Sentence:  The next landmark was an apachita 'cairn', at the top of a steep <WSD>scree</WSD>. Each pilgrim carried a stone to the summit, spat on it, and threw it on to the cairn — the purpose being, I was told, to relieve the soul of its sins ... 
Meaning of the word marked with <WSD> tags:  A slope made up of loose stony debris at the base of a cliff, mountain, etc.