Harrow and Hillingdon Geological Society

Previous Meetings

Geological Hazards in Papua New Guinea

Dr Steve Edwards

Papua New Guinea (PNG) has been inhabited for 50,000 years and is a culturally diverse, lively and exciting population speaking >850 different languages. The university has 4,000 students.

Melanesia is a sub-region of Oceania and its name means the islands of the dark-skinned people. All these islands lie on fault lines and plate boundaries and hence this is a very dynamic area. The hazards which occur include earthquakes, volcanic eruptions, mass land movements, tsunamis, storms, floods and droughts. In addition there are enormous problems with malaria, HIV/AIDS, environmental degradation from mining, deforestation and climate change.

Lying on the boundary of the Indo-Australasian plate with the Pacific plate, it is highly hazardous area with regard to earthquake and tsunami activity and is rich in active volcanoes. The climate is tropical and wet with high humidity and lots of rain. In the lowlands it is wet and dry but in the highlands it is wet and wetter!

Australia is surrounded by a shallow continental lithosphere and PNG is effectively attached to Australia. It has a central mountain range and a flatter area to the north. The major rivers originate in these mountains. There are 4 or 5 major geological zones, the stable craton of Indo- Australia, foreland fold- thrust belt, a central collision zone, the volcanic New Guinea islands and ranges and the plateau of Ontong. In addition, Australia is moving northwards at a rate of 7cm per year.

As already described this region contains every type of plate boundary, trenches and troughs, and sub-duction zones. The numerous volcanoes comprise 14 active and 22 dormant and of 4.5 million population, 200,000 are under direct threat from a volcano in the towns of Manam, Karkar, Pego, Rabaul, Ritter or Lagila Lamington. Rabaul was the original capital and was occupied by the Japanese during the war and bombed by the Americans. It is situated near two volcanoes, Vulcan and Tavurvur. In 1994 the two erupted simultaneously, covered the town in volcanic ash and killed all the vegetation. The main damage was on the east side of Rabaul where the plume reached 18km in height. These two volcanoes gave only 27 hours of warning of pending eruption but fortunately only 5 people died, probably due to the instincts of the elders who had experienced the signs before. In 1994 the capital was moved to Kokopo and many people were displaced. In Kokopo there is a mixture of tribes and this lead to civil unrest.

Most of the earthquakes in this region are sub-oceanic and hence the risk of tsunamis is very high. In the last, waves penetrated up to 1.5km inland.

The mountains are probably the most highly mineralised belts in the world containing amongst others, gold, copper, molybdenum and nickel. However, mining disturbs the steep mountains landscapes together with, high rainfall and earthquakes. The Sepik river floods in the wet season and houses were built on stilts. The Ok Tedi mine is in a mountain which is capped with gold-containing ore, lying on top of copper. The gold was extracted by cyanide leaching and all waste products were contained by a dam but an earthquake caused the dam to fail and everything flooded the river. Everything is still being dumped in the river and has been since 1984. One hundred and twenty km down the river are 150,000 people dwellings. The river has become choked with a vast area of sediment. Further down is another huge pile of sediment, this time pyrite-rich. In turn this has given rise to a high production of sulphuric acid which has killed fauna and flora and hence the food of the local people and made it impossible for them to use their canoes on the river. This mine is due to close in 2012/3 but the area will not recover for thousands of years.

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