What causes mountain climates?

A trip up a high mountain near the equator takes you through a series of climatic and plant zones that resemble those you would meet on an overland journey from the equator to the poles. This is because temperatures fall by about 6 C for every 1,000m (roughly 1o F for every 300ft), so that leave a hot equatorial climate at the bottom and reach a polar climate at the top of the mountain.