Bluejohn Canyon in southeastern Utah is narrow in places. In sections the walls close in so tightly that sunlight barely reaches the floor. Climbers move through it alone more often than not.

In April 2003, Aron Ralston was navigating one of those passages when a dislodged boulder shifted and pinned his right arm against the canyon wall.

The rock weighed several hundred pounds.

Ralston tried to free himself. He pushed against the stone. He tried to chip at it. He used the small equipment he had with him. Nothing moved the boulder.

Time began to stretch.

He had limited food and water. The canyon was remote and he had not told anyone exactly where he was going that day. Rescue was unlikely to arrive quickly.

For the first several days he tried to solve the problem in ordinary ways. He worked the rock back and forth, hoping it would shift. He rigged systems to try to gain leverage. Each attempt ended the same way.

The boulder held.

By the fourth day his water supply was nearly gone. The situation had shifted from inconvenience to survival.

Ralston later described the realization in interviews with CBS News. He understood that the rock would not move and that waiting would not change the outcome.

The remaining option was the one he had been avoiding.

He would have to remove his arm.

The tools available were minimal. He carried a small multi tool knife not designed for anything close to surgery. The process would be slow and painful.

But it was possible.

After five days trapped in the canyon, Ralston broke the bones in his forearm and used the knife to cut through the remaining tissue. Once free, he rappelled down the canyon wall and began walking out.

The journey was not over when the arm was gone. He still had to leave the canyon.

Ralston hiked several miles before encountering a family of hikers who helped alert authorities. A rescue helicopter eventually lifted him out of the desert.

Doctors treated the injuries and he survived.

The canyon remained where it always was. Narrow walls. Shifting rocks. Quiet passages that see occasional climbers passing through.

One of them left with one arm instead of two.

But he left.

Aron Ralston amputated his own arm after five days trapped by a boulder in a remote canyon and then hiked out to reach help.

That is what he did.

It is worth noticing because the situation presented a single workable option and he recognized it before time ran out.

He did not move the rock. He changed the problem.

The canyon did not release him.

He released himself.

If you were trapped with no clear rescue coming, how long would it take before you began considering the option you hoped you would never need?