This trek to Iva Bell Hot Springs combines classic Sierra Nevada granitescapes with the volcanic wonderland that is the Mammoth Mountain area. It's very easy to combine this adventure with a visit to Devil's Postpile National Monument, the hot springs of the Long Valley Caldera and Mammoth Mountain itself. Iva Bell Hot Springs exists at the southern end of the Mono-Inyo Volcanic Chain, which includes Mammoth Mountain and extends north to Mono Lake.
Your adventure will likely start at the Mammoth Lakes Welcome Center to pick up your wilderness permit. You can reserve a permit on the Reservation.gov system, and a limited amount of walk-in permits are also available at the welcome center. Next, enjoy a $7 shuttle ride from Mammoth Mountain's main lodge into Reds Meadow. Check with local authorities on shuttle start and end dates (mandatory shuttle use usually ends after Labor Day, with overnight parking available until October 15). Once in Reds Meadow, you can get on and off the shuttle as much as you like to see the various sights, including Devil's Postpile.
The hike to Iva Bell begins at the Rainbow Falls Trailhead. Follow the multitude of day hikers just a little over 1 mile south to find a sign leading you several hundred feet to Rainbow Falls. This short diversion back into Devil's Postpile National Monument is well worth the time. After visiting the falls, continue south in the Ansel Adams Wilderness toward Fish Creek. This first leg of the hike is within the burn scar of the 1992 Rainbow Fire. With the addition of a huge tree blowdown in 2012, views are wide-open and sun protection is recommended.
After about 4 miles into the hike you'll enter the John Muir Wilderness and enjoy big granite vistas of the Middle Fork of the San Joaquin River. Interspersed in this section are groves of quaking aspen and Jeffery pine with fern, asters, goldenrod, lupine and gooseberry acting as groundcover. The most strenuous (and driest) stretch of this hike comes about 7 miles in where you lose 800 feet in 1.5 miles while you descend toward Fish Creek. The final third of the hike is mostly forested and features several notably large incense cedar trees.
Cross Sharktooth Creek (a slightly higher-than-comfortable log crossing) and you will be at the lower end of Iva Bell's grassy hillside meadows. Bear left after the creek crossing to find several good campsites as well as the easiest access to the first pool. There are trails on either side of the grassy area that lead you up the hillside to higher pools. You'll have to add on several hundred feet of elevation gain to reach the highest pools. Try to minimize travel within the grassy areas to reduce your impact and to keep dry.
Only several miles away (but a very steep descent) from the Pacific Crest Trail and the John Muir Trail, these hot springs are a popular side-trip for thru-hikers. If you have several days, you can extend your hike on to the PCT to explore the Duck Pass area.