How does Jack Kerouac use imagery in The Dharma Bums?

Imagery:

Now the mountains were getting that pink tinge, I mean the rocks, they were just solid rock covered with the atoms of dust accumulated there since beginningless time. In fact I was afraid of those jagged monstrosities all around and over our heads.

"Meanwhile scores of people stood around in the darkened gallery straining to hear every word of the amazing poetry reading as I wandered from group to group, facing them and facing away from the stage, urging them to glug a slug from the jug, or wandered back and sat on the right side of the stage giving out little wows and yesses of approval and even whole sentences of comment with nobody's invitation but in the general gaiety nobody's disapproval either. It was a great night."