The World on Turtle's Back

In the beginning, there was no land, only a great ocean that stretched out infinitely. Above this great ocean was a Sky-World occupied by Gods who were like the Iroquois people. At the center of the universe stood a Great Tree. Its massive roots spread out over the floor of the Sky-World. The tree was sacred and was not to be marred by any of the dwellers of the Sky-World.

In the Sky-World, there was a man who aimed to please his pregnant wife. His wife told him that she wanted some bark from the roots of the Great Tree. Though the husband knew it was wrong, he dug up the roots of the tree for his wife. In doing so, he broke a hole in the floor of the Sky-World and was shocked to find empty space underneath. He was terrified and told his wife what he did.

Why did the husband become terrified?