Shell middens were formed when people in the past discarded waste, such as the remains of shellfish that had been consumed, animal bones, and other types of waste. The calcium carbonate in the shells neutralizes the acidic soil, and so animal bones are well preserved in these shell middens.
The Dongsam-dong shell midden in Busan contained various traces of Neolithic lives, including shells, fish and sea mammal bones, pottery, fishing tools, craft objects, and ceremonial items. This is a cross-section of the shell midden that was excavated by Busan Museum in 1999. Around 3.5 meters tall, the soil layers represent the accumulation of 8,000 years.