In the past, storms and other disturbances have felled many hectares of kauri forest in Northland, some as long as 30,000 to 50,000 years ago. Trees like this log were often preserved in swamps. Since the large-scale felling of kauri has ceased, these buried trees have become an important source of timber. Transformed by thousands of years in acidic swamps, swamp kauri is mottled in lustrous shades of grey-green and brown. It can be made into ornaments and furniture. However, it is not as strong as fresh wood and cannot be used for structural purposes.