The ideas discussed in the passage are
C. Nature can destroy creations that were thought indestructible; humans aren't as powerful as the forces of nature.
Explanation:
The passage given here is principally concerned with the nature of the power of nature over humans. In that, the nature can and will be superior over whatever the human power will achieve as it can make it erode and wither away.
Even the things that the humans would think would be indestructible are fairly easy to collapse and to destroy.
So the permanence of the human power over nature is disputed here in the two concurrent ideas of the destructibility of everything and nature's dominion over humans.