Entering into silence is like stepping into cool clear water. The dust and debris are quietly washed away, and we are purified of our triviality. This cleansing takes place whether we are conscious of it or not: the very choice of silence, of desiring to be still, washes away the day's grime.
It seems to me that a mountain is an image of the soul as it lifts itself up in contemplation. For in the same manner as the mountain towers above the valleys and lowlands at its foot, so does the soul of the one who prays mount into the higher regions up to God like an eagle taking wing.