Recently some tiny but active terrace-forming springs have made their appearance very close to the Upper Terrace Drive. Now park geologist Hank Heasler has determined that water up to 152 degrees Fahrenheit (67 ºC) is bubbling out near the road. News sources say the feature became visibly active in May and is creating new small terraces too close to the drive for visitor safety. As a result the Park Service has closed the road.
When I visited early one morning in mid June, checking up on one of my favorite features, Canary Spring, I noticed that the area around Grassy Spring seemed very hot, with little terraces appearing since I was last there and a tiny new spring above the first major parking area, where I usually park to visit Canary.
If you’re visiting Mammoth this summer or fall, you can still park just outside the entrance to the Upper Terrace Drive and walk down the Canary Spring boardwalk or beyond the new hot activity to see my other favorite feature, Narrow Gauge Terrace.
For more about Mammoth Hot Springs and a video of Canary’s activity last year, see my September 18, 2014, post. Here’s what the spring and terrace looked like in 2009:
You can locate the features mentioned here in Yellowstone Treasures (print version, map page 265 and text pages 271 to 274) or check it out in the e-book version of that guidebook. You can also find information about this part of Mammoth in our companion/derivative e-book, Visiting Geyserland, pages 11 to 15.