Here is the answer: rappelling! The guides who accompany guests on the trip unhooked the two cables, one at a time, from the zip lines to another cable mechanism that allowed them to drop us straight down to a platform over the river at the base of the canyon.
I should mention that the zip line adventure uses a double cable system so that visitors are attached to a cable at all times. When it is time to switch from one cable to another, the first cable is detached and then reattached before the second cable is detached and reattached. The straps, cables and hooks all appear to be in good condition. But it can still be scary.
A couple of days ago I showed you that there is more than one way to ride down the zip lines, including the regular way, or with no hands, or "super-chica" style. Guess what? There is more than one way to go down repelling. What is the other way? The answer will be shown in two photos tomorrow.