Hankow Reef, Bismarck Volcanic Arc, Papua New Guinea: Source of Yomba Island myth?

Abstract

Hankow Reef off the coast of Madang Province, New Guinea has been linked to a large eruption at a former island known as 'Yomba' by legends told by people living in the Madang province. However some doubts have been made about the accuracy of their comments. I present evidence for a low-lying volcanic island that may have existed at Hankow Reef and its links to the Yomba stories.

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International Journal of Scientific and Research Publications, Volume 4, Issue 12, December 2014 1
ISSN 2250-3153
www.ijsrp.org
Hankow Reef, Bismarck Volcanic Arc, Papua New
Guinea: Source of Yomba Island myth?
Lucas Wilson*
* 34 Fenwick Drive, Woodside, Bradford, UK
Abstract- Hankow Reef off the coast of Madang Province, New
Guinea has been linked to a large eruption at a former island
known as ‘Yomba’ by legends told by people living in the
Madang province. However some doubts have been made
about the accuracy of their comments. I present evidence for a
low-lying volcanic island that may have existed at Hankow
Reef and its links to the Yomba stories.
Index Terms- Yomba, oral tradition, volcanic collapse,
phreatomagmatic, Papua New Guinea
1. INTRODUCTION
Legends tell of an island that once sat between the Karkar
and Long islands called Yomba that erupted causing a ‘time
of darkness’ but then sunk beneath the waves. It has been a
matter of debate for decades as to whether the oral traditions of
the people of New Guinea are fanciful or contain elements of
truth. It is noteworthy to a make mention of Russell J Blong’s
work on Long Island which had a major volcanic eruption 400
years ago as his work using oral tradition helped date the
eruption of the volcano (Blong 1982). Much of this information
is based on work by Mary R. Mennis (1981, 2005) who
surveyed various settlements in the Madang area in the 1970’s.
2. REGIONAL SETTING
Hankow Reef, located between Karkar Island and Long Island
(see Figure 1), forms part of a chain of volcanoes called the
Bismarck Volcanic Arc that stretches for more than 1000 km. It
forms the submerged summit of a large underwater seamount,
the largest in the Bismarck Volcanic Arc. The Bismarck
Volcanic Arc is an intra-oceanic subduction system forming at
the southern margin of the Bismarck Sea (Woodhead et al
2009). Tectonics in the Eastern (New Britain) and Western
parts of the volcanic arc differ. The Western part of the
volcanic arc, where Hankow Reef is located, is forming
through the convergence of the Australian and South Bismarck
plates in a region of arc-continent collision (Woodhead et al
2009)
The Bismarck Volcanic Arc contains the majority of Papua
New Guinea’s active volcanoes (Siebert et al 2010) most of
which are located close to the coast of the island of New
Guinea. The danger from tsunamis and pyroclastic density
currents reaching the coast ofNew Guinea makes the area
inherently at risk from a volcanic disaster.
3. SUMMARY OF THE YOMBA ISLAND STORY
In a comprehensive survey by Mary R. Mennis (1981, 2005)
villagers in various settlements in the Madang area and
surrounding islands were asked to relate the story of Yomba
Island. The general story is as follows:
Before Long Island erupted (~ 400 years ago) there was an island
between Crown Island and Bagabag Island, people lived on the
island and made pots. Some accounts mention an earthquake
which may have signalled the onset of the eruption. At some
point, a vent on Yomba Island erupted, producing ash fall and
pumice fall, audible noises were also heard. People living on the
island escaped in canoes and on coconuts. A ‘time of darkness’
similar to the one reported at Long Island (Blong 1982) is also
frequently mentioned. Most accounts state that Yomba then
collapsed producing a tsunami. In the aftermath of the event,
Yomba Island was gone.
A. PREVIOUS INTERPRETATIONS OF EVENTS
Many of the stories related to Mennis (1981, 2005) tell of a large
catastrophic eruption destroying the island of Yomba, such as the
one that destroyed Krakatau in Indonesia in 1883 (Self &
Rampino 1981; Simkin & Fiske 1983). Mennis (2005) infers
from satellite data that there is a crater at Yomba Island; however
bathymetric data does not support this. Large eruptions often
leave large pyroclastic deposits (Self 2006) but none have been
found in the vicinity of Yomba Island (Mennis 2006).
Nunn & Pastorizo (2007) considered the Yomba Island stories to
relate to a flank collapse of the island. Collapses on volcanoes
can occur from weak or unstable flanks caused by over-
steepening, tectonic and fault related activity (McGuire 1996) or
through hydrothermal related processes (Reid et.al. 2001; Reid
2004). A collapse at steep-sided Ritter Island Volcano in the
Dampier strait between Umboi and New Britain Island in 1888
destroyed the island and left a large avalanche scar on its western
flank (Ray et.al. 2014). However, no large debris avalanches
were found near Hankow Reef during bathymetric surveys in the
area in 2004 (Mennis 2006). This suggests that the islands
geology was significantly different than has been described
previously.
4. A NEW INTERPRETATION
Many accounts collected state that people were living on the
island, this means they most likely had ready access to the sea.
Several descriptions of Yomba also note that it didn’t have one
central volcano but a few volcanic constructs, perhaps more akin
to a volcanic field rather than a typical oceanic stratovolcano. It
appears that Simon Day’s comments in Mennis (2006) appears
L

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the most likely option, Yomba Island was low-lying, built up of
small cones and pyroclastic fragments.
Figure 1. Map showing the location of Hankow Reef and surrounding islands.
A. SEQUENCE OF EVENTS
Yomba Island was most likely a low-lying island consisting of
a couple of tuff rings/cones, probably less than 200 m high,
sitting on a platform of pyroclastic deposits, much like the
island of Mundua in the Witu islands, north of New Britain
(Johnson & Blake 1972).
A violent eruption resulting from the interaction between water
and magma (phreatomagmatic) may have destroyed major
sections of the island leaving just a small platform of
unconsolidated pyroclastic deposits. These platforms are very
vulnerable to wave erosion as it consists of layers of weak
fragments (Scarth 1994). Several cones produced by the same
surtseyan activity thought to have formed Yomba have been
quickly eroded (e.g. Cole et.al. 2001).
B. CONSTRAINING THE DATE OF THE ERUPTION
Many stories told by those interviewed place the date of the
eruption just before the large eruption of Long Island (Mennis
2005). The eruption of Long Island took place sometime
between 1640 and 1670 (Blong 1982). This may mean that the
eruption of Yomba Island may have occurred only a few
decades prior to the eruption of Long Island.
5. CONCLUSIONS
In the late 15th century or early 16th century a minor eruption
took place on Yomba Island, causing islanders to flee the
volcano. During the course of the eruption violent
phreatomagmatic eruptions destroyed the volcanic structures on
the island with the rest of the island collapsing in a series of
small landslides, possibly producing small tsunamis, with the
rest of the deposits being eroded by wave action.
Hankow Reef has been identified as a potentially active
submarine volcano that is the source of the Yomba Island
myth. More detailed work needs to be done both geologically
and orally to determine fully the accuracy of the events
described. The events at Yomba Island 400-500 years ago
demonstrate the volcanic hazards of the Bismarck Volcanic
Arc, such as the generation of tsunamis, and more work should
be undertaken on the islands to better quantify the risk of a
major volcanic event in the region
ACKNOWLEDGMENT
I would like to thank John Corkett for his helpful reviews on
this manuscript.
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AUTHOR
Lucas Wilson. Lucashas been studying volcanoes in Papua New
Guinea for 3 years. His current research focuses on the volcanic
history of the Bismarck Volcanic Arc.
lucaswilson97@hotmail.co.uk