The park service does not recommend this extremely steep, unmaintained trail, but some folks brave it. People report needing ice axes and good route finding skills. This grueling slog through lots of loose scree and over shifting blocks of lava is treacherous because a false step can start a rock slide or launch you over a drop-off.
Upon reaching river level, the trail turns right to follow the bank where you'll find a few sandy beaches and a viewpoint. The trail ends on cliffs above the famous Lava rapid where, if you're lucky, you'll see rafters caroming through. There is no shade or water on this serious excursion so plan accordingly. (River water must be filtered prior to drinking)
The Hiking Project mobile app
may be useful for wayfinding but make sure your data is current and you device charged!
Beware of rattlesnakes and scorpions. Cactus, yucca.