Living with volcanoes in Papua New Guinea Case Study Click on the following links for further information about this case study: Teacher's Notes Student Activities Tectonic movement A global phenomenon caused by natural processes is the movement of tectonic plates. The upper layer of the earth is made up of small and large tectonic plates varying in thickness from 50 to 125 kilometres. The plates move slowly about the earth's surface. Volcanic eruptions are one effect of plate movements, and there is a very strong spatial association between the volcanoes and tectonic plate boundaries. About two thirds of the world's visible volcanoes are located on the boundary of the Pacific plate. Eighty are located within Papua New Guinea (PNG). Fourteen of these are active, 22 dormant, the remainder being extinct. Papua New Guinea volcanoes The PNG volcanoes were formed as a consequence of the Australian and Pacific plates colliding (along with several other smaller plates). The region is geologically complex. The Pacific plate, moving ten centimetres north west per year, is colliding with the Australian plate, which is moving northwards at the rate of eight centimetres a year. Pieces of these two plates have broken off in the collision, creating several micro plates. The volcanoes were formed from magma, which has forced its way to the earth's surface from depths of 150-200 kilometres. The magma formed from micro plates that melted while descending beneath the Australian plate. Friction between the moving plates also causes earthquakes in the region. The volcanoes appear at the surface about 150 kilometres from the collision zone. Fourteen of PNG's volcanoes have erupted within the last 150 years. Of these, five (Rabaul, Manam, Karkar, Ulawun and Lamington) are high-risk volcanoes situated near significant numbers of people whose lives and property would threatened if they were to erupt. Figure 1. Dangerous Volcanoes of Papua New Guinea Monitoring the volcanoes In Papua New Guinea, the Rabaul Volcanological Observatory is responsible for monitoring the 14 dangerous volcanoes. The Observatory has an array of instruments that will give advance warning of an impending eruption. Within the region of the Rabaul volcano these include: Tide gauge-monitoring stations that measure rising of magma underneath the harbour by recording changes in height above sea level Seismic stations around the harbour that detect earthquakes' seismic wave activity deep inside the volcano Surveying instruments that measure uplift tilt, and sideways movement of the ground Heat flow instruments which measure heat levels under the caldera in order to determine where magma is close to the surface Thermometers that measure changes in the surface temperature of the volcano. Volcanic eruption evacuation plan By 'listening' to the volcanoes, the volcanologists are in a position to alert the authorities and the surrounding communities of any increased restlessness and the imminent eruption of a volcano. There is a four stage alert/warning system. Stage 1. The Provincial Disaster Controller is alerted of increased volcanic activity. All emergency services will be made ready. There is no public announcement at this stage. Stage 2. There is a radio announcement that an eruption is likely in the near future. People are instructed to pack and be ready to leave the region if/when advised. Stage 3. A radio announcement alerts people that they must be ready to leave the region at very short notice. Stage 4. A radio announcement and continuous sirens alert people to leave the region immediately. The Rabaul volcano The Rabaul volcano is subject to frequent eruptions. Major eruptions occur every two to three thousand years, the last about 1 400 years ago, while minor ones occur about every 20 to 60 years, the most recent one in 1994. The last two major eruptions saw the magma chamber collapse, forming a circular depression or caldera. This created Simpson Harbour, one of the best harbours in the South Pacific. Today, there are seven volcanoes distributed around the edge of the caldera, each fed by a new magma chamber beneath the caldera. The town of Rabaul is located on one side of Simpson Harbour. The 1994 eruption On Sunday morning, 18 September 1994, earthquake activity caused eruptions of two Rabaul cones, Tavurvur and Vulcan. Continuous earthquakes the Sunday before the eruption, led many people to abandon the town before an official evacuation was announced. Thousands of tonnes of ash, gas and pumice forced the evacuation of 100, 000 people. Five people were killed and many of Rabaul's buildings and infrastructure was destroyed. By mid October, large regions were buried beneath 50-100 cm of volcanic ash, while the harbour itself was covered by a sheet of pumice up to a metre thick in places. Figure 2. Rabaul Harbour Australia's response The Australian Government was quick to respond to the eruption with two important projects: Volcanological Support Services Project. The purpose of this $6.4 million project between 1994-1999 was to strengthen the capacity of the Rabaul Volcanological Observatory to monitor the five high-risk volcanoes and to improve the early-warning and research capability. Two important parts of the project were a major geophysical survey that aimed to probe the interior of the volcano, and a volcanic-hazard mapping facility that mapped the probable location and distribution of areas to be affected by a future eruption. Such a map will assist emergency forces in preparing for the effects of a future eruption. Gazelle Reconstruction Project. The Australian Government provided more than $40 million to this project which aimed to move the entire Rabaul town population and functions to Kokopo, a safer location in the Gazelle Peninsula region. The focus of the project centred on infrastructure construction in the key sectors of roads, education and police. Today, a revitalized Rabaul town continues to act as the main distribution harbour and port in the region, while Kokopo is the main administrative and provincial centre. Top © Commonwealth of Australia