How were the fertile basins of Papua New Guinea’s Highlands formed?

The fertile basins found within the Highlands of Papua New Guinea were formed in the recent geologic past through a combination of natural processes. These enclosed upland basins were created by impeded drainage, which allowed for the accumulation of lake deposits. Over time, these areas were further enriched by soil wash from the surrounding mountains and the deposition of layers of volcanic ash, or tephra, originating from nearby volcanoes, some of which have been active in recent times.1