Within the coalfield, as a result of mining activities, there are a number of areas of artificially made ground, consisting for the most part of spoil from both opencasting for coal and deep mining. A high profile example is that of the Canada Tips, an area of excavation and deposition of Coal Measures rocks north of Blaenavon associated in particular with opencasting during the Second World War. It is now included within the Blaenavon Industrial Landscape World Heritage Site. Other areas are formed by material such as slag from former ironworks.
