In Paragraph 11, highlight the clues that convey how dangerous the trail?

The creek he knew was frozen clear to the bottom—no creek could contain water in that arctic winter—but he knew also that there were springs that bubbled out from the hillsides and ran along under the snow and on top of the ice of the creek. He knew that the coldest snaps never froze these springs, and he knew likewise their danger. They were traps. They hid pools of water under the snow that might be three inches deep, or three feet. Sometimes a skin of ice half an inch thick covered them, and in turn, was covered by the snow. Sometimes there were alternate layers of water and ice-skin, so that when one broke through he kept on breaking through for a while, sometimes wetting himself to the waist.