The last days of operations of the Pedro de Valdivia nitrate office, near Maria Elena. The dust in suspension that is seen in the background is a result of the extraction of caliche (nitrate salt deposits in the pampa of atacama desert) in the surroundings of the nitrate office. Unfortunately, all SQM railways (Tocopilla, Maria Elena, Coya, Pedro de Valdivia) closed at the end of 2015.