Papua New Guinea - Huon Terraces - Stairway to the Past

This portion of New Guinea has a turbulent geologic history, being located on the junction between the Australian and Pacific crustal plates. The surface geology of this eco-region is a combination of Miocene siltstone, conglomerate, volcanics, and limestone. It has been subject to a long history of volcanism, earthquakes, tsunamis, faulting and other fragmentation. In turn, this has resulted in fragmentation of the biological habitat and hence a high level of localisation and endemism. The Pacific plate is subducted beneath the Australian, and the land is one of the most rapidly rising areas of the world. The Finisterre and Saruwaged Ranges each consist of a massive ridge of limestone dipping steeply to the ocean. The most significant feature of the region is the remarkable sequence of coastal terraces, particularly well expressed and preserved at Sialum. These are not only spectacular, but have proven to be of immense value as testimony to the geo-climatic history of the Pacific region (and even the world) over the last 300,000 years. These are certainly the finest sequence of such terraces in the world, and have attracted a great deal of attention and continuing research. Further, as the land has emerged, the surface is generally covered with tephra - a layer of volcanic dist and rock shards, often referred to as volcanic ash. This serves to protect the emerging landscapes and to preserve the landscape history to a remarkable degree. It thus provides an invaluable resource for understanding of landscape evolution, biological history and human occupation. The ranges themselves have extensive underground drainage, with springs occurring both on the terraces and at sea level. However, there are freshwater risings in the ocean some 15 km. from the coast, probably based upon groundwater flows through karst conduits. The various nutrients carried with the freshwater apparently provide for a rich marine fauna and hence the rising is a key resource for the fishing industry of the North Coast.