go hiking in the mountains 和climb the mountain 是动词性词组，都有爬山的意思；mountain climbing 是名词性词组，可以译为爬山运动。另外还有go climbing等。

“周末我将去爬山”可译为“I will go climbing this weekend”或者“I will spend this weekend climbing in the mountain”等多种译法都可以。