Earth brain allegory of life and death
Left alone in his house after Elizabeth dies, Joseph has a stream of thoughts about life and death. Out of those thoughts comes the allegory of the brain of the earth towering above mountains, valleys, and ranges. The brain does everything to preserve the perfection of the life of these valleys mountains and ranges below but it knows that the earth has to move some day destroying everything that was being built over millions of years. This brain feels helpless knowing that it can't do anything against this. The earth starts moving and all that was built is gone. Taking into consideration what happened, this appears to be an allegory of life and death. Whole life is spent building something creating something and then death comes. Death is inevitable and sudden and it takes everything that was built during the life with it.
Oak tree symbol
The oak tree is at first a symbol of Joseph coping with his father's death and believing that his father is with him even after death, which strengthens his intent of making a life on that ranch. The tree is his comfort and escape. After some time the oak tree is given a new meaning unconsciously by Joseph. The tree becomes the heart of the ranch and Joseph starts basing every decision on the signs the tree gives him. Eventually, the tree gets a more mystical meaning; it could be said that it becomes Joseph's figure of worship to which he unconsciously gives sacrificial offerings.
Moss-covered rock symbol
The symbolism of the moss-covered rock is similar to the oak tree in that it represents the heart of the land and holds some mystical powers over people. After the drought, the place around the rock is the only place left with traces of life. Joseph starts ritualistically watering the moss one the rock hoping that if that moss is alive then there is hope for rebirth of his land. The rain comes and the land is reborn only when Joseph makes a final and most important sacrifice to that rock.
