The moment that Terron placed a hand on the ceiling of the cave he had expanded, everyone was silent. They knew that he was using his exceptional control of earth mana to sense where and what might be above.
As his face showed different emotions, Walker also placed a hand on the wall next to him. He was able to use his own understanding of earth elemental mana to feel the same things that Terron was doing.
This would be foolish if he was going to add his own mana. However, Walker felt that it was best to learn something and just see what Terron might actually be doing to make him change his facial expressions so much. But when Walker felt the small flow of Terron's mana he could see that things were much different than he thought.