What was the unsusal rock formation that Stanley saw at the top of the moutans in holes?

In "Holes" by Louis Sachar, Stanley Yelnats discovers a striking rock formation at the top of the mountains that resembles a thumb, which he names "God's thumb." This unusual formation symbolizes hope and serves as a pivotal point in the story, representing a place of refuge and realization for Stanley. The discovery of the rock formation ultimately leads him to a deeper understanding of his family's history and his own journey.