The soup is boiled not over a fire but by dropping a red-hot volcanic stone straight into the bowl, which hisses and rolls the broth to a boil at the table.
Calapurca is a thick Andean stew of llama or beef, potatoes, and chuño (freeze-dried potato) served bubbling from the heat of the stone dropped inside it. Market cooks in Arica's Andean quarters ladle it into clay bowls for workers heading up to the altiplano.