Open Question: Can you help me tell what this quote means?

"our skulls rise to the surface like rocks in the bed of a drying stream." 25th high school reunion by Linda Pastan We come to hear the endings of all the stories in our anthology of false starts: how the girl who seemed as hard as nails was hammered into shape; how the athletes ran out of races; how under the skin our skulls rise to the surface like rocks in the bed of a drying stream. Look! We have all turned into ourselves.