
2011) (Fig. 1). This event is the best-known catastrophic collapse in
the Philippines and was chosen because it produced a typical
widespread debris avalanche, numerous hummocks are preserved,
and the conical shape of the pre-collapse volcano can be inferred
from the remnant topography because the avalanche source area is
preserved, unlike at many other volcanoes (Fig. 3), thus allowing a
reasonable estimate of the volume of the collapse. The similarity of
the geological and tectonic settings of Japan and the Philippines
was also a strong motivation for this choice.
of the lower plain, forming horsts and grabens within the
hummocks.
Although the present summit of Iriga is ca. 1,200 m a.s.l. (above sea
level), its pre-collapse maximum height would have been ca. 1,300 m
a.s.l. (Fig. 4), assuming that the pre-collapse volcano was a symmetrical cone with a summit crater with a diameter of ca. 500 m or more
(Aguila et al. 1986). The immediate surroundings of the volcano are
typically flat (ca. 50 m a.s.l.). Although the distal part was impeded by
the flank of Malinao volcano and may have caused deflection of the
avalanche to the south and east, as seen on the map of Paguican et al.
(2012a, b), such constraints are minor in the following topographic
analysis of the hummocks whose number is relatively low in the distal
area. The dimensions of the avalanche deposit, namely, the fall height
(H=1.25 km) and runout distance (L=11 km), indicate a coefficient of
friction (H/L) of 0.114.
As mentioned above, numerous hummocks on the depositional
surface can still be easily recognized. Thus they allow comparison
of the size–distance relationship of hummocks in the debris avalanche deposit at Iriga volcano with those of Japanese volcanoes
reported by Yoshida et al. (2012).
Fig. 3 Shaded relief map of the area around Iriga volcano showing the distribution
of hummocks on the southeastern flank of the volcano, as interpreted from aerial
photographs. White dashed lines are elevation contours (meters a.s.l. at 100-m
intervals; ≥ 200-m). The southeastern sector of the volcano clearly shows the Ushaped scar (heavy black line) of the catastrophic collapse. Solid lines labeled
AB and CD mark locations of two topographic profiles shown in Fig. 4. The
underlying image is based on digital elevation models from the ASTER Global Digital
Elevation Model produced by the Earth Remote Sensing Data Analysis Center
Sector collapse and associated debris avalanche at Iriga volcano
Iriga volcano is an active volcano in central Luzon Island in the
Philippines, and forms part of the Bicol volcanic chain on the
western edge of the Pacific Ocean (Fig. 1). According to Aguila et
al. (1986), Iriga lavas range from olivine–pyroxene basalts to pyroxene, pyroxene–hornblende, and hornblende andesites. A massive
rockslide-debris avalanche occurred at Iriga volcano in the historical
period; the collapse was possibly caused by a relatively small phreatic
explosion (Aguila et al. 1986; Fig. 3). Recent work implies that this
younger collapse event occurred about 1,500 years BP on the basis of
dating of the basal sediments in a small lake on the debris avalanche
depositional surface (Belousova et al. 2011). More recently, another
older volcanic debris avalanche deposit has been identified from
Iriga volcano, although the associated collapse scar is no longer
visible (Paguican et al. 2012a).
Topographic evidence for the rockslide-debris avalanche about
1,500 years BP includes a southeast opening U-shaped amphitheater within the edifice of the volcano and a thick avalanche deposit
with a hummocky surface (Fig. 3). The amphitheater is just over 2
km wide by 3 km long, yielding a missing sector volume of ca. 1.5
km3 (Aguila et al. 1986). The debris avalanche traveled 11 km
downslope to the southeast to cover an area of ca. 70 km2
(Aguila et al. 1986) (Fig. 3). Much of the northern extent of the
debris avalanche lies beneath Lake Buhi (Aguila et al. 1986;
Paguican et al. 2012a). According to Paguican et al. (2012a, b),
the collapse has been attributed to a major strike-slip fault under
the volcano, and the debris avalanche spread out over a wide area
Data and method of analysis
The longitudinal distribution of hummocks on the rockslide-debris
avalanche was examined by the methods of Yoshida et al. (2010,
2012). Individual hummock sizes and locations were measured on
the basis of stereographic analysis of aerial photographs using the
Geographical Information System (GIS). The basal area of a hummock (plan view, uncorrected for ground slope) is affected relatively
little by topographic changes after a rockslide-debris avalanche and
can thus be taken to represent hummock size (Yoshida et al. 2012).
The hummocks of the Iriga debris avalanche are particularly fresh
because the sector collapse was recent in geological timescale.
The distance of each hummock from the landslide source
(assumed to be the pre-collapse summit) was calculated as the
length of a horizontal line from the landslide source to the centroid of the hummock (Yoshida et al. 2012). The position of the
pre-collapse summit of Iriga volcano was determined to be within
the U-shaped amphitheater, taking into account the assumed almost perfect conical shape of the volcanic edifice.
Data were acquired by the following procedure. First, the outlines of
hummocks were traced onto aerial photographs (scale, about 1:36,000)
taken in 1988 by the National Mapping and Resource Information
Authority of the Philippines. Scanned digital images of the interpreted
photographs were then converted to digital orthophotographs, rectified,
and referenced to the ASTER GDEM digital elevation models (DEMs)
of the Japanese Earth Remote Sensing Data Analysis Center. Production
of orthophotographs is normally expensive, requiring professional skills
and the use of advanced GIS software such as TNTmips (MicroImages,
Inc.). By using existing DEMs in this study, simplified digital
orthophotographs were produced on a personal computer with sufficient accuracy for geospatial analysis (MicroImages 1997). The outlines
of hummocks were digitized and input to a GIS to calculate hummock
areas (sizes) and distances from source. Finally, regression analysis of
the size–distance relationship of the hummocks was undertaken with
Microsoft Excel.
Longitudinal distribution of hummocks
In this study, 303 hummocks were identified from aerial photographs (Fig. 3). Generally, the larger hummocks (ca. 300,000 m2 in
Landslides 10 & (2013)
667
Technical Note
b
a
d
c
Fig. 4 Topographic profiles across Iriga volcano. The vertical axes are exaggerated twice
maximum basal area, 500–1,000 m basal diameter) are concentrated in the proximal region of the avalanche deposit (Figs. 3 and 5).
A general decrease in size was observed toward the distal and
marginal areas, as was the case for the Japanese debris avalanches
studied by Yoshida et al. (2010, 2012). However, wide ranges of
hummock size were observed throughout the longitudinal extent
of the deposit. On the basis of a semi-log graph of the relationship
between hummock area (size) and distance from source, an exponential function was appropriate for statistical analysis of the
longitudinal distribution of hummock size (Fig. 5b).
Regression analysis of decrease of hummock size with distance
from source
The methods of Yoshida et al. (2010, 2012) were applied to examine
the relationship of size to distance from the source of hummocks
of the Iriga rockslide-debris avalanche. First, the landslide course
was divided into 500-m intervals and average hummock sizes and
distances from the source were calculated for each interval.
Averages were also calculated in overlapping 500-m intervals
stepping downslope by 200 m for successive average calculations.
These two datasets were collectively used in the following analysis.
Following the approach of Yoshida et al. (2010, 2012), data from the
uppermost (most proximal) interval and the two lowermost (most
distal) intervals were excluded from the regression analysis because of the small number of hummocks within those intervals.
668
Landslides 10 & (2013)
A plot of average hummock size versus average distance from
the source for the Iriga debris avalanche (Fig. 6) shows an exponential decrease in size away from the source, as expressed by Eq.
(1) with α=184,254.4 and β=0.000359. Analyses of Japanese rockdebris avalanches by Yoshida et al. (2012) gave different values of α
and β for each of the seven avalanches they studied. In each case,
the intercept of the regression expression, α, indicated the average
size of the initial mass at 0 km distance, thus representing the
collapse volume. The slope of the regression expressions, β, indicated the rate of decrease of hummock size with distance from the
source, reflecting the mobility of the debris avalanche. In the
following sections, the above relationships are investigated for
the rockslide-debris avalanche at the Iriga volcano.
Relationship of initial hummock size to collapse volume at Iriga
When a volcanic mass collapses, it breaks up into numerous
blocks during its downslope movement (Voight et al. 1983;
Takarada et al. 1999; Clavero et al. 2002; Shea and van Wyk de
Vries 2008; Thompson et al. 2010; Paguican et al. 2012b). The single
original mass (the edifice) breaks up into several smaller blocks at
the initiation of collapse and the number of blocks increases
geometrically as the avalanche proceeds downslope. Because surviving hummocks are necessarily rock masses of considerable
cohesion, the extrapolated hummock size at 0 km distance is
considered to represent the size of the block created at the source
Fig. 5 Distribution of the basal area of
hummocks with distance from the
source for hummocks identified on the
southeastern flank of Iriga volcano. a
Normal plot and b Semi-logarithmic
plot
a
b
area during the initial stage of collapse, that is, the collapse volume
(Yoshida et al. 2012).
Aguila et al. (1986) previously estimated the collapse volume of
the sector collapse at Iriga volcano to be 1.5 km3. Although they did
not describe the calculation of this volume in detail, it is reliable
Fig. 6 Semi-logarithmic plot of
relationship of the basal area of
hummocks to distance from source for
the Iriga debris avalanche. The heavy
black line is the regression line
and is used in this study (Table 1). As already noted, estimates of
the collapse volumes of the 1888 (Sekiya and Kikuchi 1889) and
Pleistocene events (Inokuchi 1988; Yamamoto and Suto 1996) at
Bandai volcano were too high (Yoshida 2012, 2013). Recent considerations of the size–distance relationships of hummocks and the
A = 184254.4 exp (–0.000359 D)
(R = –0.882)
Landslides 10 & (2013)
669
Technical Note
Table 1 Comparison of collapse scar of Iriga volcano (Philippines) with scars of two collapse events at the Bandai volcano (Japan)
Volcano
DAD
Scar
area
(km2)
Area ratio
Height
ratio
(Iriga: 1.0)
Volume
ratio
(Iriga: 1.0)
Collapse
volume
(km3)
References
(Iriga: 1.0)
Relative
height
(km)
Iriga
Younger DAD (Buhi)
6.0–6.5
1.0
1.05
1.0
1.0
1.5
Aguila et al. (1986),
Paguican et al.
(2012a)
Bandai
1888 A.D.
2.6–3.0
0.40–0.50
0.75
0.71
0.29–0.36
0.49
Yonechi (1988),
Yonechi et al.
(1989)
Pleistocene Age
(Okinajima)
8.0–8.5
1.23–1.42
1.2
1.14
1.41–1.62
2.0–2.5
Yoshida (2013)
dimensions of the U-shaped amphitheaters strongly indicate that
the collapse volumes were about half those previously reported
(Yonechi et al. 1989; Yonechi 2006; Yoshida 2012, 2013). Comparing
a
700
Japanese 7 cases (Yoshida et al. 2012)
V ( 107 m3
Fig. 7 a Relationship of the collapse
volume (V) to coefficient α, the
intercept coefficient of the empirical
function of Eq. (1) for seven Japanese
rockslide-debris avalanches, two
Bandai avalanches, and the Iriga
volcanic avalanche (this study).
b Relationship of the equivalent
coefficient of friction (H/L) to
coefficient β, the slope coefficient of
the empirical function of Eq. (1) for
seven Japanese rockslide-debris
avalanches, two Bandai avalanches,
and the Iriga avalanche (this study).
Regression lines (solid black; Eqs.
(2) and (3)) are from seven Japanese
cases by Yoshida et al. (2012)
sizes of the collapse scar at Iriga volcano with those at Bandai
volcano (Table 1), the volume of material that collapsed, causing
the Iriga scar, must have been about three times the volume of the
600
Bandai, 1888
(Yoshida 2012; V = 0.492 km3 by Yonechi et al. 1989)
500
Bandai, Okinajima (Yoshida 2013; V = 2.5 km3
from the scar dimension as maximum)
400
Iriga (this study)
300
200
100
0
α
b
0.200
Japanese 7 cases (Yoshida et al. 2012)
Bandai, 1888 (Yoshida 2012)
Bandai, Okinajima (Yoshida 2013)
Iriga (this study)
H/L
0.150
0.100
0.050
β
670
Landslides 10 & (2013)
1888 Bandai event (3×0.49=1.47 km3) or about the same as the
estimated collapse volume at Iriga of ca. 1.5 km3 (Table 1).
For the seven Japanese avalanches studied by Yoshida et al.
(2012), the values of α obtained from Eq. (1) correlate strongly with
collapse volume (Fig. 7a), indicating that the initial block size was
controlled by the volume of the collapsing mass. Two Bandai
avalanches (Yoshida 2012, 2013) show the same relationship.
Furthermore, initial block size is influenced by scar geometry
and the normal faults that form during collapse (Andrade and
van Wyk de Vries 2010). For the seven Japanese examples investigated by Yoshida et al. (2012), the relation between α and V is
V ¼ 0:000601α þ 30:325666;
ð2Þ
with a correlation coefficient of 0.994 (Fig. 7a). The data from the
Iriga avalanche show good concordance with the empirical relationship of the Japanese examples including two Bandai avalanches (Fig. 7a). When the value of α (184254.4) is substituted
into Eq. (2), we obtain a collapse volume of 1.41 km3, which agrees
reasonably well with the empirically derived volume of 1.5 km3 of
Aguila et al. (1986).
Relationship of the rate of decrease of hummock size to mobility
of the Iriga debris avalanche
For the Iriga debris avalanche, there are fewer large hummocks as
distance from the source increases (Figs. 5 and 6), similar to the
seven Japanese avalanches studied by Yoshida et al. (2012). It is
interpreted that this phenomenon to reflect the breakup of hummocks due mainly to avalanche spreading with an extensional
regime. Analogue modeling and numerical modeling support this
simple scenario (Andrade and van Wyk de Vries 2010; Paguican et
al. 2012b; Sosio et al. 2012). According to Yoshida et al. (2012), the
rate of decrease of hummock size is clearly different for each of the
seven debris avalanches that they studied, and the coefficient β of
the regression function of Eq. (1), which is an indicator of the rate
of decrease of size of hummocks, is also different for each of those
avalanches. Yoshida et al. (2012) observed the following relationship between β and the mobility of these avalanches:
.
H L ¼ 130:051003β þ 0:069545;
ð3Þ
with a correlation coefficient of 0.939 (Fig. 7b), where H is the
elevation difference between the point of maximum runout and the
pre-collapse summit, and L is the maximum runout distance.
Therefore, H/L, which is equivalent to the coefficient of friction of
the debris avalanche, is the height-to-length ratio representing the
mobility of mass movement. By substituting the β value of the Iriga
avalanche into Eq. (3), we obtain a value of 0.116 for H/L, which is
almost the same as the value (0.114) derived from the spatial dimensions of the avalanche deposit as described above (Fig. 7b).
Furthermore, this value of H/L lies within the range (0.05–0.20)
reported for volcanic debris avalanches by Siebert et al. (1987).
Summary and conclusions
When a volcano undergoes catastrophic sector collapse, brittle domains separate from each other during the initial stage of collapse
and are then transported and distributed along the course of the
debris avalanche, forming hummocks. Morphometric analyses of the
longitudinal distribution of hummocks of the southeastern rock-
debris avalanche deposits of Iriga volcano in the Philippines, using
aerial photographs and GIS techniques, indicate that hummocks
decrease in size with increasing downstream distance, and the
size–distance relationship can be expressed by an exponential function. Yoshida et al. (2012) demonstrated that initial hummock size,
estimated by extrapolation of this type of regression formula, is
strongly correlated with the collapse volume of the volcanic edifice,
and that the rate of decrease of hummock size with distance from
source shows a strong negative correlation with mobility for the
seven Japanese debris avalanches they studied. That is, although it
is often difficult to estimate the volume of collapsed mass and thus
reconstruct the pre-collapse landform, the size–distance relation of
hummocks in even parts of the avalanche can help to reveal the
magnitude of a volcanic sector collapse. Application of this method
to the collapse and debris avalanche at Iriga volcano suggested a
collapse volume of 1.5 km3 and a coefficient of friction of 0.114 for the
avalanche. The relationship of hummock size to distance from
source for the Iriga debris avalanche is comparable, along with the
two Bandai cases (Yoshida 2012, 2013), to the empirical relationships
obtained for seven freely spreading debris avalanches in Japan
(Yoshida et al. 2012). The relationships so defined appear to be a
geometric effect related to the areal extent of hummocky avalanche
deposits, especially their longitudinal dimensions.
Acknowledgments
I acknowledge the following colleagues at PHIVOLCS for their invaluable help with data collection: Dr. Renato U. Solidum, Dr.
Bartolome C. Bautista, Dr. Maria Leonila P. Bautista, Perla J. Delos
Reyes, Maria Lynn P. Melosantos, and Analyn Aquino. I am also
grateful to Emeritus Prof. N. Abeki and Emeritus Prof. I. Matsuda of
Kanto Gakuin University for their help and support in my communications with PHIVOLCS. My thanks to Lee Siebert for his critical
review to benefit the paper, and Prof. Toshihiko Sugai, and Emeritus
Prof. Hiroo Ohmori of the University of Tokyo for their constructive
comments and suggestions. This research was funded by a grant-inaid from the Ministry of Education, Culture, Sports, Science, and
Technology of the Japanese government (no. 22700858) and an
annual grant-in-aid for scientific research from Meiji University.
References
Aguila LG, Newhall CG, Miller CD, Listanco EL (1986) Reconnaissance geology of a large
debris avalanche from Iriga volcano, Philippines. Philipp J Volcanol 3:54–72
Alloway B, McComb P, Neall V, Vucetich C, Gibb J, Sherburn S, Stirling M (2005)
Stratigraphy, age, and correlation of voluminous debris-avalanche events from an
ancestral Egmont Volcano: Implications for coastal plain construction and regional
hazard assessment. J R Soc N Z 35:229–267
Andrade S, van Wyk de Vries B (2010) Structural analysis of the early stages of catastrophic
stratovolcano flank-collapse using analogue models. Bull Volcanol 72:771–789
Begét JE (2000) Volcanic tsunamis. In: Sigurdsson H, Houghton BF, McNutt SR, Rymer H,
Stix J (eds) Encyclopedia of volcanoes. Academic Press, San Diego, pp 1005–1013
Belousova A, Belousova M, Listanco E (2011) The youngest eruptions and edifice collapse
of Iriga volcano, Philippines. IUGG General Assembly, Melbourne
Capra L, Macias JL (2002) The cohesive Naranjo debris-flow deposit (10 km3): a dam
breakout flow derived from the Pleistocene debris-avalanche deposit of Nevado de
Colima volcano (Mexico). J Volcanol Geotherm Res 117:213–235
Carrasco-Núñez G, Díaz-Castellón R, Siebert L, Hubbard B, Sheridan MF, Rodríguez SR
(2006) Multiple edifice-collapse events in the Eastern Mexican Volcanic Belt: the role
of sloping substrate and implications for hazard assessment. J Volcanol Geotherm Res
158:151–176
Landslides 10 & (2013)
671
Technical Note
Clavero JE, Sparks RSJ, Huppert HE (2002) Geological constraints on the emplacement
mechanism of the Parinacota debris avalanche, northern Chile. Bull Volcanol 64:40–
54
Crandell DR (1989) Gigantic debris avalanche of Pleistocene age from ancestral Mount
Shasta volcano, California, and debris-avalanche hazard zonation. Bull US Geol Surv
1861:32
Crandell DR, Miller CD, Glicken HX, Christiansen RL, Newhall CG (1984) Catastrophic debris
avalanche from ancestral Mount Shasta volcano, California. Geology 12:143–146
Dufresne A, Davies TR (2009) Longitudinal ridges in mass movement deposits.
Geomorphology 105:171–181
Geronimo-Catane S (1994) Mode of emplacement of two debris-avalanche deposits at
Banahao volcano, southern Luzon, Philippines. Bull Volcanol Soc Jpn 39:113–127
Glicken H (1996) Rockslide-debris avalanche of May 18, 1980, Mount St. Helens volcano,
Washington. USGS Open-file Report 96–677:1–90
Inokuchi T (1988) Gigantic landslides and debris avalanches on volcanoes in Japan—case
studies on Bandai, Chokai and Iwate volcanoes. Rep Nat Res Cent Disas Preve 41:163–
275 (in Japanese with English abstract)
Kienle J, Kowalik Z, Murty TS (1987) Tsunamis generated by eruption from Mt. St.
Augustine volcano, Alaska. Science 236:1442–1447
Lagmay AMF, van Wyk de Vries B, Kerle N, Pyle DM (2000) Volcano instability induced by
strike-slip faulting. Bull Volcanol 62:331–346
Lipman PW, Mullineaux DR (eds) (1981) The 1980 eruptions of Mount St. Helens,
Washington. USGS Professional Paper 1250, pp 844
Lipman PW, Normark WR, Moore JG, Wilson JBG, Gutmacher CE (1988) The giant
submarine Alika debris slide, Mauna Loa, Hawaii. J Geophys Res 89:4279–4299
MicroImages (1997) Reference Manual for TNTmips. http://www.microimages.com
Mizukoshi H, Murakami H (1997) Quantitative estimation of the Kobandai collapse
volume using a pre-collapse map “Der Bandaisan”. Trans JGU 18:21–36 (in
Japanese with English abstract)
Mizukoshi H, Hoshino M, Yonechi F, Nakamura Y, Tsuzawa M, Koarai M, Ohya T, Kitahara
T, Takeda R (1994) Former terrain model of Bandai volcano before the 1888 collapse.
Earth Planetary Science and Related Society, summary of 1994 annual meeting, 357
Moriya I (1980) “Bandaian eruption” and landforms associated with it. In:
Executive Committee for memory of retirement of Prof. K. Nishimura (ed)
Collection of articles in memory of retirement of Prof. K. Nishimura from
Tohoku University, Faculty of Science, Tohoku University, Sendai, pp 214–219
(in Japanese with English abstract)
Moriya I (1988) Geomorphological development of Bandai volcano. J Geogr 97:293–300
(in Japanese)
Nakamura Y, Glicken H (1997) Debris avalanche deposits of the 1888 eruption, Bandai
volcano. In: Research Group for the Origin of Debris Avalanche Research (ed) Bandai
Volcano—recent progress on hazard prevention. Nat Res Inst Earth Sci Disas Prev,
Tsukuba, Japan, pp 135–147
Paguican EMR, van Wyk de Vries B, Lagmay AMF (2012a) Volcano-tectonic controls and
emplacement kinematics of the Iriga debris avalanches (Philippines). Bull Volcanol
74:2067–2081
Paguican EMR, van Wyk de Vries B, Lagmay AMF (2012b) Hummocks: how they form and how
they evolve in rockslide-debris avalanches. Landslides. doi:10.1007/s10346-012-0368-y
Sekiya S, Kikuchi Y (1889) The eruption of Bandaisan. J Coll Sci Imp Univ Jpn 3:91–172
Shea T, van Wyk de Vries B (2008) Structural analysis and analogue modeling of the
kinematics and dynamics of rockslide avalanches. Geosphere 4:657–686
Shea T, van Wyk de Vries B (2010) Collapsing volcanoes: the sleeping giants’ threat. Geol
Today 26:72–77
Siebert L (1984) Large volcanic debris avalanches: characteristics of source areas, deposits, and associated eruptions. J Volcanol Geotherm Res 22:163–197
Siebert L (1992) Threats from debris avalanches. Nature 356:658–659
Siebert L, Glicken H, Ui T (1987) Volcanic hazards from Bezymianny- and Bandai-type
eruptions. Bull Volcanol 49:435–459
672
Landslides 10 & (2013)
Silver E, Day S, Ward S, Hoffmann G, Llanes P, Driscoll N, Appelgate B, Saunders S (2009)
Volcano collapse and tsunami generation in the Bismarck Volcanic Arc, Papua New
Guinea. J Volcanol Geotherm Res 186:210–222
Sosio R, Crosta GB, Hungr O (2012) Numerical modeling of debris avalanche propagation
from collapse of volcanic edifices. Landslides 9:315–334
Takarada S, Ui T, Yamamoto Y (1999) Depositional features and transportation mechanism of
valley-filling Iwasegawa and Kaida debris avalanches, Japan. Bull Volcanol 60:508–522
ten Brink US, Geist EL, Andrews BD (2006) Size distribution of submarine landslides and
its implication to tsunami hazard in Puerto Rico. Geophys Res Lett 33, L11307.
doi:10.1029/2006GL026125
ten Brink US, Barkan R, Andrews BD, Chaytor JD (2009) Size distributions and failure
initiation of submarine and subaerial landslides. Earth Planet Sci Lett 287:31–42
Thompson N, Bennett MR, Petford N (2010) Development of characteristic volcanic debris
avalanche deposit structures: new insight from distinct element simulations. J
Volcanol Geotherm Res 192:191–200
Thouret J-C (2005) The stratigraphy, depositional processes, and environment of the late
Pleistocene Polallie-period deposits at Mount Hood volcano, Oregon, USA.
Geomorphology 70:12–32
Ui T (1983) Volcanic dry avalanche deposits—identification and comparison with
nonvolcanic debris stream deposits. J Volcanol Geotherm Res 18:135–150
Ui T, Glicken H (1986) Internal structural variations in a debris-avalanche deposit from
ancestral Mount Shasta, California, USA. Bull Volcanol 48:189–194
Ui T, Takarada S, Yoshimoto M (2000) Debris avalanches. In: Sigurdsson H, Houghton BF,
McNutt SR, Rymer H, Stix J (eds) Encyclopedia of volcanoes. Academic Press, San
Diego, pp 617–626
Vallance JW, Scott KM (1997) The Osceola mudflow from Mount Rainier: sedimentology
and hazard implications of a huge clay-rich debris flow. GSA Bull 109:143–163
Vallance JW, Siebert L, Rose WI, Girón JR, Banks NG (1995) Edifice collapse and related
hazards in Guatemala. J Volcanol Geotherm Res 66:337–355
Voight B, Janda RJ, Glicken H, Douglass PM (1983) Nature and mechanism of the Mount
St. Helens rockslide-avalanche of May 1980. Geotechnique 33:243–273
Ward SN (2002) Slip-sliding away. Nature 415:973–974
Yamamoto T, Suto S (1996) Eruptive history of Bandai volcano, NE Japan, based on
tephrastratigraphy. Bull Geol Surv Jpn 47:335–359 (in Japanese with English abstract)
Yonechi F (1988) Aspect of the landscape of Bandai-san before the eruption. J Geogra
97:317–325 (in Japanese)
Yonechi F (2006) Bandaisan Bakuhatsu (The eruption of Bandai volcano). Kokon-Shoin,
Tokyo, p 201 (in Japanese)
Yonechi F, Chiba N, Ozawa A, Ishimaru S (1989) Large scale slope failure caused by Mt. Bandai's
eruption in 1888. Abst 27th annual meeting Jpn Landslide Soc, 20–21 (in Japanese)
Yoshida H (2012) Evaluation of sector-collapse volume of Bandai volcano in 1888, Japan,
in terms of the size-distance distribution pattern of debris avalanche hummocks.
Trans JGU 33:45–60 (in Japanese with English abstract)
Yoshida H (2013) Reexamination of volume loss due to the catastrophic sector-collapse
causing the Okinajima debris avalanche of Bandai volcano, Japan. Trans JGU 34:1–19
(in Japanese with English abstract)
Yoshida H, Sugai T, Ohmori H (2010) Longitudinal downsizing of hummocks by the
freely-spreading volcanic debris avalanches in Japan. Quat Res (Tokyo) 49:55–67
Yoshida H, Sugai T, Ohmori H (2012) Size-distance relationship for hummocks on
volcanic rockslide-debris avalanche deposits in Japan. Geomorphology 136:76–87
H. Yoshida ())
Department of Geography, School of Arts and Letters,
Meiji University,
Tokyo, Japan
e-mail: yoshidah@meiji.ac.jp