Volcanic formations Mt. Balbi

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2.2 Physical Characteristics of the Rotokas Area

The “Rotokas area,” as used in this writeup, is located within the Kieta Sub-District Aita Census Division and Rotokas Census Division from Inus Plantation at the northern boundary to Tenekau Bay and Plantation at the southern boundary. From the west coast of the island to the east coast in this central area of the island, Rotokas speakers are found. On the west coast, the area is included in the Keriaka Census Division of Buka Passage Sub-District.

2.2.1 Volcanic formations Mt. Balbi

The Balbi Volcanics occupy an area of over 200 square miles and consist of agglomerate, tuff, ash, andesite lava, and derived fan deposits. The volcanic rocks were erupted from the dormant Balbi volcano, a complex stratovolcano rising to a height of 8502 feet [2593 meters] at the southeastern end of the Emperor Range, northwest Bougainville…The maximum thickness of the formation is probably greater than 6000 feet [1830 meters]. The Balbi Volcanics are considered to range in age from late Pleistocene to Recent…The last eruption from Balbi volcano is reputed to have occurred some time between 1800 and 1850 and is said to have killed a number of people. The present activity of the volcano is confined to solfataras in the summit area and in the northeastern amphitheatre, and to hot springs on the flanks. The volcano is considered potentially active, and nuees ardentes are likely to be emitted during its next eruption… Plate 6. a Vertical air-photograph mosaic of Balbi volcano. R.A.F. photograph; sortie 543A418. Nos. 11 12. 24 June 1963. 30 b Interpretation of mosaic. Map 3 – Balbi Volcanics [There is a story told by the Rotokas that could very well be related to the last eruption of Balbi Volcano. The skies were darkened for three days while the people sacrificed black pigs. Finally, after the third day, a white pig was sacrificed and the skies cleared. No one remembers now if there were many deaths or much destruction.] Map 4 – Fold-out sketch of Balbi Panorama Balbi Volcano is made up of a number of coalescing volcanic cones aligned roughly north-west. The flanks of the volcano are covered by dense tropical rain forest up to 4000 feet [1220 meters], bamboo and moss forest between 4000 feet [1220 meters] and 7500 feet [2290 meters], and alpine rush above 7500 feet Blake, et al. 1967:21, 24. 32 In May of 1974, during one of four trips to the top of Balbi volcano from Togarao village, I logged the following approximate travel times: Departure Togarao Village 10:15 a.m. [May 11] Arrival Rest Camp 3:15 p.m. Departure Rest Camp 6 a.m. [May 12] Pass Alpine rush flag 8 a.m. Arrival rim of Crater B 9 a.m. Departure area of Crater B and C 10:30 a.m. Pass Alpine rush flag 11 a.m. Arrival Rest Camp 12:30 p.m. Departure Rest Camp 1:40 p.m. Arrival Togarao Village 4:40 p.m. A significant Rotokas story is told of a Keriaka man climbing the west flanks of Mt. Balbi called Viasiito in Keriaka at the same time a Rotokas man was climbing from the eastern, Rotokas side, where the mountain is called Tutue. The two men met at the top and established a meeting place. They decided to exchange articles produced by their respective places at a later date. On the designated day, the Rotokas man climbed to the spot marked for the return meeting. This place can be identified to this day at the top of the volcanic complex. He had with him the bows and arrows which were to be exchanged. He then proceeded to wait for an unusually long period of time. Finally, looking towards the Keriaka side, he spotted smoke coming from the area from which he knew the man was to come. He concluded that something was amiss and that the man’s spirit was angry. He imagined that the spirit was chasing him, so he hastily left the spot and came crashing down the mountain back to the safety of a Rotokas village. To this day, the trails of the two men are sometimes used by both Rotokas and Keriaka people as a route when traveling between the western and eastern sides of the island. Mt. Bagana The Bagana Volcanics crop out over about 40 square miles in central Bougainville and are the products of Bagana, an active stratovolcano which rises 5730 feet [1747 meters] above sea level, 12 miles [19 kilometers] north-east of Torokina. The formation consists of dark grey andesite lava flows, subordinate tuff and agglomerate, and derived alluvial fan deposits. Bagana is [was] the most active volcano in the [Papua] New Guinea area [at least when Fisher described it in 1954 and 1957]. It may well have been entirely built up since the end of the Pleistocene. Its activity was recorded by Guppy 1887, who visited the Solomon Islands in 1882, and it has probably been more or less continuously active since. The most recent manifestations of activity include powerful explosive eruptions [accompanied by numerous nuees ardentes descending the flanks of the volcano and the emission of lava flows]. When examined in June 1965, the youngest lava flow was still moving down the south-west side of the volcano. Half way down the volcano this flow had split into four arms, two flowing west and two south. Their fronts had reached the base of the cone and were advancing at the rate of 1 foot or less a day…Several hot springs issue from the base of the cone Blake, et al. 1967:27–28. 33 Plate 11. Fig. 1. The active Bagana Volcano, 23 May 1960, from the northeast. One of the 1946–7 lava flows is shown on the extreme left of the photograph. Photo G. A. Taylor. Fig. 2. Bagana Volcano, 7 October 1964, from the south. The 19645 lava flow, darker in colour than the older flows, is shown descending the western flank of the volcano. About half way down the flank this flow has divided into four main arms, two of which flow to the west and two to the south see Plate 10. Photo C. D. Branch. Two views of Mt. Bagana The following is an account of the eruption of Bagana Volcano called Tooki in Rotokas, which took place on April 19, 1975. Up to the time of the eruption, the activity of the volcano had increased noticeably. For several months, the lava had been flowing down a trough on the northern flank. The top of the cone 34 glowed red and was visible for miles at night. During the evening of the 18th, we could hear deep sounds from within the earth, as if it were groaning. At about 4:35 a.m. on the 19th, Mt. Bagana erupted with a very powerful report. However, it was heard neither in Kieta, nor even as close as Asitavi, near Wakunai. Within minutes the smoke and ash climbed to a height of between 10,600 and 12,200 meters as estimated by a visiting Bougainville Air Services’ pilot. Throughout the column of smoke and ash, lightning flashed. Various people of Togarao village said that they had never seen anything like it before. The top of the cloud drifted to the east while the middle section drifted west out over the sea. There was light rain with ash which fell about one and a half hours later. This resulted in a light coat of ash on the vegetation. Within three hours of the explosion, the sky had cleared and the volcano had quieted again. A pilot flying near the cone later in the day said that there was no great noticeable difference in the shape of the cone nor in the subsequent emission of steam and smoke. Map 5 – Bagana Volcanics A secondary cloud of smoke and ash went up on Sunday, April 27, at 1 p.m. It was preceded by a few rumbling noises the night before. The cloud did not go as high possibly about 4,500 to 6,000 meters and quickly dissipated over the Solomon Sea to the west. NumaNuma Volcanics The NumaNuma Volcanics are the products of a previously unnamed extinct volcano, here called the NumaNuma volcano, which is situated south-east of Mount Balbi. The formation covers an area of about 175 square miles and is named after NumaNuma river, which flows down the north flank of the volcano to NumaNuma plantation, on the north-east coast of Bougainville. Most of the NumaNuma Volcanics are probably Pleistocene…[The volcano] is a densely forested complex stratovolcano…The summit area consists of an erosion caldera, a dome, 35 and a deeply eroded volcanic cone. The erosion caldera is more than 1000 feet deep and 2 miles wide…On the gently sloping flanks of the volcano deep gullies separated by sharp ridges extend radially outwards from the summit area…The highest part of the complex is on the southern rim of the caldera [5035 feet1535 meters]. Billy Mitchell Volcanics The Billy Mitchell Volcanics comprise both the rocks which were erupted from the extinct Billy Mitchell Volcano and the fan deposits derived by erosion of the eruptive rocks. The formation covers an area of about 80 square miles in central Bougainville and consists of pumice, tuff, agglomerate, and sand… The Billy Mitchell Volcanics have a maximum thickness of about 5000 feet…The highest and steepest parts of the volcano are covered with kunai grass and scattered trees, while tropical rain forest covers the lower flanks. In the centre of the volcano Lake Billy Mitchell occupies a well formed crater 1.5 miles in diameter. A small island occurs near the southern shore of the lake. The highest point on the rim of the crater is 5028 feet [1533 meters], and the water level of the lake is at about 3500 feet [1067 meters]: the maximum depth of water in the lake is not known. The eastern flank of the volcano descends smoothly for 14 miles to the sea, but the other sides have rough irregular surfaces and are much less extensive Blake, et al. 1967: 25–26]. In 1973, during the PNG Defense Force’s presence in the Rotokas area, an exercise was planned which would take the men near Lake Billy Mitchell and on to Panguna along the top of the Crown Prince range. Guides were chosen from Lesiopaia and Beteriopaia to help the troops over the first part of the trail. As the men neared the lake, the guides started to desert and eventually, the men were left to themselves to find their way through this very dense forested area. A senior officer, who observed the men from his plane each day, told us that at times they were unable to make even four kilometers a day. The men eventually finished the exercise at Panguna, but without the help of the guides. It turned out later that the guides had been worried about spirit beings believed to be present in the area of Lake Billy Mitchell.

2.2.2 Rivers and waterfalls